JP2025186541A - Filter Generator - Google Patents

Abstract

A filter generation device for generating a filter suitable for out-of-head localization processing is provided.
[Solution] The processing device 201 includes a frequency characteristic acquisition unit 221 that acquires frequency characteristics based on the sound signals collected by microphones 2L and 2R, and generates axis-transformed data at equal intervals on the auditory scale by interpolating low-frequency band data using the frequency axis as an auditory scale close to human hearing; a judgment unit 242 that judges the performance of the playback device; a level range setting unit 224 that sets a level range depending on the judgment result of the judgment unit 242; a correction unit 225 that calculates correction characteristics by correcting the frequency characteristics based on the level range with respect to the frequency amplitude characteristics of the auditory scale; and a filter generation unit 230 that generates, based on the correction characteristics, a spatial acoustic filter used in out-of-head localization processing or an inverse filter that cancels the characteristics from the playback device to the user's ears.
[Selected Figure] Figure 12

Description

This disclosure relates to a filter generation device.

One sound image localization technology is out-of-head localization, which uses headphones to localize a sound image outside the listener's head. Out-of-head localization technology localizes a sound image outside the head by canceling the characteristics from the headphones to the ears (headphone characteristics) and providing two characteristics from one speaker (monaural speaker) to the ears (spatial acoustic transfer characteristics).

In out-of-head localization playback using stereo speakers, measurement signals (such as impulse sounds) emitted from two-channel (hereinafter referred to as ch) speakers are recorded by microphones (hereinafter referred to as mics) placed at the ears of the listener. A processing device then generates a filter based on the collected signal obtained by collecting the measurement signal. Out-of-head localization playback can be achieved by convolving the generated filter with the two-channel audio signal.

Furthermore, in order to generate a filter (also called an inverse filter) that cancels the characteristics from the headphones to the ear, the characteristics from the headphones to the eardrum (external ear canal transfer function ECTF) are calculated.
, also called ear canal transfer characteristics) is measured using a microphone placed in the listener's own ear.

Patent Document 1 discloses an apparatus for performing out-of-head localization processing. Furthermore, Patent Document 1 discloses that the out-of-head localization processing is performed by applying a dynamic range compensation (DRC) to a playback signal.
In the DRC process, the processing unit smooths the frequency characteristics. Furthermore, the processing unit performs band division based on the smoothed characteristics.

JP 2019-62430 A

In such out-of-head localization listening, it is desirable to perform processing without being limited to a specific playback device. For example, even if the playback device is a user's own headphones,
It is desirable to perform appropriate out-of-head localization processing, or to reproduce the spatial acoustic transmission characteristics in an environment where the user's usual speakers are installed as playback equipment.

Changing the playback device may change the transfer characteristics. Therefore, it is preferable to measure the user's personal characteristics (spatial acoustic transfer characteristics and ear canal transfer characteristics) using the playback device that the user is currently using. Even when personal characteristics are measured, sharp peaks and dips may occur in the frequency characteristics, which may cause clipping of the out-of-head localization processed signal.

Peaks and dips vary depending on the characteristics of playback devices such as speakers and headphones, or the acoustic characteristics of the room in which the measurement is performed. Peaks and dips also vary depending on the shape of the user's head and ears. Therefore, the levels and frequencies of peaks and dips vary due to various factors. Depending on the playback device and measurement environment, it becomes necessary to check the characteristics and make adjustments accordingly.

The present disclosure has been made in consideration of the above points, and has an object to provide a filter generation device capable of generating a filter suitable for out-of-head localization processing.

The filter generation device according to this embodiment includes a frequency characteristic acquisition unit that acquires frequency characteristics based on a signal picked up by a microphone and generates axis-transformed data at equal intervals on an auditory scale by interpolating low-frequency band data on the frequency axis, using an auditory scale approximating human hearing; a determination unit that determines the performance of the playback device; a level range setting unit that sets a level range in accordance with the determination result of the determination unit; a correction unit that calculates correction characteristics by correcting the frequency characteristics based on the level range relative to the frequency amplitude characteristics of the auditory scale; and a filter generation unit that generates, based on the correction characteristics, a spatial acoustic filter used in out-of-head localization processing or an inverse filter that cancels the characteristics from the playback device to the user's ears.

The filter generation device according to this embodiment includes a frequency characteristic acquisition unit that acquires frequency characteristics based on a signal picked up by a microphone and generates axis-transformed data at equal intervals on an auditory scale by interpolating low-frequency band data on a frequency axis that is an auditory scale similar to human hearing; a level calculation unit that calculates a reference level for the frequency characteristics; a correction unit that calculates correction characteristics by correcting the frequency characteristics so that the frequency amplitude characteristics of the auditory scale fall within a predetermined level range that includes the reference level; and a filter generation unit that generates a spatial acoustic filter or an inverse filter used in out-of-head localization processing based on the correction characteristics.

According to the present disclosure, it is possible to provide a filter generation device capable of generating a filter suitable for out-of-head localization processing.

1 is a block diagram showing an out-of-head localization processing device according to an embodiment of the present invention; FIG. 1 is a diagram illustrating a configuration of a measurement device for measuring spatial acoustic transfer characteristics. FIG. 1 is a diagram illustrating a configuration of a measurement device for measuring ear canal transfer characteristics. FIG. 2 is a control block diagram showing the configuration of the processing device. 1 is a flowchart illustrating a method for generating a filter in a processing device. 10 is a flowchart illustrating a first example of a correction process. 10 is a graph showing frequency amplitude characteristics before and after correction according to processing example 1. 10 is a flowchart illustrating a second example of the correction process. 10 is a graph showing frequency amplitude characteristics before and after correction according to processing example 2. 10 is a flowchart illustrating a fourth example of a correction process. 10 is a graph showing frequency bands according to processing example 4. FIG. 10 is a block diagram showing a configuration of a processing device according to a second embodiment;

An overview of the sound image localization processing according to this embodiment will be described. The out-of-head localization processing according to this embodiment is performed using spatial acoustic transfer characteristics and ear canal transfer characteristics. The spatial acoustic transfer characteristics are the transfer characteristics from a sound source such as a speaker to the ear canal. The ear canal transfer characteristics are the transfer characteristics from a speaker unit of headphones or earphones to the eardrum. In this embodiment, the spatial acoustic transfer characteristics are measured when headphones or earphones are not worn, and the ear canal transfer characteristics are measured when headphones or earphones are worn, and the out-of-head localization processing is realized using these measurement data. This embodiment is characterized by a microphone system for measuring the spatial acoustic transfer characteristics or the ear canal transfer characteristics.

The out-of-head localization processing according to this embodiment is executed by a user terminal such as a personal computer, a smartphone, or a tablet PC. The user terminal is an information processing device having processing means such as a processor, storage means such as a memory or a hard disk, display means such as an LCD monitor, and input means such as a touch panel, buttons, a keyboard, or a mouse. The user terminal may have a communication function for transmitting and receiving data. Furthermore, output means (output unit) having headphones or earphones is connected to the user terminal. The connection between the user terminal and the output means may be wired or wireless.

Embodiment 1.
(Extracranial localization processing device)
A block diagram of an out-of-head localization processing device 100, which is an example of a sound field reproduction device according to this embodiment, is shown in Fig. 1. The out-of-head localization processing device 100 reproduces a sound field for a user U wearing headphones 43. To this end, the out-of-head localization processing device 100 performs sound image localization processing on the left and right channel stereo input signals XL and XR.
L and XR are analog audio playback signals output from a CD (Compact Disc) player or the like, or digital audio data such as MP3 (MPEG Audio Layer-3). Audio playback signals and digital audio data are collectively referred to as playback signals. In other words, the left and right channel stereo input signals XL and XR are playback signals.

The out-of-head localization processing device 100 is not limited to being a single physical device, and some of the processing may be performed by different devices. For example, some of the processing may be performed by a smartphone or the like, and the remaining processing may be performed by a DSP (Digital Signal Processor) built into the headphones 43.

The out-of-head localization processing device 100 includes an out-of-head localization processing unit 10, a filter unit 41 that stores an inverse filter Linv, a filter unit 42 that stores an inverse filter Rinv, and headphones 43. Specifically, the out-of-head localization processing unit 10, the filter unit 41, and the filter unit 42 can be realized by a processor or the like.

The out-of-head localization processing unit 10 includes convolution calculation units 11-12, 21-22 that store spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs, and adders 24 and 25. The convolution calculation units 11-12, 21-22 perform convolution processing using the spatial acoustic transfer characteristics. Stereo input signals XL and XR from a CD player or the like are input to the out-of-head localization processing unit 10. The spatial acoustic transfer characteristics are set in the out-of-head localization processing unit 10.
is a filter of spatial acoustic transfer characteristics (hereinafter,
The spatial acoustic transfer characteristic may be a head-related transfer function (HRTF) measured on the subject's head or pinna, or may be a head-related transfer function of a dummy head or a third party.

A set of four spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs is defined as a spatial acoustic transfer function. Data used for convolution in the convolution calculation units 11, 12, 21, and 22 becomes a spatial acoustic filter. A spatial acoustic filter is generated by cutting out the spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs with a predetermined filter length.

The spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs are each acquired in advance by impulse response measurement or the like. For example, a user U wears a microphone on each of his left and right ears. Left and right speakers placed in front of the user U output impulse sounds for impulse response measurement. Then, the measurement signals such as the impulse sounds output from the speakers are picked up by the microphone. The spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs are calculated based on the signals picked up by the microphone.
The spatial acoustic transfer characteristic Hls between the left speaker and the left microphone, the spatial acoustic transfer characteristic Hlo between the left speaker and the right microphone, the spatial acoustic transfer characteristic Hro between the right speaker and the left microphone, and the spatial acoustic transfer characteristic Hrs between the right speaker and the right microphone are measured.

The convolution calculation unit 11 then convolves the left channel stereo input signal XL with a spatial acoustic filter according to the spatial acoustic transfer characteristic Hls. The convolution calculation unit 11 outputs the convolution calculation data to the adder 24. The convolution calculation unit 21 convolves the right channel stereo input signal XR
The convolution unit 21 convolves a spatial acoustic filter corresponding to the spatial acoustic transfer characteristic Hro with the signal. The convolution unit 21 outputs the convolution operation data to the adder 24. The adder 24 adds the two pieces of convolution operation data together and outputs the result to the filter unit 41.

The convolution calculation unit 12 calculates the spatial acoustic transfer characteristic H1 for the left channel stereo input signal XL.
The convolution operation unit 12 convolves the Rch stereo input signal XR with a spatial acoustic filter corresponding to the spatial acoustic transfer characteristic Hrs. The convolution operation unit 22 outputs the convolution operation data to the adder 25. The adder 25 adds the two pieces of convolution operation data and outputs the result to the filter unit 42.

The filter units 41 and 42 are provided with inverse filters Linv and Rinv that cancel headphone characteristics (characteristics between the headphone playback unit and the microphone). The playback signal (convolution signal) processed by the out-of-head localization processing unit 10 is then filtered by the inverse filters Linv and Rinv.
The filter unit 41 convolves the Lch signal from the adder 24 with the inverse filter Linv of the Lch headphone characteristics.
The Rch signal from the headphone amplifier 5 is convolved with an inverse filter Rinv of the Rch headphone characteristics. When the headphones 43 are worn, the inverse filters Linv and Rinv cancel the characteristics from the headphone unit to the microphone. The microphone may be placed anywhere between the entrance of the ear canal and the eardrum.

The filter unit 41 outputs the processed Lch signal YL to the left unit 43L of the headphones 43. The filter unit 42 outputs the processed Rch signal YR to the right unit 43R of the headphones 43. A user U wears the headphones 43. The headphones 43 are
The Lch signal YL and the Rch signal YR (hereinafter, the Lch signal YL and the Rch signal YR are also collectively referred to as stereo signals) are output toward the user U. This makes it possible to reproduce a sound image localized outside the head of the user U.

In this way, the out-of-head localization processing device 100 calculates the spatial acoustic transfer characteristics Hls, Hlo, Hro,
The out-of-head localization process is performed using a spatial acoustic filter according to Hrs and inverse filters Linv and Rinv of the headphone characteristics.
Spatial acoustic filters according to lo, Hro, Hrs and inverse filters Lin for headphone characteristics
v and Rinv are collectively referred to as the out-of-head localization processing filter. In the case of a 2-channel stereo playback signal, the out-of-head localization filter is composed of four spatial acoustic filters and two inverse filters. The out-of-head localization processing device 100 then performs out-of-head localization processing by performing convolution operation processing on the stereo playback signal using a total of six out-of-head localization filters. It is preferable that the out-of-head localization filter is based on individual measurements of the user U. For example, the out-of-head localization filter is set based on a sound signal picked up by a microphone attached to the user U's ear.

In this way, the spatial acoustic filter and the headphone characteristic inverse filters Linv and Rinv are filters for audio signals. These filters are used to filter the playback signal (stereo input signal XL
, XR), the out-of-head localization processing device 100 executes out-of-head localization processing.
In this embodiment, one of the technical features is the process of generating a spatial acoustic filter.
Specifically, in the process of generating the spatial acoustic filter, the level range of the frequency characteristics is compressed.

(Spatial Acoustic Transfer Characteristics Measurement Device)
A measurement device 200 for measuring spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs will be described with reference to Fig. 2. Fig. 2 is a diagram schematically illustrating a measurement configuration for measuring a subject 1. Note that, in this example, the subject 1 is the same person as user U in Fig. 1, but may be a different person.

As shown in Fig. 2, the measurement device 200 has a stereo speaker 5 and a microphone unit 2. The stereo speaker 5 is installed in a measurement environment. The measurement environment may be a room in the user U's home, an audio system sales store or showroom, or the like. The measurement environment is preferably a listening room equipped with speakers and acoustics.

In this embodiment, the processing device 201 of the measuring device 200 performs arithmetic processing for appropriately generating a spatial acoustic filter. The processing device 201 has, for example, a music player such as a CD player. The processing device 201 can be implemented by a personal computer (PC),
The processing device 201 may be a tablet terminal, a smartphone, etc. The processing device 201 may also be a server device itself.

The stereo speakers 5 include a left speaker 5L and a right speaker 5R. For example, the left speaker 5L and the right speaker 5R are placed in front of the subject 1. The left speaker 5L and the right speaker 5R output impulse sounds and the like for measuring impulse responses. In the following description of this embodiment, the number of speakers serving as sound sources is two (stereo speakers), but
The number of sound sources used for measurement is not limited to two, but may be one or more.
Alternatively, this embodiment can be similarly applied to a so-called multi-channel environment such as 5.1ch or 7.1ch.

The microphone unit 2 is a stereo microphone having a left microphone 2L and a right microphone 2R. The left microphone 2L is placed at the left ear 9L of the subject 1, and the right microphone 2R is placed at the left ear 9L of the subject 1.
Specifically, it is preferable to install the microphones 2L and 2R at positions from the entrance of the ear canal to the eardrum of the left ear 9L and the right ear 9R. The microphones 2L and 2R pick up the measurement signals output from the stereo speakers 5 and obtain the picked-up sound signals.
outputs the collected sound signal to the processing device 201. The subject 1 may be a person or a dummy head. That is, in this embodiment, the subject 1 is a concept that includes not only a person but also a dummy head.

As described above, the impulse sounds output from the left speaker 5L and the right speaker 5R are input to the microphone 2.
The impulse response is measured by measuring the left speaker 5L and the right speaker 2R. The processing device 201 stores the picked-up signal obtained by the impulse response measurement in a memory or the like.
and the left microphone 2L, the spatial acoustic transfer characteristic Hls between the left speaker 5L and the right microphone 2R, the spatial acoustic transfer characteristic Hlo between the right speaker 5R and the left microphone 2L,
ro, and the spatial acoustic transfer characteristic Hrs between the right speaker 5R and the right microphone 2R is measured. That is, the left microphone 2L picks up the measurement signal output from the left speaker 5L, and the spatial acoustic transfer characteristic Hls is acquired.
The spatial acoustic transfer characteristic Hlo is obtained by the left microphone 2L collecting the measurement signal output from the right speaker 5R. The spatial acoustic transfer characteristic Hro is obtained by the left microphone 2L collecting the measurement signal output from the right speaker 5R.
The measurement signal output from the right speaker 5R is picked up by the right microphone 2R, and the spatial acoustic transfer characteristic Hrs is acquired.

Furthermore, the measuring device 200 may generate spatial acoustic filters according to spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs from the left and right speakers 5L and 5R to the left and right microphones 2L and 2R based on the collected sound signals.
The processing device 201 may extract Hlo, Hro, and Hrs using a predetermined filter length. The processing device 201 may correct the measured spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs.

In this way, the processing device 201 generates a spatial acoustic filter used in the convolution operation of the out-of-head localization processing device 100. As shown in FIG.
is the spatial acoustic transfer characteristic Hl between the left and right speakers 5L, 5R and the left and right microphones 2L, 2R.
The out-of-head localization processing is performed using a spatial acoustic filter according to Hs, Hlo, Hro, and Hrs. That is, the out-of-head localization processing is performed by convolving the spatial acoustic filter with the audio playback signal.

The processing device 201 performs the same processing on the picked-up sound signals corresponding to the spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs.
, Hlo, Hro, and Hrs. This allows spatial acoustic filters corresponding to the spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs to be generated.

(Ear canal transfer characteristic measuring device)
The ear canal transfer characteristic measuring device 300 will be described with reference to FIG.
The measurement device 300 measures the ear canal transfer characteristics in order to generate an inverse filter. The measurement device 300 includes a microphone unit 2 and
The device is equipped with headphones 43 and a processing device 301. Here, the subject 1
Although the user is the same person as user U in FIG. 1, the user may be a different person.

In this embodiment, the processing device 301 of the measurement device 300 performs arithmetic processing to appropriately generate a filter according to the measurement results. The processing device 301 is a personal computer (PC), tablet terminal, smartphone, etc., and includes a memory and a processor. The memory stores a processing program, various parameters, measurement data, etc.
The processor executes a processing program stored in the memory. The processor executes the processing program, thereby performing each process. The processor may be, for example, a CPU (Central Processing Unit).
Processing Unit), FPGA (Field-Programmable Gate Array), DSP (Digital Si
gnal Processor), ASIC (Application Specific Integrated Circuit), or GPU
(Graphics Processing Unit), etc.

Furthermore, the processing device 301 in Fig. 3 may be physically the same processing device as the processing device 301 in Fig. 2, or may be a different processing device. In other words, the measurements in Fig. 2 and Fig. 3 are not limited to being performed using the same processing device. For example, the measurement shown in Fig. 2 may be performed using a processing device 201 dedicated to measurement installed in a listening room or the like, and the measurement shown in Fig. 3 may be performed using a general-purpose processing device 301 such as a smartphone.

The processing device 301 is connected to a microphone unit 2 and headphones 43. The microphone unit 2 may be built into the headphones 43. The microphone unit 2 includes a left microphone 2L and a right microphone 2R. The left microphone 2L is connected to the left ear 9L of the user U.
The right microphone 2R is attached to the right ear 9R of the user U. The processing device 301
The processing device may be the same as the extracranial localization processing device 100 or may be a different processing device.
It is also possible to use earphones instead of the headphones 43 .

The headphones 43 are composed of a headphone band 43B, a left unit 43L, and a right unit 43
The headphone band 43B has a left unit 43L and a right unit 43R.
The left unit 43L outputs sound to the left ear 9L of the user U. The right unit 43R outputs sound to the right ear 9R of the user U. The headphones 43 may be of any type, including closed, open, semi-open, or semi-closed type. With the microphone unit 2 attached to the user U, the user U puts on the headphones 43. That is,
The left unit 43L and right unit 43R of the headphones 43 are attached to the left ear 9L and right ear 9R, respectively, on which the left microphone 2L and right microphone 2R are attached. The headphone band 43B generates a biasing force that presses the left unit 43L and right unit 43R against the left ear 9L and right ear 9R, respectively.

The left microphone 2L picks up sound output from the left unit 43L of the headphones 43. The right microphone 2R picks up sound output from the right unit 43R of the headphones 43. The microphone portions of the left microphone 2L and the right microphone 2R are placed in sound collection positions near the external ear canals. The left microphone 2L and the right microphone 2R are configured so as not to interfere with the headphones 43. In other words, the user U can wear the headphones 43 with the left microphone 2L and the right microphone 2R placed in appropriate positions on the left ear 9L and right ear 9R.

The processing device 301 outputs a measurement signal to the headphones 43. This causes the headphones 43 to generate impulse sounds and the like. Specifically, the impulse sound output from the left unit 43L is measured by the left microphone 2L. The impulse sound output from the right unit 43R is measured by the right microphone 2R. When the measurement signal is output, the microphones 2L and 2R acquire the picked-up sound signals, thereby performing impulse response measurement.

The processing device 301 performs similar processing on the sound signals picked up from the microphones 2L and 2R to generate inverse filters Linv and Rinv.

(Level range compression)
At least one of the measurement devices 200 and 300 performs a range compression process so that the frequency characteristics of the picked-up signal fall within a predetermined level range.
The following describes the process of compressing the level range of the frequency characteristics of the picked-up signal corresponding to the spatial acoustic transfer characteristics Hls and Hlo in the measuring device 200. That is, the process of compressing the level range of the frequency characteristics of the picked-up signal corresponding to the spatial acoustic transfer characteristics Hro and Hrs in the measuring device 200 is the same as the process described below, and therefore the description will be omitted as appropriate.
Similarly, the process of compressing the level range of the frequency characteristics of the picked-up signal for the left and right ear canal transfer characteristics in the measuring device 300 is similar to the process described below, and therefore will not be described again as appropriate.

4 is a block diagram showing the configuration of the processing device 201 of the measuring device 200. The processing device 201 includes a measurement signal generating unit 211, a picked-up signal acquiring unit 212, a segmental power acquiring unit 215, a frequency characteristic acquiring unit 221, a level calculating unit 223, a level range setting unit 224, a correcting unit 225, an adjusting unit 231, and an inverse transforming unit 232. The inverse transforming unit 232 and the adjusting unit 231 function as a filter generating unit 230.

The measurement signal generator 211 includes a D/A converter, an amplifier, and the like, and generates a measurement signal for measuring the spatial acoustic transfer characteristics and the ear canal transfer characteristics. The measurement signal is, for example, an impulse signal or a TSP (Time Stretched Pulse) signal. Here, the measuring device 200 performs impulse response measurement using an impulse sound as the measurement signal. The measurement signal generator 211 outputs the measurement signal to each of the stereo speakers 5.
Here, an example will be described in which a measurement signal is output from the left speaker 5L to obtain a picked-up signal corresponding to the spatial acoustic transfer characteristics Hls and Hlo.

The left microphone 2L and the right microphone 2R of the microphone unit 2 each pick up a measurement signal and output the picked-up signal to the processing device 201. The picked-up signal acquisition unit 212
The collected signal acquisition unit 212 may include an A/D converter that performs A/D conversion on the collected signals from the microphones 2L and 2R.
The sound pickup signal is cut out at a predetermined time interval. In other words, the sound pickup signal acquisition unit 212 extracts a sound pickup signal of a preset number of data (time width). The sound pickup signal acquisition unit 212 may synchronously add signals obtained by multiple measurements. The sound pickup signal acquired using the left microphone 2L is
The sound signal obtained by using the right microphone 2R is represented by hlo.
The extracted signals hls and hlo are signals sampled at a sampling frequency of 48 kHz.
Of course, the sampling frequency and the filter length are not limited to the above values.

The segmental power acquisition unit 215 acquires the segmental power of the picked-up sound signal h ls and the picked-up sound signal h lo. For example, the segmental power of the picked-up sound signal h ls and the picked-up sound signal h lo is
Let hlsP and hloP be the segmental powers. The segmental power hlsP is the sum of squares of the amplitude values contained in the collected signal hls. The segmental power hloP is the sum of squares of the amplitude values contained in the collected signal hlo. In the time domain, if the collected signal hls and the collected signal hlo have 4096 pieces of data, the sum of squares of the 4096 amplitude values will be the segmental powers hlsP and hloP.

The frequency characteristic acquisition unit 221 acquires frequency characteristics based on the collected sound signals h ls and h lo. The frequency characteristic acquisition unit 221 calculates the frequency characteristics of the collected sound signals h ls and h lo by discrete Fourier transform or discrete cosine transform. The frequency characteristic acquisition unit 221, for example,
The frequency characteristics are calculated by performing FFT (Fast Fourier Transform) on the time domain picked-up signal.
The frequency characteristics include an amplitude spectrum and a phase spectrum. The frequency characteristics acquisition unit 221 may generate a power spectrum instead of the amplitude spectrum.
The frequency amplitude characteristics of Fhls and Fhlo are Fhls and Fhlo, respectively.
s and Fhlo are the spectrum data of the amplitude spectrum.

The level calculation unit 223 calculates the reference level for the frequency characteristics Fhls and Fhlo. For example, the level calculation unit 223 calculates the average level (mean value) of the frequency characteristics Fhls and Fhlo and sets it as the reference level. For example, if FFT is performed with a filter length (number of samples) T, the level value (dB) of each frequency in the frequency amplitude characteristic is calculated and the average value is obtained. The real (real part) and imag (imaginary part) after T-point FFT are defined as real[i] and imag[i], respectively. Here, i is an integer between 0 and (T-1). The sound pressure level Amp_dB[i] at each i-point is calculated using the following formula (
1)
Amp_dB[i]＝log10(sqrt(real[i]*real[i]＋imag[i]*imag[i])) ・・・(1)
In (1), i=1 to (T/2+1), and sqrt is the square root.

Furthermore, if the frequency (Hz) at point i is freq[i] and the sampling frequency is fs, freq[i] can be obtained by the following equation (2).
freq[i]=(T/fs)*i...(2)

The reference level A in the entire frequency band is obtained by the following equation (3).

If the reference level of the frequency characteristic Fhls is Ahls and the reference level of the frequency characteristic Fhlo is Ahlo, the reference level A is (Ahls+Ahlo)/2.

Furthermore, the level calculation unit 223 calculates the maximum level maxL and the minimum level mi of the frequency amplitude characteristic.
The maximum level maxL is the maximum value among the amplitude values included in the two spectrum data of the frequency characteristics Fhls and Fhlo. The minimum level minL is the
The reference level A, maximum level maxL, and minimum level minL are the minimum amplitude values included in the two spectrum data of the frequency characteristics Fhls and Fhlo.
It becomes a common value at lo.

The level range setting unit 224 sets the level range X to be compressed. The level range setting unit 224 inputs the level range X according to, for example, the playback device. To obtain an appropriate out-of-head localization effect, it is preferable to set X to 40 dB or more. Furthermore, if the amplifier of the playback device does not have high performance in terms of audio output efficiency or quality, X can be set to 20 dB.
It is preferable that X is 20 dB or more and 40 dB or less, but there is no particular limitation to this range.

The correction unit 225 calculates the correction characteristics by correcting the frequency characteristics Fhls and Fhlo so that they fall within a predetermined level range X including the reference level A. In other words, the correction unit 225 calculates the correction characteristics by correcting the frequency characteristics Fhls and Fhlo so that the amplitude value of the frequency characteristics falls within the level range X.
For example, when the level range X is 40 dB, the amplitude value is compressed so that it falls within the range of the reference level A ±20 dB, and the correction unit 225 corrects the frequency characteristic Fh1.
The characteristics corrected by the correction unit 225 are called correction characteristics. The correction characteristics for the frequency characteristic Fhls are called NewFhls, and the correction characteristics for the frequency characteristic Fhlo are called NewFh.
Let's say it's lo.

Here, the amplitude value before correction at an arbitrary frequency is denoted by L, and the amplitude value after correction is denoted by NewL. In other words, the frequency characteristics Fhls and Fhlo are a set of amplitude values L before correction, and the correction characteristics NewFhls and NewFhlo are a set of amplitude values NewL.

For example, the correction unit 225 can correct the frequency characteristics using the following equations (4) and (5).
When L is equal to or greater than A, NewL=A+(L−X)*(X/2)/(maxL−A) (4)
When L is less than A, NewL=A+(L−X)*(X/2)/(A−minL) (5)

By doing this, NewL falls within the level range X centered on the reference level. In other words, NewL has an amplitude value greater than or equal to (A-(X/2)) and less than or equal to (A+(X/2)). Then, the correction unit 225 performs the following for all data (amplitude value L) within the correction band:
The corrected amplitude value NewL is calculated using the above equations (1) and (2). The set of corrected amplitude values NewL is the correction characteristic. The correction characteristic is obtained by correcting the amplitude value of the frequency characteristic Fhls. Furthermore, by performing correction using (1) and (2), it is possible to compress the range while maintaining the spectral shapes of the frequency characteristics Fhls and Fhlo before correction.

The frequency band corrected by the correction unit 225 may be the entire band or a part of the band. For example, the correction band for correcting the frequency characteristics Fhls and Fhlo may be set to 10 Hz to 20 kHz.
Hz. In other words, the correction unit 225 does not correct the amplitude values in the band between the lowest frequency (for example, 1 Hz) and less than 10 Hz, or in the band between 20 kHz and the highest frequency. Therefore, the amplitude values of the frequency characteristics Fhls and Fhlo are used as they are outside the correction band. The correction band may be changed depending on the playback band of the headphones 43 that perform out-of-head localization playback, i.e., the headphones 43 in FIG. 1.

The filter generation unit 230 generates a correction filter based on the correction characteristics. Specifically, the filter generation unit 230 includes an inverse transformation unit 232 and an adjustment unit 231. The inverse transformation unit 232 inversely transforms the correction characteristics to generate a correction signal in the time domain.
A time-domain correction signal is calculated from the correction characteristics and phase characteristics by inverse discrete Fourier transform or inverse discrete cosine transform. The inverse transform unit 232 generates a time-domain correction signal by performing IFFT (inverse fast Fourier transform) on the correction characteristics and phase characteristics. The correction signal obtained from the correction characteristics NewFhls is designated as hls2. The correction signal obtained from the correction characteristics NewFhlo is designated as hlo2. The correction signals hls2 and hlo2 are filtered with the same filter length as the extracted picked-up signal.

The phase characteristic calculated by the frequency characteristic acquisition unit 221 can be used as is. That is, the inverse transform unit 232 generates the correction signal hls2 by performing an inverse Fourier transform on the phase characteristic corresponding to the frequency characteristic Fhls and the correction characteristic NewFhls.
A correction signal hlo2 is generated by performing an inverse Fourier transform on Fhlo.

The segmental power acquisition unit 215 acquires the segmental power of the corrected signal hls2 and the corrected signal hlo2. As described above, the segmental power can be the sum of squares of the amplitude values of the time domain signal. The segmental power of the corrected signal hls2 is acquired by hls2
P, and the segmental power of the correction signal hlo2 is hlo2.

The adjustment unit 231 adjusts the correction signal hls so as to maintain the power ratio (energy ratio) between the left and right.
2. The power of hlo2 is adjusted. The adjustment unit 231 amplifies the correction signal so that the power ratio before and after correction is the same. For example, the adjustment unit 231 multiplies the amplitude value of the correction signal by a predetermined number.
The predetermined number for the correction signal hls2 is (hlsP/hlsP2), and the correction signal hlo
The predetermined number for 2 is (hloP/hloP2).

The correction signals hls2 and hlo2 after adjusting the power ratio are passed through the correction filters hls3 and hlo
The product of the amplitude value of the correction signal hls2 and the predetermined number (hlsP/hlsP2) becomes the amplitude value of the correction filter hls3.
2) is the amplitude value of the correction filter hlo3. Therefore, the segmental power of the correction filter hls3 is the same as the segmental power of the picked-up sound signal hls. The segmental power of the correction filter hlo3 is the same as the segmental power of the picked-up sound signal hlo.

In this way, an appropriate correction filter can be generated. That is, the processing device 201 can generate a correction filter that is suitable for the playback device.
s3 and hlo3 are set as spatial acoustic filters in the convolution operation units 11 and 12 shown in Fig. 1. This allows the out-of-head localization processing device 100 to perform reproduction with a high out-of-head localization effect.

Specifically, the correction characteristics are generated so that the sound falls within a level range X suited to the playback device. This makes it possible to perform measurements and out-of-head localization processing in a state suited to the playback device.
It is possible to generate a filter suitable for out-of-head localization processing.

Furthermore, in the above embodiment, the adjustment unit 231 adjusts the left-right balance. Out-of-head localization reproduction with good left-right balance can be realized. Of course, the adjustment of the power balance by the adjustment unit 231 can be omitted. For example, for a single picked-up sound signal hls,
When the processing device 201 performs the processing, the processing of the adjustment unit 231 is omitted. In this case, the correction signal hls2 is set as it is in the convolution operation unit 11 as a correction filter.

The processing device 201 can also process the collected sound signals indicating the spatial acoustic transfer characteristics Hro and Hrs in a similar manner. In this case, the filter generation unit 230 adjusts the correction signal so that the segmental power ratio of the collected sound signals indicating the spatial acoustic transfer characteristics Hro and Hrs is maintained before and after correction. Furthermore, the processing device 201 can also process the ear canal transfer characteristics of both ears in a similar manner. In the processing device 201, the filter generation unit 230 adjusts the correction signal so that the segmental power ratio between the ear canal transfer characteristic ECTFL of the left ear and the ear canal transfer characteristic ECTFR of the right ear is maintained before and after correction.

Next, a filter generation method according to this embodiment will be described with reference to FIG.
1 is a flowchart illustrating a filter generation method.

First, the measurement device 200 measures the transfer characteristics using an impulse sound or the like (S101
That is, the measurement signal generating unit 211 outputs a measurement signal such as an impulse sound from the left speaker 5L. The collected sound signal acquiring unit 212 acquires a collected sound signal from the microphone unit 2 (S10
2) The collected sound signal acquisition unit 212 cuts out the collected sound signals from the left microphone 2L and the right microphone 2R using a predetermined filter length, thereby obtaining the collected sound signals hls and hlo.

The segmental power acquisition unit 215 calculates the segmental power of each of the picked-up sound signals hls and hlo (S103). The frequency characteristic acquisition unit 221 performs a Fourier transform on the picked-up sound signals (
S104) As a result, the frequency characteristics Fhls and Fhlo are obtained. The frequency characteristics are frequency amplitude characteristics (amplitude spectrum), but may also be frequency power characteristics (power spectrum).

The level calculation unit 223 calculates the reference level (S105). As described above, the reference level is the average value of the amplitude values of the two frequency characteristics Fhls and Fhlo.
23 calculates the maximum and minimum levels of the frequency characteristics Fhls and Fhlo. The reference level, maximum level, and minimum level may be calculated from the amplitude values of the entire band, or may be calculated from the amplitude values of some of the bands.

Further, the level range setting unit 224 sets the level range to be compressed (S106). The level range is set depending on the model, performance, etc. of the playback device. For example, the user or a staff member responsible for generating filters may input the level range X. Then, the correction unit 225 compresses and corrects the frequency characteristics Fhls and Fhlo so that the amplitude values of the frequency characteristics Fhls and Fhlo fall within the level range X including the reference level (S107). As a result, the correction characteristics NewFhls and NewFhlo are obtained.
The amplitude value of hlo is included in the level range X.

Next, the inverse transform unit 232 performs an inverse Fourier transform on the correction characteristics (S108). In the inverse Fourier transform, the frequency amplitude characteristics are the correction characteristics, and the frequency phase characteristics are the frequency phase characteristics calculated by the Fourier transform in S104. As a result, the correction signals hls2 and hlo2 in the time domain are obtained.

The adjustment unit 231 adjusts the amplitude levels of the correction signals hls2 and hlo2 so as to maintain the segmental power ratio between the collected sound signals hls and hlo (S109).
The adjustment unit 231 adjusts a predetermined number according to the segmental power ratio to the correction signal hls2 and the correction signal h
As a result, correction filters hls3 and hlo3 are obtained. The adjustment unit 231 adjusts the power ratio, thereby generating a filter with good left-right balance.

(Correction Processing Example 1)
Next, an example of the correction step in step S107 will be described with reference to FIG.
10 is a flowchart showing a first example of correction processing by the correction unit 225.

First, the correction unit 225 determines whether the level difference of the frequency amplitude characteristic is equal to or greater than the level range X (S201). The level difference is the difference between the maximum value (maximum level maxL) and the minimum value (minimum level m
The maximum level and minimum level may be the maximum and minimum values of the frequency amplitude characteristics in the entire band, or may be the maximum and minimum values of a part of the band.

If the level difference is smaller than the level range X (NO in S201), the correction unit 225 ends the process without performing correction. If the difference is larger than the level range X (NO in S201), the correction unit 225 compresses the level (amplitude value) of each frequency toward the reference level (S202).
This corrects the frequency characteristics so that the level at each frequency falls within the level range X.

7 is a graph showing frequency amplitude characteristics before and after correction in Processing Example 1. That is, FIG.
10 shows the amplitude spectrum of the frequency characteristic Fhls before correction and the corrected characteristic NewFhls.
As shown in Fig. 7, the frequency amplitude characteristics after correction are contained within a level range X centered on a reference level A. In Fig. 7, the reference level A = -9.4 dB, the level range X = 20 dB.
Furthermore, in FIG. 7, the correction band is set to 10 Hz to 20 kHz.

(Correction Processing Example 2)
Next, another example of the correction step of step S107 will be described with reference to FIG.
8 is a flowchart showing a processing example 2 of the correction processing by the correction unit 225. In processing example 2, the correction unit 225 corrects only the levels (amplitude values) that are greater than the reference level.

First, the correction unit 225 determines whether the level difference of the frequency amplitude characteristic is equal to or greater than the level range X (S301). The level difference is the difference between the maximum value (maximum level maxL) and the minimum value (minimum level mi
The maximum level and minimum level may be the maximum and minimum values of the frequency amplitude characteristics in the entire band, or may be the maximum and minimum values of a part of the band.

If the level difference is smaller than the level range X (NO in S301), the correction unit 225 ends the process without performing correction. If the difference is larger than the level range X (YES in S301),
The correction unit 225 compresses only the levels (amplitude values) of each frequency that are greater than the reference level toward the reference level (S302). The correction unit 225 reduces the levels that are higher than the reference level.

In the processing example 2, the corrector 225 does not perform correction for levels lower than the reference level. Therefore, for frequencies lower than the reference level, the amplitude values before and after correction are the same.

Furthermore, in processing example 2, the correction unit 225 corrects only levels higher than the reference level, but it may also correct only levels lower than the reference level. In other words, in processing example 2, the correction unit 225 corrects only one of levels higher than the reference level and levels lower than the reference level. The correction unit 225 only needs to correct the frequency characteristics at either levels equal to or higher than the reference level or levels equal to or lower than the reference level.

FIG. 9 is a graph showing frequency amplitude characteristics before and after correction in Processing Example 2. In FIG. 9, the reference level A is −9.4 dB and the level range X is 20 dB. Furthermore, in FIG. 9, the correction band is set to 10 Hz to 20 kHz. As shown in FIG. 9, the reference level A
The corrected frequency amplitude characteristic falls within the level range X for amplitude values higher than the reference level A. In this case, a level lower than the reference level A may not fall within the level range X. In other words, in the processing example 2, when the frequency amplitude characteristic is equal to or higher than the min level, (A+(X/2))
It falls within the following level ranges:

(Correction Processing Example 3)
In processing example 3, the frequency axis of the frequency amplitude characteristic is a logarithmic scale. The reason for converting the frequency axis to a logarithmic scale will be explained. It is generally said that human sensory quantities are converted to logarithms. Therefore, it is important to consider the frequency of audible sounds on a logarithmic scale as well. By converting the scale, data is spaced equally in the above sensory quantities, so that data can be treated equally in all frequency bands. As a result, mathematical operations, frequency band division and weighting become easier, and stable results can be obtained. The frequency characteristic acquisition unit 221
The envelope data may be converted into a scale (called an auditory scale) that is not limited to a logarithmic scale but is closer to human hearing. The auditory scale may be a logarithmic scale (Log scale), a mel scale, a Bark scale, an Equivalent Rectangular Bandwidth (ERB) scale, or the like, for axis conversion.

The frequency characteristic acquisition unit 221 performs scale conversion of the spectral data on the auditory scale by data interpolation. For example, the frequency characteristic acquisition unit 221 interpolates data in the low-frequency band, which has coarse data intervals on the auditory scale, to make the data in the low-frequency band denser. Data that is evenly spaced on the auditory scale becomes data that is dense in the low-frequency band and coarse in the high-frequency band on a linear scale. In this way, the frequency characteristic acquisition unit 221 can generate axis-transformed data that is evenly spaced on the auditory scale. Of course, the axis-transformed data does not have to be data that is completely evenly spaced on the auditory scale. In this way, the correction unit 225 and the like perform processing on the frequency amplitude characteristics on the logarithmic scale. Furthermore, in order to match the frequency phase characteristics and the number of samples, the frequency axis may be returned to a linear scale before inverse conversion.

(Correction Processing Example 4)
In the processing example 4, the correction unit 225 corrects the entire correction band, but corrects the level range X
The amplitude value is corrected only at frequencies around the peak exceeding the upper limit of the amplitude correction factor α. Processing example 4 will be described with reference to Fig. 10. Fig. 10 is a flowchart showing processing example 4.

First, the correction unit 225 determines whether the level difference of the frequency amplitude characteristic is equal to or greater than the level range X (S401). The level difference is the difference between the maximum value (maximum level maxL) and the minimum value (minimum level mi
The maximum level and minimum level may be the maximum and minimum values of the frequency amplitude characteristics in the entire band, or may be the maximum and minimum values of a part of the band.

If the level difference is smaller than the level range X (NO in S401), the correction unit 225 ends the process without making correction. If the difference is larger than the level range X (NO in S201), the correction unit 225 compresses the amplitude value toward the reference level around the peak frequency that is the peak exceeding the upper limit value (A+X/2) of the range (S402).

For example, the correction unit 225 determines crossover frequencies that cross the upper limit before and after the peak frequency. The correction unit 225 calculates a first crossover frequency that is lower than the peak frequency and a second crossover frequency that is higher than the peak frequency. The correction unit 225 compresses the amplitude value toward a reference level in a frequency band defined by the first crossover frequency and the second crossover frequency.

Specifically, the correction unit 225 determines a first crossover frequency that intersects with the upper limit of the range on the lower frequency side of the peak frequency. The correction unit 225 determines a second crossover frequency that intersects with the upper limit of the range on the higher frequency side of the peak frequency. The correction unit 225 corrects the amplitude values in the frequency band from the first crossover frequency to the second crossover frequency. In this way, it is possible to correct amplitude values that exceed the upper limit of the range around the peak.

FIG. 11 is a graph showing three frequency bands (a) to (c) defined by crossover frequencies. The frequency band (a) is the frequency band including the first peak P1.
Frequency band (a) is defined by the crossover frequencies before and after the first peak P1. Frequency band (b) is a frequency band including the second peak P2. Frequency band (c) is a frequency band including the third peak P3. Furthermore, as shown in FIG. 11 , one frequency band may include multiple peaks that are close to each other.

In this way, in the processing example 4, only the amplitude values that exceed only the upper limit value of the range are compressed toward the reference level.
The amplitude value may be corrected at a frequency around the dip below 1/(1/f).
The correction unit 25 calculates the crossover frequency at which the frequency crosses the lower limit value before and after the dip below the lower limit value.
The correction unit 225 may compress the amplitude values in a frequency band defined by two crossover frequencies. Of course, the correction unit 225 may compress the amplitude values in both the frequency band including the peak and the frequency band including the dip. Alternatively, the correction unit 225 may compress the amplitude values only in the frequency band including the peak, or only in the frequency band including the dip.

(Correction Processing Example 5)
In the processing example 5, the correction unit 225 performs correction using a different method. Specifically, the level of the amplitude value is corrected using smoothing processing such as moving average.
The frequency characteristics (spectral data) are smoothed using techniques such as an olay filter, a smoothing spline, a cepstrum transform, a cepstrum envelope, etc. The correction unit 225 performs a smoothing process on the frequency characteristics to correct them so that they fall within the level range X.

(Correction Processing Example 6)
In processing example 6, a collected signal for ear canal transfer characteristics is processed. That is, the measurement is performed by the measuring device 300 shown in FIG. 3. Specifically, in the processing device 201 shown in FIG. 4, the measurement signal generation unit 211 outputs a measurement signal to the headphones 43, not the speaker 5L. In this case, the left and right microphones 2L and 2R collect collected signals indicating the ear canal transfer characteristics of the left and right ears. Frequency amplitude characteristics are acquired. A reference level, a maximum level, and a minimum level are acquired from the two frequency amplitude characteristics. Contents other than those described above are the same as those of the above-mentioned embodiments and processing examples, and therefore description thereof will be omitted.

(Correction Processing Example 7)
In the processing example 7, multi-channel speakers such as 5.1ch or 7.1ch are used, and the adjustment unit 231 performs adjustment so that the power ratio of the picked-up signals is maintained for each channel.

In 5.1ch multi-channel, the left and right front speakers, the left and right rear speakers,
In this case, the adjustment unit 231 adjusts the correction signal so that the power ratio between the front and rear speakers is maintained.
The adjustment unit 231 multiplies each correction signal by a coefficient such that the segmental power ratio before and after correction is the same.

Specifically, the measurement device 200 sequentially performs measurements using speakers of different channels. For example, the measurement signal generator 211 generates measurement signals and outputs them sequentially to the speakers of each channel. The collected signal acquirer 212 acquires acquired signals by sequentially collecting measurement signals from the speakers of each channel. The frequency characteristic acquirer 221 acquires multiple frequency characteristics based on the collected signals obtained by collecting the measurement signals output from the speakers of different channels.

The segmental power acquisition unit 215 calculates the left and right segmental powers of the picked-up signal for each channel. The adjustment unit 231 adjusts the level of the correction signal so as to maintain the power ratio. In this way, a filter with good balance between channels can be generated. Note that the level range X may be different for each channel or may be the same for all channels.

The process of maintaining the power ratio between channels is not limited to multi-channels such as 5.1ch, but can also be applied to the 2ch measurement device shown in Fig. 2. For example, measurements may be performed on the left and right speakers, and adjustments may be made to maintain the power ratio.

The above processing examples 1 to 7 can be combined as appropriate. For example, in the case of correcting the amplitude value around the peak frequency or the dip frequency as in processing example 4, the correction unit 2
25 may use the frequency axis conversion process of the processing example 3 or the smoothing process of the processing example 5.

In this way, according to this embodiment, the frequency characteristics are corrected so that they fall within a predetermined level range X including the reference level. Therefore, even with various playback devices, equipment, and measurement environments,
It is possible to reproduce a filter that can obtain an appropriate out-of-head localization effect. In other words, it is possible to automatically correct the filter so that the signal processed for out-of-head localization does not clip. It is possible to perform out-of-head localization listening according to the user's preference, speakers, headphones, and measurement environment. Furthermore, automatic correction according to the playback device is possible.

Embodiment 2.
An apparatus and method according to the second embodiment will be described with reference to Fig. 12. Fig. 12 is a block diagram showing the configuration of a processing device 201. One of the technical features of the second embodiment is the process of setting a level range X. Therefore, the processing device 201 shown in Fig. 12 has a determination unit 242 added to the configuration of Fig. 4. The configuration and process other than the determination unit 242 are the same as those of the first embodiment, and therefore will not be described as appropriate.

The determination unit 242 determines the performance of the playback device. For example, the determination unit 242 evaluates the performance of an amplifier of the playback device. The level range setting unit 224 sets a level range X according to the determination result of the determination unit 242. The correction unit 225 calculates correction characteristics by correcting the frequency characteristics based on the level range X. Filter generation unit 2
30 generates a correction filter based on the correction characteristics.

For example, the determination unit 242 determines, based on the frequency characteristics acquired by the frequency characteristics acquisition unit 221,
The determination unit 242 can make a determination. The determination unit 242 detects the level difference (maxL-minL) between the maximum level (maxL) and the minimum level (minL) of the frequency amplitude characteristic. The determination unit 242 acquires the output level (output sound pressure level) and the S/N ratio of the playback device based on the level difference. The determination unit 242 then determines the performance based on the output level or the S/N ratio. The determination unit 242 may determine the level range X according to the level difference between the maximum level and the minimum level of the frequency amplitude characteristic.

For example, for a playback device with a large level difference, the level range X is set to about 80% of the level difference. The determination unit 242 sets the variable to 0.8. For a playback device with a small level difference, the level range X is set to about 40% of the level difference. The level range setting unit 224 sets the level range X by multiplying the level difference by a variable corresponding to the determination result.

Furthermore, the processing device 201 can set the level range X without using a variable. For example, the determination unit 242 calculates the level difference (maxL-minL) in a part of the determination band. The determination band can be, for example, 100 Hz to 8 kHz. In other words, the determination unit 242 calculates the maximum level (maxL) and minimum level (
Then, the determination unit 242 makes a determination based on the level difference (maxL-minL). Alternatively, the determination unit 242 may have a conversion formula or a conversion table for converting the level difference into the level range X.

In this way, the determination unit 242 makes a determination based on the frequency characteristics of the picked-up signal obtained by measurement using a playback device. The determination unit 242 makes a determination based on the level difference between the maximum level and the minimum level of the frequency characteristics.

Alternatively, the determination unit 242 may acquire playback device information about the playback device and determine the performance based on the playback device information. The level range setting unit 224 then sets the level range X according to the performance of the playback device. For example, if the amplifier of the playback device is high performance, the level range setting unit 224 sets X to 40 dB. If the amplifier is low performance, the level range setting unit 224 sets X to 20 dB. Of course, the determination by the determination unit 242 is not limited to two levels, high performance and low performance, and may be three or more levels.

Furthermore, the determination unit 242 may have a table indicating the performance for each model number of the playback device. The determination unit 242 acquires playback device information indicating the model number of the playback device. The determination unit 242 determines the performance according to the model number of the playback device. The playback device information regarding the playback device may be acquired automatically or may be input by the user, for example. For example, in the case of a playback device with a Bluetooth connection, the determination unit 242 can automatically acquire information regarding the playback device.

For example, the measurement device 200 or the measurement device 300 performs measurements to acquire frequency characteristics for each playback device in advance. Then, as described above, the determination unit 242 determines the performance according to the level difference of the frequency characteristics and stores the determination results in a table.
The determination can be made by referring to the table.

The playback device may be the speakers 5L and 5R and their amplifiers shown in Fig. 2, or the headphones 43 shown in Fig. 3. That is, the playback device may be a playback device used during measurement. Alternatively, it may be the headphones 43 in the out-of-head localization processing device shown in Fig. 1. That is, the playback device may be the headphones 43 or earphones used during out-of-head localization listening. In the second embodiment, any one or more of the above processing examples 1 to 7 may be used.

As described above, according to this embodiment, it is possible to automatically set the level range X according to the performance of the playback device. Then, the correction unit 225 performs correction based on the level range X. Therefore, it is possible to reproduce a filter that can obtain an appropriate out-of-head localization effect even with various playback devices, equipment, and measurement environments. In other words, it is possible to automatically correct a filter that does not clip the signal that has been processed for out-of-head localization. It is possible to perform out-of-head localization listening according to the user's preferences, speakers, headphones, and measurement environment. Furthermore, automatic correction according to the playback device is possible.

A part or all of the above processes may be executed by a computer program. When the above program is loaded into a computer, it can perform the processes described in the embodiments.
or more functions on a computer (or software code)
The program may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, the computer-readable medium or tangible storage medium may include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state memory, etc.
solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD)
, Blu-ray discs or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices. The program may be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable medium or communication medium may be electrical, optical, acoustic,
or other forms of propagated signals.

The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention.

REFERENCE SIGNS LIST U User 1 Person to be measured 2 Microphone unit 2L Left microphone 2R Right microphone 5 Stereo speakers 5L Left speaker 5R Right speaker 10 Out-of-head localization processing unit 11 Convolution calculation unit 12 Convolution calculation unit 21 Convolution calculation unit 22 Convolution calculation unit 24 Adder 25 Adder 41 Filter unit 42 Filter unit 43 Headphones 200 Measuring device 201 Processing device 211 Measurement signal generation unit 212 Sound pickup signal acquisition unit 215 Segmental power acquisition unit 221 Frequency characteristic acquisition unit 223 Level calculation unit 224 Level range setting unit 225 Correction unit 230 Filter generation unit 231 Adjustment unit 232 Inverse conversion unit 242 Determination unit

Claims (2)

a frequency characteristic acquisition unit that acquires frequency characteristics based on a sound signal collected by a microphone, and interpolates low-frequency band data using a frequency axis as an auditory scale similar to human hearing, thereby generating axis-transformed data at equal intervals on the auditory scale;
a determination unit that determines the performance of the playback device;
a level range setting unit that sets a level range according to the determination result of the determination unit;
a correction unit that calculates a correction characteristic by correcting the frequency characteristic of the frequency amplitude characteristic of the hearing scale based on the level range;
and a filter generation unit that generates, based on the correction characteristics, a spatial acoustic filter used in out-of-head localization processing or an inverse filter that cancels the characteristics from the playback device to the user's ears. a frequency characteristic acquisition unit that acquires frequency characteristics based on a sound signal collected by a microphone, and interpolates low-frequency band data using a frequency axis as an auditory scale similar to human hearing, thereby generating axis-transformed data at equal intervals on the auditory scale;
a level calculation unit that calculates a reference level in the frequency characteristic;
a correction unit that calculates a correction characteristic by correcting the frequency characteristic so that the frequency amplitude characteristic of the hearing scale falls within a predetermined level range including the reference level;
and a filter generation unit that generates a spatial acoustic filter or an inverse filter used in out-of-head localization processing based on the correction characteristics.