JPH0374914A - Audio signal processor - Google Patents

Abstract

PURPOSE:To control an optimum frequency characteristic in response to the signal state by detecting a signal level of a signal processing section at an optional point, and controlling a graphic equalizer based on the detected level. CONSTITUTION:An audio signal obtained at an input terminal 1 from an audio signal source is adjusted to a prescribed frequency characteristic by a graphic equalizer 3, and amplified by a preamplifier 4. The level of an output audio signal from the preamplifier 4 is adjusted based on the adjustment quantity by a sound volume adjustment variable resistor 5, amplified to a sufficient power level at a power amplifier 6 to drive a speaker 7 and fed to the speaker 7. When the automatic correction mode is set by an operation key 11, a CPU 10 changes an equalizing level based on various data fed to the CPU 10 via an A/D converter 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an audio signal processing device suitable for application to, for example, an amplifier device with a graphic equalizer incorporated in a component stereo.

[Summary of the invention]

The present invention is an audio signal processing device suitable for component stereo, etc., which detects the signal level of a signal processing section at an arbitrary point, controls a graphic equalizer based on the detected level, and optimizes the signal according to the signal state. This makes it possible to control frequency characteristics.

[Conventional technology]

In general, the human ear has a characteristic that as the volume decreases, it becomes harder to hear low frequencies. Therefore, conventional loudness control circuits have been proposed that electrically correct this problem so that even at low volumes, the sound can be heard in a well-balanced manner over the entire frequency band.

This conventional loudness control circuit is provided in conjunction with a volume for adjusting the volume of an amplifier device, and as the volume is turned down (lower the volume), the degree of bass enhancement increases.

However, in conventional loudness control circuits, the amount of boost was determined by the volume position (attenuation amount), so when using a large signal manually or when used in conjunction with a tone control device, the audio output amplification circuit of the amplifier device There is a risk that the audio signal in the enhanced frequency part may be clipped, and the supplied audio signal level, i.e. the connected audio equipment (tape recorder, tuner, CD player, etc.)
If the volume is different, even if you adjust the volume and listen at the same volume, the degree of bass enhancement will be determined by the position of this polygon, which is inconvenient.

For this reason, the applicant developed a loudness control circuit (Japanese Unexamined Patent Application Publication No. 62-117) that first detects the output signal level of the amplifier circuit and changes the amount of boost in the low range according to this detection level.
(Refer to Publication No. 81109). According to this loudness control circuit, the amount of low-frequency boost is set according to the actual input signal level, so that good loudness control can be performed according to the signal level.

[Problem to be solved by the invention]

However, such conventional loudness control simply boosts a preset low frequency band.
31, and it is not possible for the user to finely control equalizing characteristics such as to what extent the frequency band is boosted.

In addition, in recent years, some stereo devices have built-in graphic equalizers, and devices equipped with this graphic equalizer allow the user to freely adjust the equalizer level for each frequency band divided into multiple frequency bands. frequency characteristics can be adjusted freely. However, since the amount of adjustment by this graphic equalizer is constant regardless of the volume, it has been difficult to perform adjustments such as loudness control using the graphic equalizer.

In view of this point, it is an object of the present invention to enable optimal control depending on the signal state using free frequency characteristics set by the user.

[Means to solve the problem]

The audio signal processing device of the present invention, as shown in FIG.
A graphic equalizer (3) is provided in the audio signal processing device that processes the signal using a power amplifier (6) etc. and supplies it to the speaker (7), and the signal from the input section of the graphic equalizer to the output terminal connected to the speaker (7) is provided with a graphic equalizer (3). The signal level at any point is digitally converted by an analog/digital converter (9), and the graphic equalizer is controlled based on this digitally converted signal.

In addition, the output of the graphic equalizer (3) is supplied to the spectrum analyzer band-pass filter (8) to detect the signal level for each band (i), and based on the signal level of each band, the graphic equalizer (3) It is designed to control.

[Effect]

According to this configuration, the equalizing level of the graphic equalizer is adjusted according to the actual signal level, and the arbitrary frequency characteristics set by the user are set in an optimal state according to the signal level.

〔Example〕

Hereinafter, one embodiment of the audio signal processing device of the present invention will be described with reference to the accompanying drawings.

This example shows an example in which the present invention is applied to an amplifier device used for component stereo etc., and is configured as shown in FIG. In this FIG. 1, (1) indicates an audio signal input terminal,
Audio signals from various audio signal sources such as a cheese, CD player, tape deck, etc. are supplied to this input terminal (1) via an input selector switch. The audio signal obtained at the input terminal (1) is then supplied to the graphic equalizer (3) via the input buffer (2). This graphic equalizer (3) is capable of processing an input audio signal by dividing it into multiple frequency bands (for example, into 7) and amplifying or attenuating each divided band by an arbitrary amount.
In this example, the central control unit (hereinafter referred to as CPU) (
10) so that the equalizing level is controlled. This CPU (10) is a circuit that controls each circuit of the amplifier device, and is composed of a microcomputer. In this example, when the automatic correction mode is set in the CPU (10), the set equalizing level is
It is designed to automatically change based on various data supplied to the CPU (10). As for this automatic control, when it is determined from various data that the speaker output is high volume, control is performed to reduce the equalizing level.

Then, the output signal of the graphic equalizer (3) is
Volume (5) for volume adjustment via preamp (4)
The audio signal whose level has been adjusted by the volume adjustment volume (5) is supplied to an output terminal (not shown) of this amplifier device via a power amplifier (6), and the audio signal is connected to this output terminal. the speaker (7).

In this example, the output signal of the manual buffer (2) and the output signal of the power amplifier (6) are supplied to an analog/digital converter (hereinafter referred to as A/D converter) (9) to level the signal level. is converted into digital data, and the respective digital data is supplied to the CPU (10).The output signal of the graphic equalizer (3) is also supplied to the spectrum analyzer band pass filter (8).This spectrum analyzer band The pass filter (8) is
It consists of multiple bandpass filters and divides the audio signal into multiple frequency bands.The output signal of each bandpass filter (i.e., each divided frequency band) is sent to an A/D converter (9) and a fluorescent display. The signal level of each frequency band supplied to the A/D converter (9) is converted into digital data, and the digital data of each frequency band is supplied to the CPU (10). Further, the fluorescent display tube drive circuit (12) displays the frequency distribution of the input signal on the fluorescent display tube (13) based on the signals of each frequency band supplied from the spectrum analyzer band-pass filter (8). Create a drive signal to do this.

Furthermore, after converting the adjustment amount data of the volume adjustment volume (5) into digital data using an A/D converter (9),
Supply to PU (10).

In addition, (11> in the figure indicates an operation key, and this operation key (
Operation commands 11) are supplied to the CPU (10), and various operations of the amplifier device can be set using the operation keys (11). For example, the operation keys (11) can be used to set the equalizing level in the graphic equalizer (3) and to switch between manual mode, which fixes the set equalizing level, and automatic correction mode, which changes the equalizing level according to the signal condition. can.

Further, in this example, equalizer level control data is supplied from the CPU (10) that controls the equalizer level to the fluorescent display tube drive circuit (12), and based on this control data, the fluorescent display tube drive circuit ( 12) displays the equalizing level of each frequency band on the fluorescent display tube (13).

Next, to explain the operation of this amplifier device, the audio signal obtained from the audio signal source to the input terminal (1) is adjusted to a predetermined frequency characteristic by the graphic equalizer (3), and then preamplified by the preamplifier (4). positional amplification is performed.

After the output audio signal of the preamplifier (4) is level-adjusted based on the amount of adjustment by the volume adjustment volume (5), the output audio signal is sufficient to drive the speaker (7) by the power amplifier (6). It is amplified to a power level of
).

Here, it is assumed that the frequency characteristic of the graphic equalizer (3) is set to a non-flat state by operating the operation key (11). At this time, when the manual mode is set using the operation key (11), the setting state of this frequency characteristic (equalizing level) is fixed under the control of the CPU (10), and the operation key (11) is used to change the equalizing level. The sound is reproduced from the speaker with the same frequency characteristics until the

Furthermore, when the automatic correction mode is set using the operation key (11), the cPU (10
) Based on various data supplied to the CPU (lO)
changes the equalizing level. That is, as shown in the flowchart of FIG. 2, when the CPU (10) determines that the mode is the automatic correction mode, the A/
The D converter (9) detects various redigitized data. When it is determined that the volume output from the speaker is low, the equalizing level is left as is, and when it is determined that the volume output from the speaker is high, the equalizing level is reduced in proportion to the volume. At this time, the control amount for reducing the equalizing level can be determined by storing a correction table (conversion table for output audio level into correction data) in the CPU (to>), or calculating the control amount using this correction table. The control data may be obtained through arithmetic processing based on the output audio level data.Then, in order to set the control amount obtained in this way, the CPU (
10) supplies equalizing level control data to the graphic equalizer (3), and also supplies equalizing level control data to the fluorescent display tube drive circuit (12) to set the equalizing level of each frequency band to the fluorescent display tube (13). Display.

At this time, an example of the display on the fluorescent display tube (13) is not shown, but for example, as shown in Figure 3, the operation key (11) is set to emphasize the bass around 100 by about 4 dB, and automatic correction is performed. In this mode, when the playback volume determined by the CPU (10) is at a low level, the equalizing level is set so that the current setting is maintained, and as the playback volume increases, the degree of bass emphasis is lowered. At this time, the equalizing level displayed on the fluorescent display tube (13) is also changed according to the change in the actual equalizing level.In the case of the example shown in FIG. In this example, the user can freely set the equalizing level, so as shown in Figure 4, for example, as shown in Figure 4, we have set a frequency characteristic that emphasizes the bass. It is also possible to set a sharp frequency characteristic that emphasizes the bass near the bass and slightly emphasizes the treble.In this case as well, when the playback volume is at a low level, it is played back with the same frequency response, and when the playback volume is at a low level, it is played back with the same frequency response, As the level increases, the equalizing level of each frequency band is gradually brought closer to Ode.

In this way, according to this example, the graphic equalizer (3
) can be used to perform good low-frequency emphasis (equivalent to conventional loudness control) based on the actual playback volume.
) Correction is performed based on the playback volume of the arbitrary frequency characteristic set in ). Therefore, for example, if the equalization level is set high as shown in the example in Figure 4, at low volumes the music will be played with the sharpness of the setting, and at high volumes the equalization will not be applied too strongly and the reproduced sound will not be distorted. The playback sound is not distorted even if the equalizing level is set high.

In this case, in this example, the CPU (10) uses the input level of the graphic equalizer (3) and the spectrum analyzer band-pass filter (8) to determine the data.
and the output level of the power amplifier [6],
Since there is a plurality of adjustment data for the volume (5), more precise control can be achieved. For example, since the output level of each frequency band can be determined from the output of the spectrum analyzer bandpass filter (8), automatic correction can be performed only when the signal level of the frequency band for which the equalizing level is set high is large. Allows for more detailed control.

However, in reality, it is possible to judge the playback volume based only on the output level of the power amplifier (6), for example, without detecting all the level data and volume adjustment data of each part as shown in the example in Figure 1. CPU (1) via converter (9)
0) may be reduced as appropriate.

In the above embodiment, the amplifier device and the graphic equalizer B are integrated, but the automatic correction described above may be performed by the graphic equalizer alone. In this case, the reproduction volume discrimination data may be obtained from the control section of the amplifier device.

Further, in the above embodiment, the equalizing level is compressed when the volume is high, but it may be changed in the opposite manner.

Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations.

〔Effect of the invention〕

According to the present invention, arbitrary frequency characteristics set by the user are set in an optimal state according to the signal level to be reproduced, and the reproduced sound is not distorted even when the equalizing level is set high, for example.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, FIG. 2 is a flowchart diagram for explaining one embodiment, and FIGS.
Each figure is a route map for explaining one embodiment. (1) is an audio signal input terminal, (3) is a graphic equalizer, (5) is a volume for volume adjustment, (8) is a band pass filter for spectrum analyzer, and (10) is a central control unit (CPU). Figure 2 Ichisara P24 No. 1 talent*m'. Figure 1 Display example Figure 4

Claims (1)

[Claims] 1. In an audio signal processing device that processes an audio signal supplied from an audio signal source and supplies it to a speaker, a graphic equalizer is provided, and an output connected from an input section of the graphic equalizer to the speaker. An audio signal processing device that digitally converts a signal level at any point up to a terminal, and controls the graphic equalizer based on the digitally converted signal. 2. The output of the graphic equalizer is supplied to a spectrum analyzer to detect the signal level for each band, and the graphic equalizer is controlled based on the signal level for each band. audio signal processing device.