JP5859218B2 - Acoustic device and volume correction method - Google Patents

Description

  The present invention relates to an acoustic device and a volume correction method for correcting the volume of an acoustic signal.

  2. Description of the Related Art Conventionally, acoustic devices that reproduce acoustic signals from a plurality of acoustic sources, such as radio tuners and CD (Compact Disc) players, are known. In addition, there are many types of such audio devices such as stationary component audio and in-vehicle audio devices.

  In particular, in-vehicle audio devices can be played back with DVD (Digital Versatile Disc), DTV (Digital Television) tuner, or AUX (Auxiliary) terminal input through integration with recent car navigation systems and cooperation with portable digital music players. Diversification of sound sources is progressing.

  By the way, the characteristics of each acoustic source are usually different from each other as shown in the reproduction band, the type of signal such as analog and digital, and the like. Such a difference in characteristics tends to cause a change in volume when the sound source is switched, and tends to give a sense of discomfort to the listener.

  In addition, with the widespread use of portable digital music players connected to the AUX terminal, such volume change has become more noticeable not only when switching sound sources but also between songs of the same sound source.

  Therefore, a technique for calculating a gain based on a signal level value of an acoustic signal at the time of switching between an acoustic source and a music so as not to cause such a volume change and correcting (amplifying / attenuating) the volume based on the gain is disclosed. (For example, refer to Patent Document 1).

  Conventionally, the development of automobiles has generally been required to reduce costs. Therefore, cost reduction is always required for an on-vehicle acoustic device mounted on such an automobile.

JP 2001-359184 A

  However, when the conventional technique is used, there is a problem that it is insufficient from the viewpoint of the above-described cost reduction. For example, Patent Document 1 does not mention such a cost reduction viewpoint.

  For these reasons, it has become a major issue how to realize an audio apparatus or a sound volume correction method capable of appropriately correcting the sound volume while reducing the cost.

  The present invention has been made to solve the above-described problems caused by the prior art, and relates to an audio apparatus and a sound volume correction method that can appropriately correct the sound volume while reducing costs.

In order to solve the above-described problems and achieve the object, the present invention is an acoustic device that corrects the volume of the acoustic signal based on the signal level value of the acoustic signal, and has a volume correction gain based on the signal level value. Gain storage means for storing; and latest sound volume correction gain calculating means for subtracting the latest signal level value from a predetermined reference level value or subtracting the reference level value from the signal level value to calculate a latest sound volume correction gain; When the latest volume correction gain calculated by the latest volume correction gain calculation means is compared with the volume correction gain stored by the gain storage means, and the latest volume correction gain is smaller than the volume correction gain, of updating a gain value updating means for updating the volume correction gain stored by said gain storing means by the latest volume correction gain by the gain value updating means It characterized in that a sound volume correcting means for correcting the playback volume of the sound signal by the sound volume correcting gain was.

The present invention is also an acoustic device that corrects the volume of the acoustic signal based on the maximum value when the maximum value of the signal level value of the acoustic signal is updated, the signal level from a predetermined reference level value Stores a calculated gain that is an integer value obtained by subtracting a value or an integer value obtained by subtracting the reference level value from the signal level value, and based on a comparison result between the stored calculated gain and the latest calculated gain. determines a target gain used for correction of volume, is smaller than the calculated gain with the latest of the calculation gain and the storage, the gain processing to perform the process of updating the calculated gain to the storage to the latest of the calculation gain And a sound volume correction means for correcting the sound volume based on the target gain determined by the gain processing means.

  According to the present invention, there is an effect that the sound volume can be appropriately corrected while reducing the cost.

FIG. 1 is a diagram showing an outline of a volume correction method according to the present invention. FIG. 2 is a diagram illustrating a configuration example of the acoustic device according to the embodiment. FIG. 3 is a diagram illustrating a configuration example of a circuit block of the DSP. FIG. 4 is an explanatory diagram of the calculated gain calculated by the target gain determining unit. FIG. 5 is a diagram illustrating an operation example of the gain comparison unit. FIG. 6 is a timing chart showing an example of control for smoothly amplifying an acoustic signal. FIG. 7 is a flowchart illustrating a processing procedure of processing executed by the DSP according to the embodiment.

  Exemplary embodiments of a sound volume correction method according to the present invention will be described below in detail with reference to the accompanying drawings. In the following, the outline of the sound volume correction method according to the present invention will be described with reference to FIG. 1, and then an embodiment of the sound device and the sound volume correction method to which the sound volume correction method according to the present invention is applied will be described with reference to FIGS. This will be described using.

  First, an outline of an example of a volume correction technique according to the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an outline of the volume correction method. 1A shows an example of a waveform representing a change in the signal level value of the acoustic signal with the time axis T as the horizontal axis, and FIG. 1B shows an example of a volume correction method. FIG. 1C shows an outline of the volume correction method.

  Ideally, the sound signal volume is corrected by determining the amplifier gain (attenuator attenuation) based on the level distribution (basically the maximum level) of the entire song. However, in the case of this method, it is necessary to analyze the entire music before the music reproduction to determine the gain, and there is a problem that the processing load is large, the gain determination takes time and reproduction is not performed quickly. In view of this, a method has been devised in which the signal level value is monitored while the music is played, and the volume correction is performed based on the maximum value of the signal level value when the maximum value of the signal level value is updated. In this case, the correction value is determined by monitoring only for a predetermined period at the beginning of the song, and thereafter (during playback of the song), the method using the correction value is used, or if a signal exceeding the maximum value is detected thereafter. Has also been devised, such as a method that temporarily reduces the volume. More specifically, for example, the gain is calculated based on the difference between the maximum value of the signal level value and the predetermined reference level value, and the process of amplifying (or attenuating) the acoustic signal based on the calculated gain is performed. .

  For example, in the example of the waveform shown in FIG. 1A, the signal level value (see the downward arrow in the figure) at the time T1, time T2, and time T4 when the maximum values are updated and a predetermined reference level value. Each gain is determined based on each difference.

  Therefore, each gain is preferably calculated on the condition that the update of the maximum value of the signal level value is detected in the monitoring while monitoring the fluctuation of the signal level value. Therefore, this point will be briefly shown in the processing block configuration in the case where it is realized by a program or a circuit.

  In this case, for example, as shown in FIG. 1 (B), an acoustic signal is input, and the signal level value of the acoustic signal is compared with the “maximum value” γ until the previous time held in the internal memory or the like. The processing unit that monitors the update of the value ”(when the“ maximum value ”γ is updated, the new maximum value is stored as the“ maximum value ”γ) and the gain is calculated based on the updated“ maximum value ”γ. This is realized by a “gain processing unit” that stores “control gain” α and controls the amplifier (see “AMP” in the figure) using this “control gain” α. As shown in FIG. 1B, the original acoustic signal is delayed by a time constant “τ” and input to the amplifier.

  In the case of such a processing block configuration, the “processing unit that monitors the update of the maximum value” determines whether or not the new input signal updates the “maximum value” α so far. The “maximum value” α needs to be stored in the internal memory, and the “gain processing unit” stores the gain control value “gain” α in the internal memory in order to control the gain of the amplifier without delay. It is necessary (see FIG. 1B).

  As shown in FIG. 1B, when the sound source or the music is switched, the gain is calculated again according to the signal level value of the new sound source or the music, and the “processing unit for monitoring the update of the maximum value” is performed. It is necessary to initialize the “maximum value” γ of “”.

  With such a processing block configuration, it is possible to surely calculate the “gain” α corresponding to the updated “maximum value” γ, so that it is possible to perform an appropriate volume correction based on the “gain” α. It is feasible. However, if the viewpoint of cost reduction is taken into account, each processing block requires an internal memory, which is uneconomical.

  Here, attention is paid to the “maximum value” γ and the “gain” α held in the internal memory. The “maximum value” γ and the “gain” α are both values based on the maximum signal level value of the acoustic signal.

  Therefore, in this sound volume correction method, the storage of the “maximum value” γ in the processing is omitted. That is, the signal level value fluctuation monitoring process performed by the “processing unit for monitoring update of the maximum value” in FIG. 1B using the “maximum value” γ is shown in FIG. As described above, the update of the “maximum value” γ in the processing can be monitored by the “gain” α stored in the “gain processing unit”.

  Specifically, as shown in FIG. 1C, in the volume correction method according to the present invention, the “gain processing unit” inputs an acoustic signal, and whether the signal level value updates the maximum value up to the previous time. Regardless of whether or not, the latest gain at the present time is calculated, it is determined whether the calculated gain is lower than the stored “gain” α, and if it is lower, the “gain” α is updated with the new gain. . That is, since the acoustic signal level and the gain are in a contradictory relationship, the update of the maximum value in the “maximum value” γ of the acoustic signal level is determined by the update of the minimum value in the “gain” α, and the “gain” α for the amplifier is determined. Update processing is performed.

  Details of the processing of the “gain processing unit” including predetermined comparison conditions will be described later with reference to FIGS. 4 and 5.

  Also, as shown in FIG. 1C, the “gain processing unit” initializes the “gain” α with an arbitrary value when the switching of the sound source or the music is detected. This point will be described later with reference to FIG.

  As described above, in this sound volume correction method, the monitoring of the fluctuation of the signal level value of the acoustic signal is replaced by monitoring the fluctuation of the gain. Therefore, it is only necessary to hold the gain α up to the previous time without holding the maximum signal level value γ up to the previous time. Volume correction can be performed.

  Below, the Example about the audio equipment and the sound volume correction method to which the sound volume correction method demonstrated using FIG. 1 is applied is described in detail. In the following, in order to make the explanation easy to understand, a gain obtained by subtracting the signal level value of the latest acoustic signal from a predetermined reference level value is referred to as “calculated gain” as a definition of the term. Moreover, it may be paraphrased as “latest volume correction gain”.

  Further, it corresponds to the calculated gain corresponding to the maximum signal level value up to the previous time, in other words, the “gain” α stored in the internal memory of the “gain processing unit” shown in FIG. The calculated gain is described as “comparison value”. Moreover, it may be paraphrased as “volume correction gain”.

  In addition, after comparison between “calculated gain” and “comparison value”, a gain determined to be a gain corresponding to the maximum value of the signal level value is referred to as “comparison gain”. The gain obtained by converting the “compared gain” into a coefficient is referred to as “target gain”.

  In the following description, when “amplification” of an acoustic signal is described, the “amplification” includes the meaning of “attenuation”, that is, negative amplification.

  FIG. 2 is a diagram illustrating a configuration example of the acoustic device 1 according to the present embodiment. As shown in FIG. 2, the acoustic device 1 according to the present embodiment includes a microcomputer 2, an operation unit 3, a display unit 4, a selector 5, an acoustic source 6, a main amplifier 7, a storage unit 8, DSP 10 is provided. A speaker 9 is arranged outside.

  The DSP 10 is a microprocessor that corrects the volume of the sound signal of the sound source 6 input via the selector 5. Further, the DSP 10 outputs an acoustic signal subjected to volume correction to a main amplifier 7 described later.

  The DSP 10 can perform various digital signal processing related to the sound signal as well as the correction of the volume. In the present embodiment, the DSP 10 will be described specifically for the function of correcting the volume. Details of the DSP 10 will be described later with reference to FIG.

  The microcomputer 2 is a central control unit that controls the entire acoustic device 1. The microcomputer 2 may be configured by a plurality of units that are differentiated for each function. In the present embodiment, description will be made assuming that the microcomputer 2 is a single unit.

  In addition, the microcomputer 2 notifies the DSP 10 of a switching signal including such a message at the time of switching between an acoustic source 6 and a music to be described later. The switching signal can include an “initial value” used for volume correction in the DSP 10. This will be described later.

  The operation unit 3 is an operation component that accepts user input operations. Such operation parts include not only hardware parts such as dials and buttons but also software parts such as buttons displayed on the display unit 4 described later.

  The display unit 4 is an output device that displays display information to the user. The selector 5 is a device that selects a specific acoustic source from among acoustic sources 6 described later based on a switching request from the microcomputer 2 and outputs an acoustic signal of the selected acoustic source to the DSP 10.

  The acoustic source 6 is a group of acoustic devices such as an FM tuner, an AM tuner, or a CD player. Such an acoustic source 6 is controlled by the microcomputer 2. The main amplifier 7 is a device that amplifies the sound signal based on the volume adjustment amount by the user input from the operation unit 3 via the microcomputer 2 and the sound signal input from the DSP 10. The main amplifier 7 outputs the amplified acoustic signal to the speaker 9.

  The speaker 9 is an output device that changes the acoustic signal input from the main amplifier 7 into physical vibration and outputs it as sound. Although FIG. 2 shows a single speaker 9, the actual number of devices is not limited. Therefore, it may be a monaural speaker or a stereo speaker.

  The storage unit 8 is a storage unit including a storage device such as a hard disk, a nonvolatile memory, and a register.

  Next, details of the DSP 10 will be described with reference to FIG. FIG. 3 is a diagram illustrating a configuration example of a circuit block of the DSP 10. In FIG. 3, only components necessary for explaining the features of the DSP 10 are shown, and descriptions of general components are omitted. In the following description, each component is described as a circuit block, but the properties of the component are not limited. For example, the function of each component may be realized by software.

  As shown in FIG. 3, the DSP 10 includes a communication I / F (interface) 11, a delay processing unit 12, a volume correction unit 13, a BPF group including a first BPF (Band-Pass Filter) 14 and a second BPF 15, A signal level calculation unit 16, a target gain determination unit 17a, and a gain comparison unit 17b are provided. The target gain determination unit 17a and the gain comparison unit 17b function as the “gain processing unit” illustrated in FIG. 1 (see the gain processing unit 17 surrounded by a broken-line rectangle in the drawing).

  The sound volume correction unit 13 further includes an amplifier 13a and an internal memory that stores the target gain 13b. The signal level calculation unit 16 further includes a first integration circuit 16a, a second integration circuit 16b, and a selection unit 16c. The gain comparison unit 17b further includes an internal memory that stores the comparison value 17ba.

  As shown in FIG. 3, the acoustic signal input to the DSP 10 is branched into two systems at the previous stage of the delay processing unit 12. In the following description, a “straight system” is shown when a system via the delay processing unit 12 is shown, and a “correction system” is shown when the other system is shown.

  The communication I / F 11 is a communication device that performs communication with the microcomputer 2. The “initial value” described above is input from the microcomputer 2 via the communication I / F 11. Details of the initial value will be described later.

  The delay processing unit 12 is a circuit block that delays the acoustic signal input from the selector 5 by a predetermined time and outputs the delayed signal to the volume correction unit 13. Such a delay is performed in order to synchronize the acoustic signal input from the selector 5 and the target gain output from the target gain determination unit 17a.

  The sound volume correction unit 13 stores the target gain input from the target gain determination unit 17a in the internal memory as the target gain 13b, and multiplies the target gain 13b by using the amplifier 13a, thereby multiplying the target gain from the delay processing unit 12. It is a circuit block that amplifies an input direct sound signal. The volume correction unit 13 outputs the amplified acoustic signal to the main amplifier 7 (see FIG. 2).

  Further, the sound volume correction unit 13 can initialize the target gain 13b based on the initial value notified from the microcomputer 2 when the sound source 6 or the music is switched. Alternatively, only the switching signal for notifying such switching may be received from the microcomputer 2, and the volume correction unit 13 may initialize the target gain 13b with a fixed value.

  The target gain 13b is preferably stored as a coefficient to be multiplied by the direct sound signal, but the data format of the initial value notified from the microcomputer 2 is not limited.

  Therefore, if the target gain 13b is stored as a coefficient and the initial value is notified as a difference value between the reference level value and the signal level value, the volume correction unit 13 converts the difference value into a coefficient. What should I do?

  Further, the initial value is preferably 1 or less when expressed as a coefficient. This is because when the target gain 13b is a gain of an acoustic signal having a small signal level value (that is, a gain of 1 or more that greatly corrects the volume) immediately before initialization by the initial value, the target gain 13b is set to a gain of 1 or less. This is because the initialization can prevent a sudden increase in volume when the signal level value of a new acoustic signal is large.

  The BPF group including the first BPF 14 and the second BPF 15 is a filter that passes only a predetermined frequency band of the acoustic signal input from the selector 5. In this embodiment, a configuration example including at least two BPFs of the first BPF 14 and the second BPF 15 is shown.

  The first BPF 14 is a filter that mainly passes high-frequency components in the audible band of the acoustic signal. Further, the first BPF 14 outputs a high-frequency acoustic signal that has passed therethrough to the first integration circuit 16a. Similarly, the second BPF 15 is a filter that mainly passes a low frequency component. Further, the second BPF 15 outputs a low-frequency acoustic signal that has passed therethrough to the second integration circuit 16b.

  The signal level calculation unit 16 is a circuit block that calculates a representative value of the signal level value of the acoustic signal input from each BPF such as the first BPF 14 and the second BPF 15. The representative value is the maximum value of the signal level average value calculated in each system corresponding to each BPF.

  The first integrating circuit 16a averages the signal level value mainly input from the first BPF 14 with a short time constant suitable for a sharp fluctuation of the acoustic signal, and the signal level value after the averaging (first average) Value) is output to the selector 16c.

  Further, the second integration circuit 16b averages the signal level value mainly for the low frequency input from the second BPF 15 with a long time constant suitable for the gentle fluctuation of the acoustic signal, and the averaged signal level value ( 2nd average value) is output with respect to the selection part 16c.

  In the present embodiment, the time constant is simply divided into two types of “short” and “long”, and the two integration circuits of the first integration circuit 16a and the second integration circuit 16b are described as examples. However, the time constant may be divided into three or more stages and three or more integration circuits corresponding to this may be provided.

  For example, if it is further provided with an integration circuit with a small time constant in units of microseconds, and if a large signal level value is output by the integration circuit with such a time constant, it is determined as noise due to signal discontinuity. Also good.

  The selection unit 16c uses the maximum value of the average values input from the integration circuits such as the first average value and the second average value as the representative value calculated by the signal level calculation unit 16, and outputs the maximum value to the target gain determination unit 17a. Is a circuit block to output.

  The target gain determination unit 17 a determines a “target gain” as the final volume correction “coefficient” based on the representative value input from the signal level calculation unit 16, and the target gain is sent to the volume correction unit 13. This is a circuit block to output.

  The gain comparison unit 17b stores, in the internal memory, a comparison value 17ba that is a gain value corresponding to the maximum value of the signal level value (strictly, “representative value”) of the acoustic signal until the previous time, and the comparison value 17ba This is a circuit block that compares the latest calculated gain input from the target gain determination unit 17a.

  The gain comparison unit 17b updates the comparison value 17ba with the calculated gain when the comparison value 17ba needs to be updated by the comparison, and holds the comparison value 17ba when the comparison value 17ba does not need to be updated. The comparison value 17ba is output as a post-comparison gain to the target gain determination unit 17a.

  Here, the target gain determination unit 17a and the gain comparison unit 17b will be described in more detail with reference to FIGS. FIG. 4 is an explanatory diagram of the calculated gain calculated by the target gain determination unit 17a, and FIG. 5 is a diagram illustrating an operation example of the gain comparison unit 17b.

  First, the calculated gain calculated by the target gain determining unit 17a will be described with reference to FIG. As shown in FIG. 4, the target gain determining unit 17a calculates a calculated gain by subtracting the representative value input from the signal level calculating unit 16 from the reference level value. Note that the waveform of FIG. 4 represents the variation of the representative value with the time axis T as the horizontal axis.

  Here, as shown in FIG. 4, it is assumed that the reference level value is “−3” dB. In this case, the target gain determination unit 17a calculates the calculated gain corresponding to the representative value “−4” dB at time T1 as “+1.0” (= (− 3) − (− 4)) dB.

  Similarly, the calculated gain corresponding to the representative value “−2” dB at time T2 is “−1.0” dB, and the calculated gain corresponding to the representative value “−3.5” dB at time T3 is “+0”. .5 ”dB and a calculated gain corresponding to the representative value“ −1.5 ”dB at time T4 are calculated as“ −1.5 ”dB, respectively.

  The calculated gain at time T0 may be an indefinite value. In FIG. 4, such an indefinite value is represented by “−”. In the following, each calculated gain shown in the description of FIG. 4 will be used for the description.

  Then, the target gain determining unit 17a outputs the calculated gain to the gain comparing unit 17b every time T1 to T4 when the calculated gain is calculated.

  Next, the operation of the gain comparison unit 17b based on the calculated gain input from the target gain determination unit 17a will be described with reference to FIG. 5A shows a comparison condition between the calculated gain and the comparison value 17ba, and FIG. 5B shows an operation example of the gain comparison unit 17b. “Initial” shown in FIG. 5B indicates that the stored value of the comparison value 17ba is the initial value notified from the microcomputer 2.

  Here, initialization of the comparison value 17ba will be described. As in the case of the volume correction unit 13 described above, the gain comparison unit 17b can initialize the comparison value 17ba based on the initial value notified from the microcomputer 2 when the sound source 6 or the music is switched. Further, only the switching signal for notifying such switching may be received from the microcomputer 2, and the gain comparison unit 17b may initialize the comparison value 17ba with a fixed value.

  The comparison value 17ba is preferably stored as a difference value between the reference level value and the signal level value, that is, an “increase / decrease amount” with respect to the volume of the direct sound signal, but the initial value notified from the microcomputer 2 The data format is not limited.

  Therefore, if the comparison value 17ba is stored as an increase / decrease amount, if the initial value is notified as a “coefficient” by which the direct sound signal is multiplied, the gain comparison unit 17b converts the coefficient to the increase / decrease amount. It may be converted.

Returning to the description of FIG. As shown in (A) of FIG. 5, the gain comparator unit 17b calculates the gain at time T _n is compared value 17Ba (i.e., the maximum value of the signal level value up to the immediately preceding "time T _n-1" It can be used as a comparison condition whether it is smaller than the corresponding gain value (see “calculated gain T _n <compared value 17ba” in the figure).

Then, as shown in FIG. 5A, the gain comparison unit 17b “changes” the comparison value 17ba with the value of the calculated gain T _n if the comparison condition is “true”. Further, the gain comparison unit 17b “holds” the comparison value 17ba if the comparison condition is “false”.

  Specifically, as shown in FIG. 5B-1, at time T1, the gain comparison unit 17b performs the calculation gain “+1.0” at time T1 and the comparison value 17ba (that is, stores at time T0). The value “First”).

  However, when the comparison value 17ba is the initial value as described above, the gain comparison unit 17b can not be based on the comparison condition shown in FIG. The dashed double-headed arrow in the figure indicates that it is not based on such a comparison condition.

  For example, at this time, when the difference value between the calculated gain at time T1 and the comparison value 17ba exceeds a predetermined threshold, the gain comparison unit 17b sets the comparison value 17ba as shown in (B-1) of FIG. “Change” from the initial value “initial” to “+1.0”. Here, an upper limit value, a lower limit value, or both of which a proper sound volume correction cannot be performed with the initial value of the comparison value 17ba may be set as the predetermined threshold value.

  Then, the gain comparison unit 17b outputs “+1.0”, which is the comparison value 17ba after “change”, to the target gain determination unit 17a as a post-comparison gain.

  Further, as shown in FIG. 5B-2, at time T2, the gain comparison unit 17b performs the calculated gain “−1.0” at time T2 and the comparison value 17ba (that is, after comparison at time T1). And a gain value “+1.0”) corresponding to the gain.

  Here, since the comparison condition shown in FIG. 5A is satisfied (see “true” in FIG. 5B-2), the gain comparison unit 17b changes the comparison value 17ba from “+1.0”. “Change” to “−1.0”.

  Then, the gain comparison unit 17b outputs “−1.0” which is the “changed” comparison value 17ba to the target gain determination unit 17a as a post-comparison gain.

  Further, as shown in FIG. 5B-3, at time T3, the gain comparison unit 17b sets the calculated gain “+0.5” at time T3 and the comparison value 17ba (that is, the gain after comparison at time T2). The corresponding gain value “−1.0”) is compared.

  Here, since the comparison condition shown in FIG. 5A is not satisfied (see “false” in FIG. 5B-3), the gain comparison unit 17b sets the comparison value 17ba to “−1.0. "Retain".

  Then, the gain comparison unit 17b outputs “−1.0”, which is the “held” comparison value 17ba, to the target gain determination unit 17a as a post-comparison gain. When the value of the comparison value 17ba is “held” as described above, the output to the target gain determination unit 17a may not be performed.

  Further, as shown in FIG. 5B-4, at time T4, the gain comparison unit 17b performs the calculated gain “−1.5” at time T4 and the comparison value 17ba (that is, the gain after comparison at time T3). Is compared with the gain value “−1.0”) corresponding to.

  Since the comparison condition shown in FIG. 5A is satisfied (see “true” in FIG. 5B-4), the gain comparison unit 17b sets the comparison value 17ba to “−1.0”. “Change” from “−1.5” to “−1.5”.

  Then, the gain comparison unit 17b outputs “−1.5” which is the “changed” comparison value 17ba to the target gain determination unit 17a as a post-comparison gain.

  Although not shown, the target gain determination unit 17a converts the post-comparison gain as the “increase / decrease amount” input from the gain comparison unit 17b into the target gain as the “coefficient”. For example, it is assumed that the reference level value is “−3” dB and the post-comparison gain is “−1.5” dB (that is, 1.5 dB excess).

  In such a case, as an example, the target gain determination unit 17a calculates the target gain as “10 ^ (− 1.5 / 20)”. Here, a conversion table for target gain calculation prepared in advance may be used. Then, the target gain determination unit 17a outputs the calculated target gain to the volume correction unit 13.

  Then, the volume correction unit 13 described above multiplies the value of the target gain 13b with respect to the direct system acoustic signal while storing the target gain input from the target gain determination unit 17a as the target gain 13b. .

  Here, the volume correction unit 13 can perform control to smoothly amplify the direct system acoustic signal. This point will be described with reference to FIG. FIG. 6 is a timing chart showing an example of control for smoothly amplifying an acoustic signal.

  The “switching signal” shown in FIG. 6 is a switching signal notified from the microcomputer 2 when the sound source 6 or the music is switched, and “current gain” is the target gain 13b currently applied in the volume correction unit 13. The gain value “target gain” indicates a new target gain input from the target gain determination unit 17a. Further, a, b, and c in the figure indicate different gain values, and the underlined a corresponds to the initial value.

  As shown in FIG. 6, when a switching signal is input from the microcomputer 2 at time t1, the sound volume correction unit 13 uses the current gain that has taken the gain value c, that is, the gain value of the target gain 13b, as the gain value a. Update with. Then, it is assumed that a new acoustic signal is input and a target gain of a new gain value b is input from the target gain determination unit 17a at time t2.

  At this time, the sound volume correction unit 13 gradually brings the gain value a closer to the gain value b so that the current gain smoothly changes from the gain value a to the target gain value b (from time t2 in the figure). (See “Current Gain” over time t3). As a result, fluctuations in volume caused by the instantaneous increase or decrease in volume can be reduced. That is, it is possible to reduce the uncomfortable feeling given to the user by such fluctuation.

  Next, a processing procedure executed by the DSP 10 according to the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart illustrating a processing procedure of processing executed by the DSP 10 according to the present embodiment.

  As shown in FIG. 7, the DSP 10 inputs any acoustic signal from the acoustic source 6 via the selector 5 (step S101). Then, in the “correction system” described above, the acoustic signal is extracted by being divided into a plurality of bands (step S102). Although not shown, in the above-described “straight system”, the delay processing unit 12 waits for the input acoustic signal.

  Then, the signal level calculation unit 16 calculates a signal level value (strictly, an average value) for each integration circuit such as the first integration circuit 16a and the second integration circuit 16b corresponding to each band (step S103).

  Then, the signal level calculation unit 16 compares the signal level value for each integration circuit in the selection unit 16c and selects the largest signal level value (step S104). Then, the signal level calculation unit 16 outputs the selected signal level value as a representative value to the target gain determination unit 17a.

  Then, the target gain determination unit 17a calculates a calculated gain based on the representative value input from the signal level calculation unit 16 (step S105).

  Subsequently, the sound volume correction unit 13 or the gain comparison unit 17b determines whether or not the sound source 6 or the music switching signal has been received (step S106). If a switching signal is received (step S106, Yes), the volume correction unit 13 initializes the target gain 13b, and the gain comparison unit 17b initializes the comparison value 17ba with an initial value (step S107).

  On the other hand, when the determination condition of step S106 is not satisfied (step S106, No), the gain comparison unit 17b determines whether or not the calculated gain is larger than the value of the comparison value 17ba (step S108). Here, when the calculated gain is larger than the value of the comparison value 17ba (step S108, Yes), the gain comparison unit 17b holds the value of the comparison value 17ba (step S109).

  If the determination condition in step S108 is not satisfied (No in step S108), the gain comparison unit 17b updates the value of the comparison value 17ba with the calculated gain (step S110).

  Then, the target gain determination unit 17a determines the target gain based on the post-comparison gain (that is, the value of the comparison value 17ba) input from the gain comparison unit 17b (step S111). Then, the sound volume correction unit 13 corrects the gain of the acoustic signal so as to gradually approach the target gain determined by the target gain determination unit 17a (step S112), and the corrected acoustic signal is externally (main amplifier 7). Output (step S113).

  As described above, in this embodiment, the target gain determination unit calculates the calculated gain based on the representative value of the signal level value of the acoustic signal, and the gain comparison unit stores the comparison value and the calculated gain stored in the internal memory. Output a post-comparison gain corresponding to the maximum value of the signal level of the acoustic signal based on the comparison result, and the target gain determination unit determines the gain obtained by coefficientizing the post-comparison gain as the target gain, and corrects the volume. The acoustic device is configured so that the unit corrects the volume based on the target gain. Accordingly, it is possible to appropriately correct the sound volume while reducing the cost.

  In the above-described embodiment, the case where the target gain 13b and the comparison value 17ba can be initialized based on the initial value or the switching signal notified from the microcomputer 2 when the sound source 6 or the music is switched is described. However, this initialization method is not limited.

  For example, the continuous time of the silent section in the acoustic signal is counted, and if the continuous time exceeds a predetermined time, it is determined that the switching of the acoustic source 6 or the music has occurred, and the target gain 13b or the comparison is made. The value 17ba may be initialized. Here, it is preferable that the predetermined time is set to a different silent time according to the product.

  In the above-described embodiment, the case where the gain based on the latest acoustic signal (that is, “calculated gain”) is a value obtained by subtracting the signal level value from the predetermined reference level value has been described. The gain may be a difference between the signal level value and the reference level value. For example, the gain may be a value obtained by subtracting the reference level value from the signal level value. In this case, the magnitude relationship between the calculated gain and the comparison value is opposite to that in the above-described embodiment, but the direction of the inequality sign in the comparison condition shown in FIG. 5 may be reversed.

  In the above-described embodiment, the DSP 10 performs the processing shown in FIG. 7. However, the signal level is considered in consideration of the characteristics of the DSP that is good at arithmetic processing such as music signals and the characteristics of the microcomputer that is good at judgment processing. The DSP and the microcomputer may share the processing while performing data communication with each other. For example, the DSP may perform the above calculation, band division processing, and the like, and the microcomputer may perform switching signal determination and gain comparison.

  As described above, the acoustic device and the sound volume correction method according to the present invention are useful when it is desired to appropriately correct the sound volume while reducing the cost, and in particular, the on-vehicle acoustic device that is strongly demanded to reduce the cost. Suitable for application to.

DESCRIPTION OF SYMBOLS 1 Audio | voice apparatus 2 Microcomputer 3 Operation part 4 Display part 5 Selector 6 Sound source 7 Main amplifier 8 Storage part 9 Speaker 10 DSP
11 Communication I / F
12 delay processing unit 13 volume correction unit 13a amplifier 13b target gain 14 1st BPF
15 2nd BPF
16 signal level calculation unit 16a first integration circuit 16b second integration circuit 16c selection unit 17 gain processing unit 17a target gain determination unit 17b gain comparison unit 17ba comparison value

Claims (4)

An acoustic device that corrects the volume of the acoustic signal based on a signal level value of the acoustic signal,
Gain storage means for storing a volume correction gain based on the signal level value;
Latest volume correction gain calculating means for calculating the latest volume correction gain by subtracting the latest signal level value from a predetermined reference level value or subtracting the reference level value from the signal level value;
When the latest volume correction gain calculated by the latest volume correction gain calculation means is compared with the volume correction gain stored by the gain storage means, and the latest volume correction gain is smaller than the volume correction gain, Gain value updating means for updating the volume correction gain stored by the gain storage means with the latest volume correction gain;
A sound device comprising: sound volume correction means for correcting the reproduction sound volume of the sound signal by the sound volume correction gain updated by the gain value update means . When the maximum value of the signal level value of the acoustic signal is updated, the acoustic device corrects the volume of the acoustic signal based on the maximum value,
And stores the calculated gain is an integer value obtained by subtracting the reference level value from an integer value or the signal level value obtained by subtracting the signal level value from the predetermined reference level value, said a calculated gain to the storage, the latest of the calculation based on the comparison result between the gain determining a target gain used for correction of the volume is smaller than the calculated gain with the latest of the calculation gain and the stored latest the calculating the calculated gain to the storage Gain processing means for performing processing to update to gain;
An audio apparatus comprising: sound volume correction means for correcting the sound volume based on the target gain determined by the gain processing means. The calculated gain is
An integer value obtained by subtracting the signal level value from the reference level value,
The gain processing means includes
If the latest of the calculation gain is smaller than the calculated gain and the stored, the calculated gain to the storage to determine the latest of the calculation gain and updates to the latest of the calculation gain as the target gain, latest If the calculated gain is the stored said calculated gain above, according to the calculated gain without updating the said calculated gain to the storage to claim 2, characterized in that to determine as the target gain Acoustic device. A volume correction method for correcting the volume of the acoustic signal based on the maximum value when the maximum value of the signal level value of the acoustic signal is updated,
And stores the calculated gain is an integer value obtained by subtracting the reference level value from an integer value or the signal level value obtained by subtracting the signal level value from the predetermined reference level value, said a calculated gain to the storage, the latest of the calculation based on the comparison result between the gain determining a target gain used for correction of the volume is smaller than the calculated gain with the latest of the calculation gain and the stored latest the calculating the calculated gain to the storage A gain processing step for performing processing for updating to gain;
And a volume correction step of correcting the volume based on the target gain determined by the gain processing step.

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