JP2007089029A - Acoustic signal compression apparatus and acoustic signal compression program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acoustic signal compression apparatus and acoustic signal compression program with which an acoustic signal of a wide dynamic range can be compressed with high quality. <P>SOLUTION: An acoustic signal compression apparatus comprises: a compression property determining means 1 for determining compression property for detecting an excessive acoustic signal whose amplitude level is an excessive amplitude level greater than a predetermined maximum amplitude level, and compressing the excessive amplitude level to the maximum amplitude level or lower; and a compressed acoustic signal generating means 2 for compressing an original acoustic signal based on the compression property to generate a compressed acoustic signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an acoustic signal compression apparatus and an acoustic signal compression program, and more particularly to an acoustic signal compression apparatus and an acoustic signal compression program capable of compressing an acoustic signal having a wide dynamic range with high quality.

  When converting an original sound signal having a wide dynamic range, such as a symphony recorded in the original master, to a sound signal for media having a limited dynamic range, such as a sound signal for television broadcasting or an MP3 file, It is necessary to compress the amplitude level of the original sound signal so that the dynamic range of the sound signal falls within the dynamic range of the media sound signal. However, if the amplitude level of the original audio signal is converted to a media audio signal by uniformly compressing it, the amplitude level of the portion with a small amplitude level will be further reduced, especially in playback under circumstances where the background noise level is high. The sound signal cannot be heard clearly.

  Therefore, an audio correction apparatus that automatically changes the level of a reproduced sound signal in accordance with the level of background noise has already been proposed (see, for example, Patent Document 1).

  In addition, when the amplitude level of the original sound signal becomes larger than the upper limit value of the amplitude level of the media sound signal, the amplitude level of the original sound signal is limited to the upper limit value of the media sound signal by a limiter, or the original sound signal When the signal exceeds the dynamic range width of the audio signal for media, a recording signal processing device that suppresses the amplitude level of the original audio signal below the upper limit of the amplitude level of the audio signal for media by an attenuator that compresses the dynamic range of the original audio signal Has already been proposed (see, for example, Patent Document 2).

Patent Document 2 also discloses that the limiter or the attenuator is changed stepwise.
JP-A-2005-62713 ([0026]-[0029], FIG. 3) JP-A-8-55428 ([0020]-[0042], FIGS. 3 and 5)

  However, the conventional audio correction device described in Patent Document 1 changes the amplitude level of the reproduced sound signal in accordance with the background noise level, and does not depend on the amplitude level of the original sound signal. Since the amplitude level changes, there has been a problem of causing auditory unnaturalness.

  In addition, the conventional recording signal processing apparatus described in Patent Document 2 has a problem that it cannot be avoided that distortion occurs in the reproduced sound signal when the amplitude level of the original sound signal is compressed by the limiter. It was. In addition, when the dynamic range of the original sound signal is compressed by the attenuator, it is not possible to avoid the occurrence of auditory unnaturalness due to a sudden change in the amplitude level of the reproduced sound signal even when the attenuator is changed stepwise. There was a problem.

  The present invention has been made to solve the conventional problems, and an object of the present invention is to provide an acoustic signal compression apparatus and an acoustic signal compression program capable of compressing an original acoustic signal having a wide dynamic range with high quality. And

  The acoustic signal compression device of the present invention detects an excessive acoustic signal whose amplitude level is larger than a predetermined maximum amplitude level from an original acoustic signal, and compresses the excessive amplitude level to be equal to or lower than the maximum amplitude level. A compression characteristic determining unit that determines a compression characteristic to be compressed, and a compressed acoustic signal generating unit that compresses the original acoustic signal based on the compression characteristic to generate a compressed acoustic signal.

  With this configuration, an original acoustic signal having a wide dynamic range can be naturally compressed acoustically.

  Also, in the acoustic signal compression device according to the present invention, the compression characteristic determining means is configured to perform a compression from zero decibel to a target compression amount (<0) determined based on a difference between the excessive amplitude level and the maximum amplitude level when detecting the excessive acoustic signal. Preprocessing gain determining means for determining a preprocessing gain to be applied to the original acoustic signal before the detection of the excessive acoustic signal, and changing at a predetermined preprocessing change rate per unit time (<0); A post-processing gain that changes from a compression amount to zero decibel at a predetermined post-processing change rate (> 0) per unit time and determines a post-processing gain to be applied to the original acoustic signal after the detection of the excessive acoustic signal Determining means.

  With this configuration, it is possible to perform compression without distortion and perceptual unnaturalness on an original acoustic signal having a wide dynamic range.

  Further, in the acoustic signal compression device according to the present invention, the compression characteristic determining means is predetermined from zero decibel to a target compression amount determined based on a difference between the excessive amplitude level and the maximum amplitude level when detecting the excessive acoustic signal. Pre-processing gain determining means for determining a pre-processing gain to be applied to the original sound signal before the detection of the over-acoustic signal, which changes at a pre-processing change rate per unit time; and the over-acoustic signal detection for the target compression amount Target compression amount maintaining means for maintaining a predetermined target compression amount maintaining time from the time, and the target compression amount maintaining time changing from the target compression amount to zero decibel at a predetermined post-processing change rate per unit time. Post-processing gain determining means for determining a post-processing gain to be applied to the original sound signal after the lapse.

  With this configuration, it is possible to perform higher-quality compression without distortion and auditory unnaturalness on an original acoustic signal with a wide dynamic range.

  In the acoustic signal compression device according to the present invention, the compression characteristic determining means may be configured such that, when the preprocessing gain, the target compression amount, and the postprocessing gain overlap in time, the preprocessing gain and the target compression. Selecting means for selecting a quantity and a minimum value of the post-processing gain as the compression characteristics;

  With this configuration, it is possible to perform high-quality compression without distortion and perceptual unnaturalness even on an original acoustic signal having a wide dynamic range in which an excessive amplitude level is frequently detected.

  The present invention compresses an over-amplitude level below a maximum amplitude level to generate a compressed acoustic signal, so that an original acoustic signal having a wide dynamic range can be audibly and naturally compressed. An apparatus and an acoustic signal compression program can be provided.

  Hereinafter, an acoustic signal compression apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the present specification, compression means a process of setting the amplitude level of the original sound signal to be equal to or lower than the upper limit value of the amplitude level of the media sound signal.

(First embodiment)
FIG. 1 is a block diagram showing a functional configuration of an acoustic signal compression apparatus according to an embodiment of the present invention.

  That is, the acoustic signal compression apparatus 10 according to the present invention detects an excessive acoustic signal whose amplitude level is an excessive amplitude level larger than a predetermined maximum amplitude level from the original acoustic signal, and the excessive amplitude level is equal to or lower than the maximum amplitude level. Compression characteristic determining means 1 for determining a compression characteristic to be compressed, and compressed acoustic signal generating means 2 for compressing the original acoustic signal based on the compression characteristic to generate a compressed acoustic signal.

  Then, the compression characteristic determining means 1 pre-changes the preprocessing rate per unit time from zero decibel to a target compression amount (<0) determined based on the difference between the excessive amplitude level and the maximum amplitude level when detecting the excessive acoustic signal. (<0), preprocessing gain determining means 3 for determining a preprocessing gain to be applied to the original acoustic signal before the detection of the excessive acoustic signal, and a predetermined unit time from the target compression amount to zero decibel And post-processing gain determining means 4 for determining a post-processing gain to be applied to the original sound signal after the detection of the excessive sound signal, changing at a post-processing change rate (> 0).

  FIG. 2 is a block diagram showing a hardware configuration of a personal computer that functions as the acoustic signal compression device according to the embodiment of the present invention, and includes an acoustic signal reading interface (I / F) 11 that reads an original acoustic signal, and a program And a memory 12 for storing calculation values, a CPU 13 for executing processing based on a program, a compressed acoustic signal output interface (I / F) 14 for outputting a compressed acoustic signal, a display device 15, a keyboard 16, and a pointing device 17 A peripheral device interface (I / F) 18 to which a peripheral device is connected is connected to each other by a bus 19.

  Then, by installing the program in the memory 12, the personal computer operates as an acoustic signal compression device.

  Next, the operation of the acoustic signal compression apparatus according to the first embodiment of the present invention will be described with reference to the flowchart of the acoustic signal compression program installed in the memory 12.

  FIG. 3 is a flowchart of the acoustic signal compression program. First, the CPU 13 sets appropriate initial values for variables stored in the memory 12 (step S1).

  Next, the CPU 13 makes it possible to read the sampling data x (i) of the original sound signal (step S2), and the sampling data x (i) within a preset time limit after the processing reaches step S2. Is read (step S3). When the sampling data x (i) is read within the time limit, the CPU 13 increments the index i indicating the order of the sampling data (step S4). It is assumed that i is initially set to “0” in step S1.

Next, the CPU 13 calculates the amplitude level L (i) [dBFs] of the sampling data x (i) from [Equation 1] (step S5).

Next, the CPU 13 determines whether or not the amplitude level L (i) is an excessive amplitude level larger than _a predetermined maximum amplitude level L _a [dBFs] (step S6). When the amplitude level L (i) is greater than the maximum amplitude level _{L a} is CPU 13, the target compression amount is the difference between the amplitude level L (i) and the maximum amplitude level _{L a} sampling data x (i) L _d (i) [dB] (<0) is calculated from [Equation 2] as schematically shown in FIG. 4A (step S7). It is assumed that the initial value of the target compression amount L _d (i) is set to “0” in step S1.

Next, the CPU 13 determines a preprocessing gain and a postprocessing gain for the target compression amount L _d (i) (step S8). Details of this processing will be described later as a compression characteristic calculation routine. Further, the CPU 13 determines a compression characteristic from the pre-processing gain and the post-processing gain obtained in step S8 (step S9). This process will be described later as a compression characteristic determination routine.

If the processing in the case the amplitude level L (i) is equal to or smaller than the maximum amplitude level L _a and S9 is completed in step S6, CPU 13 reads the next sampling data back to the step S2.

  In step S3, if the CPU 13 determines that the sampling data x (i) has not been read within the time limit, that is, if the CPU 13 determines that all the sampling data has been read, the CPU 13 generates a compressed acoustic signal to be described later. A compressed acoustic signal is generated based on the compression characteristic determined in step S9 in the routine (step S10), and the program is terminated.

In step S3, the CPU 13 determines whether or not the sampling data x (i) has been read within the time limit, or has a code or signal indicating that sampling data has been completely input been detected? It may be judged.

  FIG. 5 is a flowchart of the compression characteristic calculation routine executed in step S8 of the acoustic signal compression program of FIG.

First, the CPU 13 compresses the sampling data before x (i) to compress the amplitude level L (i) of the sampling data x (i) by the target compression amount L _d (i) (<0) [dB]. A sampling data number A indicating whether or not the amplitude level L (j) (j ≦ i) should be compressed at a pre-processing change rate Δdd [dB / s] (<0) determined in advance. It is calculated from [Equation 3] (step S20). Here, the sampling frequency of the original acoustic signal is Fs [Hz].

Note that the preprocessing change rate Δdd is a predetermined value, and auditory unnaturalness does not occur when the preprocessing change rate Δdd is about −1 to −1.5 [dB / s].

Next, the CPU 13 substitutes “i−A” for the index j (step S21), and compresses the amplitude level L (i) of the sampling data x (i) by the target compression amount L _d (i) [dB]. The compression amount D _i (j) [dB] for the amplitude level L (j) (j ≦ i) before x (i) is schematically shown as a preprocessing gain in FIG. Formula 4] is calculated (step S22). It is assumed that the compression amount D _i (j) is initially set to “0” in step S1 of the acoustic signal compression program of FIG.

  Next, the CPU 13 determines whether j is smaller than i (step S23). If j is smaller than i, the CPU 13 increments j (step S24) and returns to step S22.

If j is greater than or equal to i in step S23, the CPU 13 changes at a predetermined post-processing change rate Δdi [dB / s] (> 0) per unit time from the target compression amount L _d (i) to zero decibels. When determining the post-processing gain to be performed, the sampling data number B indicating how many amplitude levels L (j) (i <j) of the sampling data after achieving the target compression amount should be compressed is expressed by [Equation 5]. (Step S25). The post-processing change rate Δdi (> 0) may be about 1 to 1.5 [dB / s] or a slightly larger value.

Next, the CPU 13 substitutes “i + 1” for j (step S26), and the compression amount D _i (j) for the amplitude level L (j) (i <j) is schematically shown as a post-processing gain in FIG. 4B. As shown specifically, it is calculated from [Equation 6] (step S27).

  Next, the CPU 13 determines whether j is smaller than i + B (step S28). If j is smaller than i + B, the CPU 13 increments the value of j (step S29) and returns to step S27. If j is equal to or greater than i + B in step S28, the CPU 13 ends the compression characteristic calculation routine.

  FIG. 6 is a flowchart of the compression characteristic determination routine executed in step S9 of the acoustic signal compression program of FIG. In the present embodiment, it is assumed that the occurrence frequency of the excessive amplitude level is sufficiently low and the compression characteristics for different excessive amplitude levels do not overlap in time.

First, the CPU 13 substitutes “i−A” for the index j (step S30), and substitutes the compression amount D _i (j) for D (j) (step S31). The compression amount D (j) is assumed to have an initial value set to “0” in step S1 of the acoustic signal compression program of FIG.

  Next, the CPU 13 determines whether j is smaller than i + B (step S32). If j is smaller than i + B, the CPU 13 increments the value of j (step S33) and returns to step S31. If j is equal to or greater than i + B in step S32, the CPU 13 ends the compression characteristic determination routine.

  FIG. 7 is a flowchart of the compressed acoustic signal generation routine executed in step S10 of the acoustic signal compression program of FIG.

  First, the CPU 13 sets the number of sampling data counted in step S4 of the acoustic signal compression program as the number N of all input sampling data (step S40), and substitutes “1” for the index i (step S41).

Next, the CPU 13 calculates the compression acoustic signal y (i) from [Equation 7] using the compression characteristic, that is, the compression amount D (i) (≦ 0) (step S42).

  Next, the CPU 13 determines whether i is smaller than N (step S43). If i is smaller than N, the CPU 13 increments the value of i (step S44) and returns to step S42. When i is N or more, the CPU 13 ends the compressed acoustic signal generation routine.

  As described above, the acoustic signal compression device according to the first embodiment of the present invention determines the excessive amplitude level of the original acoustic signal based on the compression characteristic that changes at a predetermined rate of change per unit time. By compressing to below the maximum amplitude level and generating a compressed acoustic signal, the original acoustic signal with a wide dynamic range can be compressed without distortion and perceptual unnaturalness.

(Second Embodiment)
FIG. 8 is a block diagram showing a functional configuration of an acoustic signal compression apparatus according to the second embodiment of the present invention. Since the present embodiment is configured in substantially the same manner as the above-described first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 8, in addition to the configuration shown in the first embodiment, the acoustic signal compression device 30 determines a compression characteristic for maintaining the target compression amount for a predetermined target compression amount maintaining time from the detection of the excessive acoustic signal. Target compression amount maintaining means 5 is provided.

  Since the acoustic signal compression apparatus according to the second embodiment is also configured by installing a program in a personal computer as in the first embodiment, description of hardware is omitted.

  Next, the operation of the acoustic signal compression apparatus according to the second embodiment will be described with reference to a flowchart of a program installed in the memory 12. The acoustic signal compression program is the same as that shown in FIG.

  FIG. 9 is a flowchart of a compression characteristic calculation routine with a compression amount maintaining function executed in step S8 of the acoustic signal compression program of FIG. Note that the same steps as those in the compression characteristic calculation routine of FIG.

After step S23, the CPU 13 substitutes “i + 1” for j (step S50), and as shown schematically in FIG. 10B, the target compression amount L _d (i) is set to a predetermined target compression amount. Only the maintenance time Δth is maintained (step S51). At this time, the compression amount D _i (j) is expressed as [Equation 8]. Note that it is preferable to set a value of about 10 to 100 msec as Δth because the waveform of the compressed acoustic signal finally generated reproduces the waveform of the original acoustic signal well and no distortion occurs.

  Next, the CPU 13 determines whether j is smaller than i + Δth * Fs (step S52). If j is smaller than i + Δth * Fs, the CPU 13 increments the value of j (step S53) and returns to step S51.

  If j is greater than or equal to i + Δth * Fs + B in step S52, the CPU 13 proceeds to the processing after step S25.

  The CPU 13 substitutes “i + Δth * Fs + 1” for j (step S54), determines whether j is smaller than i + Δth * Fs + B (step S55), and if j is equal to or greater than i + Δth * Fs + B, the compression amount maintaining function. The attached compression characteristic calculation routine is terminated.

  Note that the processing of the compression characteristic determination routine, which is a subroutine of step S9 of the acoustic signal compression program in the present embodiment, except that the CPU 13 determines whether j is smaller than i + Δth * Fs + B in step S32. Then, the same processing as the compression characteristic determination routine of FIG.

  As described above, the acoustic signal compression apparatus according to the second embodiment of the present invention uses a compression characteristic that maintains the target compression amount for a predetermined target compression amount maintaining time from the time of detection of the excessive acoustic signal. Higher quality compression without distortion and auditory unnaturalness can be applied to an original acoustic signal with a wide dynamic range.

(Third embodiment)
FIG. 11 is a block diagram showing a functional configuration of an acoustic signal compression device according to the third embodiment of the present invention. Since the present embodiment is configured in substantially the same manner as the above-described second embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 11, in addition to the configuration shown in the second embodiment, the acoustic signal compressing device 40 has a preprocessing gain, a target processing amount, and a target processing amount when the preprocessing gain, the target compression amount, and the postprocessing gain overlap in time. Selection means 6 is provided for selecting the compression value and the minimum value of the post-processing gain, that is, the one having the maximum absolute value as the compression characteristic.

  Since the acoustic signal compression apparatus according to the third embodiment is also configured by installing a program in a personal computer as in the first and second embodiments, description of hardware is omitted.

  Next, the operation of the acoustic signal compression apparatus according to the third embodiment will be described with reference to a flowchart of a program installed in the memory 12.

  FIG. 12 is a flowchart of an acoustic signal compression program with a compression characteristic selection function. In addition, about the process same as the acoustic signal compression program of FIG. 3, the same step number is attached | subjected and description is abbreviate | omitted.

  As schematically shown in FIGS. 13A to 13C, when the preprocessing gain, the target compression amount, and the postprocessing gain for different over-amplitude levels overlap with each other in time, the CPU 13 The minimum value of the processing gain, the target compression amount, and the post-processing gain is set as a new compression characteristic (step S60). Details of the processing in step S60 will be described later as a compression characteristic selection routine.

  FIG. 14 is a flowchart of the compression characteristic selection routine executed in step S60 of the acoustic signal compression program with a compression characteristic selection function in FIG.

First, the CPU 13 initializes the index j to “i-A” (step S70). Next, the CPU 13 determines whether Min (j) that gives the minimum value of the current compression amount is larger than the compression amount D _i (j) (step S71). When Min (j) is larger than D _i (j), the CPU 13 substitutes D _i (j) for Min (j) (step S72). It is assumed that Min (j) is initially set to “0” in step S1 of the acoustic signal compression program with a compression characteristic selection function in FIG.

  Next, the CPU 13 determines whether j is smaller than i + Δth * Fs + B (step S73). When j is smaller than i + Δth * Fs + B, the CPU 13 increments j (step S74) and returns to step S71.

If Min (j) is equal to or less than D _i (j) in step S71, the CPU 13 proceeds to step S74 without updating the value of Min (j).

  If j is greater than or equal to i + Δth * Fs + B in step S73, the CPU 13 ends the compression characteristic selection routine, returns to step S2 of the acoustic signal compression program with a compression characteristic selection function in FIG. Read.

  In the acoustic signal compression program with a compression characteristic selection function in FIG. 12, when the processing of step S60 is completed for all sampling data, the compression characteristics are all excessive as shown schematically by the black line in FIG. The minimum value of the compression amount given by the compression characteristic with respect to the amplitude level is selected at each time.

Finally, the CPU 13 uses the compression characteristic, that is, the compression amount Min (i) (≦ 0), to generate the compressed acoustic signal y (i) from [Equation 9] in the compressed acoustic signal generation routine of FIG. The sound signal compression program is terminated.

  As described above, in the acoustic signal compression device according to the third embodiment of the present invention, when the preprocessing gain, the target compression amount, and the postprocessing gain overlap in time, the preprocessing gain and the target compression By selecting the minimum compression amount given by the amount and post-processing gain as the compression characteristic, distortion and auditory unnaturalness can be reduced even for a wide dynamic range acoustic signal in which excessive amplitude levels are frequently detected. There can be no high quality compression.

  As described above, the acoustic signal compression device according to the present invention has an effect that the original acoustic signal can be audibly and naturally compressed, and is effective as an acoustic signal processing device or the like.

The block diagram of the acoustic signal compression apparatus in the 1st Embodiment of this invention The block diagram which shows the hardware constitutions of the personal computer which comprises the acoustic signal compression apparatus which concerns on the 1st Embodiment of this invention. Flowchart of an acoustic signal compression program executed by the CPU of the acoustic signal compression device according to the present invention. Schematically shows a target compression amount L _{d (i)} and compression properties Flowchart of compression characteristic calculation routine executed by CPU of acoustic signal compression apparatus according to the present invention Flowchart of compression characteristic determination routine executed by CPU of acoustic signal compression apparatus according to the present invention A flowchart of a compressed acoustic signal generation routine executed by the CPU of the acoustic signal compression apparatus according to the present invention. The block diagram of the acoustic signal compression apparatus in the 2nd Embodiment of this invention The flowchart of the compression characteristic calculation routine with a compression amount maintenance function which CPU of the acoustic signal compression apparatus which concerns on this invention performs Schematically shows a target compression amount L _{d (i)} and compression properties The block diagram of the acoustic signal compression apparatus in the 3rd Embodiment of this invention. Flowchart of acoustic signal compression program with compression characteristic selection function executed by CPU of acoustic signal compression device according to the present invention The figure which shows a mode that the compression characteristic for two or more excessive amplitude levels overlaps in time Flowchart of compression characteristic selection routine executed by CPU of acoustic signal compression apparatus according to the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compression characteristic determination means 2 Compressed acoustic signal generation means 3 Pre-processing gain determination means 4 Post-processing gain determination means 5 Target compression amount maintenance means 6 Selection means 10, 30, 40 Acoustic signal compression apparatus 11 Acoustic signal reading interface (I / F) )
12 memory 13 CPU
14 Compressed sound signal output interface (I / F)
15 Display Device 16 Keyboard 17 Pointing Device 18 Peripheral Device Interface (I / F)
19 Bus

Claims (5)

Compression characteristic determination for detecting an excessive acoustic signal whose amplitude level is an excessive amplitude level larger than a predetermined maximum amplitude level from the original acoustic signal and determining a compression characteristic for compressing the excessive amplitude level below the maximum amplitude level Means,
An acoustic signal compression apparatus including compressed acoustic signal generation means for compressing the original acoustic signal based on the compression characteristic to generate a compressed acoustic signal. The compression characteristic determining means;
Changes from zero decibel to a target compression amount (<0) determined based on the difference between the excessive amplitude level and the maximum amplitude level at the time of detection of the excessive acoustic signal at a predetermined preprocessing change rate (<0) per unit time. And preprocessing gain determining means for determining a preprocessing gain to be applied to the original acoustic signal before the detection of the excessive acoustic signal;
After changing from the target compression amount to zero decibel with a predetermined post-processing change rate (> 0) per unit time, and determining a post-processing gain to be applied to the original sound signal after the detection of the excessive sound signal The acoustic signal compression apparatus according to claim 1, further comprising processing gain determination means. The compression characteristic determining means;
From zero decibel, when the excessive acoustic signal is detected, the target compression amount determined based on the difference between the excessive amplitude level and the maximum amplitude level is changed at a predetermined preprocessing change rate per unit time, and when the excessive acoustic signal is detected. Preprocessing gain determining means for determining a preprocessing gain to be applied to the previous original acoustic signal;
Target compression amount maintaining means for maintaining the target compression amount for a predetermined target compression amount maintenance time from the detection of the excessive acoustic signal;
Post-processing gain determination that changes at a predetermined post-processing change rate per unit time from the target compression amount to zero decibel and determines a post-processing gain to be applied to the original acoustic signal after the target compression amount maintaining time has elapsed. The acoustic signal compression apparatus according to claim 1, comprising: means. The compression characteristic determining means;
Selection means for selecting the preprocessing gain, the target compression amount, and the minimum value of the post-processing gain as the compression characteristics when the pre-processing gain, the target compression amount, and the post-processing gain overlap in time The acoustic signal compression apparatus of Claim 2 or Claim 3 containing this. On the computer,
Compression characteristic determination for detecting an excessive acoustic signal whose amplitude level is an excessive amplitude level larger than a predetermined maximum amplitude level from the original acoustic signal and determining a compression characteristic for compressing the excessive amplitude level below the maximum amplitude level Processing,
An acoustic signal compression program for executing a compressed acoustic signal generation process for generating a compressed acoustic signal by compressing the original acoustic signal based on the compression characteristic.

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