JP5545192B2 - Acoustic signal processing apparatus, acoustic signal processing method and program - Google Patents

Description

  The present invention relates to an acoustic signal processing apparatus, an acoustic signal processing method, and a program.

  In the technical field that handles acoustic signals, the dynamic range of acoustic signals has been processed using compressors, limiters, expanders, and the like.

  For example, Patent Documents 1 and 2 disclose an acoustic signal processing apparatus that compresses a signal having a magnitude equal to or larger than a threshold value among acoustic signals.

  Patent Document 2 discloses an acoustic signal processing device (compression device) that compresses a portion exceeding the threshold with a predetermined compression ratio when a level sensor that detects the level of the input signal detects a signal that is equal to or higher than the threshold. Has been.

Japanese Patent No. 3898971 JP 11-68493 A

  Depending on the sound source, the output signal level may increase or decrease. In addition, when the sound source is switched and used, the level (range) of the input signal may change depending on the sound source.

  When there is always only a low level input (when the range is small), the signal level does not exceed the threshold. In this case, the acoustic signal processing apparatuses described in Patent Documents 1 and 2 do not perform any processing, and thus the processing effect does not appear.

  Although it is possible to switch the threshold value, it is complicated and it is difficult to set a threshold value appropriately according to the input level.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an acoustic signal processing apparatus, an acoustic signal processing method, and a program capable of automatically setting a threshold value according to the level of an input signal.
It is another object of the present invention to provide an acoustic signal processing apparatus, an acoustic signal processing method, and a program that can process a dynamic range regardless of the level of an input signal.

The acoustic signal processing apparatus according to the first aspect of the present invention is:
A signal strength analysis unit that identifies the maximum value among the values representing the magnitude of the input signal in a predetermined time interval;
A threshold setting unit for setting a threshold based on the maximum value and a predetermined threshold rate;
Among the input signals, a processing unit that sets an output signal obtained by compressing a signal having an absolute value equal to or greater than the threshold with a preset compression rate;
It is characterized by providing.

  For example, the time interval may be a time interval between a time point when the output signal is output and a time point that goes back a preset period from the time point.

  For example, the signal strength analysis unit may include means for setting the predetermined period based on the period of the input signal.

  For example, the value indicating the magnitude of the input signal in the predetermined time interval may be a scalar value derived from the value of the input signal.

  For example, the threshold setting unit may set the threshold based on a product of the threshold rate and the scalar value.

  For example, the acoustic signal processing device may further include a setting unit that sets at least one of the threshold rate and the compression rate.

The acoustic signal processing method according to the second aspect of the present invention includes:
A signal strength analysis identifying a maximum value among the values representing the magnitude of the input signal during a predetermined time zone,
A threshold setting step for setting a threshold based on the maximum value and a predetermined threshold rate ;
Among the input signals , a processing step to set a signal having an absolute value equal to or greater than the threshold value as an output signal compressed at a preset compression rate;
It is characterized by providing.

The program according to the third aspect of the present invention is:
On the computer,
A signal strength analysis identifying a maximum value among the values representing the magnitude of the input signal during a predetermined time zone,
A threshold setting step for setting a threshold based on the maximum value and a predetermined threshold rate ;
Among the input signals , a processing step to set a signal having an absolute value equal to or greater than the threshold value as an output signal compressed at a preset compression rate;
Is executed.

  According to the present invention, the dynamic range can be processed regardless of the absolute magnitude of the input signal. Further, even when the magnitude of the input signal changes, the threshold value is automatically changed, and the dynamic range can be processed according to the magnitude of the input signal.

It is a block diagram which shows the structural example of the acoustic signal processing apparatus which concerns on Embodiment 1 of this invention. 3 is a graph illustrating an example of an input signal and an output signal in the first embodiment. It is the graph which expanded a part of period when the input signal of FIG. 2 is small. It is the graph which expanded a part of period when the input signal of FIG. 2 is large. It is a block diagram which shows the structural example of the acoustic signal processing apparatus which concerns on Embodiment 2 of this invention. 6 is a graph illustrating an example of an input signal and an output signal in the second embodiment. It is the graph which expanded a part of period when the input signal of FIG. 6 is small. It is the graph which expanded a part of period when the input signal of FIG. 6 is large. It is a block diagram which shows the structural example of the acoustic signal processing apparatus which concerns on Embodiment 3 of this invention.

  Hereinafter, an acoustic signal processing apparatus, an acoustic signal processing method, or an acoustic system including a program according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
The acoustic system 100 according to the first embodiment includes a plurality of sound sources 20 (20 _{1 to} 20 _n ), a sound source selector 21, an acoustic signal processing device 10, a D / A converter 22, an amplifier 23, and a speaker 24. Is composed of.

The sound sources 20 _{1 to} 20 _n are composed of a CD (Compact Desk) reproducing device, a broadcast receiving device, and the like, and each output a digital acoustic signal having a predetermined sampling rate. The level ranges of the acoustic signals output from the sound sources 20 _{1 to} 20 _n are different from each other.

Tone selector 21 selects one of the sound source ₂₀ 1 to 20 _n, and supplies the audio signal processing apparatus 10 selects the sound signal from the sound source ₂₀ 1 to 20 _n selected.

  The acoustic signal processing device 10 performs processing such as expansion of the dynamic range on the supplied acoustic signal and outputs the processed signal. Details of the configuration and operation of the acoustic signal processing apparatus 10 will be described later.

  The D / A (digital / analog) converter 22 converts the digital acoustic signal output from the acoustic signal processing apparatus 10 into an analog acoustic signal.

The amplifier 23 amplifies and outputs the acoustic signal output from the D / A converter 22.
The speaker 24 is driven by the acoustic signal from the amplifier 23 and emits sound.

  The acoustic signal processing apparatus 10 is physically configured by a DSP (digital signal processor) or the like, and functionally includes an input terminal 11, a delay circuit 12, a signal analyzer 13, a setting device 14, and an arithmetic operation. A device 15 and an output terminal 16 are provided.

  The input terminal 11 is a terminal for inputting a digital acoustic signal from the sound source selector 21.

The signal analyzer (signal strength analysis unit) 13 specifies the maximum value of the absolute values of the input acoustic signal in a predetermined time interval, and includes four delay devices 17 _{1 to} 17 ₄ connected in series. And a maximum value selector 18.
Each of the delay units 17 _{1 to} 17 ₄ outputs the input acoustic signal with a delay of one sampling period.
The maximum value selection unit 18, a sound signal input, of the output sound signal of the delay circuit 17 ₁ to 17 _4, the absolute value is selected maximum one, to transmit the maximum absolute value selecting the setting unit 14 .

The setting unit (threshold setting unit) 14 is used for the calculation unit 15 to set a threshold T and a compression rate CR for determining whether or not to compress an acoustic signal. The setting device 14 stores the threshold rate TR and the compression rate CR in the internal memory. The threshold rate TR is a value indicating how much the absolute value of the acoustic signal of interest is larger than the maximum value of the absolute value of the acoustic signal in a predetermined time segment, and the dynamic range is processed. The compression rate CR is a value indicating a ratio for compressing a portion exceeding the threshold value T of the input acoustic signal.
The setter 14 multiplies the maximum absolute value transmitted from the signal analyzer 13 and the threshold rate TR, and sets the product to the threshold T. The threshold value T is a positive real number. Further, the setting device 14 transmits the obtained threshold T and the compression rate CR stored in advance to the computing device 15.

Delay circuit 12, the process is the delay circuit for timing adjustment, consists delay unit 12 ₁ and the delay unit 12 ₂ which is one sampling period delays the audio signal, the input audio signal 2 sampling period delay to operation To the instrument 15.

  The computing unit (processing unit) 15 processes the acoustic signal transmitted from the delay circuit 12 based on the threshold value T and the compression rate CR transmitted from the setting unit 14. The computing unit 15 outputs the processed acoustic signal via the output terminal 16.

  The output terminal 16 outputs the acoustic signal transmitted from the calculator 15.

Next, how the acoustic signal processing apparatus 10 processes the acoustic signal supplied from any of the sound sources 20 _{1 to} 20 _n via the sound source selector 21 will be described.

  In the following description, an input signal at time t is represented as x (t) and an output signal is represented as y (t). For example, x (t + 1) represents an input signal after one sampling period from t.

  The acoustic signal x (t) input from the input terminal 11 is transmitted to the delay circuit 12 and the signal analyzer 13.

At this stage, the input signal of the delay device 17 ₁ is x (t), the output signal of the delay device 17 _{1 and} the input signal of the delay device 17 ₂ are x (t−1), and the output signal of the delay device 17 ₂ . a delay unit 17 _third input signal are x (t-2), and the delay device 17 ₃ output signal of the delay device 17 _fourth input signal are x (t-3) and the output signal of the delay device 17 ₄ Becomes x (t-4).
As a result, the input signals x (t), x (t−1), x (t−2), x (t−3), and x (t−4) are transmitted to the maximum value selector 18 at time t. .

The maximum value selector 18 receives the input signal x (t) and the delay signals x (t−1), x (t−2), x (t−3) transmitted from the delay units 17 _{1 to} 17 ₄ at time t. ), X (t−4) is obtained, the largest one of the obtained absolute values is selected, and the selected absolute value is transmitted to the setting device 14.

  The setter 14 multiplies the threshold rate TR stored in the internal memory by the maximum value transmitted from the maximum value selector 18, sets the product as the threshold T, and transmits the product to the calculator 15 together with the compression rate CR.

  For example, at time t, x (t) = 1, x (t-1) =-3, x (t-2) = 2, x (t-3) = 0, x (t-4) = 1. 5, the threshold rate TR is 0.6, and the compression rate CR is 0.8. In x (t) to x (t−4), the maximum absolute value is 3 of | x (t−1) |, so that 3 × 0.6 = 1.8 is the threshold value T. The setter 14 transmits the obtained threshold T = 1.8 and the compression rate CR = 0.7 stored in advance to the calculator 15.

  The delay circuit 12 outputs the input signal with a delay of two sampling clock periods, and outputs the input signal x (t−2) at time t.

  The computing unit 15 compares the value of the input signal with the threshold value T set by the setting unit 14, and if the absolute value of the input signal X (x (t-2)) is smaller than the threshold value T, the input signal X As an output signal Y, and when the absolute value of the value of the input signal X is equal to or greater than the threshold T, the input signal X is compressed at a preset compression rate. Specifically, when the absolute value of the value of the input signal X is equal to or greater than the threshold value T, the computing unit 15 compresses a portion where the absolute value is equal to or greater than the threshold value with the compression ratio CR and outputs the result as the output signal Y.

This can be summarized in equation (1).
Y = X | X | <T
Y = (X−T) · CR + T X> 0 and X ≧ T
Y = (X + T) · CR−T X <0 and X ≦ −T
... (1)

  When the specific example is applied to Expression (1), the delay circuit 12 outputs the signal x (t−2) = 2 at time t. The computing unit 15 obtains the absolute value | x (t−2) | = 2 of the value of the signal x (t−2), compares the obtained absolute value 2 with the threshold value T = 1.8, and obtains the absolute value | x (t−2) | Since the absolute value 2 is equal to or greater than the threshold value 1.8, the specified compression ratio CR = 0.7 and the absolute value of the signal x (t−2) = 2 is 0.2 exceeding the threshold value 1.8. The portion is compressed and 0.2 · 0.7 + 1.8 = 1.94 is output as the output signal y (t).

  That is, the arithmetic unit 15 centers the signal x (t−2) on the input signal for a predetermined four sampling periods, that is, the signal x (t−2) itself and the two-step signal (x (t), x (T−1), x (t−3), x (t−4)) is set based on the absolute value of the acoustic signal value, and a threshold value T is set. -2) is determined whether or not to be compressed, and based on the determination result, the signal x (t-2) is compressed or output as an output signal y (t) via the output terminal 16 without being compressed. To do.

  The D / A converter 22 converts y (t) into analog, and the amplifier 23 amplifies it, and the speaker 24 emits the sound.

  Subsequently, when the next input signal t (t + 1) is input via the sound source selector 21, the input signals of the maximum value selector 18 are x (t + 1) to x (t-3), and the maximum value selector 18 selects the maximum of the absolute values of these signals.

The setter 14 sets a threshold T from the selected maximum value and the threshold rate TR.
The computing unit 15 is supplied with an input signal x (t−1), and the computing unit 15 centers on the signal x (t−1) itself, that is, an input signal for a predetermined four sampling periods, that is, a signal x (t −1) and the threshold T set based on the signals (x (t + 1), x (t), x (t−2), x (t−3)) of two steps before and after, x (t− It is determined whether or not 1) is to be compressed, and output as an output signal y (t + 1) based on the determination result, with or without being compressed.

  Thereafter, the acoustic signal processing apparatus 10 repeats the same operation, and the acoustic signal processing apparatus 10 receives the input signals x (t + 2), x (t + 3). . . On the other hand, signal processing is performed to output output signals y (t + 2) and y (t + 3).

  Here, it is assumed that the output range of the acoustic signal output from the sound source 20 selected by the sound source selector 21 is reduced, or the range of the acoustic signal is reduced because the sound source selector 21 switches the sound source 20. . In this case, after 5 clocks have passed after the range has changed, compression processing is performed by comparison with a threshold value determined by the intensity of the signal itself.

  That is, the threshold value T corresponding to the level (range) of the input signal is automatically set and the signal is processed. That is, the acoustic signal processing apparatus 10 sets the threshold value T to be larger if the level of the input signal is large, and smaller if the level of the input signal is small, regardless of the level (range) of the input signal. The dynamic range of the input signal can be processed.

  Here, the point that the acoustic signal processing apparatus 10 processes the acoustic signal regardless of the level of the input signal will be described with reference to a specific example.

  When the input signal x (t) indicated by the thick line in FIG. 2 is input to the input terminal 11 of the acoustic signal processing apparatus 10, the output signal y (t) indicated by the thin line in FIG.

  2 to 4, the horizontal axis is a time axis, the unit is msec, and the vertical axis indicates the value of the acoustic signal, which is unitless. The input signal x (t) is a sine wave with a period of 5 msec, and the range (amplitude) of the input signal x (t) is 0.5 in the period of 0 to 20 msec and 1 in the period of 20 to 50 msec. The sampling period is 0.2 msec. The threshold rate TR is 0.6, and the compression rate CR is 0.7. The threshold value T is 0.6 times the maximum absolute value of the input signal during the 0.8 msec period before output. The output signal y (t) is delayed by two sampling periods (0.4 msec) from the input signal by the delay circuit 12.

  FIG. 3 is an enlarged view of the period of 10 to 20 msec in FIG. FIG. 4 is an enlarged view of the period of 30 to 40 msec in FIG. 3 and 4, the phase difference between the input signal and the output signal is corrected to 0 so that the comparison is easy. As shown in FIGS. 3 and 4, even in a period of 0 to 20 msec where the absolute value of the displacement of the input signal is small, dynamic range compression is performed in the same manner as in a period of 20 to 50 msec where the absolute value of the displacement is large. .

  As described above, the acoustic signal processing apparatus 10 according to the first embodiment automatically sets the threshold value T according to the level (range) of the input signal, so that the higher the level of the input signal, the higher the level of the input signal. If the level of the input signal is small, processing is performed to a smaller level. That is, the dynamic range of the input signal can be processed in the same manner regardless of the level (range) of the input signal.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation and application are possible.

  For example, in the first embodiment, five input signals for four clock periods are supplied to the maximum value selector 18, but the signal supplied to the maximum value selector 18 may be longer than the above example. It can be short. For example, three signals for two sampling periods or seven signals for six sampling periods may be used. Further, the period may be arbitrarily set by the user. Further, the acoustic signal input to the maximum value selector 18 may be every sampling period, but may be every longer period.

  Further, the signal input to the calculator 15 is preferably the central signal among the signals input to the maximum value selector 18, but is not limited thereto. For example, in FIG. 1, the delay circuit 12 is removed, and the threshold value T of the input signal x (t) is set based on the input signal in the last four sampling periods, or the number of delay devices constituting the delay circuit 12 The threshold number T of the input signal x (t) may be set based on the input signal in the immediately following four sampling periods, assuming that the number of delay units constituting the signal analyzer 13 is the same four.

(Embodiment 2)
In the first embodiment, the threshold value T is obtained based on the maximum absolute value of the signal within the four sampling periods immediately before the output timing.
The setting method for the predetermined period is not limited to this, and is arbitrary. For example, it is possible to select the maximum absolute value of a signal within a predetermined period in consideration of the frequency of the input signal. As an example, a second embodiment in which the threshold value T is set according to the maximum value of the absolute value of the input signal in the half cycle period until the sign of the input signal is inverted and then inverted will be described below with reference to FIG. To do.

  The configuration of the acoustic signal processing apparatus 50 in the second embodiment is basically the same as the configuration of the acoustic signal processing apparatus 10 in the first embodiment. However, the configuration of the signal analyzer 13 is different from that of the acoustic signal processing apparatus 10. The delay time of the delay circuit 12 is set in advance to the maximum value of the half cycle of the assumed input signal.

  The signal analyzer 13 according to the second embodiment includes a code detector 51 and a maximum value selector 52 as shown in FIG.

  The sign detector 51 detects when the sign of the input signal is inverted (zero cross point) and outputs a sign inversion signal to the maximum value selector 52.

  The maximum value selector 52 observes the absolute value of the value of the input signal during a half cycle period from when the sign inversion signal is supplied to when the sign inversion signal is supplied next, and the maximum value of the absolute values is determined. Record in internal memory. When receiving the sign inversion signal from the code detector 51, the maximum value selector 52 transmits the absolute maximum value stored in the internal memory to the setter 14, and then clears the internal memory to generate a new maximum value. Start selecting absolute values.

  The delay circuit 12 delays the input signal by a preset sampling period n corresponding to the maximum value s of the half cycle of the input signal, and transmits the delayed input signal to the computing unit 15.

  Next, the operation of the acoustic signal processing apparatus 50 will be described.

  The acoustic signal x (t) input from the input terminal 11 is transmitted to the delay circuit 12 and the signal analyzer 13.

  The acoustic signal transmitted to the signal analyzer 13 is supplied to the code detector 51 and the maximum value selector 52.

  The sign detector 51 detects the sign of the input signal x (t), and outputs a sign inversion signal when it detects sign inversion.

  The maximum value selector 52 obtains a half cycle period CT from the time when the sign inversion signal is supplied to the next time when the sign inversion signal is supplied and the absolute value of the input signal to be supplied. Select the maximum value. When the sign inversion signal is supplied, the maximum value selector 52 notifies the setting device 14 of the maximum absolute value selected so far, then clears the maximum absolute value and selects a new maximum absolute value. Start.

  The setter 14 obtains the product of the notified maximum absolute value and the threshold rate TR, sets the obtained product as the threshold T, and notifies the calculator 15 together with the compression rate CR stored in the internal memory.

  The delay circuit 12 delays the input signal by a preset period s and transmits it to the calculator 15.

  The computing unit 15 processes the supplied acoustic signal according to the level based on the threshold value T and the compression rate CR supplied from the setting unit 14 in accordance with the equation (1) (that is, set in advance). Compressed at a compression rate) and output via the output terminal 16.

  Here, the point that the acoustic signal processing device 50 according to the second embodiment processes the acoustic signal regardless of the level of the input signal will be described with reference to FIGS.

  When an input signal x (t) indicated by a thick line in FIG. 6 is input to the input end 11, an output signal y (t) indicated by a thin line is output from the output end 16.

  6 to 8, the horizontal axis is a time axis, the unit is msec, and the vertical axis indicates the value of the acoustic signal, which is unitless. The input signal x (t) is a sine wave with a period of 5 msec, and the absolute value (amplitude) of the maximum value is 0.5 for a period of 0 to 20 msec and 1 for a period of 20 to 50 msec. The sampling period is 0.2 msec. The threshold rate is 0.6 and the compression rate is 0.7. The delay time set in the delay device 12 is 2.5 msec.

  The threshold value T of the output signal y (t) is 0.6 times the maximum value of the absolute value of the input signal during the positive or negative 2.5 msec half cycle completed immediately before output. The output signal y (t) is delayed by a half cycle (2.5 msec) from the input signal by the delay circuit 12.

  FIG. 7 is an enlarged view of the period of 10 to 20 msec in FIG. FIG. 8 is an enlarged view of the period of 30 to 40 msec in FIG. 7 and 8, the phase difference between the input signal and the output signal is corrected to 0 so that the comparison is easy. As shown in FIGS. 7 and 8, even in a period of 0 to 20 msec in which the absolute value of the displacement of the input signal is small, the dynamic range is compressed in the same manner as in a period of 20 to 50 msec in which the absolute value of the displacement is large. .

  As described above, the acoustic signal processing apparatus 50 according to the second embodiment also controls the threshold value T flexibly according to the signal level regardless of the absolute magnitude of the acoustic signal, regardless of the size of the signal range. The dynamic range can be processed.

(Embodiment 3)
In the second embodiment, the signal x (ts) input to the calculator 15 is calculated by a threshold T determined based on the level of the input signal during the period from time t-CT to time t. For this reason, there arises a problem that the threshold value T does not reflect the signal level at the time (ts) when the calculation is performed.

  In order to solve this problem, a third embodiment in which the threshold value T is delayed and transmitted to the computing unit 15 will be described with reference to FIG.

  The configuration of the acoustic signal processing apparatus 90 in the third embodiment is basically the same as the configuration of the acoustic signal processing apparatus 50 in the second embodiment. However, the function of the code detector 91 is different from that of the code detector 51. Another difference is that a delay unit 92 that delays the threshold value T and the compression rate CR output from the setting unit 14 and transmits them to the computing unit 15 is provided.

  As shown in FIG. 9, the signal analyzer 13 according to the third embodiment includes a code detector 91 and a maximum value selector 52.

  The sign detector 91 detects when the sign of the input signal is inverted (zero cross point). The code detector 91 includes an internal timer, and counts the period (half cycle CT) between the previous zero cross point and the current zero cross point. When detecting the zero cross point, the sign detector 91 outputs a sign inversion signal to the maximum value selector 52, obtains a numerical value m by the following calculation, and transmits it to the delay unit 92.

  The numerical value m is obtained by dividing the time obtained by subtracting the counted half cycle CT and the processing time a in the setter 14 from the delay time s of the delay circuit 12 by the sampling cycle ST.

  Note that a is a period required for the setter 14 to receive the maximum value from the maximum value selector 52 and output the threshold value T and the compression rate CR, and is stored in the internal memory of the code detector 91.

This can be summarized in equation (2).
m = (s-CT-a) / ST
... (2)

  Note that the sign detector 91 performs processing assuming that the sign is reversed and the sign is reversed when the sign inversion of the input signal does not occur for a certain period or longer. This is to prevent the sign detector 91 from continuing counting when the sign of the input signal does not invert, such as when the input signal is composed of only a direct current component. The count is terminated when the maximum time stored in advance in the internal memory of the code detector is exceeded. The maximum time is the same as the delay time s in the delay circuit 12.

  The maximum value selector 52 is the same as that of the second embodiment.

  The delay circuit 12 is the same as that of the second embodiment.

  The setting device 14 has the same function as that of the second embodiment. The setting device 14 transmits the threshold value T and the compression rate CR to the delay device 92.

  The delay unit 92 transmits the threshold value T and the compression ratio CR transmitted from the setting unit 14 to the computing unit 15 with a delay of m sampling periods transmitted from the code detector 91.

  The calculator 15 is the same as that of the second embodiment.

  Next, the operation of the acoustic signal processing apparatus 90 will be described.

  The acoustic signal x (t) input from the input terminal 11 is transmitted to the delay circuit 12 and the signal analyzer 13.

  The acoustic signal transmitted to the signal analyzer 13 is supplied to the code detector 91 and the maximum value selector 52.

  The sign detector 91 detects the sign of the input signal x (t), outputs a sign inversion signal when the sign inversion is detected, calculates m based on the above equation (2), and transmits it to the delay unit 92. .

  The maximum value selector 52 observes the absolute value of the value of the input signal during a half cycle period from when the sign inversion signal is supplied to when the sign inversion signal is supplied next, and the maximum value of the absolute values is determined. Record in internal memory. When receiving the sign inversion signal from the code detector 51, the maximum value selector 52 transmits the absolute maximum value stored in the internal memory to the setter 14, and then clears the internal memory to generate a new maximum value. Start selecting absolute values.

  The setter 14 obtains the product of the notified maximum absolute value and the threshold rate TR, sets the obtained product as the threshold T, and transmits it to the delay unit 92 together with the compression rate CR stored in the internal memory.

  The delay unit 92 delays the numerical value m transmitted from the code detector 91 by a time multiplied by the sampling period, and transmits the threshold value T and the compression rate CR transmitted from the setting unit 14 to the computing unit 15.

  The delay circuit 12 delays the input signal by a preset period s and transmits it to the calculator 15.

  The computing unit 15 compresses the supplied acoustic signal based on the threshold value T and the compression rate CR supplied from the setting unit 14 according to the above equation (1), and outputs the compressed acoustic signal via the output terminal 16.

  Note that the method for reflecting the input signal level at the time when the threshold T is calculated is not limited to the method described in the third embodiment. For example, the delay circuit 12 may be replaced with a delay circuit that delays the input signal by the half cycle CT counted by the code detector 91. In this case, since the signal input to the calculator 15 is x (t-CT), the threshold T reflects the signal level input to the calculator 15 without the delay unit 92.

  As described above, according to the acoustic signal processing apparatus 90 of the third embodiment, the dynamic range can be processed based on the threshold value T reflecting the signal level at the time of processing.

  Embodiments 1 to 3 described above are examples of the present invention, and the acoustic signal processing apparatuses 10, 50, and 90 according to the present invention are not limited to this.

  First, in the above embodiment, as an example of processing the input signal, an example of compressing the input signal has been shown. However, the present invention can also be applied to other processing methods such as applying a limiter to the input signal and expanding the input signal. is there. However, as described above, this is particularly effective when the input signal is compressed at a preset compression rate according to the equation (1).

  Further, for example, in the above embodiment, the threshold rate TR is set to a predetermined value stored in the setting device 14, but the threshold rate TR may be set by the user. At this time, the acoustic signal processing apparatus includes an operation unit that registers the threshold rate TR in response to a user operation.

  In the above description, the threshold rate TR is a constant that does not change depending on the nature of the acoustic signal, but may be a value that changes dynamically. For example, the threshold rate TR may be a dynamic value determined by a function having the intensity, frequency (period), and other numerical values of acoustic signals as variables.

  Further, the compression rate CR is not limited to a fixed value, and may be a value designated by the user or a value dynamically determined by a function.

  Further, the value subjected to the maximum value determination in the signal analyzer 13 is not limited to the absolute value of the input signal, and may be a scalar value representing the signal level. For example, the square value of the input signal or the square root of the absolute value of the input signal may be used.

  In addition, the signal analyzer 13 selects the absolute value of the input signal or the maximum value of its square value during a predetermined period and transmits it to the setter 14 instead of selecting the average value or absolute value of the absolute value during that period. An intermediate value or the like of the value may be detected and transmitted to the setting device 14.

  In the above embodiment, an example in which the acoustic signal supplied from the sound source 20 is a digital signal is shown, but an analog signal may be used. In this case, the acoustic signal processing apparatus may be configured from an analog circuit, or the input signal may be processed by A / D conversion.

  You may distribute, install, transmit, receive, etc. the program which performs the said process operation to computers, such as DSP and CPU which comprise an acoustic signal processing apparatus.

DESCRIPTION OF SYMBOLS 10 Acoustic signal processing apparatus 11 Input terminal 12 Delay circuit 13 Signal analyzer (signal strength analysis part)
14 Setting device (threshold setting unit)
15 Calculator (Processing part)
DESCRIPTION OF SYMBOLS 16 Output terminal 17 Delay device 18 Maximum value selector 20 Sound source 21 Sound source selector 22 D / A converter 23 Amplifier 24 Speaker 50 Acoustic signal processing device 51 Code detector 52 Maximum value selector 90 Acoustic signal processing device 91 Code detector 92 Delayer 100 Acoustic system

Claims (8)

A signal strength analysis unit that identifies the maximum value among the values representing the magnitude of the input signal in a predetermined time interval;
A threshold setting unit for setting a threshold based on the maximum value and a predetermined threshold rate;
Among the input signals, a processing unit that sets an output signal obtained by compressing a signal having an absolute value equal to or greater than the threshold with a preset compression rate;
An acoustic signal processing apparatus comprising: The time interval is a time interval between a time point when the output signal is output and a time point that goes back a preset period from the time point.
The acoustic signal processing apparatus according to claim 1. The signal strength analysis unit is configured to set the predetermined period based on a cycle of the input signal;
The acoustic signal processing apparatus according to claim 1, comprising: The value representing the magnitude of the input signal in the predetermined time interval is a scalar value derived from the value of the input signal.
The acoustic signal processing apparatus according to any one of claims 1 to 3, wherein The threshold setting unit sets the threshold based on a product of the threshold rate and the scalar value;
The acoustic signal processing apparatus according to claim 4. Setting means for setting at least one of the threshold rate and the compression rate;
The acoustic signal processing apparatus according to claim 5, further comprising: A signal strength analysis identifying a maximum value among the values representing the magnitude of the input signal during a predetermined time zone,
A threshold setting step for setting a threshold based on the maximum value and a predetermined threshold rate ;
Among the input signals , a processing step to set a signal having an absolute value equal to or greater than the threshold value as an output signal compressed at a preset compression rate;
Features and to Ruoto sound signal processing method that comprises a. On the computer,
A signal strength analysis identifying a maximum value among the values representing the magnitude of the input signal during a predetermined time zone,
A threshold setting step for setting a threshold based on the maximum value and a predetermined threshold rate ;
Among the input signals , a processing step to set a signal having an absolute value equal to or greater than the threshold value as an output signal compressed at a preset compression rate;
A program characterized by having executed.

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