JP2006324786A - Acoustic signal processing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acoustic signal processing apparatus and method that perform reproduction without variance in sense of a low-pitched sound obtained by adding harmonics. <P>SOLUTION: A fundamental wave extracting filter 12 extracts a fundamental wave signal from an input acoustic signal inputted to an input terminal 10. A harmonic generating means 13 generates harmonic signals of the extracted fundamental wave signal. The respective generated harmonic signals have gains controlled by a gain control means 14 and are put together. A masking quantity detecting means 15 detects masking quantities by specified bands based upon the composite signal generated by the gain control means 14 and the input acoustic signal. A correcting means 16 sets a correction quantity based upon the detected masking quantities by the specified bands so that a masking phenomenon is suppressed. Then frequency amplitude characteristics of the composite signal are corrected in accordance with the correction quantity. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an acoustic signal processing apparatus and method thereof, and more specifically, an acoustic signal processing apparatus and method for improving bass feeling in reproduced sound by adding harmonics of a fundamental wave belonging to a low frequency range to an acoustic signal, and It relates to that method.

  In general, it is difficult to reproduce low sounds with a small speaker. In view of this, conventionally, a method of reproducing harmonics in place of bass that is difficult to reproduce has been proposed (see, for example, Patent Document 1). Hereinafter, a conventional acoustic signal processing device 9 will be described with reference to FIG. FIG. 12 is a block diagram showing a configuration of a conventional acoustic signal processing device 9.

  In FIG. 12, the acoustic signal processing device 9 includes an input terminal 90, an adder 91, a fundamental wave extraction filter 92, a harmonic overtone generation unit 93, a gain adjustment unit 94, and an output terminal 95. An acoustic signal is input to the input terminal 90. The acoustic signal input to the input terminal 90 is branched into two systems. In the first system, all components of the acoustic signal are input to one input unit of the adder 91. In the second system, all components of the acoustic signal are input to the fundamental wave extraction filter 92.

  The fundamental wave extraction filter 92 includes a low-pass filter and a band-pass filter having preset characteristics. The fundamental wave extraction filter 92 extracts a signal having a fundamental wave as a component (hereinafter referred to as a fundamental wave signal) from all components of the input signal based on the preset characteristics. The extracted fundamental wave signal is input to the overtone generation means 93.

  The harmonic overtone generation unit 93 includes a second overtone generation unit 931, a third overtone generation unit 932,..., An nth (n is a natural number of 2 or more) overtone generation unit 933. The second overtone generation unit 931 generates a second overtone signal of the input fundamental wave signal. The third harmonic generation unit 932 generates a third harmonic signal of the input fundamental wave signal. In other words, if expressed using i (i is an arbitrary natural number from 2 to n), the i th harmonic generation means generates the i th harmonic signal of the input fundamental wave signal. The gain of each generated harmonic signal is the same as that of the fundamental wave signal. Each harmonic signal is input to the gain adjusting means 94. A harmonic signal having a frequency n times the frequency of the fundamental wave signal (hereinafter referred to as a fundamental frequency) is referred to as an nth harmonic signal.

  Here, there are several methods for generating a harmonic signal. Of these, the zero cross method will be described with reference to FIG. FIG. 13 is a diagram schematically showing a method of generating a harmonic signal by the zero cross method. Hereinafter, the fundamental wave signal is considered as a sine wave shown in FIG.

  In the sine wave waveform shown in FIG. 13A, a point at which the signal level changes from positive to negative or from negative to positive is defined as a zero cross point. Here, zero cross points from negative to positive are defined as point P1, point P2, and point P3. In the case of generating the second overtone signal, the original waveform (waveform of the fundamental wave signal) is compressed by half in the time axis direction in the zero cross point section (section P1-P2, section P2-P3). Then, the waveform compressed to ½ is reproduced twice. As a result, as shown in FIG. 13B, the generated signal is a signal having a double frequency. Other order harmonics (third harmonic, fourth harmonic,..., Nth harmonic) signals are also generated by the above method. That is, the nth harmonic signal is generated by compressing the waveform of the fundamental wave signal to 1 / n in the time axis direction and reproducing it repeatedly n times in the zero cross point section.

  The gain adjusting unit 94 includes a second overtone gain adjusting unit 941, a third overtone gain adjusting unit 942,..., An nth overtone gain adjusting unit 943, and an adder 944. The gain adjusting means 94 has a harmonic structure in which each input harmonic signal is set in advance “second harmonic, third harmonic,..., N th harmonic = x2 (dB), x3 (dB),..., Xn (dB) The gain of each overtone signal is adjusted so that X2 to xn are integers. The adder 944 adds and synthesizes each overtone signal whose gain is adjusted to one signal. The added and synthesized signal is input to the other input unit of the adder 91. The adder 91 adds and synthesizes the signal added and synthesized by the adder 944 and the first system acoustic signal, and outputs the resultant signal to the output terminal 95. The signal output from the output terminal 95 is finally reproduced by a speaker.

As described above, when reproduction is performed by adding overtones to an acoustic signal, an auditory phenomenon called a virtual pitch effect occurs. This auditory phenomenon makes it sound as if the fundamental signal is being reproduced. That is, in the conventional acoustic signal processing apparatus, even if the speaker to be used is a small speaker that is difficult to reproduce with low sound, it is possible to improve the low sound feeling without changing the reproduction band of the speaker.
JP 2004-101797 A

  Here, how to hear the original sound (reproduced sound of the acoustic signal) and overtones is considered. The above-mentioned auditory phenomenon occurs when the user can hear overtones. However, from the viewpoint of volume, for example, when the volume of the original sound is high, it is difficult to hear overtones. Conversely, if the volume of the original sound is low, overtones are easy to hear. This is a phenomenon that occurs because the original sound masks overtones. That is, a masking phenomenon (including a frequency phenomenon and a temporal phenomenon) occurs in which the original sound is a masker and the overtone is a maskee. In the frequency masking phenomenon, for example, there is a qualitative property that the amount masked by the masker (hereinafter referred to as masking amount) is larger as the masky frequency is closer to the masker frequency. In addition, there is a property that the masking amount by the masker increases as the volume of the masker increases. Therefore, for example, when the volume of the original sound is high, the overtone is greatly masked by the original sound, making it difficult to hear. As described above, the conventional acoustic signal processing apparatus has a problem in that the ease of overtones changes due to the masking phenomenon, and the low-pitched feeling varies.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an acoustic signal processing apparatus and method capable of reproducing the bass sound obtained by adding overtones without variation.

  According to a first aspect of the present invention, there is provided an extraction means for extracting a fundamental wave signal from an input acoustic signal, a plurality of types of harmonic signals of the fundamental wave signal extracted by the extraction means, and a signal obtained by synthesizing the plurality of types of harmonic signals. Supply means for supplying, detection means for detecting a masking amount for masking each overtone signal by the input acoustic signal, and the gain of each overtone signal included in the synthesized signal so as to increase according to the detected masking amount An acoustic signal processing apparatus comprising: a correcting unit that corrects a combined signal; and an adding unit that adds the combined signal corrected by the correcting unit and an input acoustic signal.

  In a second aspect based on the first aspect, the detecting means detects a masking amount for each predetermined frequency band based on the synthesized signal and the input acoustic signal supplied by the supplying means, and the correcting means For each overtone signal included in the synthesized signal, the gain of the overtone signal is corrected according to the masking amount detected for a predetermined frequency band including the frequency of the overtone signal.

  In a third aspect based on the first aspect, the detecting means detects the level of the input acoustic signal as a masking amount, and the correcting means is a synthesized signal as the level of the input acoustic signal detected by the detecting means increases. The gain of the synthesized signal is corrected so that the gain of the signal becomes larger.

  In a fourth aspect based on the third aspect, the correction means increases the gain of the composite signal as the level of the input acoustic signal increases within a range where the level of the input acoustic signal is equal to or higher than a predetermined level. And correcting the gain of the combined signal.

  In a fifth aspect based on the third aspect, the correction means increases the gain of the composite signal as the level of the input acoustic signal increases within a range where the level of the input acoustic signal is equal to or lower than a predetermined level. And correcting the gain of the combined signal.

  In a sixth aspect based on the third aspect, the detection means detects the level of the input acoustic signal in a predetermined frequency band.

  According to a seventh aspect, in the sixth aspect, the predetermined frequency band is a frequency band including the frequency of each overtone signal.

  According to an eighth aspect of the present invention, there is provided an extraction step for extracting a fundamental wave signal from an input acoustic signal, a plurality of types of overtone signals of the fundamental wave signal extracted in the extraction step, and a signal obtained by synthesizing the plurality of types of overtone signals. A supply step for supplying, a detection step for detecting a masking amount by which the input acoustic signal masks each harmonic signal, and a gain for each harmonic signal included in the synthesized signal so as to increase according to the detected masking amount. An acoustic signal processing method including a correction step of correcting a combined signal and an adding step of adding the combined signal corrected in the correction step and an input acoustic signal.

  According to the first aspect of the invention, the phenomenon that the input acoustic signal masks each harmonic signal (masking phenomenon) by correcting the synthesized signal so that the gain of each harmonic signal is increased according to the detected masking amount. Can be suppressed. Thereby, the reproduction | regeneration which does not have dispersion | variation in the low pitch feeling obtained by adding a harmonic can be implement | achieved.

  According to the second aspect, it is possible to individually correct the gain of each harmonic signal. In other words, among a plurality of types of overtone signals, for example, when the masking amount is large only in a predetermined frequency band including the frequency of one type of overtone signal, it is possible to correct only the gain of that one type of overtone signal. As a result, it is possible to realize reproduction that is more natural and has no variation in the low-pitched sound according to the actual masking phenomenon.

  According to the third aspect, the level of the input sound signal is detected, and the gain of the synthesized signal is corrected according to the level of the input sound signal. That is, the gain of the synthesized signal is corrected by equivalently treating the level of the input acoustic signal as a masking amount. This eliminates the need for a complicated circuit for detecting the actual masking amount, and can provide a simpler and smaller apparatus.

  According to the fourth aspect of the invention, the composite signal is corrected within a range where the level of the input acoustic signal is equal to or higher than the predetermined level. Thereby, for example, a more stable correction can be performed by setting a predetermined level to a stable operating voltage of the apparatus.

  According to the fifth aspect of the invention, it is possible to prevent the gain of the synthesized signal from becoming excessive when the level of the input acoustic signal is larger than the predetermined level. That is, it is possible to prevent each harmonic signal from being excessively output.

  According to the sixth aspect, weighting of a predetermined frequency band is possible for correction of the composite signal, and correction for suppressing the masking phenomenon can be performed more efficiently.

  According to the seventh aspect of the invention, it is possible to perform correction in accordance with the property of the masking phenomenon that the masking amount increases as the frequencies of the masker (input acoustic signal) and the maskee (each harmonic signal) are closer. As a result, the masking phenomenon can be suppressed more efficiently.

  The eighth invention has the same effect as the first invention.

(First embodiment)
Hereinafter, the acoustic signal processing device according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of an acoustic signal processing device 1 according to the first embodiment. In FIG. 1, the acoustic signal processing apparatus 1 includes an input terminal 10, an adder 11, a fundamental wave extraction filter 12, a harmonic overtone generation unit 13, a gain adjustment unit 14, a masking amount detection unit 15, a correction unit 16, and an output terminal 17. Prepare.

  An acoustic signal is input to the input terminal 10. The input acoustic signal is input to one input unit of the adder 11, the fundamental wave extraction filter 12, and the masking amount detection means 15.

  The fundamental wave extraction filter 12 is configured by a low-pass filter or a band-pass filter having preset characteristics. The fundamental wave extraction filter 12 extracts a fundamental wave signal belonging to the low frequency range from all the components of the acoustic signal based on the preset characteristics. The extracted fundamental wave signal is input to the overtone generation means 13. Note that the frequency band of the extracted fundamental wave signal is a band including a desired bass. That is, it is a low frequency band to be reproduced in a pseudo manner by a harmonic signal.

  The harmonic overtone generation unit 13 includes a second overtone generation unit 131, a third overtone generation unit 132,..., And an nth (n is a natural number of 2 or more) overtone generation unit 133. The second overtone generating means 131 generates a second overtone signal of the input fundamental wave signal. The third harmonic generation unit 132 generates a third harmonic signal of the input fundamental wave signal. In other words, if expressed using i (i is an arbitrary natural number from 2 to n), the i th harmonic generation means generates the i th harmonic signal of the input fundamental wave signal. The gains of the second to nth overtone signals are the same as the gain of the fundamental wave signal. Then, the second to nth overtone signals are input to the gain adjusting means 14. For example, the above-described zero cross method is used as a method for generating a harmonic signal.

  The gain adjusting unit 14 includes a second overtone gain adjusting unit 141, a third overtone gain adjusting unit 142,..., An nth overtone gain adjusting unit 143, and an adder 144. The gain adjusting means 14 is configured to set a harmonic overtone in which each harmonic overtone signal is set in advance “second overtone, third overtone,..., Nth overtone = x2 (dB), x3 (dB),..., Xn (dB) The gain of each overtone signal is adjusted so that X2 to xn are integers. Specifically, the gain adjusting unit 14 adjusts the gain of each overtone signal by a predetermined adjustment amount. The predetermined adjustment amount is a gain adjustment amount set in advance for each harmonic signal. Each harmonic signal is adjusted in gain by a predetermined adjustment amount by the gain adjusting unit 14 to have the above-described harmonic structure. For example, it is assumed that the second to fourth overtone signals are generated in the overtone generation means 13. Further, the gain of the fundamental wave signal is “0 dB”, and the preset harmonic structure is “second harmonic, third harmonic, fourth harmonic = 0 (dB), −3 (dB), −6 (dB)”. And In this case, the gains of the second to fourth harmonic signals input to the gain adjusting unit 14 are the same as the gain of the fundamental wave signal. That is, the gain of the second to fourth overtone signals is “0 (dB)”. Therefore, in order for the second to fourth overtone signals to have a preset overtone structure, each harmonic overtone signal has a predetermined adjustment amount “second overtone, third overtone, fourth overtone = 0 (dB), −3 (DB), −6 (dB) ”may be used for gain adjustment. Each overtone signal whose gain has been adjusted is added and synthesized by the adder 144 into one signal. The synthesized signal of each overtone signal added and synthesized is input to the masking amount detection means 15 and the correction means 16.

  The masking amount detection means 15 detects the masking amount by the acoustic signal (the amount by which the acoustic signal masks the harmonic signal) based on the acoustic signal input to the input terminal 10 and the synthesized signal of each harmonic signal. The acoustic signal is a masker, and the harmonic signal is a maskee. As shown in FIG. 2, the masking amount detection means 15 includes an acoustic signal analysis means 151, a harmonic signal analysis means 152, and a band-specific masking amount detection means 153. FIG. 2 is a block diagram showing an example of the internal configuration of the masking amount detection means 15.

  In FIG. 2, the acoustic signal analysis means 151 analyzes the level of the acoustic signal input from the input terminal 10 for each predetermined frequency band (hereinafter referred to as a predetermined band). Information (analysis information) indicating the result of analysis by the acoustic signal analysis means 151 is input to the band-specific masking amount detection means 153. The predetermined band is, for example, a critical band. The critical band is a frequency band based on human auditory characteristics. Specifically, it is a frequency band in which individual signal sounds cannot be discerned from the sense of hearing and are audible by adding the magnitudes of the individual signal sounds. The synthesized signal is input from the gain adjusting unit 14 to the harmonic signal analyzing unit 152. The harmonic signal analyzing means 152 analyzes the level of each harmonic signal included in the synthesized signal for each predetermined band. The analysis information indicating the analysis result by the harmonic signal analysis unit 152 is input to the band-specific masking amount detection unit 153. As an analysis method in the acoustic signal analysis means 151 and the harmonic signal analysis means 152, for example, after obtaining the frequency amplitude characteristic by FFT (Fast Fourier Transform), the signal level is obtained as a signal level for each predetermined band. There is a way to calculate power. Further, for example, there is a method of measuring the power of the output signal as a signal level after passing through a band pass filter having the predetermined band as a pass band.

  The band-specific masking amount detection means 153 detects the masking amount for each predetermined band based on the analysis information analyzed by the acoustic signal analysis means 151 and the harmonic signal analysis means 152. Note that the masking amount of the predetermined band is detected based on each analysis information analyzed in the same band as the predetermined band. The detected information is input to the correction means 16. As a method for detecting the masking amount, two typical methods are known. As a first detection method, there is a method for detecting a masking amount due to band noise and pure tone. In this case, it is assumed that the acoustic signal is band noise and the harmonic signal is a pure tone. As a second detection method, there is a method of detecting a masking amount between pure tones. In this case, both the acoustic signal and the harmonic signal are assumed to be pure tones. In this way, the masking amount is detected by the above detection methods. The masking amount may be detected using a detection method other than the above detection method.

  Based on the masking amount for each predetermined band detected by the masking amount detection unit 15, the correction unit 16 adjusts the frequency amplitude characteristics of the composite signal input from the gain adjustment unit 14 so that the gain of each harmonic signal increases. to correct. Note that the synthesized signal is a signal obtained by adding and synthesizing each overtone signal as described above. Accordingly, the gain of each harmonic signal can be individually corrected by correcting the frequency amplitude characteristic of the synthesized signal. As shown in FIG. 3, the correction unit 16 includes a correction amount setting unit 161 and a frequency amplitude characteristic correction unit 162. FIG. 3 is a block diagram showing an example of the internal configuration of the correction means 16.

  In FIG. 3, the correction amount setting unit 161 sets the correction amount so as to suppress the masking phenomenon due to the acoustic signal based on the detected masking amount for each predetermined band. The correction amount is set for each predetermined band. Here, an example of setting the correction amount will be described. For example, it is assumed that the masking amount is detected as “+6 dB” in a predetermined band “100 Hz to 200 Hz”. The masking amount “+6 dB” means that the acoustic signal masks the harmonic signal “+6 dB” in the reproduction stage. Therefore, in order to suppress the masking phenomenon due to the acoustic signal, the gain of the harmonic signal in the predetermined band “100 Hz to 200 Hz” may be amplified by “+6 dB”, for example. That is, the correction amount may be set to “+6 dB” in the predetermined band. As described above, the correction amount setting means 161 sets the correction amount for each predetermined band based on the masking amount for each predetermined band. In the above numerical example, the masking amount is set to be completely canceled as the correction amount “+6 dB” with respect to the masking amount “+6 dB”, but the present invention is not limited to this. Even if the correction amount is set to a value that does not completely cancel the masking amount, there is a certain effect.

  The frequency amplitude characteristic correcting unit 162 corrects the frequency amplitude characteristic of the synthesized signal of each harmonic signal input from the harmonic signal generating unit 13 according to the correction amount for each predetermined band set by the correction amount setting unit 161. Here, an example of a method for correcting the frequency-amplitude characteristic of the synthesized signal will be described. The synthesized signal is input from the harmonic signal generating unit 13 to the frequency amplitude characteristic correcting unit 162. The input composite signal is cut out with a predetermined time width by FFT and converted into a frequency amplitude characteristic. The frequency amplitude characteristic of the synthesized signal is weighted according to the correction amount for each predetermined band. That is, each overtone signal is amplified with a gain based on the corresponding masking amount. The weighted synthesized signal is converted again into a time characteristic by inverse FFT. As described above, the frequency amplitude characteristic correcting unit 162 corrects the frequency amplitude characteristic of the synthesized signal according to the correction amount for each predetermined band. Note that a method other than the above may be used as a method of correcting the frequency amplitude characteristic. For example, the composite signal is input to a multi-stage IIR filter and FIR filter. There is also a method of correcting the frequency amplitude characteristic of the synthesized signal by switching the filter coefficient in accordance with the set correction amount.

  The combined signal corrected by the correcting unit 16 is input to the other input unit of the adder 11. The adder 11 adds and synthesizes the synthesized signal and the acoustic signal input from the input terminal 10 and outputs the resultant signal to the output terminal 17. The signal output from the output terminal 17 is finally reproduced by a speaker.

  Next, with reference to the flowchart shown in FIG. 4, the operation | movement flow of the acoustic signal processing apparatus 1 which concerns on this embodiment is demonstrated. FIG. 4 is a flowchart showing an operation flow of the acoustic signal processing apparatus 1 according to the present embodiment.

  First, an acoustic signal is input to the input terminal 10 (step S1). The fundamental wave extraction filter 12 extracts a fundamental wave signal from the input acoustic signal (step S2). Hereinafter, for explanation of the processing in steps S3 to S7, for example, one wave of a signal having a fundamental frequency among all the signals that have passed through the filter of the fundamental wave extraction filter 12 is referred to as a fundamental wave signal. The harmonic overtone generating means 13 generates the second to nth overtone signals of the fundamental wave signal extracted in step S2 (step S3). The gain adjusting means 14 adjusts the gain of each harmonic sound signal generated in step S3, and then synthesizes it (step S4). The masking amount detection means 15 detects the masking amount for each predetermined band based on the input acoustic signal input in step S1 and the synthesized signal synthesized in step S4 (step S5). Based on the masking amount detected in step S5, the correction unit 16 sets a correction amount for each predetermined band so as to suppress the masking phenomenon caused by the input acoustic signal (step S6). Then, according to the correction amount set in step S6, the frequency amplitude characteristic in the synthesized signal of each harmonic signal is corrected (step S7). In step S8 after step S7, if the processes in steps S3 to S7 are completed for all the fundamental wave signals extracted in step S2, the process shown in FIG. 4 is terminated. If all the fundamental wave signals are not processed in steps S3 to S7, the process proceeds to steps S3 to S7. This is the end of the description of the processing flow of the acoustic signal processing device 1.

  Here, the processing of steps S5 to S7 will be described more specifically with a numerical example. It is assumed that the masking amount detected in step S5 is “+6 dB” in the predetermined band “100 Hz to 200 Hz”. In step S6, it is assumed that the correction amount in the predetermined band is set to “+6 dB”. Hereinafter, a second overtone signal having a frequency of “120 Hz” is considered. The frequency “120 Hz” of the second overtone signal is a frequency within a predetermined band “100 Hz to 200 Hz”. Therefore, the second overtone signal is masked by “+6 dB” by the acoustic signal. However, in step S6, the correction amount of the predetermined band is set to “+6 dB”. Therefore, in step S7, the frequency amplitude characteristic of the synthesized signal is corrected, and the gain of the second overtone signal is amplified by the correction amount “+6 dB”. As a result, even if the “+6 dB” is masked by the acoustic signal, it is possible to avoid the second harmonic signal from becoming difficult to hear due to hearing. That is, the masking phenomenon due to the acoustic signal can be suppressed.

  As described above, in this embodiment, the masking amount for each predetermined band is detected using the acoustic signal as a masker and the overtone signal as a mask. Then, based on the masking amount, the frequency amplitude characteristic of the synthesized signal is corrected. Thereby, the masking phenomenon by the reproduction | regeneration sound of an acoustic signal can be suppressed. As a result, it is possible to realize reproduction in which there is no variation in the low-frequency feeling obtained by adding overtones. Further, in the present embodiment, by correcting the frequency amplitude characteristic of the synthesized signal, the gain of each overtone signal included in the synthesized signal can be individually corrected. That is, the correction corresponding to the masking amount changing in frequency can be performed. As a result, it is possible to realize reproduction with a more natural bass feeling variation.

  In the above-described harmonic overtone generation unit 13, harmonics are generated using the zero cross method, but other methods may be used. Those methods can be applied to the present invention by appropriate modifications.

(Second Embodiment)
Hereinafter, the acoustic signal processing device according to the second embodiment will be described with reference to FIG. FIG. 5 is a block diagram illustrating a configuration of the acoustic signal processing device 2 according to the second embodiment. As described above, the masking phenomenon has a qualitative property that the larger the masker level, the larger the masking amount. In the second embodiment, using this qualitative property, the level of the acoustic signal that is a masker is equivalently treated as a masking amount, and each harmonic signal is corrected. That is, the second embodiment is greatly different from the first embodiment in that the level of the acoustic signal is detected as an equivalent masking amount. Hereinafter, different points will be mainly described.

  In FIG. 5, the acoustic signal processing apparatus 2 includes an input terminal 10, an adder 11, a fundamental wave extraction filter 12, a harmonic overtone generation unit 13, a gain adjustment unit 14, a masking amount detection unit 25, a correction unit 26, and an output terminal 17. Prepare. In FIG. 5, the input terminal 10, the adder 11, the fundamental wave extraction filter 12, the harmonic overtone generation unit 13, the gain adjustment unit 14, and the output terminal 17 are the same as those in the first embodiment described above, and thus are the same. The description will be omitted.

  In FIG. 5, the acoustic signal input to the input terminal 10 is input to the masking amount detection means 25. The masking amount detection means 25 detects an equivalent masking amount, that is, the level of the acoustic signal based on the acoustic signal. As shown in FIG. 6, the masking amount detection means 25 includes an absolute value conversion circuit 251, a peak hold circuit 252, a time constant circuit 253, and a level detection circuit 254. FIG. 6 is a block diagram showing an example of the internal configuration of the masking amount detection means 25.

  In FIG. 6, the absolute value conversion circuit 251 is constituted by a full-wave rectification circuit, for example. Then, the level of the input acoustic signal is converted to an absolute value. The peak hold circuit 252 detects the peak of the acoustic signal level converted into an absolute value. The time constant circuit 253 is composed of, for example, a CR circuit. Then, the peak of the acoustic signal level detected by the peak hold circuit 252 is smoothed. The level detection circuit 254 detects the level of the acoustic signal smoothed by the time constant circuit 253. Thus, in this embodiment, the level of the acoustic signal is detected as an equivalent masking amount.

  In FIG. 5, the correction means 26 is configured by an equalizer having a predetermined correction curve. The correction means 26 receives the level information of the acoustic signal detected by the masking amount detection means 25 as input. The correction unit 26 performs correction for amplifying the gain of the combined signal input from the gain adjustment unit 14 according to a predetermined correction curve. This gain for amplification is a gain determined by a predetermined correction curve and an acoustic signal level. In the first embodiment, the frequency amplitude characteristic of the synthesized signal is corrected. However, in the present embodiment, the gain of the synthesized signal itself is corrected. That is, each overtone signal included in the synthesized signal is corrected with a uniform gain. An example of the correction curve is shown in FIG. FIG. 7 is a diagram illustrating an example of the correction curve. In FIG. 7, the solid line indicates a correction curve (the gain curve of the combined signal after correction), and the dotted line indicates the gain of the combined signal before correction. According to the correction curve shown in FIG. 7, the gain of the synthesized signal increases as the acoustic signal level increases. The equalizer having such a correction curve increases the gain of the synthesized signal when the acoustic signal level is high. Accordingly, it becomes possible to perform correction in accordance with the qualitative property that the masking amount is larger as the masker level is larger, and the acoustic signal level can be equivalently handled as the masking amount.

  As described above, in this embodiment, the acoustic signal level is corrected using an equivalent masking amount. As a result, the present embodiment does not require a complicated circuit for detecting the actual masking amount, as compared with the first embodiment. Therefore, the acoustic signal processing device according to the present embodiment can be realized with a simpler and smaller configuration.

  The masking amount detection means 25 described above may further include a filter 250 as shown in FIG. FIG. 8 is a block diagram showing an example of the internal configuration of the masking amount detection means 25 further provided with a filter 250. The filter 250 is composed of, for example, a band pass filter. Then, the filter 250 selectively passes a predetermined frequency band out of the entire frequency band of the acoustic signal. In the masking amount detection means 25, the acoustic signal level in the predetermined frequency band selected by the filter 250 is detected. Thereby, weighting of a predetermined frequency band can be performed for correction of the composite signal. For example, in the masking phenomenon, as described above, there is a property that the masking amount is larger as the frequency of the masker and the maskee is closer. Therefore, for example, the filter 250 may be set to pass an acoustic signal in a frequency band including each generated harmonic signal. Thus, more effective correction can be performed in accordance with the qualitative property. In addition, a signal including an audio signal (for example, music or a movie) generally has an audio signal level higher than that of other signals. That is, the masking amount by the audio signal is often large. Therefore, the filter 250 may be set to pass an acoustic signal in a frequency band (for example, a frequency band of 200 Hz to 4 kHz) including the audio signal. Thereby, more effective correction can be performed on a signal including an audio signal. In this way, by weighting the predetermined frequency band, even if the actual masking amount changes in frequency, it is possible to select and correct a frequency band having a large masking amount. As a result, the masking phenomenon can be suppressed more efficiently.

  Further, the correction means 26 described above may be provided between the output of the fundamental wave extraction filter 12 and the input of the harmonic overtone generation means 13 as shown in FIG. FIG. 9 is a block diagram illustrating another configuration example of the acoustic signal processing device 2 according to the second embodiment. At this time, the correction means 26 corrects the gain of the fundamental wave signal by a correction method similar to that of the above-described composite signal. The correcting means 26 corrects the gain of the composite signal at the stage of the fundamental wave signal. Further, although the correction means 26 described above has the correction curve shown in FIG. 7, it may have the correction curves shown in FIGS. 10 and 11. 10 and 11 are diagrams showing another example of the correction curve. In the correction curve shown in FIG. 10, the level of P1 is a threshold level (threshold) at which the apparatus can be stably operated. That is, if the correction curve shown in FIG. 10 is used, the gain of the composite signal is corrected above the threshold level. Thereby, the correction operation can be performed more stably. In addition, the correction curve shown in FIG. 11 is constant without increasing the amount of gain to be corrected above the level of P2. Thus, by providing the upper limit (P2) to the gain amount to be corrected, it is possible to prevent the level of the synthesized signal, that is, each harmonic signal from becoming excessive.

  The present invention relates to an acoustic signal processing apparatus and method thereof, and is also applied to a pseudo bass reproduction apparatus, an audio device, and the like that can improve bass feeling by adding a harmonic signal to the acoustic signal.

The block diagram which shows the structure of the acoustic signal processing apparatus 1 which concerns on 1st Embodiment. The block diagram which shows the example of an internal structure of the masking amount detection means 15 Block diagram showing an example of the internal configuration of the correction means 16 The flowchart which shows the flow of operation | movement of the acoustic signal processing apparatus 1 which concerns on this embodiment. The block diagram which shows an example of a structure of the acoustic signal processing apparatus 2 which concerns on 2nd Embodiment. The block diagram which shows the example of an internal structure of the masking amount detection means 25 Diagram showing an example of a correction curve The block diagram which shows the internal structural example of the masking amount detection means 25 further provided with the filter 250 The block diagram which shows the other structural example of the acoustic signal processing apparatus 2 which concerns on 2nd Embodiment. Figure showing another example of correction curve Figure showing another example of correction curve The block diagram which shows the structure of the conventional acoustic signal processing apparatus 9 The figure which shows the method of generating the harmonic signal by the zero cross method typically

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Acoustic signal processing apparatus 10 Input terminal 11, 144 Adder 12 Fundamental wave extraction filter 13 Overtone production | generation means 14 Gain adjustment means 15, 25 Masking amount detection means 16, 26 Correction means 17 Output terminal 131 2nd overtone production means 132 3rd harmonic generation means 133 nth harmonic generation means 141 2nd harmonic gain adjustment means 142 3rd harmonic gain adjustment means 143 nth harmonic gain adjustment means 151 Acoustic signal analysis means 152 Overtone signal analysis means 153 Bandwidth masking amount detection means 161 Correction amount setting means 162 Frequency amplitude characteristic correction means 250 Filter 251 Absolute value conversion circuit 252 Peak hold circuit 253 Time constant circuit 254 Level detection circuit

Claims (8)

Extracting means for extracting a fundamental wave signal from the input acoustic signal;
A supply means for generating a plurality of types of harmonic signals of the fundamental wave signal extracted by the extraction means, and supplying a signal obtained by synthesizing the plurality of types of harmonic signals;
Detecting means for detecting a masking amount by which the input acoustic signal masks each harmonic signal;
Correction means for correcting the synthesized signal so that the gain of each harmonic signal included in the synthesized signal is increased according to the detected masking amount;
An acoustic signal processing apparatus comprising: an adding unit that adds the combined signal corrected by the correcting unit and the input acoustic signal. The detection means detects the masking amount for each predetermined frequency band based on the synthesized signal and the input acoustic signal supplied by the supply means,
The correction means corrects the gain of the harmonic signal in accordance with a masking amount detected for a predetermined frequency band including the frequency of the harmonic signal for each harmonic signal included in the synthesized signal. The acoustic signal processing device according to 1. The detection means detects the level of the input acoustic signal as the masking amount,
The correction means corrects the gain of the composite signal so that the gain of the composite signal increases as the level of the input acoustic signal detected by the detection means increases. Acoustic signal processing device.   The correction means corrects the gain of the synthesized signal so that the gain of the synthesized signal increases as the level of the input acoustic signal increases within a range where the level of the input acoustic signal is equal to or higher than a predetermined level. The acoustic signal processing device according to claim 3, wherein:   The correction means corrects the gain of the synthesized signal so that the gain of the synthesized signal increases as the level of the input acoustic signal increases within a range where the level of the input acoustic signal is equal to or lower than a predetermined level. The acoustic signal processing device according to claim 3, wherein:   The acoustic signal processing apparatus according to claim 3, wherein the detection unit detects a level of an input acoustic signal in a predetermined frequency band.   The acoustic signal processing apparatus according to claim 6, wherein the predetermined frequency band is a frequency band including a frequency of each overtone signal. An extraction step of extracting a fundamental signal from the input acoustic signal;
Supplying a plurality of types of overtone signals of the fundamental wave signal extracted in the extraction step, and supplying a signal in which the plurality of types of overtone signals are combined; and
A detection step of detecting a masking amount by which the input acoustic signal masks each harmonic signal;
A correction step of correcting the synthesized signal so that the gain of each harmonic signal included in the synthesized signal is increased according to the detected masking amount;
An acoustic signal processing method including an adding step of adding the combined signal corrected in the correcting step and the input acoustic signal.

Images