JP2015195432A - Audio signal processing device, control method and program for audio signal processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an audio signal processing device, control method and program for an audio signal processing device, capable of efficiently adding harmonic sound only to musical instrument sound which does not contain harmonic sound such as bass drum or the like.SOLUTION: An audio signal processing device includes: an extraction part for extracting a low frequency component of an inputted audio signal; an attack period detection part 11 for detecting an attack period of an extracted audio signal; a resonance sound emphasis component generation part 15 for generating integer-order harmonic sound of the extracted audio signal; and adding parts 16, 17, and 18 for adding generated integer-order harmonic sound to an inputted audio signal, during a period based on a detection signal of an attack period.

Description

  The present invention relates to an audio signal processing device that performs enhancement processing on an input audio signal, a control method for the audio signal processing device, and a program.

Conventionally, as this type of audio signal processing device (heavy bass correction system), a low-pass filter that extracts the low frequency band component of the input audio signal, and the extracted low frequency band component to the original 2 ⁿ times frequency band 2. Description of the Related Art A harmonic circuit unit that shifts to produce 2 ⁿ harmonics and an adder that adds an output signal of the harmonic circuit unit to an audio signal input from a sound source are known (see Patent Document 1). ). That is, in this audio signal processing device, the harmonic circuit unit generates even-order harmonics of the extracted low frequency band components, and adds the generated even-order harmonics to the original sound. As a result, a missing fundamental effect can be realized and the listener can perceive a low-frequency sound that cannot be reproduced by the speaker.

JP 2001-245399 A

  However, in the conventional configuration, overtones are uniformly generated and added to the entire audio signal of the low frequency band component. For this reason, for instrument sounds that originally contain overtones, such as bass sounds, harmonics are generated / added in the same way as instrument sounds that do not contain overtones, such as bass drum sounds. As a result, there has arisen a problem that the tone color of the instrument sound is changed or the distorted feeling is generated with respect to the instrument sound that originally contains overtones.

  The present invention provides an audio signal processing device capable of effectively adding overtones only to specific musical instrument sounds that do not include overtones, such as bass drum sounds, and a control method and program for the audio signal processing device. Is an issue.

  An audio signal processing device according to the present invention includes an extraction unit that extracts a low frequency band component of an input audio signal, an attack detection unit that detects an attack position of the extracted audio signal, and an integer overtone of the extracted audio signal. A harmonic overtone generation unit to be generated, and an addition unit that adds the generated integer order overtone to the input audio signal during a period based on the detected attack position. The “attack position” here refers to the time position of the attack sound, and the “attack sound” refers to a sudden and shocking sound at the beginning of the instrument. The period based on the attack position is preferably a period of about 100 ms to 200 ms from the attack end position. That is, the duration of the period based on the attack position is preferably set in accordance with the assumed duration of the bass drum sound.

  An audio signal processing device control method according to the present invention includes an extraction step of extracting a low frequency band component of an input audio signal, an attack detection step of detecting an attack position of the extracted audio signal, and an integer of the extracted audio signal A harmonic overtone generating step for generating the next overtone, and an adding step for adding the generated integer overtone to the input audio signal during a period based on the detected attack position.

  In the audio signal processing device, the adding unit amplifies the integer-order harmonics generated by the harmonic generating unit according to the signal level of the audio signal extracted by the extracting unit, and then adds the amplified harmonic signal to the input audio signal Is preferred.

  The attack detection unit further includes an amplifying unit that detects an attack period composed of an attack start position and an attack end position, and amplifies medium and high frequency band components of the input audio signal during the detected attack period. preferable. The “attack period” here is a so-called attack time.

  In this case, it is preferable that the adding unit adds the generated integer order overtone to the input audio signal in a period starting from the attack end position of the attack period detected by the attack detecting unit.

  On the other hand, the harmonic generation unit may be configured to generate only odd-order overtones among odd-order overtones and even-order overtones.

  A program according to the present invention causes a computer to execute each step in the above-described method for controlling an audio signal processing device.

It is a block diagram of the reproduction | regeneration system which concerns on one Embodiment of this invention. It is the circuit block diagram which showed the audio | voice signal processing part. It is the circuit block diagram which showed the attack period detection part and the resonance period detection part. FIG. 4 is a waveform diagram in which a bass drum audio signal, an attack period detection signal, and a resonance period detection signal are superimposed. It is the flowchart which showed the process of the resonance period detection circuit. FIG. 3 is a circuit configuration diagram showing an attack sound enhancement component generation unit, an attack sound enhancement component amplifier, a resonance sound enhancement component generation unit, and a resonance sound enhancement component amplifier. (A) is the wave form diagram which showed the audio | voice signal input into the audio | voice signal processing part. (B) is a waveform diagram showing an attack sound enhancement component output from the attack sound enhancement component amplifier. (C) is a waveform diagram showing the resonance emphasis component output from the resonance emphasis component amplifier. (D) is a waveform diagram showing an audio signal after enhancement.

  Hereinafter, an audio signal processing device, a control method of the audio signal processing device, and a program according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the present embodiment, an audio signal processing unit to which the audio signal processing device of the present invention is applied, and a playback system including the same are exemplified. In particular, this playback system effectively enhances the bass drum sound by adding an integer overtone to the resonance part of the bass drum sound, and realizes a missing fundamental effect for the resonance part. .

  As shown in FIG. 1, the reproduction system SY includes a sound source 1, an audio signal processing unit 2, a power amplifier 3, and a speaker 4.

  The sound source 1 supplies an audio signal to the audio signal processing unit 2, and includes various storage media (CD, SD card, USB memory, etc.), various electronic devices (audio player, personal computer, tablet terminal, mobile phone). Etc.) and various servers (servers on the Web, servers on the LAN network, etc.).

  The audio signal processing unit 2 performs various audio processes on the audio signal supplied from the sound source 1. In particular, in the present embodiment, by performing bass drum sound enhancement processing, a music reproduction with a beat is realized. The audio signal processing unit 2 may be realized by software such as a DSP (Digital Signal Processor) or an analog device.

  The power amplifier 3 amplifies the audio signal processed by the audio signal processing unit 2 and drives the speaker 4. The speaker 4 outputs an audio signal by driving the power amplifier 3. The power amplifier 3 may be built in the speaker 4. Further, headphones or earphones may be used instead of the speakers 4.

  In addition, the playback system SY of this embodiment is suitable for DJ equipment such as a DJ speaker, DJ mixer, DJ player, etc., where bass drum sound is highly emphasized, but also for other playback systems (minicomponents, headphone amplifiers, etc.). Applicable.

  Next, the configuration of the audio signal processing unit 2 will be described with reference to FIGS. The audio signal processing unit 2 has an attack sound enhancement function for enhancing the attack sound of the bass drum sound, and sounds (decay sound, sustain sound and release sound) other than the bass drum attack sound (hereinafter referred to as resonance sounds). And a resonance sound enhancement function to emphasize. The “attack sound” here refers to the sound at the moment when the bass drum mallet hits the striking surface. The audio signal processing unit 2 emphasizes the middle and high frequency band components in the attack period in which the attack sound is sounded, and adds an integer order overtone in the resonance sound period in which the resonance sound is sounded. These enhance the bass drum sound well. The resonance period is a period starting from the end position of the attack period.

  FIG. 2 is a circuit configuration diagram of the audio signal processing unit 2. As shown in the figure, the audio signal processing unit 2 includes an attack period detection unit (attack detection unit) 11, a resonance sound period detection unit 12, an attack sound enhancement component generation unit 13, and an attack sound enhancement component amplifier 14. , A resonance enhancement component generation unit (overtone generation unit) 15, a resonance enhancement component amplifier 16, a first adder 17, and a second adder 18. In the audio signal processing unit 2, the input audio signal is branched into four systems. A first adder 17 is disposed in the first system. In the second system, an attack sound enhancement component generation unit 13, an attack sound enhancement component amplifier 14, and a second adder 18 are disposed, and an output terminal is connected to the first adder 17. In the third system, a resonance enhancement component generation unit 15 and a resonance enhancement component amplifier 16 are disposed, and an output terminal is connected to the second adder 18. In the fourth system, an attack period detection unit 11 and a resonance period detection unit 12 are arranged. The output end of the attack period detection unit 11 is supplied to the attack sound enhancement component amplifier 14 and the output of the resonance period detection unit 12 is output. The ends are respectively connected to the resonance emphasis component amplifier 16. As will be described in detail later, the audio signal processing unit 2 uses the first adder 17 and the second adder 18 to generate the attack sound enhancement component and the resonance sound enhancement component generated in the second system and the third system. By adding to the audio signal (original sound) of the system, enhancement processing is performed on the audio signal input to the audio signal processing unit 2.

  Next, the attack period detecting unit 11 and the resonance period detecting unit 12 will be described with reference to FIG. As shown in FIG. 3, the attack period detection unit 11 includes a first low-pass filter (hereinafter referred to as LPF) 21, a first absolute value calculation circuit (hereinafter referred to as ABS) 22, a second LPF 23 having a time constant 1, and a time constant. 2, a third LPF 24, a subtractor 25, a limiter 26, and an amplitude envelope amplifier 27.

  The attack period detection unit 11 first extracts a low frequency band component of the input audio signal by the first LPF 21 (cutoff frequency 240 Hz) (extraction step). The audio signal (low frequency band component) extracted by the first LPF 21 takes an absolute value by the first ABS 22 and applies two types of LPFs 23 and 24 having different time constants, thereby applying two types of amplitude envelopes for the audio signal. Is generated.

  The condition is that the time constant 1 of the second LPF 23 is smaller than the time constant 2 of the third LPF 24. In this case, the amplitude envelope of the second LPF 23 having a small time constant rises earlier than the amplitude envelope on the side of the third LPF 24 having a large time constant at a sharp rising portion such as the moment when the bass drum sound is produced. Thereafter, as the lingering sound of the bass drum sound becomes smaller, all amplitude envelopes turn downward. At this falling portion, the second LPF 23 having a smaller time constant than the amplitude envelope of the third LPF 24 having a larger time constant. The amplitude envelope becomes smaller sooner. As described above, a period in which the amplitude envelope of the second LPF 23 is larger than the amplitude envelope of the third LPF 24 occurs due to the difference in time constant.

  As shown in FIG. 3, when two types of envelopes are generated by the second LPF 23 and the third LPF 24, the subtracter 25 subtracts the amplitude envelope of the third LPF 24 from the amplitude envelope of the second LPF 23 (decibel conversion), and the limiter 26 When the output value x1 of the subtractor 25 becomes 0 or less, it is limited to 0. Thus, the attack start position and the attack end position (attack period) are detected (attack detection step). That is, as described above, a period in which the amplitude envelope of the second LPF 23 is larger than the amplitude envelope of the third LPF 24 occurs, but the time position at which the output value of the second LPF 23 is equal to or greater than the output value of the third LPF 24 is the attack start position (attack). The time position at which the output value of the second LPF 23 becomes less than the output value of the third LPF 24 thereafter corresponds to the attack end position (the end position of the attack sound). Therefore, by subtracting the amplitude envelope of the third LPF 24 from the amplitude envelope of the second LPF 23 and limiting 0 or less to 0, a detection signal indicating each position is generated. That is, it is possible to obtain a detection signal that detects the attack start position and the attack end position, that is, a detection signal for the attack period. The detection signal for the attack period generated here is denoted by reference numeral L1 in FIG. FIG. 4 is a waveform diagram in which a bass drum sound signal, an attack period detection signal, and a later-described resonance sound period detection signal are superimposed. The detection signal for the attack period generated here is output to the resonance period detector 12 and also to the attack sound enhancement component amplifier 14.

  On the other hand, the amplitude envelope generated on the second LPF 23 side is attenuated by 0.5 times by the amplitude envelope amplifier 27 and then output to the resonance period detector 12. As described above, the attack period detection unit 11 outputs the amplitude envelope (x2) of the low frequency band component and the detection signal (x3) of the attack period to the resonance period detection unit 12.

  The resonance period detection unit 12 includes a resonance period detection circuit 31 and a fourth LPF 32 having a time constant of 3. FIG. 5 is a flowchart showing processing in the resonance period detection circuit 31. As shown in FIG. 5, in the processing of the resonance period detection circuit 31, the amplitude envelope (x2) of the low frequency band component obtained from the attack period detection unit 11 and the detection signal (x3) of the attack period are used as input values. . For these inputs, first, it is determined whether or not the detection signal of the attack period is not 0 (S1). If the attack period detection signal is not 0 (S1: Yes), the time counter is reset (S2). That is, the time counter is continuously reset within the attack period. On the other hand, when the attack period detection signal is 0 (S1: No), the time counter is incremented (counted up) (S3). That is, when the attack period ends and the value of the detection signal becomes 0, time counting is performed. Therefore, the value of this time counter indicates the elapsed time from the end of the previous attack period.

  Next, it is determined whether or not the value of the time counter is 0 (S4). As described above, since the time counter is continuously reset within the attack period, it is determined that the value of the time counter is 0 within the attack period. When it is determined that the value of the time counter is 0 (S4: Yes), the output value x4 of the resonance period detection circuit 31 is set to 0 (S5), and the process of the resonance period detection circuit 31 is terminated.

  On the other hand, when it is determined that the value of the time counter is not 0, it is determined whether or not the value of the time counter exceeds a limit value (for example, 1 msec) (S6). When the value of the time counter exceeds the limit value (S6: Yes), that is, when a predetermined time or more has elapsed since the end of the attack period, the output value x4 of the resonance period detection circuit 31 is set to 0. (S7), the process of the resonance period detection circuit 31 is terminated.

  On the other hand, when the value of the time counter does not exceed the limit value (S6: No), the input amplitude envelope value x2 is set to the output value x4 of the resonance period detection circuit 31 (S8) to detect the resonance period. The process of the circuit 31 is finished.

  By such processing, the input amplitude envelope is limited to a signal after the attack period, so that the signal indicates the attack end position, that is, the start position of the resonance. On the other hand, the time position where the value is 0 in the amplitude envelope corresponds to the end position of the resonance sound. Therefore, the resonance sound period detection circuit 31 limits the amplitude envelope to the signal after the attack period, thereby generating a detection signal indicating the start position and the end position of the resonance sound. That is, it is possible to obtain a detection signal that detects the start position and end position of the resonance, that is, a detection signal for the resonance period. The detection signal of the resonance period generated here is indicated by a symbol L2 in FIG. The amplitude envelope input here (the amplitude envelope generated on the second LPF 23 side) is generated such that the duration of the resonance period is about 100 ms to 200 ms. That is, the duration of this resonance period is adjusted in accordance with the duration of the resonance in the assumed bass drum sound.

  As shown in FIG. 3, when a resonance signal detection signal is generated by the resonance signal period detection circuit 31, a fourth LPF 32 having a time constant of 3 is applied to the signal. Thereafter, the detection signal is output to the resonance enhancement component amplifier 16.

  Next, the attack sound enhancement component generation unit 13, the attack sound enhancement component amplifier 14, the resonance enhancement component generation unit 15, and the resonance enhancement component amplifier 16 will be described with reference to FIG. As shown in FIG. 6, the attack sound enhancement component generation unit 13 includes a fifth LPF 41 and a first high-pass filter (hereinafter HPF) 42.

  The attack sound enhancement component generation unit 13 generates an attack sound enhancement component by applying the fifth LPF 41 and the first HPF 42 to the input sound signal and extracting the middle and high frequency band components of the sound signal. That is, the extracted middle and high frequency band components are used as attack sound enhancement components.

  On the other hand, the attack sound enhancement component amplifier 14 amplifies the attack sound enhancement component generated by the attack sound enhancement component generation unit 13. The attack sound enhancement component amplifier 14 is a variable amplifier, and amplifies the attack sound enhancement component at the signal level of the detection signal of the attack period input from the attack period detection unit 11. As a result, the attack sound enhancement component is limited to signals within the attack period. Further, since the detection signal in the attack period is generated by the difference between the two types of amplitude envelopes, the attack sound enhancement component is amplified according to the level of the difference. FIG. 7B shows the attack sound enhancement component limited and amplified by the signal within the attack period. The attack sound enhancement component is output to the first adder 17 via the second adder 18. As a result, the attack sound enhancement component is added to the audio signal (original sound) of the first system.

  The resonance enhancement component generation unit 15 includes a sixth LPF 51, an even-order overtone generation unit 52, an odd-order overtone generation unit 53, a harmonic overtone adder 54, a second HPF 55, and a seventh LPF 56.

  The resonance enhancement component generation unit 15 extracts the low frequency band component of the input audio signal by the sixth LPF 51 (cutoff frequency 100 Hz). Then, the even-order overtone generation unit 52 and the odd-order overtone generation unit 53 generate even-order overtones and odd-order overtones of the extracted audio signal, respectively.

  The even-order overtone generating unit 52 is configured by the second ABS 61. In the even-order overtone generation unit 52, the second ABS 61 converts the extracted audio signal into an absolute value, thereby generating an even-order overtone of the audio signal (overtone generation step).

The odd-order overtone generating unit 53 includes a third ABS 62, an eighth LPF 63 having a time constant of 4, a first variable amplifier 64, a slice circuit 65, and a second variable amplifier 66. The odd-order overtone generation unit 53 first takes the absolute value of the extracted audio signal by the third ABS 62 and applies it to the eighth LPF 63 with the time constant 4 to generate the amplitude envelope x5 of the extracted audio signal. The first variable amplifier 64 multiplies the extracted audio signal by (1 / x5 × 1.1) to normalize the extracted audio signal and multiply it by 1.1. Thereafter, the slicing circuit 65 performs limiting at the threshold ± 1 level to generate odd harmonics.
Further, the second variable amplifier 66 multiplies (x5 / 1.1) to restore the level multiplied by 1.1. In this way, the extracted audio signal is normalized, multiplied by 1.1, sliced, and multiplied by the reciprocal of the 1.1-fold coefficient to generate odd harmonics of the audio signal (harmonic generation step).

  When the even-order overtone generation unit 52 and the odd-order overtone generation unit 53 generate even-order overtones and odd-order overtones, these are added together by the overtone adder 54, and the combined overtones are added to the second HPF 55 (cut-on frequency 10 Hz) and By applying 7LPF 56 (cutoff frequency 700 Hz), a resonance emphasis component is generated.

  On the other hand, the resonance enhancement component amplifier 16 amplifies the resonance enhancement component generated by the resonance enhancement component generator 15. The resonance enhancement component amplifier 16 is a variable amplifier, and amplifies the resonance enhancement component at the signal level of the detection signal of the resonance period input from the resonance period detector 12. As a result, the resonance enhancement component is limited to signals within the resonance period. In addition, the resonance enhancement component is amplified according to the level of the detection signal during the resonance period. FIG. 7C shows a resonance enhancement component limited and amplified by a signal within the resonance period. The resonance enhancement component is output to the second adder 18 and added to the first system audio signal (original sound) together with the attack enhancement component by the first adder 17 (addition step).

  The attack sound enhancement component and the resonance sound enhancement component are added to the sound signal (original sound) of the first system, so that the sound signal input to the sound signal processing unit 2 is added to the sound signal processing unit 2 as shown in FIG. In the bass drum sound attack period, the middle and high frequency band components are amplified, and in the resonance sound period of the bass drum sound, an integer overtone is added (added). Thus, the enhancement process is performed on the audio signal input to the audio signal processing unit 2.

  In addition, the “extraction unit” described in the claims includes the first LPF 21 and the sixth LPF 51. In addition, the “adding unit” described in the claims includes a resonance enhancement component amplifying unit 16, a first adder 17, and a second adder 18. Further, the “amplifying unit” described in the claims includes an attack sound enhancement component generation unit 13, an attack sound enhancement component amplification unit 14, a first adder 17, and a second adder 18.

  According to the configuration as described above, a specific instrument that does not include overtones such as bass drum sounds by detecting an attack period and adding an integer overtone in a period (resonance period) based on the detected attack period. Overtones can be effectively added to only the sound. In other words, the duration of the overtone addition period can be set to match the bass drum sound with a relatively short duration. The emphasis effect can be maintained. Therefore, it is possible to suppress changing the tone color of the musical instrument having a harmonic structure from the base or the like, or it is possible to suppress the generation of a sense of distortion. On the other hand, the missing fundamental effect with respect to the bass drum sound can be realized with good quality, and the listener can recognize (perceive) the low sound below the output limit of the speaker 4. It is also possible to hear the overtones of the bass drum sound itself, making it easier to hear the rhythm. For example, even when using audio as a pacemaker during running in the city, the bass drum sound can be heard clearly without being distracted by ambient noise. In other words, the bass drum sound reproduction band can be expanded, and the S / N ratio can be improved by band.

  Further, the resonance tone enhancement component amplifier 16 amplifies the generated integer order harmonic in accordance with the amplitude envelope of the low frequency band component, thereby enhancing the bass drum sound with an enhancement amount that matches the intensity of the bass drum sound. be able to. Therefore, it is possible to prevent the bass drum sound from being emphasized at unnecessary timing.

  Furthermore, the bass drum sound can be effectively enhanced by amplifying the middle and high frequency band components of the input audio signal during the attack period by the attack sound enhancement function.

  In the above embodiment, both odd harmonics and even harmonics are generated and both are added (added), but only odd harmonics of odd harmonics and even harmonics are selected. It may be configured to generate and add (add). According to such a configuration, an edged bass drum sound can be output.

  Further, in the above-described embodiment, in the attack period, the medium and high frequency band components are amplified and emphasized, and in the resonance sound period, the harmonic sound is added and emphasized, but also in the attack period, A configuration in which emphasis is performed by adding overtones may be used. Further, the enhancement process may be performed by overlapping the amplification period of the medium and high frequency band components and the harmonic addition period.

  In addition, it is possible to provide each component and each process of playback system SY (especially audio | voice signal process part 2) shown in the said embodiment as a program. Further, the program can be provided by being stored in various storage media (CD-ROM, flash memory, etc.). That is, a program for realizing each component or each processing step (each step) of the reproduction system SY and a storage medium storing the program are also included in the scope of the right of the present invention.

  Moreover, in the said embodiment, although the case where the audio | voice signal processing part 2 ("audio | voice signal processing apparatus" in a claim) was applied to reproduction | regeneration system SY was illustrated, not only a reproduction | regeneration exclusive apparatus but a personal computer, a tablet terminal, You may apply to other electronic devices, such as a mobile telephone or a car navigation apparatus. Further, the audio signal processing unit 2 may be applied to cloud computing, such as realized by a server on the Web or a server on a LAN network. Other modifications can be made as appropriate without departing from the scope of the present invention.

  2: sound signal processing unit, 11: attack period detection unit, 13: attack sound enhancement component generation unit, 14: attack sound enhancement component amplifier, 15: resonance sound enhancement component generation unit, 16: resonance sound enhancement component amplifier, 17: First adder 18: Second adder 21: First LPF 22: First ABS 23: Second LPF 51: Sixth LPF

Claims (7)

An extraction unit for extracting a low frequency band component of the input audio signal;
An attack detection unit for detecting an attack position of the extracted audio signal;
A harmonic overtone generator that generates an integer overtone of the extracted audio signal;
An audio signal processing apparatus comprising: an adder that adds the generated integer overtone to the input audio signal during a period based on the detected attack position.   The adding unit amplifies the integer harmonics generated by the harmonic generating unit according to a signal level of the audio signal extracted by the extracting unit, and then adds the amplified harmonic signal to the input audio signal. The audio signal processing apparatus according to claim 1. The attack detection unit detects an attack period composed of an attack start position and an attack end position,
The audio signal processing apparatus according to claim 1, further comprising: an amplifying unit that amplifies medium and high frequency band components of the input audio signal during the detected attack period.   The adding unit adds the generated integer overtone to the input audio signal in a period having the attack end position of the attack period detected by the attack detection unit as a start position. The audio signal processing apparatus according to claim 3.   5. The audio signal processing apparatus according to claim 1, wherein the overtone generation unit generates only the odd-order overtones among odd-order overtones and even-order overtones. An extraction step of extracting a low frequency band component of the input audio signal;
An attack detection step of detecting an attack position of the extracted audio signal;
A harmonic overtone generating step for generating an integer overtone of the extracted audio signal;
A control method for an audio signal processing apparatus, comprising: an adding step of adding the generated integer overtone to the input audio signal during a period based on the detected attack position.   The program for making a computer perform each step in the control method of the audio | voice signal processing apparatus of Claim 6.

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