JP6205758B2 - SOUND DEVICE, SOUND DEVICE CONTROL METHOD AND PROGRAM - Google Patents

Description

  The present invention relates to an acoustic device that amplifies an input audio signal, a method for controlling the acoustic device, and a program.

  Conventionally, a boost circuit that amplifies an input signal (audio signal) includes a limit circuit that attenuates a high-level signal of the input signal and an expansion circuit that exponentially amplifies the output signal of the limit circuit. It is known (see, for example, Patent Document 1). In this boost circuit, since only the high-level signal is attenuated and then amplified exponentially by the expansion circuit, the input signal can be boosted without narrowing the dynamic range.

Japanese Patent No. 2977567

  However, in the boost circuit described above, since the input signal is amplified exponentially, when the input level is small, the amount of amplification becomes extremely small, and the volume feeling (low-pitched sound) is impaired. In other words, there arises a problem that the dynamic range becomes unnecessarily large.

  In view of the above problems, an object of the present invention is to provide an acoustic device, a method for controlling an acoustic device, and a program that can effectively amplify an audio signal without impairing the sense of volume.

The acoustic device of the present invention includes an input unit that inputs an audio signal, and a first amplification process and an audio signal based on a first amplification characteristic that linearly amplifies the audio signal with respect to the audio signal input from the input unit. An audio signal processing unit capable of executing a second amplification process based on a second amplification characteristic that is amplified in a curve; and an output unit that outputs an audio signal after the audio signal processing by the audio signal processing unit; The processing unit extracts a specific frequency band component from the audio signal input from the input unit, and for the specific frequency band component, one of the first amplification process and the second amplification process is performed according to the signal level. Amplification switching processing is performed in which the switching is selectively performed, and the amplification switching processing is not executed for frequency band components other than a specific frequency band component.
In the acoustic apparatus of the above SL, the audio signal processing unit, in a specific frequency band components, in accordance with the signal level of each unit time, with respect to the audio signals of each unit time, of the first amplification and the second amplification Either one is selectively performed.
In the above acoustic device, the audio signal processing unit includes a first amplifier having a first amplification characteristic and a second amplifier having a second amplification characteristic, and the first amplifier has a first frequency characteristic according to the signal level of a specific frequency band component. Amplifying processing is performed by one of the first amplifier and the second amplifier.
In the above acoustic apparatus, the audio signal processing unit includes one amplifier capable of switching between the first amplification process and the second amplification process, and performs the amplification process of the one amplifier according to the signal level of a specific frequency band component. It is characterized by switching.
In the above acoustic apparatus, the specific frequency band component is a low frequency band component.
In the above acoustic apparatus, the audio signal processing unit selects the first amplification process when the signal level of the low frequency band component is equal to or lower than the first threshold value, and selects the second amplification process when the signal level exceeds the first threshold value. It is characterized by doing.
In the above acoustic apparatus, when the signal level of the audio signal amplified by the audio signal processing unit exceeds the second threshold, the audio device further includes a dynamic range compression unit that adjusts the signal level to a constant level, and the output unit is a dynamic unit The audio signal adjusted by the range compression unit is output.
An audio device control method according to the present invention includes: an input step for inputting an audio signal; a first amplification process based on a first amplification characteristic for linearly amplifying the audio signal with respect to the audio signal input in the input step; An audio signal processing step capable of executing a second amplification process based on a second amplification characteristic for amplifying the audio signal in a curved manner, and an output step for outputting the audio signal processed by the audio signal processing step are executed. Then, the audio signal processing step extracts a specific frequency band component from the audio signal input in the input step, and for the specific frequency band component, a first amplification process and a second amplification process are performed according to the signal level. Amplification switching processing that selectively performs either of the above is executed, and amplification switching processing is not executed for frequency band components other than a specific frequency band component. And features.
A program according to the present invention causes a computer to execute each step in the above-described method for controlling an audio device.
The following configuration may be used.
The acoustic device of the present invention includes an input unit that inputs an audio signal, and the first amplification process and the first amplification characteristic based on the first amplification characteristic according to the signal level of the audio signal input from the input unit. An audio signal processing unit that selectively performs one of second amplification processes based on different second amplification characteristics, and an output unit that outputs an audio signal amplified by the audio signal processing unit And

  In the above acoustic apparatus, the first amplification characteristic linearly amplifies the audio signal, and the second amplification characteristic amplifies the audio signal in a curve.

  “Linear amplification” refers to amplification in accordance with a linear function. Further, “amplifying in a curve” means that amplification is performed according to a multi-order function such as a quadratic function, an exponential function, a logarithmic function, or the like.

  In the above acoustic apparatus, the audio signal processing unit performs a first amplification process and a second amplification on the audio signal for each unit time according to the signal level of the unit time for the audio signal input by the input unit. One of the processes is selectively performed.

  In the above acoustic apparatus, the audio signal processing unit includes a first amplifier having a first amplification characteristic and a second amplifier having a second amplification characteristic, and corresponds to the signal level of the audio signal input at the input unit. Thus, the amplification process is performed by one of the first amplifier and the second amplifier.

  In the above acoustic apparatus, the audio signal processing unit includes one amplifier capable of switching between the first amplification process and the second amplification process, and the one of the amplifiers is in accordance with the signal level of the audio signal input from the input unit. The amplification process is switched.

  In the above acoustic apparatus, the audio signal processing unit performs amplification processing of the specific frequency band component according to the signal level of the specific frequency band component of the audio signal input from the input unit. .

  In the above acoustic apparatus, the specific frequency band component is a low frequency band component.

  In the above acoustic apparatus, the audio signal processing unit selects the first amplification process when the signal level of the low frequency band component is equal to or lower than the first threshold value, and selects the second amplification process when the signal level exceeds the first threshold value. It is characterized by doing.

  In the above acoustic apparatus, when the signal level of the audio signal amplified by the audio signal processing unit exceeds the second threshold, the audio device further includes a dynamic range compression unit that adjusts the signal level to a constant level, and the output unit is a dynamic unit The audio signal adjusted by the range compression unit is output.

  The method for controlling an acoustic device according to the present invention includes an input step of inputting an audio signal, and a first amplification process and a first amplification based on the first amplification characteristic according to the signal level of the audio signal input in the input step. An audio signal processing step for selectively performing any one of the second amplification processes based on the second amplification characteristic different from the characteristics, and an output step for outputting the audio signal amplified in the audio signal processing step. It is characterized by that.

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

It is a block diagram of the audio equipment concerning one embodiment of the present invention. It is a graph which shows the input-output characteristic of an audio | voice signal processing part. It is a circuit block diagram of an audio | voice signal processing part. (A) is a graph which shows a linear amplification characteristic, (b) is a graph which shows a curved amplification characteristic. It is a graph which shows time transition of an input signal and a gain. It is a circuit block diagram of a dynamic range compression part.

  Hereinafter, an audio device, a control method for an audio device, and a program according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram of an audio device 1 according to the present embodiment. The acoustic device 1 includes an input terminal 11 (input unit), an audio signal processing unit 12, a dynamic range compression unit (DRC: Dynamic Range Compression) 13, a power amplifier 14, and a speaker 15. In the drawing, for simplification, two channels of LR (left signal and right signal) are shown by one line.

  The input terminal 11 inputs an audio signal from the sound source 2. Here, the sound source 2 refers to various storage media (CD, SD card, USB memory, etc.), various electronic devices (audio player, personal computer, tablet terminal, mobile phone, etc.), various servers (Web server, LAN network) Server).

  The audio signal processing unit 12 performs various audio processes on the input audio signal. In particular, in the present embodiment, amplification processing based on two types of amplification characteristics is selectively performed according to the signal level (input level) of the input audio signal. Here, the selection of the amplification process is performed every unit time (for example, several tens to several hundreds of milliseconds) in accordance with the input of the audio signal from the sound source 2 (in real time). That is, without the need for prior analysis of the music, the signal level for each unit time is detected as the music is played, and one of the two types of amplification characteristics is amplified for the audio signal for each unit time. Amplification processing based on characteristics is performed.

  FIG. 2 is a graph showing the input / output characteristics of the audio signal processing unit 12. In the figure, the horizontal axis indicates the input level, and the vertical axis indicates the output level. The audio signal processing unit 12 linearly amplifies the audio signal when the input level is equal to or lower than a predetermined threshold “γ” (first threshold) as indicated by a thick solid arrow L0 in FIG. Amplification characteristics, hereinafter referred to as “linear amplification”). On the other hand, when the input level exceeds the threshold “γ”, the audio signal is amplified in a curve (second amplification characteristic; hereinafter referred to as “curve amplification”). That is, the linear amplification and the curve amplification are switched at the inflection point P at which the input level becomes the threshold “γ”. In particular, in the present embodiment, for the low frequency band component of the audio signal (mainly the band component in which the fundamental wave of the bass drum exists, “specific frequency band component” in the claims), the thick solid arrow L0 in FIG. The amplification process shown is performed. In this embodiment, “linear amplification” means that the relationship between the input level and the output level is based on a linear function, and “curve amplification” means that the relationship between the input level and the output level is based on a quadratic function. Means that.

  When the signal level of the low frequency band component amplified by the audio signal processing unit 12 exceeds a predetermined threshold value (second threshold value), the dynamic range compression unit 13 adjusts the signal level to a constant level. Thereby, it is suppressed that it becomes an excessively large volume. Details of the audio signal processing unit 12 and the dynamic range compression unit 13 will be described later.

  The power amplifier 14 amplifies the audio signal processed by the dynamic range compression unit 13 and drives the speaker 15. The speaker 15 outputs an audio signal by driving the power amplifier 14. The “output unit” in the claims mainly includes the power amplifier 14 and the speaker 15.

  The power amplifier 14 may be built in the speaker 15. The audio signal processing unit 12 and the dynamic range compression unit 13 may be realized by software such as a DSP (Digital Signal Processor) or an analog device. Further, headphones or earphones may be used instead of the speakers 15.

  The acoustic device 1 of the present embodiment is suitable for DJ equipment with a high bass drum sound enhancement need, but can also be applied to other reproduction systems (minicomponents, headphone amplifiers, etc.).

  Next, the circuit configuration of the audio signal processing unit 12 will be described with reference to FIG. As shown in the figure, the audio signal processing unit 12 includes attenuators 21 to 25, adders 26 to 28, a first low pass filter (LPF) 29 for low frequency band extraction, and a first ABS (absolute value calculation) for detection. 30), a second LPF 31 for detection, fixed amplifiers 32 and 33, a variable amplifier 34, a switch 35, and delays 36 and 37.

  The audio signal processing unit 12 receives an audio signal separated into two channels (L signal and R signal). The input audio signals are attenuated by the first attenuator 21 and the second attenuator 21, and then synthesized by the first adder 26, and output to the first LPF 29 as a monaural signal.

  The first LPF 29 extracts a low frequency band component (mainly a band in which the fundamental wave of the bass drum exists, for example, 100 Hz or less) of the input signal synthesized by the first adder 26. Then, the absolute value of the low frequency band component extracted by the first LPF 29 is calculated by the first ABS 30, and the amplitude envelope is calculated by the second LPF 31.

  The calculated amplitude envelope (amplitude value) of the low frequency band component is amplified by the first fixed amplifier 32, and the output of the first LPF 29 is output by the first variable amplifier 34 (second amplifier) according to the amplified value. Is variably amplified. As a result, the curve amplification characteristic (characteristic shown on the right side of the thick solid line arrow L0) shown in FIG. 2 is obtained. On the other hand, the second fixed amplifier 33 (first amplifier) fixedly amplifies the output of the first LPF 29. As a result, the linear amplification characteristic (characteristic shown on the left side of the thick solid line arrow L0) shown in FIG. 2 is obtained.

  The first switch 35 switches between the output from the first variable amplifier 34 and the output from the second fixed amplifier 33. This switching is determined by whether or not the output of the second LPF 31 is equal to or less than a predetermined threshold value. Specifically, when the output of the second LPF 31 is “x” and the predetermined threshold is “γ”, and “x ≦ γ”, the first switch 35 is switched to the second fixed amplifier 33 side. On the other hand, when “x> γ”, the first switch 35 is switched to the first variable amplifier 34 side. As a result, when the signal level of the low frequency band component extracted by the first LPF 29 is small, a linear amplification characteristic is obtained, and the output level is smaller than that of the curve amplification characteristic (see the dotted line L1 in FIG. 2). It can be prevented from being too much. That is, even when the input level is small, the amount of amplification does not become extremely small, so that the sense of volume (low tone) is not impaired. On the other hand, when the signal level of the low frequency band component is large, a curve amplification characteristic is obtained, and the output level can be further increased as compared with the case of the linear amplification characteristic (see the dotted line L2 in FIG. 2). That is, the bass drum sound having a high signal level can be emphasized more effectively.

  The low frequency band component signal selected by the first switch 35 is attenuated by the third attenuator 23 and then synthesized into the L signal and the R signal by the second adder 27 and the third adder 28, respectively. . That is, when the second fixed amplifier 33 is selected by the first switch 35, the original signal and the signal obtained by amplifying the low frequency band component with a constant gain (linearly amplified signal) are combined. On the other hand, when the first variable amplifier 34 is selected by the first switch 35, the original signal and the signal amplified with a larger gain (curve amplified signal) are combined as the signal level of the low frequency band component increases. Is done. At this time, the original signals (audio signals) input to the adders 27 and 28 are delayed by the delays 36 and 37 by the time required for processing from the first LPF 29 to the third attenuator 23. Then, the synthesized L signal and R signal are attenuated by the fourth attenuator 24 and the fifth attenuator 25, respectively, and output to the dynamic range compressor 13.

  As described above, the audio signal processing unit 12 performs either the first amplification process based on the linear amplification or the second amplification process based on the curve amplification according to the signal level of the low frequency band component of the input audio signal. Selectively. As a result, the following results shown in FIGS. 4 and 5 can be obtained.

  FIG. 4 is a graph showing amplification characteristics by a general equalizer and the amplification characteristics by the audio signal processing unit 12 of the present embodiment. In the figure, the horizontal axis indicates time, and the vertical axis indicates amplitude. As shown in FIG. 4A, in the case of a general equalizer, it is always amplified (linearly amplified) with a constant gain (regardless of the input level). That is, when emphasizing the bass drum sound, the bass sound is amplified so that it gradually increases. On the other hand, as shown in FIG. 4B, the audio signal processing unit 12 according to the present embodiment has a variable gain corresponding to the input level at the moment when the bass drum sound is generated when “x> γ”. Amplify with (amplify curve). That is, the low frequency band component can be increased rapidly at the required timing. Note that the audio signal processing unit 12 of the present embodiment also performs the linear amplification shown in FIG. 4A when “x ≦ γ”.

  FIG. 5 is a graph showing the time transition of the input signal and gain. In the figure, the X axis represents time, the Y axis represents gain, and the Z axis represents frequency. As shown in the figure, the audio signal processing unit 12 of the present embodiment varies the gain (in the figure, bold line) according to the change in the input signal (in the figure, dotted line). That is, control can be performed so as to obtain a large gain only when the signal level of the low frequency band component of the input signal exceeds the threshold value. For this reason, it is possible to amplify with a large gain only at a moment required in time (for example, when “x> γ”, such as a moment when a bass drum sound is produced). That is, it is possible to amplify only a large low frequency band component such as a bass drum while preventing an adverse effect of unnecessarily amplifying an unintended low frequency band component and giving an excessively low tone. Thereby, it is possible to select and amplify the bass drum sound in terms of time.

  Next, the circuit configuration of the dynamic range compression unit 13 will be described with reference to FIG. As shown in the figure, the dynamic range compressor 13 includes a first HPF (High Pass Filter) 41, a third LPF 42, a second ABS 43, coefficient output units 44 and 45, a second switch 46, a fourth LPF 47, a second variable amplifier 48, and A fourth adder 49 is provided. In the figure, only one channel on one side of the LR2 channel is shown.

  The first HPF 41 extracts middle and high frequency band components (middle and high frequency band components) from the audio signal output from the audio signal processing unit 12. The third LPF 42 extracts a low frequency band component. That is, the bass drum band is extracted by the third LPF 42 and the parts other than the bass drum band are extracted by the first HPF 41. The absolute value of the low frequency band component extracted by the third LPF 42 is calculated by the second ABS 43, and the output value x1 is output to the subsequent coefficient output units 44 and 45.

  The coefficient output units 44 and 45 and the second switch 46 output the coefficient x2 based on the comparison result with the threshold “β” (second threshold). For example, when “x1> β”, the coefficient “β / x1” is output from the first coefficient output unit 44. On the other hand, when “x1 ≦ β”, the coefficient “1.0” is output from the second coefficient output unit 45. The coefficient x2 selected by the second switch 46 is input to the fourth LPF 47. Here, the fourth LPF 47 has a time constant for smoothly performing the amplification process.

  The second variable amplifier 48 variably amplifies the low frequency band component extracted by the third LPF 42 according to the output value of the fourth LPF 47. The fourth adder 49 in the subsequent stage adds the audio signal of the low frequency band component amplified by the second variable amplifier 48 to the medium and high frequency band component extracted by the first HPF 41 and outputs the result.

  As described above, the dynamic range compression unit 13 switches the coefficient output units 44 and 45 by the second switch 46 so that the signal level of the low frequency band component output from the audio signal processing unit 12 is equal to or higher than the threshold “β”. The signal level is adjusted to a constant level. This prevents an excessively loud volume while effectively enhancing the bass drum sound.

  As described above, when the signal level of the low frequency band component of the input audio signal is equal to or lower than the threshold “γ”, the acoustic device 1 of the present embodiment linearly amplifies the low frequency band component and the signal level is When the threshold value “γ” is exceeded, the low frequency band component is amplified by a curve. As a result, bass having a large signal level such as a bass drum can be emphasized more, and a bass having a small signal level can be reproduced naturally without becoming extremely small. In other words, the dynamic range can be prevented from becoming unnecessarily large.

  In addition, by switching the amplification processing according to the signal level for the low frequency band components, the bass drum sound with a high signal level is emphasized and the frequency characteristic balance during the period when the bass drum is not lost is not lost. There are effects such as. In addition, since the signal level of the audio signal amplified by the audio signal processing unit 12 is kept constant by the dynamic range compression unit 13, excessive enhancement of the bass drum sound can be prevented.

  As described above, the acoustic device 1 according to the present embodiment can maintain the overall balance while further enhancing the feeling of beat, so that bass drum sounds such as grab music (dance music) are characteristic audio signals. This is particularly effective when an amplification process is performed.

  In addition, the following modifications can be employed. For example, in the above embodiment, the audio signal processing unit 12 performs processing on the monaural component obtained by combining the L signal and the R signal, and distributes and combines the processing results into the L signal and the R signal. However, it is not limited to this. In the audio signal processing unit 12, each signal may be individually processed.

  Further, when the time required for processing from the first LPF 29 to the third attenuator 23 is short in the audio signal processing unit 12, the delays 36 and 37 may be omitted.

  Also, the audio signal processing unit 12 performs linear amplification and curve amplification of the audio signal using two amplifiers (the second fixed amplifier 33 and the first variable amplifier 34), and either one is selected by the first switch 35. However, the present invention is not limited to this. For example, a configuration in which the functions of the second fixed amplifier 33 and the first variable amplifier 34 described above are realized with one amplifier, and the first amplification process based on linear amplification and the second amplification process based on curve amplification are switched and amplified. It is also good.

  In the above embodiment, the bass drum sound is emphasized. However, the present invention is applicable to the case where other percussion instrument sounds or instrument sounds other than percussion instruments are emphasized. Further, the band (specific frequency band component) to be subjected to signal level determination and amplification processing is not limited to the low frequency band component, and may be another frequency band component. In addition, the band that is the signal level determination target and the band that is the target of the amplification process do not necessarily match. For example, the mid-high frequency band component may be amplified in accordance with the signal level of the low frequency band component.

  Alternatively, the audio signal processing unit 12 may perform the amplification process after examining the average level of the entire music by prior music analysis and normalizing the level. In this case, after the processing by the dynamic range compression unit 13, a process for restoring the normalized part is required. According to this configuration, a target amplification amount can be obtained regardless of the music signal level. That is, for example, the inflection point P cannot be exceeded because the signal level of the music is too small (curve amplification is not performed), and as a result, the bass drum sound cannot be effectively emphasized.

  In addition, when the average level cannot be checked offline beforehand, the level for the past 1 to 2 seconds, for example, is measured with the input of the audio signal from the sound source 2 (in real time) and applied to the normalized value. May be. According to this configuration, the target amplification amount can be obtained even when the average level cannot be examined offline in advance.

  In the above embodiment, the threshold value “γ” for switching the amplification process and the threshold value “β” for adjusting the dynamic range have been described as fixed values, but may be variable values. For example, music (audio signal) input from the sound source 2 may be analyzed, and these threshold values may be varied based on the analysis result. As an analysis result, for example, the average level, genre, and tempo (BPM (beats per minute)) of music can be considered. Moreover, it is good also as a structure which acquires a music analysis result from the exterior instead of performing music analysis with the audio equipment 1.

  In the above embodiment, the audio signal processing unit 12 selects the amplification process in accordance with the input of the audio signal from the sound source 2 (while reproducing the audio signal). Amplification processing may be selected according to the signal level for each unit time stored in advance. In addition, a configuration may be used in which amplification characteristics (linear amplification or curve amplification) for each unit time are stored after performing the above-described normalization by prior analysis.

  The selection of the amplification process is not limited to every unit time (several tens of milliseconds to several hundreds of milliseconds), but may be performed in units of beats of audio signals input from the sound source 2, units of measures of music, or units of music. In these cases, amplification processing may be selected according to the average signal level, maximum signal level, and minimum signal level in each period. Further, the unit for selecting the amplification process and the reference level may be arbitrarily set by the user.

  Moreover, it is also possible to provide each component of the audio apparatus 1 shown in said embodiment as a program. Further, the program can be provided by being stored in various recording media (CD-ROM, flash memory, etc.). That is, a program for causing a computer to function as each component of the audio device 1 and a recording medium on which the program is recorded are also included in the scope of rights of the present invention.

  Further, in the above embodiment, the case where the audio signal processing unit 12 and the dynamic range compression unit 13 are applied to the audio device 1 (reproduction-only device) is exemplified, but a personal computer, a tablet terminal, a mobile phone, a car navigation device, or the like The present invention may be applied to other electronic devices. Further, the audio signal processing unit 12 and the dynamic range compression unit 13 may be applied to cloud computing, such as being realized by a Web server or a LAN network server. Other modifications can be made as appropriate without departing from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Acoustic apparatus 2 ... Sound source 11 ... Input terminal 12 ... Audio | voice signal processing part 13 ... Dynamic range compression part 14 ... Power amplifier 15 ... Speaker 21 ... 1st attenuator 22 ... 2nd attenuator 23 ... 3rd attenuator 24 ... 4th attenuator 25 ... 5th attenuator 26 ... 1st adder 27 ... 2nd adder 28 ... 3rd adder 32 ... 1st fixed amplifier 33 ... 2nd fixed amplifier 34 ... 1st variable amplifier 35 ... switch 36 ... delay 44 ... first coefficient output unit 45 ... second coefficient output unit 46 ... second switch 48 ... second variable amplifier 49 ... fourth adder P ... inflection point

Claims (9)

An input unit for inputting an audio signal;
A first amplification process based on a first amplification characteristic for linearly amplifying the audio signal with respect to the audio signal input at the input unit and a second amplification characteristic based on a second amplification characteristic for amplifying the audio signal in a curved manner . An audio signal processing unit capable of executing two amplification processes;
An output unit that outputs an audio signal after the audio signal processing by the audio signal processing unit,
The audio signal processor is
A specific frequency band component is extracted from the audio signal input at the input unit, and for the specific frequency band component, either the first amplification process or the second amplification process is performed according to the signal level. Execute the amplification switching process to be performed selectively,
The acoustic apparatus is characterized in that the amplification switching process is not executed for frequency band components other than the specific frequency band component. The audio signal processor is
One of the first amplification process and the second amplification process is selectively performed on the audio signal for each unit time according to the signal level of the specific frequency band component for each unit time. The acoustic device according to claim 1 , wherein the acoustic device is characterized. The audio signal processor is
A first amplifier having the first amplification characteristic; and a second amplifier having the second amplification characteristic;
Wherein according to the signal level of a specific frequency band component, the acoustic apparatus according to claim 1 or 2, characterized in that the amplification process by one of the first amplifier and the second amplifier. The audio signal processor is
Including one amplifier capable of switching between the first amplification process and the second amplification process;
The acoustic device according to claim 1 or 2 , wherein amplification processing of the first amplifier is switched in accordance with a signal level of the specific frequency band component. The specific frequency band components, an acoustic device according to any one of claims 1 to 4, characterized in that the low frequency band component. The audio signal processor is
The said 1st amplification process is selected when the signal level of the said low frequency band component is below a 1st threshold value, and the said 2nd amplification process is selected when it exceeds the said 1st threshold value. 5. The acoustic device according to 5 . A dynamic range compression unit that adjusts the signal level to a constant level when the signal level of the audio signal amplified by the audio signal processing unit exceeds a second threshold;
The output unit, the acoustic apparatus according to any one of the claims 1 and outputs the adjusted audio signal by the dynamic range compressing unit 6. An input step for inputting an audio signal;
A first amplification process based on a first amplification characteristic for linearly amplifying the audio signal with respect to the audio signal input in the input step, and a second amplification characteristic based on a second amplification characteristic for amplifying the audio signal in a curved manner . An audio signal processing step capable of performing two amplification processes;
Outputting the audio signal that has been subjected to the audio signal processing in the audio signal processing step, and
The audio signal processing step includes
A specific frequency band component is extracted from the audio signal input in the input step, and for the specific frequency band component, one of the first amplification process and the second amplification process is performed according to the signal level. Execute the amplification switching process to be performed selectively,
The method for controlling an acoustic device, wherein the amplification switching process is not executed for frequency band components other than the specific frequency band component. The program for making a computer perform each step in the control method of the audio equipment of Claim 8 .

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