JP3373103B2 - Audio signal processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to audio signal processing for outputting by adding a predetermined quality control process on the audio signal
Regarding the device , in particular, even if the maximum value of the listening level changes, or even if the running noise changes, the ratio of the dynamic range of the predetermined frequency band to the dynamic range of the reference band before and after the change can be made the same, always, the audio signal processing that can listen to the music at the same frequency balance
Related to a physical device .

[0002]

2. Description of the Related Art The unit of "loudness" perceived by humans is sone, and the volume of a pure sound of 1 kHz and 40B is defined as 1 sone. The loudness of the sound perceived by a human decreases sharply as the sound intensity approaches the minimum audible value, and the degree of the decrease also differs depending on the noise level. Furthermore, loudness varies not only with sound intensity, but also with the frequency spectrum. FIG. 12 shows 1 k of a sound pressure level of xdB (x = 5 to 130 dB) in the absence of external noise.
The tone pressure level of a pure tone having the same loudness as a Hz pure tone is connected, and is called an equal loudness curve. As is clear from FIG. 12, the increase rate of the loudness is higher in the low range and the high range than in the middle range. That is, if the sound level changes uniformly over all frequencies, the relative loudness of each frequency component changes, and the sound balance is lost. For this reason, a conventional audio device is provided with a loudness circuit that raises the volume of low and high frequencies according to the amount of aperture when the volume is reduced by the volume.

[0003]

However, since the conventional loudness circuit does not take measures against the dynamic range, when the maximum value of the listening level changes, the dynamic range at each frequency changes individually, and the frequency band is changed. The overall balance is lost, making it difficult to listen to music and the like. FIG.
FIG. 3 is an explanatory diagram of a loudness curve showing a state of a change in a dynamic range. As is apparent from the loudness curve, the dynamic range differs depending on the frequency. For example, if the maximum value of the listening level is 100 dB, 1k
The dynamic range at 100 Hz is 100 dB, and the dynamic range at 100 Hz is 80 dB. If the maximum value of the listening level is 80 dB, the dynamic range of 1 kHz is 80 dB, and the dynamic range of 100 Hz is 60 dB. Therefore, if the maximum listening level is changed from 100 dB to 80 dB by the volume, the dynamic range ratio between 1 kHz and 100 Hz changes from 0.8 to 0.75 as shown in FIG. Become. The above is the case of 1 kHz and 100 Hz, but the dynamic range ratio changes over all frequencies.

[0004] In the case of a vehicle-mounted audio device, noise is generated depending on the vehicle speed. The running noise is higher in the lower frequency range and is higher than the minimum audible level. For this reason, the audio sound is masked by the running noise, the minimum audible curve changes, and the dynamic range of each frequency changes. Conventionally, since the change in the dynamic range due to such running noise is not taken into account, the balance of the entire frequency band is lost due to the vehicle speed, and it becomes difficult to listen to music.

Accordingly, a first object of the present invention is to provide an audio signal processing device capable of listening to music with the same frequency balance as that of live performance. A second object of the present invention is that even when the running noise changes and the dynamic range of each frequency band changes, the ratio between the dynamic range of each frequency band and the dynamic range of the reference band before and after the change can be made the same, An object of the present invention is to provide an audio signal processing device that can always listen to music with the same frequency balance. A third object of the present invention is to enable the ratio between the dynamic range of each frequency band and the dynamic range of the reference band to be the same before and after the change even when the maximum value of the listening level changes due to volume operation or the like. Audio signal processing device that can listen to music with frequency balance
Is to provide an installation .

[0006]

The first object of the present invention is to achieve the object of the present invention.
Divides the audio signal into two or more frequency bands
Each round based on the loudness characteristics of the current performance.
Dynamic range of wavenumber band and die of reference frequency band
The ratio to the natural range is
Dynamic range of each frequency band based on
Matches the ratio to the reference frequency band dynamic range
Compression of audio signals in each frequency band
More achieved . According to the present invention, the above-mentioned second object has a predetermined object.
Each frequency band based on loudness characteristics during driving
Dynamic range and reference frequency band dynamic
The ratio of the range to the loudness characteristics during the standard performance
Dynamic range and reference frequency of each frequency band based on
Each band should match the ratio to the dynamic range of several bands.
Achieved by compressing audio signals in the frequency band
Is done .

[0007] The third object is achieved according to the present invention. , Predetermined sound
Of each frequency band based on loudness characteristics
Dynamic range and dynamic range of reference frequency band
Ratio based on the loudness characteristics during the standard performance.
Dynamic range and reference frequency for each frequency band
Each round to match the ratio to the dynamic range of the band
Achieved by compressing audio signals in the wavenumber band
Be . According to the present invention, , Predetermined speed, predetermined volume
Of each frequency band based on loudness characteristics
Dynamic range and dynamic range of reference frequency band
Ratio based on the loudness characteristics during the standard performance.
Dynamic range of each frequency band and reference frequency band
Frequency so that it matches the ratio to the dynamic range of the
Achieved by compressing several bands of audio signal
To .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

(A) First Embodiment (a) General The maximum value of the music listening level of a live performance is generally about 100 dB [S
PL]. There is no problem if the audio signal can be reproduced at the same maximum level and dynamic range. However, in reality, the maximum value is at most about 80 dB [SPL] due to environmental problems such as nearby noise and a problem that a system capable of reproducing such a volume as an audio device becomes very large and expensive. Now, when live performance is compared, the ratio of the dynamic range of 1 kHz / 100 Hz with the maximum value of 100 dB “SPL] to the dynamic range of 1 kHz / 100 Hz with the maximum value of 80 dB“ SPL ”is shown in FIG. That is, when the maximum value is 100 dB, the dynamic range ratio is 0.8, and when the maximum value is 80 dB, the dynamic range ratio is 0.75.

If one wants to listen to music with the same dynamic range ratio as in live performance, the same dynamic range ratio can be used. To make the dynamic range ratio the same value (= 0.8), the 100 Hz dynamic range at the maximum value of 80 dB should be 64 dB. However, since there is a minimum audible characteristic, a sound lower than the minimum audible characteristic cannot be heard. Therefore, it is sufficient to compress 64 dB to 60 dB. Compression ratio τ
Is given by the following equation τ = 0.75 / 0.80 (= 60/64) = 0.9375. By applying compression with this compression ratio τ, the dynamic range becomes equal to 64 dB, the dynamic range ratio becomes 64/80 = 0.8, which is the same as the dynamic range ratio of 1 kHz, and the music has the same frequency balance as the live performance. You can hear

(B) Configuration FIG. 1 is a configuration diagram of a first embodiment of the present invention, wherein 1 is a low-frequency boost circuit for boosting a low-frequency component of an audio signal;
2 is a low-pass filter that passes the low-pass component of the audio signal, 3 is a high-pass filter that passes the high-pass component of the audio signal, 4 is a compressor (COMP) that compresses the low-pass component of the audio signal, and 5 is the output signal of the compressor 4 And a synthesizing circuit for synthesizing the output signal of the high-pass filter 3. FIG. 2 is an explanatory diagram of the compressor / expander. The compression ratio (decompression ratio) τ is defined by τ = (output level) / (input level). 0 <τ <1 results in compression (compressor) and τ> 1 results in expansion (expander). Therefore, the compression ratio and the expansion ratio are the slopes of the straight lines CL and EL shown in FIG.

Now, referring to the equal loudness curve of FIG. 12, the sharp change of the isosensitivity level is about 200 Hz.
It is near. Therefore, the cutoff frequency fc of the low-pass filter 2 and the high-pass filter 3 is set to about 200 Hz. Also, in order to listen to music with the same frequency balance as in live performance, it is only necessary to compress the low-frequency component at a compression ratio of 0.9375. Accordingly, the compressor 4 performs a compression process on the output signal of the low-pass filter 2 at a compression ratio of 0.9375. From the above,
If the ratio of the dynamic range of the low frequency component of 200 Hz or less to the high frequency component of 200 Hz or more becomes the same as the dynamic range ratio of the live performance, and if the music is listened to based on the audio signal synthesized by the synthesis circuit 5, the live performance You can listen to music with the same frequency balance as.

(C) Modification (c-1) First Modification In the first embodiment shown in FIG. 1, the compressor 4 is constituted by an analog circuit, but is constituted by a digital circuit such as a DSP (digital signal processor). You can also. In such a case, the compression requires time td. Therefore, it is necessary to delay the output of the high-pass filter 2 by td to match the signal phases. FIG. 3 shows an example in which the compressor 4 is configured by a DSP, and the same parts as those in FIG. 1 are denoted by the same reference numerals. Reference numeral 6 denotes a delay circuit that delays the time td required for the compression processing.

(C-2) Second Modification In the first embodiment shown in FIG. 1, the audio signal is divided into two frequency bands of a low frequency band of 200 Hz or less and a high frequency band of 200 Hz or more. ≧ 3) frequency bands, and the dynamic range in each frequency band and 1k
The dynamic range ratio in Hz may be the same as the dynamic range ratio in live performance.
FIG. 4 shows a modification of the first embodiment in such a case, in which 11 is a low-frequency booster or equalizer, and 12 to 15 are first to first.
Filters each having a fourth frequency band as a pass band
(Low pass, band pass, high pass filter), 16-1
9 is the dynamic range and 1 kHz in each frequency band.
Compressors (COMP1-COMP) that apply a predetermined compression to each filter output so that the dynamic range ratio of z becomes the same value as the dynamic range ratio during live performance
4) and 20 are synthesis circuits for synthesizing each compressor output. According to this modification, since the dynamic range ratio in each frequency band can be made extremely fine and equal to that during live performance, music can be heard with the same frequency balance as in live performance.

(B) Second Embodiment (a) Schematic When a vehicle runs, running noise (engine sound, etc.) is generated.
This running noise is higher in a lower frequency range, and is higher as the running speed is higher. FIG. 5 shows the loudness curve
The relationship between running noise and frequency during idling / 20 km / H running / 60 km / H running is shown. As is clear from this figure, the running noise level is higher than the minimum audible level. As a result, the audio sound is masked by the running noise, the minimum audible curve changes, and the dynamic range of each frequency changes. FIG. 6 is an explanatory diagram of the dynamic range, dynamic range ratio, and compression ratio at 1 kHz and 100 Hz with respect to the presence or absence of running noise (running speed) at the maximum sound volume of 100 dB “SPL”. As is clear from FIG.
The dynamic range at 1 kHz and 100 Hz changes and becomes as shown in FIG. As a result, the dynamic range ratio at 1 kHz and 100 Hz when there is no running noise (when quiet), idling, 20 km / H running, 60 km / H running,
They are 0.80, 0.64, 0.44, and 0.45, respectively.

Therefore, in order to listen to music at the time of idling and at the time of each running at the same dynamic range ratio as the dynamic range ratio of 1 kHz and 100 Hz (= 0.8) at the time of silence, the same idea as in the first embodiment is used. It is sufficient to compress a 100 Hz audio signal, and the respective compression ratios are τ ₁ = 0.64 / 0.8 = 0.80 τ ₂ = 0.44 / 0.8 = 0.55 τ ₃ = 0.45 / 0.8 = 0.56.

(B) Configuration FIG. 7 is a configuration diagram of a second embodiment of the present invention, wherein 1 is a low-frequency boost circuit for boosting a low-frequency component of an audio signal,
Reference numeral 2 denotes a low-pass filter that passes a low frequency component of the audio signal of 200 Hz or less, 3 denotes a high-pass filter that passes a high frequency component of the audio signal of 200 Hz or more, 4 denotes a compressor (COMP) that compresses a low-frequency component of the audio signal, 5 Is a synthesizing circuit for synthesizing the output signal of the compressor 4 and the output signal of the high-pass filter 3, 21 is an engine rotation detecting sensor for detecting engine rotation, 22 is a vehicle speed sensor for detecting the running speed of the vehicle, and 23 is according to the running state. Is a compression ratio control unit that determines the compression ratio and outputs the result to the compressor 4. The compression ratio is controlled according to noise, idling, 20km / H, 40km / H, 60km / H, etc. A table for calculating and storing the rate τ in advance is provided, and a compression rate corresponding to the current running state is obtained and input to the compressor 4.

The audio signal whose low frequency has been boosted by the low frequency booster 1 is input to a low-pass filter 2 and a high-pass filter 3 where it is separated into a low-frequency component and a high-frequency component. The components are input to the synthesis circuit 5. In parallel with the above, the compression ratio control unit 23 recognizes the running state of the vehicle based on the detection signals of the engine rotation detection sensor 21 and the vehicle speed sensor 22, obtains a compression ratio τ corresponding to the running state from a table, Enter 4 The compressor 4 performs a compression process at a compression rate τ on the input low-frequency audio signal, and inputs the resultant signal to the addition circuit 5.
The addition circuit 5 combines the signals input from the high-pass filter 3 and the compressor 4 and outputs the combined signal. As described above, even if the running state changes, the low-frequency component of 200 Hz or less and 200H
The ratio of the dynamic range of the high frequency component equal to or higher than z can be made the same as the dynamic range ratio at the time of silent operation, and music can be heard with the same frequency balance as at the time of silent operation regardless of the running state.

(C) Modified Example (c-1) The first modified example is a case where the compressor 4 is constituted by an analog circuit. However, when the compressor 4 is constituted by a DSP, the output side of the high-pass filter 3 is provided. It is necessary to provide a delay circuit, delay the compression processing time of the DSP by the delay circuit, and adjust the phases. In the above description, the engine rotation detection sensor 21 / vehicle speed sensor 22 is provided. However, a noise detection unit 24 is provided in place of the engine rotation detection sensor 21 and the vehicle speed sensor 22. It is also possible to configure so as to obtain a higher compression ratio.

(C-2) Second Modification In the second embodiment shown in FIG. 7, the audio signal is divided into two frequency bands of a low frequency band of 200 Hz or less and a high frequency band of 200 Hz or more. ≧ 3) frequency bands, and the dynamic range in each frequency band and 1k
The dynamic range ratio in Hz may be configured to have the same value even when the running state changes. FIG. 8 shows a modification of the second embodiment in such a case, and the same parts as those in FIG. 7 are denoted by the same reference numerals. 31 to 34 are filters (low-pass, band-pass, high-pass filters) each having the first to fourth frequency bands as pass bands, and 35 to 38 are the running conditions where the ratio of the dynamic range in each frequency band to the dynamic range of 1 kHz is different. Compressors (COMP1 to COMP4) for applying a predetermined compression to each filter output so as to have the same value even if it changes, and 39 is a synthesizing circuit for synthesizing each compressor output. Compression ratio control unit 23
The table (not shown) contains the following data for each frequency band: silent, idling, 20km / H, 40km / H,
During km / H traveling, a compression ratio τ corresponding to ... is calculated and stored in advance.

The audio signal whose low frequency has been raised by the low frequency booster 1 is input to each of the filters 31 to 34, where it is frequency-divided and input to the compressors 35 to 38, respectively. In parallel with the above, the compression ratio control unit 23 recognizes the running state of the vehicle based on the detection signals of the engine rotation detection sensor 21 and the vehicle speed sensor 22, and determines the compression ratios τ ₁ to の₁ to τ ₄ is obtained from the table and input to the compressors 35 to 38. The compressors 35 to 38 compress the input audio signals of the respective frequency bands at the compression ratios τ _{1 to} τ ₄ and input the compressed audio signals to the adder circuit 29.
8 and outputs the combined signal. According to this modification, since the dynamic range ratio in each frequency band can be made extremely fine and equal to that at the time of silent sound, music can be heard with the same frequency balance as that at the time of silent sound.

(C) Third Embodiment (a) As is apparent from FIG. 13, when the maximum value of the listening level is changed by the volume, the dynamic range of each frequency band changes. That is, the maximum listening level is set to 100
Assuming dB, the dynamic range of 1 kHz is 100
The dynamic range of 100 dB is 80 dB. If the maximum value of the listening level is 80 dB, 1 k
The dynamic range of Hz is 80 dB, and the dynamic range of 100 Hz is 60 dB. For this reason, if the maximum listening level is changed from 100 dB to 80 dB depending on the volume, as shown in FIG.
The dynamic range ratio changes from 0.8 to 0.75, and the balance is lost, making it difficult to listen to music.

FIG. 9 shows 1k for a maximum volume of 60 to 120 dB "SPL".
FIG. 3 is an explanatory diagram of a dynamic range, a dynamic range ratio, and a compression ratio at Hz and 100 Hz. 1kHz depending on the maximum volume,
The dynamic range at 100 Hz changes, as shown in FIG. As a result, the maximum listening level (volume position) is 1kHz, 100Hz at 60dB, 80dB, 100dB, 120dB.
The dynamic range ratios are 0.67, 0.75 and 0.
80, 0.83. Therefore, 1k at the maximum level 100dB
In order to listen to music at each maximum listening level with the same dynamic range ratio as the dynamic range ratios of Hz and 100 Hz, it is sufficient to compress the 100 Hz audio signal in the same way as in the first embodiment. The elongation ratio is τ ₁ = 0.67 / 0.8 = 0.8375 τ ₂ = 0.75 / 0.8 = 0.9375 τ ₃ = 0.8 / 0.8 = 1.0 τ ₄ = 0.8 ₃ /0.8=1.0 ₃₇₅ .

(B) Configuration FIG. 10 is a configuration diagram of a third embodiment of the present invention, wherein 1 is a low-frequency boost circuit for boosting a low-frequency component of an audio signal, and 2 is a low-frequency boost signal of 200 Hz or less. A low-pass filter that passes through, 3 is a high-pass filter that passes high-frequency components of the audio signal of 200 Hz or more, 4 is a compressor (COMP) that compresses low-frequency components of the audio signal, 5
Is a synthesizing circuit for synthesizing the output signal of the compressor 4 and the output signal of the high-pass filter 3, 41 is a volume, 51 is a compression ratio control unit which determines a compression ratio according to the volume position (maximum listening level) and outputs it to the compressor 4. And
Compression rate τ according to each maximum listening level 60dB-120dB (Fig. 9)
Is calculated and stored in advance, and a compression ratio τ corresponding to the current maximum listening level is obtained and input to the compressor 4.

The audio signal whose low frequency has been raised by the low frequency booster 1 is input to a low-pass filter 2 and a high-pass filter 3, where the audio signal is separated into a low-frequency component and a high-frequency component. The components are input to the synthesis circuit 5. In parallel with the above, the compression ratio control unit 42 determines the compression ratio τ according to the maximum listening level set by the volume 41.
Is obtained from the table and input to the compressor 4. The compressor 4 performs a compression process at a compression ratio τ on the input low-frequency audio signal and inputs the resultant signal to an addition circuit 5.
Combines the signals input from the high-pass filter 3 and the compressor 4 and outputs the combined signal. As described above, even if the maximum listening level changes depending on the volume, the ratio of the dynamic range of the low-frequency component of 200 Hz or lower to the high-frequency component of 200 Hz or higher can be made the same as the dynamic range ratio at the maximum listening level of 100 dB. Music can be heard at the dynamic range ratio at 100 dB, that is, always with the same frequency balance.

(C) Modifications Above, the audio signal is set to a low frequency of 200 Hz or less,
In the case where the frequency band is divided into two high frequency bands of 200 Hz or more, the frequency band is divided into n (≧ 3) frequency bands, and the ratio of the dynamic range in each frequency band to the dynamic range of 1 kHz changes the maximum listening level. However, they can be configured to be the same.

(D) Fourth Embodiment In the second embodiment, only the running state is considered, and in the third embodiment, only the volume position (maximum listening level) is considered. Changes,
1k in each frequency band even if the maximum listening level changes
The dynamic range ratio of Hz and 100 Hz may be configured to be a constant value. FIG. 11 is a diagram showing the configuration of the embodiment in such a case.
This is the case of dividing into the above two high frequencies, and the same parts as those in the second embodiment of FIG. 7 and the third embodiment of FIG. 10 are denoted by the same reference numerals.

1 is a low-frequency boost circuit for boosting low-frequency components of the audio signal, 2 is a low-pass filter that passes low frequencies of 200 Hz or less of the audio signal, and 3 is a high-pass filter that passes high frequencies of 200 Hz or more of the audio signal. A filter 4 is a compressor (COMP) for compressing low-frequency components of the audio signal, a synthesis circuit 5 is for synthesizing an output signal of the compressor 4 and an output signal of the high-pass filter 3, and 21 is an engine rotation detection sensor for detecting engine rotation. , 2
Reference numeral 2 denotes a vehicle speed sensor for detecting the running speed of the vehicle, 41 denotes a volume, and 51 denotes a compression ratio control unit for determining a compression ratio in accordance with the running state / volume position (maximum listening level) and outputting it to the compressor 4. When idling,
20km / H, 40km / H, 60km / H, ... In each running state, each maximum listening level 60dB ~ 12
A table 51a for calculating and storing a compression ratio τ according to 0 dB in advance is provided. A compression ratio according to the current running state and the current maximum listening level is obtained from the table and input to the compressor 4.

The audio signal whose low frequency has been boosted by the low frequency booster 1 is input to a low-pass filter 2 and a high-pass filter 3 where it is separated into a low-frequency component and a high-frequency component. The components are input to the synthesis circuit 5. In parallel with the above, the compression ratio control unit 51 recognizes the current running state of the vehicle based on the detection signals of the engine rotation detection sensor and the vehicle speed sensor, and
Recognize the current maximum listening level based on the position of. Then, the compression ratio control unit 51 obtains the compression ratio τ according to the current running state and the current maximum listening level from the table 51a and inputs the compression ratio τ to the compressor 4. The compressor 4 performs a compression process at a compression ratio τ on the input low-frequency audio signal and inputs the resultant signal to the addition circuit 5. The addition circuit 5 combines the signal input from the high-pass filter 3 and the signal input from the compressor 4 and outputs the combined signal.
By the above, even if the running state and the maximum listening level change, the ratio of the dynamic range of the low-frequency component of 200 Hz or less to the high-range component of 200 Hz or more can be made the same as the dynamic range ratio at the time of 100 dB in silent mode. You can listen to music with the same frequency balance regardless of the maximum listening level.

In the above description, the audio signal is divided into two frequency bands of a low frequency band of 200 Hz or less and a high frequency band of 200 Hz or more. Dynamic range and 1
The ratio of the dynamic range of kHz may be configured to be the same even when the running state / maximum listening level changes. As described above, the present invention has been described with reference to the embodiments. However, the present invention can be variously modified in accordance with the gist of the present invention described in the claims, and the present invention does not exclude these.

[0030]

According to the present invention, the audio signal is
Divided into two or more frequency bands,
Dynamic range for each frequency band based on the drain characteristics
The ratio between the dynamic range of the reference frequency band and the
Each frequency band based on loudness characteristics during semi-performance
Dynamic range and reference frequency band dynamics.
Audio of each frequency band to match the ratio
Since the audio signal is compressed , the music can be heard with the same frequency balance as that of live performance. According to the present invention, each loudness characteristic based on the loudness
The dynamic range of the frequency band and the
The ratio to the dynamic range is the loudness during the standard performance.
Dynamic range of each frequency band based on nest characteristics
And the ratio of the dynamic range of the reference frequency band
The audio signal of each frequency band is compressed as described above, so even if the running noise changes and the dynamic range of each frequency band changes, the dynamic range of each frequency band before and after the change and the dynamic range of the reference band The ratio of the ranges can be the same, and music can always be heard with the same frequency balance.

According to the present invention, the lau at a predetermined volume is
Dynamic range for each frequency band based on the drain characteristics
The ratio between the dynamic range of the reference frequency band and the
Each frequency band based on loudness characteristics during semi-performance
Dynamic range and reference frequency band dynamics.
Audio of each frequency band to match the ratio
Even if the maximum value of the listening level changes due to volume operation or the like, the ratio of the dynamic range of each frequency band and the dynamic range of the reference band before and after the change can be made the same, even if the maximum value of the listening level changes due to volume control, etc. You can always listen to music with the same frequency balance.

According to the present invention, at a predetermined speed and a predetermined volume,
Dyna for each frequency band based on loudness characteristics
Mic range and dynamic range of reference frequency band
Is based on the loudness characteristics during the reference performance.
Dynamic range of each frequency band and reference frequency band
Each frequency band to match the ratio with the dynamic range
The compression of the audio signal in the range ,
Regardless of the maximum listening level, the ratio of the dynamic range of each frequency band to the dynamic range of the reference band can be made the same, and music can be heard with the same frequency balance.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is an explanatory diagram of a compressor / expander.

FIG. 3 is a modification of the first embodiment.

FIG. 4 is another modification of the first embodiment.

FIG. 5 is a schematic explanatory diagram of a second embodiment.

FIG. 6 is a diagram illustrating a dynamic range, a dynamic range ratio, and a compression ratio depending on the presence or absence of running noise at a maximum sound volume of 100 dB.

FIG. 7 is a configuration diagram of a second embodiment.

FIG. 8 is a modification of the second embodiment.

FIG. 9 is an explanatory diagram of a dynamic range, a dynamic range ratio, and a compression ratio with respect to a maximum sound volume.

FIG. 10 is a configuration diagram of a third embodiment.

FIG. 11 is a configuration diagram of a fourth embodiment.

FIG. 12 is an explanatory diagram of an equal loudness curve.

FIG. 13 is a diagram illustrating a change in a dynamic range.

FIG. 14 is a diagram illustrating a dynamic range and a dynamic range ratio.

[Explanation of symbols]

1 Low frequency booth and circuit 2 Low-pass filter 3 High-pass filter 4 Compressor 5 Synthesis circuit

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI H03G 5/16 G10L 3/02 G (58) Field surveyed (Int.Cl. ⁷ , DB name) H03G 7/00 H03G 3 / 32 H03G 5/02 H03G 5/16 B60R 11/02 G10L 21/02

Claims (4)

(57) [Claims] An audio signal processing device for adding a predetermined sound quality control process to an audio signal and outputting the audio signal, comprising: a filter for dividing the audio signal into two or more frequency bands; and a filter for each frequency band based on a loudness characteristic during a current performance. Audio signals in each frequency band so that the ratio of the dynamic range to the dynamic range of the reference frequency band matches the ratio of the dynamic range of each frequency band based on the loudness characteristics during the reference performance to the dynamic range of the reference frequency band. A compression circuit for compressing the audio signal. 2. An audio signal processing apparatus for adding predetermined sound quality control processing to an audio signal and outputting the audio signal, a filter for dividing the audio signal into two or more frequency bands, a compression circuit for compressing the audio signal in each frequency band, A running speed detecting unit for detecting a running speed of the vehicle, a compression ratio control unit for determining a compression ratio of an audio signal in each frequency band based on the running speed, and a dynamic of each frequency band based on a loudness characteristic during a predetermined running. The audio signal of each frequency band is adjusted so that the ratio between the range and the dynamic range of the reference frequency band matches the ratio of the dynamic range of each frequency band based on the loudness characteristics during the reference performance and the dynamic range of the reference frequency band. Compressing the audio signal processing device. Place. 3. An audio signal processing device for adding predetermined sound quality control processing to an audio signal and outputting the audio signal, a filter for dividing the audio signal into two or more frequency bands, a compression circuit for compressing the audio signal in each frequency band, A compression rate control unit that determines a compression rate of the audio signal in each frequency band based on the set volume, and a dynamic range of each frequency band and a reference frequency band based on the loudness characteristic at a predetermined volume. Compressing the audio signal of each frequency band so that the ratio with the dynamic range matches the ratio of the dynamic range of each frequency band based on the loudness characteristic during the reference performance with the dynamic range of the reference frequency band. Audio signal processing device. 4. An audio signal processing device for adding predetermined sound quality control processing to an audio signal and outputting the signal, a filter for dividing the audio signal into two or more frequency bands, a compression circuit for compressing the audio signal in each frequency band, A running speed detecting unit that detects a running speed of the vehicle, a volume setting volume, a compression ratio controlling unit that determines a compression ratio of an audio signal in each frequency band based on the running speed and the set volume, and a predetermined speed and a predetermined volume. The ratio between the dynamic range of each frequency band based on the loudness characteristic at the time and the dynamic range of the reference frequency band is the ratio of the dynamic range of each frequency band based on the loudness characteristic during the reference performance and the dynamic range of the reference frequency band. Audio signal of each frequency band to match An audio signal processing device, characterized in that: