CN108243368B

CN108243368B - Frequency division compression circuit, audio processing method and audio processing system

Info

Publication number: CN108243368B
Application number: CN201611206196.5A
Authority: CN
Inventors: 李牧玹
Original assignee: Amtran Technology Co Ltd
Current assignee: Amtran Technology Co Ltd
Priority date: 2016-12-23
Filing date: 2016-12-23
Publication date: 2020-01-31
Anticipated expiration: 2036-12-23
Also published as: CN108243368A

Abstract

A crossover compression circuit, an audio processing method and an audio processing system, the crossover compression circuit includes a plurality of pre-filters, a plurality of crossover limiters and a plurality of post-filters, the pre-filters are used to receive the input signal and filter the input signal to output a plurality of frequency-divided signals, the crossover limiters are respectively coupled to the pre-filters to compress the frequency-divided signals to output a plurality of second frequency-divided signals, the post-filters are respectively coupled to the crossover limiters to filter the corresponding second frequency-divided signals to output a plurality of output signals, the pre-filters and the post-filters corresponding to of the crossover limiters respectively include different cut-off frequencies, the pre-filters and the post-filters filter respectively filter the pre-and post-filter and set the different pre-cut-off frequencies and post cut-off frequencies, which can ensure the output mixed signal waveform is not distorted and maintain the flatness of the frequency response under different input signals.

Description

Frequency division compression circuit, audio processing method and audio processing system

Technical Field

The present disclosure relates to frequency division compression circuits, and more particularly, to a frequency division compression circuit in audio processing systems.

Background

In the prior art, in order to protect the speaker and maintain the low distortion rate of the amplifier output, a full-channel dynamic range compressor or limiter is added to perform dynamic range limiting compression on the whole audio signal during the audio processing.

However, when the dynamic range limitation compression is performed on the signal of the whole audio, a part of the signal which does not reach the limitation compression level is limited simultaneously with the limitation of the large signal, and the loss in the expression of the maximum sound pressure occurs. The loss of sound pressure is more pronounced in loudspeaker sound systems with bass enhancement, treble enhancement or stereo surround enhancement.

Therefore, designing a frequency division compression circuit in an audio processing system is an important research topic in the field of the present technology.

Disclosure of Invention

The aspect of the present disclosure is a frequency division compression circuit, which includes a plurality of pre-filters for receiving input signals and respectively filtering the input signals to output a plurality of -th frequency division signals, a plurality of frequency division limiters electrically coupled to the plurality of pre-filters for respectively compressing the plurality of -th frequency division signals to output a plurality of second frequency division signals, and a plurality of post-filters electrically coupled to the plurality of frequency division limiters for respectively filtering the corresponding second frequency division signals to output a plurality of output signals, wherein the pre-filter and the post-filter corresponding to of the plurality of frequency division limiters respectively include different cut-off frequencies.

In some embodiments, the former-stage low-pass filter of the plurality of former-stage filters and the latter-stage low-pass filter of the plurality of latter-stage filters correspond to the low-frequency limiter of the plurality of division limiter units, and the upper-limit cutoff frequency of the former-stage low-pass filter is greater than the upper-limit cutoff frequency of the latter-stage low-pass filter.

In some embodiments, the former-stage high-pass filter of the plurality of former-stage filters and the latter-stage high-pass filter of the plurality of latter-stage filters correspond to the high-frequency limiter of the plurality of division limiter units, and the lower-limit cutoff frequency of the former-stage high-pass filter is smaller than the lower-limit cutoff frequency of the latter-stage high-pass filter.

In some embodiments, the former-stage bandpass filter of the plurality of former-stage bandpass filters and the latter-stage bandpass filter of the plurality of later-stage bandpass filters correspond to the intermediate frequency limiter of the plurality of frequency division limiter units, the lower limit cutoff frequency of the former-stage bandpass filter is smaller than the lower limit cutoff frequency of the latter-stage bandpass filter, and the upper limit cutoff frequency of the former-stage bandpass filter is larger than the upper limit cutoff frequency of the latter-stage bandpass filter.

In some embodiments, the crossover compression circuit further includes an mixing unit for receiving the output signals and mixing the output signals to output mixed signals.

Another aspect of the present disclosure is methods of audio processing, the method including filtering a input signal by a plurality of pre-filters according to a plurality of pre-cut frequencies respectively to divide the input signal into a plurality of -th divided signals corresponding to different frequency bands, compressing the plurality of -th divided signals by a plurality of frequency division limiters respectively to output a plurality of compressed second divided signals, and filtering the plurality of second divided signals by a plurality of post-filters according to a plurality of post-cut frequencies respectively different from the plurality of pre-cut frequencies to output a plurality of output signals.

In some embodiments, any of the plurality of pre-stage cut-off frequencies has an upper cut-off frequency greater than the upper cut-off frequency of its corresponding post-stage cut-off frequency, and any of the plurality of pre-stage cut-off frequencies has a lower cut-off frequency less than the lower cut-off frequency of its corresponding post-stage cut-off frequency.

In some embodiments, the audio processing method further includes receiving the plurality of output signals through an mixing unit and mixing the plurality of output signals to output a mixed signal, and receiving and amplifying the mixed signal through a power amplifier to output a amplified mixed signal to a speaker.

The aspect of the disclosure is audio processing system, which includes a 0 signal input terminal for receiving a 1 input signal, a 2 processor electrically coupled to the signal input terminal for performing a audio processing method on the input signal to output mixed signals, a power amplifier electrically coupled to the processor for amplifying the mixed signals and outputting amplified mixed signals, and a speaker electrically coupled to the power amplifier for receiving the amplified mixed signals and outputting audio, wherein the audio processing method performed by the processor includes filtering the input signal by a plurality of pre-stage filters according to a plurality of pre-cut frequencies respectively to divide the input signal into a plurality of frequency division signals corresponding to different frequency bands, compressing the plurality of frequency division signals by a plurality of frequency division limiters respectively to output a plurality of second frequency division signals after compression, outputting the plurality of second frequency division signals after compression by a plurality of post-stage filters according to a plurality of post-cut frequencies respectively to output the mixed signals after the mixed signals, and outputting the plurality of frequency division signals after the compressed mixed signals.

In summary, in the embodiments of the present disclosure, by performing filtering in the front stage and the rear stage of the frequency division limiter respectively and setting different front stage cut-off frequency and rear stage cut-off frequency, it is ensured that the frequency division compression circuit can perform dynamic range limitation compression smoothly under different input signals, so that the waveform of the output mixed signal is not distorted, and a flat frequency response is obtained near each frequency division point after mixing.

Drawings

FIG. 1 is a schematic diagram of an audio processing system according to some embodiments of the disclosure;

FIGS. 2-4 are schematic diagrams of dynamic range restriction compression according to some embodiments of the present disclosure;

FIG. 5 is a schematic diagram of an audio processing system according to some other embodiments of the disclosure;

fig. 6 is a flowchart of an audio processing method according to an embodiment of the disclosure.

Detailed Description

The following detailed description of the embodiments with reference to the accompanying drawings is provided to better understand the aspects of the present disclosure, but the embodiments are not provided to limit the scope of the present disclosure, and the description of the structural operations is not provided to limit the execution sequence thereof, and any structure resulting from the rearrangement of elements to have an equivalent function is included in the scope of the present disclosure. Moreover, the drawings are for illustrative purposes only and are not drawn to scale in accordance with industry standard and conventional practice, and the dimensions of the various features may be arbitrarily increased or decreased for clarity of illustration. In the following description, the same elements will be described with the same reference numerals for ease of understanding.

In addition, although the terms "", "second", …, etc. are used herein to describe various elements, these terms are used merely to distinguish one element from another or operation described using the same technical terms, unless the context clearly indicates otherwise, the terms are not intended to particularly refer to or imply sequence or order and are not intended to limit the present invention.

Please refer to fig. 1. Fig. 1 is a schematic diagram of an audio processing system 100 according to some embodiments of the disclosure. As shown in fig. 1, in some embodiments, the audio processing system 100 includes a signal input terminal 110, a crossover compression circuit 120, a power amplifier 130, and a speaker 140. Specifically, the signal input terminal 110 is configured to receive the input signal CH1 and output the input signal CH1 to the frequency division compression circuit 120.

In some embodiments, the crossover compression circuit 120 includes a post-processing unit 121, a high-pass filtering unit 122, a pre-filtering unit 123, a crossover limiting unit 124, a post-filtering unit 125, and a mixing unit 126, and the detailed operations thereof will be described in detail with reference to the drawings in the following paragraphs.

In some embodiments, the power amplifier 130 is electrically coupled to the frequency division compression circuit 120 for amplifying the mixed sound signal MS and outputting the amplified mixed sound signal AMS. The speaker 140 is electrically coupled to the power amplifier 130 for receiving the amplified mixed sound signal AMS and outputting audio.

As described above, the post-processing unit 121, the high-pass filtering unit 122, the pre-stage filtering unit 123, the frequency division limiting unit 124, the post-stage filtering unit 125, and the mixing unit 126 in the frequency division compression circuit 120 may be implemented by software, hardware, and/or firmware. For example, if execution speed and accuracy are paramount, the units may be essentially hardware and/or firmware based; if the design flexibility is the primary consideration, the above units can basically be selected mainly by software; alternatively, the modules may be cooperatively operated by software, hardware and firmware. It should be understood that the above examples are not intended to limit the disclosure to any particular form of the elements so described, and that those skilled in the art will be able to select particular embodiments of the elements as desired.

For example, in some embodiments, the crossover compression circuit 120 may be implemented by various processors, such as a Digital Signal Processor (DSP), in other words, the post-processing unit 121, the high-pass filtering unit 122, the pre-filtering unit 123, the crossover limiting unit 124, the post-filtering unit 125, and the mixing unit 126 may be integrated into a Processor electrically coupled to the Signal input terminal 110 and the power amplifier 130, and perform audio processing methods on the input Signal CH1 through the above units to output the mixed Signal MS.

In some embodiments, the audio processing method executed by the processor may also be implemented as a computer program and stored in the storage device. The storage device includes a non-transitory computer readable recording medium or other device with storage function. The computer program includes a plurality of program instructions. The program instructions may be executed by a central processing unit to perform the functions of the units.

In some embodiments, as shown in FIG. 1, the input signal CH1 is processed by the post-processing unit 121, and then filtered by the high-pass filtering unit 122 to remove unnecessary low-frequency signals, so , the processed input signal CH1 is provided to the pre-filtering unit 123, the frequency-division limiting unit 124 and the post-filtering unit 125 for multi-channel frequency-division dynamic compression.

For example, in the embodiment, the pre-filter unit 123 includes a pre-low pass filter LPF111, a pre-band pass filter implemented by a low pass filter LPF121 and a high pass filter HPF121, and a pre-high pass filter HPF 131. the pre-filter is configured to receive the input signal CH1 and filter the input signal CH1 to output a plurality of th frequency-divided signals S1, S2, S3. th frequency-divided signals S1, S2, and S3 corresponding to different frequency bands of the input signal CH1, for example, the frequency-divided signal S1 output after the input signal CH1 is filtered by the pre-low pass filter LPF111 corresponds to the low frequency component of the input signal CH1, the th frequency-divided signal S2 output after the input signal CH1 is filtered by the pre-band pass filter LPF121 and the high pass filter HPF121 corresponds to the high frequency-divided signal CH1 output after the input signal CH1 is filtered by the pre-high pass filter HPF 121.

Specifically, the frequency division limiting unit 124 includes frequency division limiters LM1, LM2, and lm3. the frequency division limiters LM1, LM2, and LM3 are electrically coupled to the pre-filter of the pre-filter unit 123, respectively, for compressing the -th frequency-divided signals S1, S2, and S3, respectively, to output corresponding second frequency-divided signals S1 ', S2 ', and S3 '.

The second frequency-divided signals S1 ', S2 ', S3 ' after the compression processing may be filtered again by the post-stage filtering unit 125 to obtain output signals OS1, OS2, and OS3, so , the mixing unit 126 may receive the output signals OS1, OS2, and OS3 and mix the output signals OS1, OS2, and OS3 to output a mixed signal MS.

Specifically, the post-stage filtering unit 125 includes a plurality of post-stage filters, each post-stage filter corresponds to a corresponding of the frequency-division limiters LM1, LM2, LM3 and a corresponding of the pre-stage filter, and is electrically coupled to the frequency-division limiters LM1, LM2, LM3, respectively, for filtering the corresponding second frequency-division signals S1 ', S2 ', S3 ' to output corresponding output signals OS1, OS2, and OS 3.

Please , refer to fig. 2 and 3, fig. 2 and 3 are schematic diagrams illustrating dynamic range limiting compression according to an embodiment of the present disclosure, respectively, in the embodiment illustrated in fig. 2, the second frequency-divided signals S1 ', S2 ', S3 ' are directly mixed and synthesized by the mixing unit 126 without being filtered again, as illustrated in the figure, when the input signal CH1 is greater than the system input sensitivity, the frequency response value of the second frequency-divided signals S1 ', S2 ', S3 ' output after frequency division and dynamic range limiting compression of the input signal CH1 is higher than-3 db in the vicinity of the frequency division point, such as , and when the second frequency-divided signals S1 ', S2 ', S3 ' output the mixing signal MS after mixing processing, the signals output in the vicinity of the frequency division point are superimposed and additionally enhanced, thereby generating signal distortion.

Compared with the distorted waveform of the mixing signal MS in fig. 2, in the embodiment shown in fig. 3, the second frequency-divided signals S1 ', S2 ' and S3 ' are filtered again by the post-filtering unit 125 to provide output mixing signals OS1, OS2 and OS3 which are subjected to mixing processing as such , and no distortion occurs in the mixing signal MS no matter whether the input signal CH1 exceeds the system input sensitivity, even if the input signal CH1 is too large, the frequency response values of the second frequency-divided signals S1 ', S2 ' and S3 ' near the dividing points thereof are higher than-3 dB, the post-filtering unit 125 can set appropriate cut-off frequencies for the second frequency-divided signals S1 ', S2 ' and S3 ', respectively, so that the frequency response values of the output signals OS1, OS2 and OS3 near the dividing points are about-3 dB, thereby, when the output signals OS 585, OS2 and OS3 are subjected to mixing processing by the mixing unit 126, no distortion occurs in the vicinity of the mixing point.

In other words, the post-filtering unit 125 disposed at the output side of the frequency-division limiters LM1, LM2, and LM3 filters the compressed second frequency-divided signals S1 ', S2 ', and S3 ' again, so as to avoid the distortion of the signal waveform caused by the excessive input signal CH 1.

Referring to fig. 4, fig. 4 is a schematic diagram illustrating compression of dynamic range limitation according to an embodiment of the present disclosure, in the embodiment shown in fig. 4, although the second divided signals S1 ', S2 ', S3 ' are filtered by the post-filtering unit 125 to output corresponding output signals OS1, OS2, and OS3, since the filters in the pre-filtering unit 123 and the post-filtering unit 125 set the same cut-off frequency, the signals near the divided points undergo signal attenuation repeated at the same cut-off frequency , which results in the frequency response values of the output signals OS1, OS2, and OS3 near the divided points being lower than-3 db, such as , when the output signals OS1, OS2, and OS3 output the mixing signal MS after the mixing unit 126 performs mixing processing, the output signals near the divided points are output signals too small due to insufficient superposition, and the frequency response is not flat.

Referring to fig. 1 and 3 again, as shown in fig. 1 and 3, in some embodiments of the present disclosure, the front filter in the front filter unit 123 and the corresponding rear filter in the rear filter unit 125 respectively include different cut-off frequencies, for example, in the present embodiment, the front low pass filter LPF111 and the rear low pass filter LPF111 correspond to the low frequency limiter lm1, the upper cut-off frequency FC111U of the front low pass filter LPF111 is greater than the upper cut-off frequency fc112u of the corresponding rear low pass filter LPF112, and in some embodiments, the difference between the upper cut-off frequency FC111U and the upper cut-off frequency FC112U is at least times.

Similarly, the front high pass filter HPF131 and the back high pass filter HPF132 correspond to the high frequency limiter lm3 the lower cutoff frequency FC131L of the front high pass filter HPF131 is smaller than its corresponding lower cutoff frequency fc132l of the back high pass filter HPF 132. in some embodiments, there is at least a times frequency difference between the lower cutoff frequency FC131L and the lower cutoff frequency FC 132L.

Similarly, the front stage band-pass filter and the rear stage band-pass filter correspond to the intermediate frequency limiter lm2. the lower limit cutoff frequency FC121L of the front stage band-pass filter is smaller than the lower limit cutoff frequency FC122L of the rear stage band-pass filter, the upper limit cutoff frequency FC121U of the front stage band-pass filter is larger than the upper limit cutoff frequency fc122u of the rear stage band-pass filter in some embodiments, the difference between the lower limit cutoff frequency FC121L and the lower limit cutoff frequency FC122L, and the difference between the upper limit cutoff frequency FC121U and the upper limit cutoff frequency FC122U is at least times in frequency.

Further, as shown in fig. 3, in some embodiments, the lower limit cutoff frequency FC122L of the subsequent stage band-pass filter may be set to be the same as the upper limit cutoff frequency FC112U of the subsequent stage low-pass filter LPF 112. For example, in some embodiments, the lower cutoff frequency FC122L and the upper cutoff frequency FC112U may be set to 250 Hz.

Similarly, the upper limit cutoff frequency FC122U of the latter-stage band-pass filter may be set to be the same as the lower limit cutoff frequency FC132L of the latter-stage high-pass filter HPF 132. For example, in some embodiments, the upper cutoff frequency FC122U and the lower cutoff frequency FC132L may be set to 3 KHz.

Thus , since the frequency band of the pre-filtering unit 123 is wide, the post-filtering unit 125 can ensure that the frequency response values of the output signals OS1, OS2 and OS3 are lower than-3 db due to repeated attenuation of signals when filtering the second divided signals S1 ', S2 ' and S3 ', whereby, by setting different pre-cut frequencies and post-cut frequencies for the pre-filter and the post-filter to filter, respectively, the crossover compression circuit 120 can ensure that the frequency response values of the output signals OS1, OS2 and OS3 near the dividing point will be approximately equal to-3 db when the input signal CH1 is not greater than the system input sensitivity, and when the output signals OS1, OS2 and OS3 mix the output mix signal MS through the mixing unit 126, the signal outputs near the dividing point are superimposed and thus no signal distortion or uneven is generated.

Finally, the mixing signal MS can be transmitted to the power amplifier 130 and the speaker 140 for audio output, and the detailed operation thereof is described in the previous paragraphs and will not be described herein.

It is noted that the audio processing system 100 and the frequency division compression circuit 120 shown in fig. 1 are only for illustration and not for limitation. For example, please refer to fig. 5. Fig. 5 is a schematic diagram of an audio processing system 100 according to another embodiment of the disclosure. In fig. 5, similar components related to the embodiment of fig. 1 are denoted by the same reference numerals for easy understanding, and the specific principles of the similar components have been described in detail in the previous paragraphs, which are not repeated herein. In some embodiments, as shown in fig. 5, the crossover compression circuit 120 may only provide two crossover limiters to separate the input signal into a low frequency band and a high frequency band for dynamic range-limited compression. In some embodiments, the frequency division compression circuit 120 may further include four or more frequency division limiters for dividing the input signal into more frequency bands for dynamic range limiting compression. Based on the number of the frequency-division limiters in the frequency-division limiting unit 124, a person skilled in the art will understand how to adjust the number and arrangement of the filters in the pre-stage filtering unit 123 and the post-stage filtering unit 125 to achieve the corresponding operations, and therefore the description thereof is omitted here.

Although only sets of input signals CH1 are shown in the drawings, the frequency division compression circuit 120 may also divide and compress the input signals CH1 CHn separately for the input signals CH1 CHn including multiple sets of input channels.

Please refer to fig. 6. Fig. 6 is a flow chart of an audio processing method 600 according to an embodiment of the present disclosure. For convenience and clarity of illustration, the audio processing method 600 is described with reference to the audio processing system 100 shown in fig. 1 or fig. 5, but not limited thereto, and various modifications and alterations can be made by those skilled in the art without departing from the spirit and scope of the present disclosure. As shown in fig. 6, the audio processing method 600 includes steps S610, S620, S630, S640, and S650.

First, in step S610, the input signal CH1 is filtered by the plurality of pre-filters LPF111, LPF121, HPF131 according to the plurality of pre-cut frequencies FC111U, FC121U, FC121L, FC131L, respectively, to divide the input signal CH1 into a plurality of -th divided signals S1, S2, S3 corresponding to different frequency bands.

Next, in step S620, compression processing is performed on the th divided frequency signals S1, S2, S3 by the plurality of frequency division limiters LM1, LM2, LM3, respectively, to output compression-processed second divided frequency signals S1 ', S2 ', S3 '.

Next, in step S630, the second frequency-divided signals S1 ', S2 ', S3 ' are filtered by the plurality of post-stage filters LPF112, LPF122, HPF132 according to a plurality of post-stage cut-off frequencies FC112U, FC122U, FC122L, FC132L different from the pre-stage cut-off frequencies FC111U, FC121U, FC121L, FC131L, respectively, to output corresponding output signals OS1, OS2, OS 3.

Next, in step S640, the output signals OS1, OS2, OS3 are received through the mixing unit 126, and the output signals OS1, OS2, OS3 are mixed to output a mixed signal MS.

Finally, in step S650, the mixed sound signal MS is received and amplified through the power amplifier 130 to output the amplified mixed sound signal AMS to the speaker 140.

As described in the previous paragraph, in some embodiments, the upper cutoff frequency (e.g., cutoff frequencies FC111U, FC121U) of any of the preceding cutoff frequencies is greater than the upper cutoff frequency (e.g., cutoff frequencies FC112U, FC122U) of its corresponding succeeding cutoff frequency, similarly, the lower cutoff frequency (e.g., cutoff frequencies FC121L, FC131L) of any of the preceding cutoff frequencies is less than the lower cutoff frequency (e.g., cutoff frequencies FC122L, FC132L) of its corresponding succeeding cutoff frequency.

For example, some steps may occur in different orders and/or concurrently with other steps or events apart from those illustrated and/or described herein.

Those skilled in the art can directly understand how to implement the operations and functions of the audio processing method 600 based on the audio processing system 100 and the frequency division compression circuit 120 in the above-mentioned various embodiments, and therefore, the detailed description thereof is omitted here.

In summary, in the embodiments of the present disclosure, by performing filtering in the front stage and the rear stage of the frequency division limiters LM1, LM2, LM3, respectively, and setting different front stage cut-off frequency and rear stage cut-off frequency, the frequency division compression circuit 120 can perform smooth dynamic range limitation compression under different input signals CH1, and the waveform of the output mixing signal MS is not distorted and the flatness of the frequency response is maintained.

Although the present disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the disclosure, and therefore, the scope of the disclosure should be determined by that defined in the appended claims.

Claims

1, frequency-division compression circuit, comprising:

a plurality of pre-filters for receiving input signals and filtering the input signals respectively to output a plurality of frequency-divided signals;

a plurality of frequency division limiters, electrically coupled to the pre-filters, respectively, for compressing the th frequency-divided signals to output second frequency-divided signals;

a plurality of post-stage filters electrically coupled to the plurality of frequency division limiters, respectively, for filtering the corresponding second frequency-divided signals to output a plurality of output signals;

wherein the pre-filter and the post-filter corresponding to of the plurality of divide-by limiters respectively comprise different cut-off frequencies;

wherein pre-stage low pass filters of the plurality of pre-stage filters and post-stage low pass filters of the plurality of post-stage filters correspond to low frequency limiters of the plurality of divide-by limiter units;

wherein pre-stage high-pass filters of the plurality of pre-stage filters and post-stage high-pass filters of the plurality of post-stage filters correspond to high-frequency limiters of the plurality of divide-by limiter units;

wherein pre-stage bandpass filters of the plurality of pre-stage filters and post-stage bandpass filters of the plurality of post-stage filters correspond to intermediate frequency limiters of the plurality of divide-by limiter units.

2. The frequency division compression circuit of claim 1, wherein an upper cut-off frequency of the preceding low-pass filter is greater than an upper cut-off frequency of the following low-pass filter.

3. The crossover compression circuit of claim 1, wherein the lower cutoff frequency of the preceding high-pass filter is less than the lower cutoff frequency of the succeeding high-pass filter.

4. The fractional frequency compression circuit of claim 1, wherein the lower cut-off frequency of the preceding stage bandpass filter is less than the lower cut-off frequency of the following stage bandpass filter, and the upper cut-off frequency of the preceding stage bandpass filter is greater than the upper cut-off frequency of the following stage bandpass filter.

5. The frequency division compression circuit of claim 1, further comprising:

mixing unit for receiving the output signals and mixing the output signals to output mixed signal.

6, an audio processing method, comprising:

filtering the input signal by a plurality of pre-filters according to a plurality of pre-cut frequencies respectively to divide the input signal into a plurality of divided signals corresponding to different frequency bands;

compressing the plurality of th divided signals by a plurality of division limiters, respectively, to output a plurality of compressed second divided signals, and

filtering, by a plurality of post-stage filters, the plurality of second divided signals according to a plurality of post-stage cutoff frequencies different from the plurality of pre-stage cutoff frequencies, respectively, to output a plurality of output signals;

7. The audio processing method according to claim 6, wherein an upper cutoff frequency of any of the plurality of preceding cutoff frequencies is greater than an upper cutoff frequency of its corresponding succeeding cutoff frequency, and a lower cutoff frequency of any of the plurality of preceding cutoff frequencies is less than a lower cutoff frequency of its corresponding succeeding cutoff frequency.

8. The audio processing method of claim 6, further comprising:

receiving the plurality of output signals through an mixing unit and mixing the plurality of output signals to output mixed signals, and

the mixed sound signal is received and amplified by the power amplifier to output amplified mixed sound signal to speaker.

An audio processing system of , comprising:

signal input terminal for receiving input signal;

processor electrically coupled to the signal input terminal for executing audio processing method on the input signal to output mixed sound signal;

power amplifier electrically coupled to the processor for amplifying the mixed sound signal and outputting amplified mixed sound signal, and

speaker electrically coupled to the power amplifier for receiving the amplified mixed sound signal and outputting audio;

wherein the audio processing method executed by the processor comprises:

filtering the input signal by a plurality of pre-filters according to a plurality of pre-cut frequencies respectively to divide the input signal into a plurality of -th divided signals corresponding to different frequency bands;

compressing the th frequency-divided signals by a plurality of frequency division limiters respectively to output a plurality of compressed second frequency-divided signals;

filtering, by a plurality of post-stage filters, the plurality of second divided signals according to a plurality of post-stage cutoff frequencies different from the plurality of pre-stage cutoff frequencies, respectively, to output a plurality of output signals; and

receiving the plurality of output signals through an mixing unit, and mixing the plurality of output signals to output the mixed signal;

10. The audio processing system of claim 9, wherein an upper cutoff frequency of any of the plurality of pre-stage cutoff frequencies is greater than an upper cutoff frequency of its corresponding post-stage cutoff frequency, and a lower cutoff frequency of any of the plurality of pre-stage cutoff frequencies is less than a lower cutoff frequency of its corresponding post-stage cutoff frequency.