Acoustic signal processing device, acoustic system, and method for enhancing bass

Abstract

To provide an acoustic signal processing device, an acoustic system, and a method for enhancing a low-pitched sound feeling for enhancing a low-pitched sound feeling with more natural auditory feeling.SOLUTION: An acoustic signal processing device 2 outputs an output sound signal B obtained by adding a low-pitched sound sense enhancement signal which enhances the low-pitched sound sense of a source sound signal A to the source sound signal A outputted by an audio source instrument 1 to a speaker 3. The lower limit frequency of the reproduction frequency band of the speaker 3 is considered as f0. The acoustic signal processing device 2 reduces and maps the components of the frequency band below f0 of the source sound signal A by FIF (Fractal Interpolation Functions) and generates the low-pitched sound sense enhancement signal C in the band of frequencies from f0 to f1 (f0<f1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for enhancing the bass feel of output sounds from an audio system. [Background technology]

[0002] When a speaker that is small and lightweight and has insufficient reproduction capabilities in the low frequency band is used for outputting an audio system, the bass perceived by the user may be insufficient. In such cases, a known technique for enhancing the bass sensation involves dividing the bass components of the output signal of a sound source device into frequency bands, generating harmonics for each divided signal, and adding each generated harmonic to the output signal of the sound source device to produce an output signal for the speaker (for example, Patent Document 1).

[0003] Furthermore, as a technique related to the present invention, the FIF (Fractal Interpolation Functions) technique is known (for example, Patent Documents 2, 3, and 4). FIF is a technology that upsamples audio data by dividing a time interval T into multiple time intervals, each of which is designated as an interpolation interval ti, calculating a contraction mapping function ωi() that contracts and maps the signal waveform S of the time interval T onto the interpolation interval ti, and applying the contraction mapping function ωi(S) to contract and map the signal waveform S onto each interpolation interval ti. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-320516 [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-084370 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-330144 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-229492 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the technology for enhancing the bass feeling by adding harmonics for each frequency band of the bass component of the output signal of the sound source device to the output signal described above, only harmonics are added to the output signal, so depending on the type of sound represented by the output signal of the sound source device (for example, a simple sound effect), the output sound of the speaker may give an unnatural auditory sensation.

[0006] Therefore, an object of the present invention is to enhance the bass of the output sound of an acoustic system so as to obtain a more natural listening experience. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides an audio signal processing device that adds a bass enhancement signal that enhances the bass of an input audio signal to the audio signal and outputs the result, the audio signal processing device comprising: a bass enhancement signal generating means that generates a bass enhancement signal from the input audio signal; and a synthesizing means that synthesizes the bass enhancement signal with the input audio signal. To the speaker and a synthesis means for outputting the synthesized image. Here, with the lower limit of the reproduction frequency band of the speaker being f0, The bass-enhanced signal generating means generates the bass-enhanced signal by reducing and mapping the low-frequency band components of the input acoustic signal using FIF (Fractal Interpolation Functions). Also, the bass enhancement signal generation means extracts, as feature points, the data of the acoustic signal at a sampling rate FS every I samples, and for each block of size BS, maps each feature point within the block to each interpolation interval of size TS obtained by dividing the block in a reduced manner, and I ≧ FS(f0×2) BS ≧ I×2 TS ≦ BS(f1 / f0) the relationship is satisfied.

[0008] In addition, in order to achieve the above object, the present invention provides an acoustic system including an acoustic device that outputs an acoustic signal, a speaker, and an acoustic signal processing device that adds and outputs a bass sense enhancement signal for enhancing the bass sense of the acoustic signal output from the acoustic device. The acoustic signal processing device includes bass sense enhancement signal generation means for generating a bass sense enhancement signal from the acoustic signal output from the acoustic device, and synthesis means for synthesizing the bass sense enhancement signal with the acoustic signal output from the acoustic device and outputting the synthesized signal to the speaker. Here, with the lower limit of the reproduction frequency band of the speaker being f0, the bass sense enhancement signal generation means shrinks and maps the components in the frequency band of f0 or lower of the acoustic signal output from the acoustic device by means of FIF (Fractal Interpolation Functions) to generate the bass sense enhancement signal in the frequency band from f0 to f1 (where f0 < f1).

[0009] Here, in this acoustic system, in the bass sense enhancement signal generation means, data of the acoustic signal with a sampling rate FS output from the acoustic device is extracted as feature points every I samples. For each block of size BS, each feature point within the block is shrunk and mapped to each interpolation interval of size TS obtained by dividing the block, and I ≧ FS(f0 × 2) BS ≧ I × 2 TS ≦ BS(f1 / f0) is configured to satisfy the relationship is performed . In addition, the present invention also provides a method for enhancing the bass sense of an acoustic signal. The method includes from a step of generating a bass sense enhancement signal, and To the speaker a step of synthesizing the bass sense enhancement signal with the acoustic signal and outputting the synthesized signal. Here, this method for enhancing the bass sense includes With the lower limit of the reproduction frequency band of the speaker being f0, the step of generating the bass enhancement signal is to map the components in the low-frequency band of the acoustic signal below f0 by Fractal Interpolation Functions (FIF) in a reduced manner to generate the bass enhancement signal in the frequency band from f0 to f1 (where f0 < f1). Also, the step of generating the bass enhancement signal extracts, as feature points, the data of the acoustic signal at a sampling rate FS every I samples, and for each block of size BS, maps each feature point within the block to each interpolation interval of size TS obtained by dividing the block in a reduced manner, and I ≧ FS(f0×2) BS ≧ I×2 TS ≦ BS(f1 / f0) ​

[0010] According to the above-described acoustic signal processing device, acoustic system, and bass enhancement method, a signal in a frequency band higher than the low-frequency components of the acoustic signal, which is self-similar to the low-frequency components, is used to enhance the bass, thereby achieving a more natural bass enhancement. [Effects of the Invention]

[0011] As described above, according to the present invention, the bass of the output sound of the acoustic system can be enhanced so as to provide a more natural listening experience. [Brief explanation of the drawings]

[0012] ​ 1 is a block diagram showing a configuration of an audio system according to an embodiment of the present invention. ​ FIG. 2 is a block diagram showing a configuration of an FIF processing unit according to the embodiment of the present invention. ​ FIG. 10 is a diagram illustrating an example of processing performed by an FIF processing unit according to the embodiment of the present invention. ​ FIG. 10 is a diagram illustrating an example of processing performed by an FIF processing unit according to the embodiment of the present invention. ​ FIG. 10 is a diagram illustrating an example of processing performed by an FIF processing unit according to the embodiment of the present invention. ​ 10A and 10B are diagrams illustrating an example of generating a bass enhancement signal according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described. FIG. 1 shows the configuration of an audio system according to this embodiment. As shown in the figure, the audio system includes an audio source device 1, an audio signal processing device 2, a speaker 3, and a control unit 4. In this configuration, the audio source device 1 outputs a sound source sound signal A. The audio signal processing device 2 outputs an output audio signal B, which is obtained by adding a bass enhancement signal for enhancing the bass feeling of the sound source audio signal A, to the speaker 3. The audio signal processing device 2 includes a bass enhancement signal generation unit 21 that generates and outputs a bass enhancement signal C from the sound source audio signal A, a delay unit 22 that delays the sound source audio signal A, and a mixer 23 that adjusts the gain of the output of the bass enhancement signal generation unit 21, combines it with the output of the delay unit 22, and outputs it as the output audio signal B. The delay unit 22 delays the sound source audio signal A and aligns the delay time of the sound source audio signal A with the bass enhancement signal C.

[0014] Next, the bass enhancement signal generation unit 21 includes a pre-LPF 211, a FIF processing unit 212, a post-HPF 213, and a post-LPF 214. Here, the bass enhancement signal generation unit 21 generates a bass enhancement signal C having a frequency band from f0 to f1 (f0 < f1), where f0 is the lower limit frequency of the reproduction frequency band of the speaker 3. The pre-LPF 211 extracts the components in the frequency band of f0 or less of the sound source audio signal A and outputs it as a low-frequency audio signal S to the FIF processing unit 212. The FIF processing unit 212 performs a process of generating an original bass enhancement signal D by means of FIF (Fractal Interpolation Functions). Then, the post-HPF 213 and the post-LPF 214 remove the unnecessary components in the frequency band of f0 or less and the frequency band of f1 or more of the original bass enhancement signal D, and output it as the bass enhancement signal C in the frequency band from f0 to f1 to the mixer 23.

[0015] Next, as shown in FIG. 2, the FIF processing unit 212 includes a feature point extraction unit 2121, a contraction mapping function calculation unit 2122, and a mapping processing unit 2123. The control unit 4 calculates the feature point interval I, the block size BS of the block that is a time interval, and the interpolation interval size TS of the interpolation interval obtained by dividing the block into a plurality of parts according to the sampling rate FS of the sound source audio signal A acquired from the audio source device 1 or the like, so as to satisfy the following conditions, and sets them to the FIF processing unit 212.

[0016] I ≧ FS(f0 × 2) BS≧I×2 TS≦BS(f1 / f0) Therefore, to give an example of specific numerical values, if the sampling rate of the sound source signal A is FS=48000Hz, the lower limit of the playback frequency band of the speaker 3 is f0=50Hz, and the upper limit of the bass enhancement signal C is f1=200Hz, then: I≧FS(f0×2)=480 Therefore, if I=512 is selected for ease of processing, BS≧I×2=1024 TS≦BS(f1 / f0)=256 This becomes:

[0017] The feature point extraction unit 2121 of the FIF processing unit 212 extracts every I data of the low frequency sound signal S as a feature point. For example, if I=4, data of the low frequency sound signal S with a sampling rate FS shown in FIG. 3a is extracted as feature points every fourth point as shown in FIG. 3b. Here, the feature points extracted in this manner are obtained by downsampling the low frequency sound signal S to a sampling rate of f0×2 or less, and according to the Nyquist theorem, the upper limit of the frequency band is f0 or less. Next, by setting the block size BS≧I×2, each block contains three or more feature points. For example, if the block size BS=I×2, each block contains three feature points, as shown in Figure 3c. Furthermore, by setting TS≦BS(f1 / f0), the block is divided into f1 / f0 or more interpolation sections. For example, if f1 / f0=4, a block with a block size of BS is divided into four interpolation sections with an interpolation section size of BS / 4, as shown in Figure 3d. Next, as shown in Figure 4, for each block of block size BS of the low-frequency sound signal S, the contraction mapping function calculation unit 2122 calculates a contraction mapping function wi(S) that contracts and maps the low-frequency sound signal S of the entire block to the interpolation section for each interpolation section of interpolation section size TS within the block. The calculation of the contraction mapping function wi(S) is performed using, for example, the calculation algorithm of the contraction mapping function wi(S) in each of the known techniques of the above-mentioned FIF (Fractal Interpolation Functions). Next, for each block of the block size BS of the low-frequency sound signal S, the mapping processing unit 2123 sequentially performs a reduction mapping of each feature point extracted from the block to the interpolation section of the interpolation section size TS within the block using the reduction mapping function wi(S) calculated for the interpolation section by the reduction mapping function calculation unit 2122, and outputs the result as the original bass-enhanced signal D.

[0018] For example, as shown in Figure 5a1, three feature points are extracted for each block of block size BS, and as shown in Figure 5a2, the block is divided into four interpolation intervals of interpolation interval size TS. As shown by the arrows from Figure 4a1 to Figure 4a2, the three feature points in the block are contraction-mapped to each interpolation interval using the contraction mapping function wi(S).

[0019] Furthermore, for example, if five feature points are extracted for each block of block size BS as shown in Figure 5b1, and the block is divided into four interpolation intervals of interpolation interval size TS as shown in Figure 5b2, the five feature points in the block are contraction-mapped to each interpolation interval using the contraction mapping function wi(S), as shown by the arrows from Figure 5b1 to Figure 5b2.

[0020] In this way, the generated original bass-enhanced signal D is reduced to TS / BS in the time direction, and the original bass-enhanced signal D has a frequency band whose upper limit exceeds f0, resulting in a sound that is self-similar to the low-frequency sound signal S. The embodiments of the present invention have been described above. As described above, according to this embodiment, the bass enhancement signal C added to the sound source sound signal A to enhance the bass is a signal within the reproduction band of the speaker 3 that is self-similar to the low-frequency components of the sound source sound signal A and is generated by FIF (Fractal Interpolation Functions) from the low-frequency components outside the reproduction band of the speaker 3, thereby achieving a bass enhancement that sounds more natural to the ear.

[0021] For example, Figure 6 shows an original bass-enhanced signal D62 generated by the FIF processing unit 212 from a 50 Hz sine wave 61 with FS = 48000 Hz, I = 512, BS = 1024, and TS = 3. As shown in the figure, compared to simple harmonics of the sine wave 61, a natural signal dispersed over a wide band is generated as the original bass-enhanced signal D62.

[0022] In Figure 6, the vertical axis is decibels (dB) and the horizontal axis is frequency (Hz). [Explanation of symbols]

[0023] 1...Audio source device, 2...Acoustic signal processing device, 3...Speaker, 4...Control unit, 21...Bass enhancement signal generation unit, 22...Delay unit, 23...Mixer, 211...Pre-LPF, 212...FIF processing unit, 213...Post-HPF, 214...Post-LPF, 2121...Feature point extraction unit, 2122...Contraction mapping function calculation unit, 2123...Mapping processing unit.

Claims

1. An audio signal processing device that adds a bass enhancement signal that enhances the bass of an input audio signal to the input audio signal and outputs the result, a bass enhancement signal generating means for generating a bass enhancement signal from an input acoustic signal; a synthesizing means for synthesizing the bass-enhanced signal with an input acoustic signal and outputting the resultant signal to a speaker; The lower limit of the playback frequency band of the speaker is f0, the bass-enhanced signal generating means reduces and maps components of a low frequency band equal to or lower than f0 of the input acoustic signal using FIF (Fractal Interpolation Functions) to generate the bass-enhanced signal in a frequency band from f0 to f1 (where f0<f1); The bass-enhanced signal generating means extracts feature points from every I data of the acoustic signal having a sampling rate of FS, and for each block of size BS, reduces and maps each feature point in the block to each interpolation section of size TS obtained by dividing the block, and I≧FS(f0×2) BS≧I×2 TS≦BS(f1 / f0) An acoustic signal processing device, characterized in that the following relationship is satisfied.

2. An audio system comprising an audio device that outputs an audio signal, a speaker, and an audio signal processing device that adds a bass enhancement signal that enhances the bass of the audio signal output by the audio device and outputs the added signal, The acoustic signal processing device includes: a bass enhancement signal generating means for generating a bass enhancement signal from the acoustic signal output by the acoustic device; a synthesizing means for synthesizing the bass-enhanced signal with an acoustic signal output from the acoustic device and outputting the resultant signal to the speaker; The lower limit of the playback frequency band of the speaker is f0, the bass-enhanced signal generating means reduces and maps components of a frequency band equal to or lower than f0 of the acoustic signal output by the acoustic device using FIF (Fractal Interpolation Functions) to generate the bass-enhanced signal in a frequency band from f0 to f1 (where f0<f1); The bass-enhanced signal generating means extracts feature points from every I data of the audio signal having a sampling rate of FS output by the audio device, and for each block of size BS, reduces and maps each feature point in the block to each interpolation section of size TS obtained by dividing the block, and I≧FS(f0×2) BS≧I×2 TS≦BS(f1 / f0) An acoustic system characterized in that the following relationship is satisfied.

3. A method for enhancing bass sensation of an audio signal, comprising: generating a bass-enhanced signal from the acoustic signal; and combining the bass-enhanced signal with the acoustic signal and outputting the resultant signal to a speaker. The lower limit of the playback frequency band of the speaker is f0, the step of generating the bass-enhanced signal includes performing contraction mapping of low-frequency components of the acoustic signal equal to or lower than f0 using FIF (Fractal Interpolation Functions) to generate the bass-enhanced signal in a frequency band from f0 to f1 (where f0<f1); The step of generating the bass-enhanced signal includes extracting every I data of the acoustic signal having a sampling rate of FS as a feature point, and for each block of size BS, reducing and mapping each feature point in the block to each interpolation section of size TS obtained by dividing the block, and I≧FS(f0×2) BS≧I×2 TS≦BS(f1 / f0) A method for enhancing bass sensation, characterized in that the following relationship is satisfied.

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