Bass emphasis method and bass emphasis device

Abstract

The invention relates to a bass emphasis method and a bass emphasis device, which suppress distortion of sound and persistent sound generated by a harmonic instrument and generate a signal with an emphasized low frequency band. A bass emphasis device (20) is provided with an extraction unit (21), a generation unit (22), and a synthesis unit (24). An extraction unit (21) extracts a percussion instrument signal (b2) indicating a percussion instrument sound component from an input sound signal (a1) including a harmonic instrument sound component and the percussion instrument sound component. The generation unit (22) generates a low-frequency signal (c4) on the basis of the percussion instrument signal (b2). The low-frequency signal (c4) is a signal having a frequency 1 / 2 of the frequency of the fundamental component of the percussion instrument signal (b2). A synthesis unit (24) generates a low-band emphasis signal (e1) on the basis of a low-frequency signal (c4) and an input audio signal (a1). The low-band emphasized signal (e1) is a signal in which the low-band frequency component of the input audio signal (a1) is emphasized.

Description

Technical Field

[0001] The invention relates to a bass emphasis method and a bass emphasis device. Background Art

[0002] In an audio system, a device for emphasizing the bass range of an input audio signal is known. For example, Patent Document 1 discloses a bass-emphasized playback device, which extracts a low-frequency band component from an input signal through a low-pass filter, generates an ultra-low-frequency band component with a frequency of 1 / 2 of the extracted low-frequency band component, adds the ultra-low-frequency band component to the low-frequency band component, and further adds the component obtained by adding the ultra-low-frequency band component to the low-frequency band component to the input signal, thereby obtaining an output signal with the low-frequency band emphasized.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2007-67628

[0004] The bass-emphasized playback device described in Patent Document 1 has a problem in that, when an ultra-low frequency band component is added to the original sound, the sound produced by the harmonic musical instrument and the sustained sound are perceived as being distorted greatly. Summary of the invention

[0005] In view of the above circumstances, an object of one embodiment of the present invention is to provide a bass emphasis method that suppresses distortion of sounds and sustained sounds generated by harmonic musical instruments and generates a signal with emphasized low frequency bands.

[0006] In order to solve the above problems, one embodiment of the present invention involves a bass emphasis method comprising the following steps: extracting a non-harmonic instrument signal representing a harmonic instrument sound component from an input sound signal comprising a harmonic instrument sound component and a non-harmonic instrument sound component as a component other than the harmonic instrument sound component; generating a low-frequency signal based on the non-harmonic instrument signal, the low-frequency signal having a frequency of 1 / N of the frequency of the fundamental component of the non-harmonic instrument signal, wherein N is an integer greater than 2; and generating a low-frequency band emphasis signal in which the low-frequency band frequency component of the input sound signal is emphasized based on the low-frequency signal and the input sound signal.

[0007] A bass emphasis device according to one embodiment of the present invention comprises: an extraction unit, which extracts a non-harmonic instrument signal representing a harmonic instrument sound component from an input sound signal including a harmonic instrument sound component and a non-harmonic instrument sound component as a component other than the harmonic instrument sound component; a first generation unit, which generates a low-frequency signal based on the non-harmonic instrument signal, the low-frequency signal having a frequency 1 / N of the fundamental wave component of the non-harmonic instrument signal, wherein N is an integer greater than 2; and a second generation unit, which generates a low-frequency band emphasis signal in which the low-frequency band frequency component of the input sound signal is emphasized based on the low-frequency signal and the input sound signal.

[0008] A bass emphasis device according to one embodiment of the present invention comprises: an extraction unit, which extracts a non-harmonic instrument signal representing a harmonic instrument sound component from an input sound signal including a harmonic instrument sound component and a non-harmonic instrument sound component as a component other than the harmonic instrument sound component; a generation unit, which generates a low-frequency signal based on the non-harmonic instrument signal, the low-frequency signal having a frequency of 1 / N of the frequency of the fundamental wave component of the non-harmonic instrument signal, wherein N is an integer greater than 2; and an output unit, which outputs an output sound signal including at least the low-frequency signal to an actuator that vibrates a seat. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 1 is a diagram showing a configuration of an example of an acoustic system including the bass emphasizing device according to the first embodiment.

[0010] Figure 2 Yes means Figure 1 A functional block diagram of the extraction unit.

[0011] Figure 3 This is a diagram showing an example of a spectrum having harmonic instrument sound components.

[0012] Figure 4 This is a diagram showing an example of a spectrogram having percussion instrument sound components.

[0013] Figure 5 Yes means Figure 1 A block diagram of the functions of the generation unit.

[0014] Figure 6 : is a diagram showing an example of the second bass signal.

[0015] Figure 7 It is a diagram for explaining the return of the waveform.

[0016] Figure 8 : is a diagram showing an example of a low-frequency percussion instrument signal.

[0017] Fig. 9 : is a diagram showing an example of the third bass signal.

[0018] Fig.10 1 is a diagram showing a configuration of an example of an acoustic system including a bass emphasis device according to a first variation. DETAILED DESCRIPTION

[0019] A: First embodiment

[0020] A1: Bass emphasis device structure

[0021] Figure 11 is a structural diagram showing an example of an audio system 1 including a bass emphasis device 20 according to the first embodiment. The audio system 1 is installed in a vehicle such as a car. Figure 1 As shown, the audio system 1 includes a storage device 10 , a bass emphasis device 20 , an amplifier device 30 , and a speaker device 40 .

[0022] In the acoustic system 1, the bass emphasis device 20 generates a low-frequency band emphasis signal e1 based on the input sound signal a1 input from the sound source 2, and the amplifier 30 amplifies the generated low-frequency band emphasis signal e1 and outputs it as an amplified sound signal e2 to the speaker device 40. The speaker device 40 emits sound based on the amplified sound signal e2.

[0023] The storage device 10 is a recording medium that can be read by a computer (for example, a nontransitory recording medium that can be read by a computer). The storage device 10 includes a nonvolatile memory and a volatile memory. Examples of nonvolatile memories include ROM (Read Only Memory), EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). Examples of volatile memories include RAM (Random Access Memory).

[0024] The storage device 10 stores a program p1 and various information. The program p1 defines the operation of the bass emphasis device 20. The storage device 10 may store the program p1 read from a storage device of a server (not shown). In this case, the storage device of the server is an example of a computer-readable recording medium.

[0025] The bass emphasis device 20 reads the program p1 from the storage device 10. The bass emphasis device 20 functions as an extraction unit 21, a generation unit 22, a delay unit 23, and a synthesis unit 24 by executing the program p1. At least one of the extraction unit 21, the generation unit 22, the delay unit 23, and the synthesis unit 24 can be implemented by a circuit such as a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0026] The input sound signal a1 is input to the extraction unit 21 from the sound source 2. The input sound signal a1 includes a harmonic instrument sound component and a non-harmonic instrument sound component. The harmonic instrument sound component is a component that can be decomposed into a basic frequency component and a frequency component that is an integer multiple of the basic frequency. For example, the sound obtained based on a string instrument, the sound obtained based on a wind instrument, the lead vocal sound, etc. have a harmonic instrument sound component. The harmonic instrument sound component is an element that determines the pitch and timbre, and is a continuous sound. In contrast, the non-harmonic instrument sound component is a component other than the harmonic instrument sound component. Compared with the harmonic instrument sound component, the non-harmonic instrument sound component has a random frequency component and is a non-continuous sound. The non-harmonic instrument sound component includes a percussion instrument sound component. The percussion instrument sound component is mainly a component of the sound generated by a percussion instrument. In fact, most of the non-harmonic instrument sound is a percussion instrument sound component, and it can also be said that the percussion instrument sound component is equivalent to the non-harmonic instrument sound component. For example, the sound obtained by a drum, the sound obtained by a cymbal, etc. have a percussion instrument sound component. In addition, even the sound produced by the harmonic instrument may contain percussion instrument sound components depending on the playing method. The percussion instrument sound components are elements that determine the beat and the strength of the sound.

[0027] The extraction unit 21 separates the input sound signal a1 into a harmonic instrument sound component and a percussion instrument sound component, and extracts a signal representing the separated percussion instrument sound component as a percussion instrument signal b2. The percussion instrument sound component is an example of a "non-harmonic instrument sound component", and the percussion instrument signal b2 is an example of a "non-harmonic instrument signal".

[0028] The generator 22 generates the low-frequency signal c4 based on the percussion instrument signal b2. The low-frequency signal c4 is a signal having a frequency 1 / 2 of the frequency of the fundamental wave component of the percussion instrument signal b2. The generator 22 is an example of a "first generator".

[0029] The delay unit 23 generates a delayed sound signal d1 based on the input sound signal a1. The delayed sound signal d1 is a signal obtained by delaying the input sound signal a1 by a time until the low-frequency signal c4 is generated.

[0030] The synthesizer 24 generates a low-frequency band emphasis signal e1 by synthesizing the low-frequency signal c4 and the delayed sound signal d1. The low-frequency band emphasis signal e1 is a signal in which the low-frequency band frequency component of the delayed sound signal d1 is emphasized. That is, the synthesizer 24 generates the low-frequency band emphasis signal e1 based on the low-frequency signal c4 and the input sound signal a1. The combination of the delay unit 23 and the synthesizer 24 is an example of a "second generation unit".

[0031] Below, refer to Figure 2 to Figure 4 The extraction unit 21 will be described in more detail. Figure 2 Yes means Figure 1 The functional block diagram of the extraction unit 21 is shown in FIG. Figure 2As shown, the extraction unit 21 includes a low-pass filter 211 and a percussion instrument sound extraction unit 212 .

[0032] The low-pass filter 211 is a second-order IIR filter (Infinite Impulse Response Filter). The cutoff frequency of the low-pass filter 211 is 200 Hz. The low-pass filter 211 generates the first bass signal b1 by attenuating the frequency components having a frequency greater than 200 Hz in the input sound signal a1.

[0033] In addition, the cutoff frequency of the low-pass filter 211 is not limited to 200 Hz. For example, the cutoff frequency of the low-pass filter 211 may be 200 Hz ± K% (for example, 20%). In addition, the low-pass filter 211 is not limited to a 2nd-order IIR filter. For example, the low-pass filter 211 may be a 1st-order IIR filter or a 3rd-order IIR filter, or may be a digital filter different from an IIR filter such as a FIR filter (Finite Impulse Response Filter).

[0034] The percussion sound extraction unit 212 separates the first bass signal b1 into harmonic instrument sound components and percussion instrument sound components and extracts a percussion instrument signal b2. The percussion sound extraction unit 212 uses, for example, the well-known HPSS (Harmonic-Percussive Source Separation) as a method of separating the harmonic instrument sound components and the percussion instrument sound components.

[0035] HPSS is a technology that decomposes the sound signal in the time-frequency domain by short-time Fourier transform, and filters the sound signal by utilizing the different characteristics represented by the harmonic instrument sound component and the percussion instrument sound component. Short-time Fourier transform is to cut out the sound signal using a window function of a constant size, perform Fourier transform on the cut signal and calculate the spectrum. The time-frequency domain is a plane whose vertical axis is represented by frequency and whose horizontal axis is represented by time. A graph that displays the intensity of the sound signal after short-time Fourier transform in the time-frequency domain is called a spectrogram. The vertical axis of the spectrogram represents frequency, and the horizontal axis of the spectrogram represents time. Therefore, the vertical axis is also called the frequency axis, and the horizontal axis is also called the time axis.

[0036] Figure 3 This is a diagram showing an example of a spectrum having harmonic instrument sound components. Figure 4 This is a diagram showing an example of a spectrogram having percussion instrument sound components.

[0037] The harmonic instrument sound component is a sustained sound with an easily identifiable pitch. Figure 3 As shown, when observed in the time-frequency domain, the harmonic instrument sound component has the characteristics of being steep along the frequency axis and smooth along the time axis.

[0038] On the other hand, percussion instrument sound components are non-continuous sounds, and are sounds whose pitches are difficult to identify. Figure 4 As shown, when observed in the time-frequency domain, the percussion instrument sound component has the characteristics of being smooth along the frequency axis and steep along the time axis.

[0039] As described above, by utilizing the anisotropy of smoothness between the harmonic instrument sound components and the percussion instrument sound components on the spectrum and filtering the spectrum, the harmonic instrument sound components and the percussion instrument sound components can be separated.

[0040] As a filter for extracting harmonic instrument sound components, for example, a vertically long rectangular filter can be considered. Using a vertically long rectangular filter, averaging is performed along the vertical axis of the spectrogram to extract the harmonic instrument sound components. In addition, averaging is performed along the time axis within the range of the filter, thereby removing the influence of the percussion instrument sound components.

[0041] As a filter for extracting percussion instrument sound components, for example, a horizontally long rectangular filter can be considered. Using a horizontally long rectangular filter, averaging is performed along the horizontal axis of the spectrogram to extract the percussion instrument sound components. In addition, averaging is performed along the frequency axis within the range of the filter, thereby removing the influence of harmonic instrument sound components.

[0042] Therefore, more specifically, the percussion instrument sound extraction unit 212 performs short-time Fourier transform on the first bass signal b1, and outputs the result of the short-time Fourier transform as a spectrogram. The percussion instrument sound extraction unit 212 extracts the percussion instrument sound component by filtering the output spectrogram. Then, the percussion instrument sound extraction unit 212 transforms the extracted percussion instrument sound component into a sound signal in the time domain by inverse short-time Fourier transform and outputs it as a percussion instrument signal b2.

[0043] Next, refer to Figures 5 to 9 The generation unit 22 will be described in detail. Figure 5 Yes means Figure 1 The block diagram of the function of the generating unit 22. Figure 5 As shown, the generator 22 includes a low-pass filter 221 , a low-band generator 222 , a low-pass filter 223 , and a gain controller 224 .

[0044] The low-pass filter 221 extracts the low-frequency band component from the percussion instrument signal b2 and outputs it as the second bass signal c1. The cutoff frequency of the low-pass filter 221 is 200 Hz. Therefore, the low-pass filter 221 extracts the low-frequency band component below 200 Hz in the percussion instrument signal b2. In addition, the cutoff frequency of the low-pass filter 221 may not be 200 Hz. For example, the cutoff frequency of the low-pass filter 221 may be a frequency within the range of 200 Hz ± K% (for example, 20%).

[0045] The low-frequency band generating unit 222 generates a signal having a component with a frequency half the fundamental wave component frequency of the percussion instrument signal b2 based on the second bass signal c1 outputted from the low-pass filter 221. The generated signal is a signal at one octave higher than the second bass signal c1, and is therefore referred to as a low-frequency band percussion instrument signal c2.

[0046] As for the method of generating the low-frequency percussion instrument signal c2, there are known methods of generating in the time domain and methods of generating in the frequency domain. As for the method of generating the low-frequency percussion instrument signal c2 in the time domain, there are the usual zero crossing detection method, the method of generating a waveform with a double period by folding back the waveform at the zero crossing point, and the like.

[0047] The zero-crossing detection method is a method that utilizes the change in the output state of the comparator when the signal waveform crosses the zero reference voltage. A rectangular wave with a period equal to the period of the signal waveform is obtained by zero-crossing detection. Furthermore, a low-frequency band component with a frequency of 1 / 2 is obtained by dividing the obtained rectangular wave by two.

[0048] In addition, for a method of generating a low-frequency percussion signal c2 in the frequency domain, there is a method of transforming a time domain signal into a frequency domain signal through FFT (Fast Fourier Transform), detecting the pitch in the frequency domain, and using a VCO (Voltage Controlled Oscillator) to generate a signal with a frequency 1 / 2 of the frequency of the detected pitch.

[0049] In this embodiment, a method of folding back the waveform at the zero crossing point is adopted. Figure 6 to Figure 8 A method for generating the low-frequency band percussion instrument signal c2 by the low-frequency band generating unit 222 will be described. Figure 6 : is a diagram showing an example of the second bass signal c1.

[0050] Figure 7 It is a diagram for explaining the return of the waveform. Figure 8 : is a diagram showing an example of the low-frequency band percussion instrument signal c2.

[0051] The second bass signal c1 input to the low frequency band generating unit 222 is as follows: Figure 6 The following description will be made by taking the case of the sinusoidal waveform shown in FIG. Figure 7 As shown, the phase range TR of 720°, which corresponds to two periods of the sine waveform, is set as a repetition unit, and the sine waveform is folded back at the zero level line every 360° in the phase range TR. More specifically, the low-frequency band generating unit 222 does not fold back the sine waveform in the interval T1 and folds back the sine waveform in the interval T2, among the two intervals T1 and T2 of the phase range TR.

[0052] Therefore, through Figure 7 The processing shown in the figure shows a waveform Figure 8 Changes as shown. Figure 8 The period of the waveform shown is twice the period of the original percussion instrument signal b2. Thus, based on the second bass signal c1 extracted by the low-pass filter 221, a low-frequency band percussion instrument signal c2 having a period twice, that is, one octave, is generated.

[0053] Fig. 9 is a diagram showing an example of the third bass signal c3. Fig. 9 As shown, the low-pass filter 223 removes the redundant high harmonics contained in the low-frequency percussion instrument signal c2. The cutoff frequency of the low-pass filter 223 is 100 Hz. Thus, the third bass signal c3 from which the redundant high harmonics are removed is output from the low-pass filter 223. In addition, the cutoff frequency of the low-pass filter 223 is not limited to 100 Hz. For example, the cutoff frequency of the low-pass filter 223 can be 100 Hz ± K% (for example, 20%).

[0054] The gain controller 224 adjusts the gain of the third bass signal c3 output from the low pass filter 223. The gain controller 224 outputs the third bass signal c3 with the adjusted gain as the low frequency signal c4 to the synthesizer 24. The gain of the gain controller 224 can be appropriately set by the user who sets the acoustic system 1.

[0055] The delay unit 23 delays the input sound signal a1. The delay unit 23 generates the delayed input sound signal a1 as the delayed sound signal d1 and outputs it to the synthesizing unit 24. The delay time realized by the delay unit 23 is preset to be equal to the sum of the delay time generated in the extracting unit 21 and the delay time generated in the generating unit 22. In other words, the delay time realized by the delay unit 23 is the time until the low-frequency signal c4 is generated based on the input sound signal a1.

[0056] In addition, the rising edge of the signal in the bass range is delayed compared with the signal in the middle range or the high range. Therefore, the delay time can be set so that the timing of the low-frequency signal c4 relative to the delayed sound signal d1 is advanced. In other words, the delay time achieved by the delay unit 23 can be set to be longer than the time until the low-frequency signal c4 is generated based on the input sound signal a1. Thus, the bass feeling is further emphasized. In addition, the delay unit 23 can have the function of a gain controller.

[0057] The synthesizer 24 generates a low-frequency band emphasis signal e1 based on the low-frequency signal c4 and the delayed sound signal d1. More specifically, the synthesizer 24 generates the low-frequency band emphasis signal e1 by adding the delayed sound signal d1 and the low-frequency signal c4. The low-frequency band emphasis signal e1 is a signal in which the low-frequency band frequency component of the input sound signal a1 is emphasized. The combination of the delay unit 23 and the synthesizer 24 is an example of a "second generation unit".

[0058] The amplifier device 30 amplifies the low-frequency-band emphasized signal e1 to a level suitable for speaker driving, and outputs the amplified sound signal e2 to the speaker device 40 .

[0059] The speaker device 40 emits a sound corresponding to the amplified sound signal e2.

[0060] A2: Summary of the first implementation method

[0061] As described above, the bass emphasis method involved in the first embodiment includes the following steps: extracting the percussion instrument signal b2 from the input sound signal a1; generating the low-frequency signal c4 based on the percussion instrument signal b2; and generating the low-frequency band emphasis signal e1 based on the low-frequency signal c4 and the input sound signal a1. The input sound signal a1 is a signal containing harmonic instrument sound components and non-harmonic instrument sound components. The low-frequency signal c4 is a signal having a frequency of 1 / 2 of the fundamental wave component frequency of the percussion instrument signal b2. The low-frequency band emphasis signal e1 is a signal in which the low-frequency band frequency component of the input sound signal a1 is emphasized.

[0062] In order to emphasize the bass of the harmonic musical instrument sound component, a low-frequency band signal having a frequency of 1 / 2 of the fundamental component frequency of the harmonic musical instrument sound component is generated and added to the original harmonic musical instrument sound component, sometimes the overtones of the low-frequency band signal do not exist in the harmonic musical instrument sound component after adding the low-frequency band signal. In addition, the harmonic musical instrument sound component is a continuous sound, so the harmonic musical instrument sound component after adding the low-frequency band signal is sometimes recognized as an unnaturally distorted sound. On the other hand, the non-harmonic musical instrument sound component has a random frequency component compared to the harmonic musical instrument sound component, and is a non-continuous sound, so even if the bass of the non-harmonic musical instrument sound component is emphasized, it is not easy to be recognized as distortion. Therefore, according to this method, the bass of the harmonic musical instrument sound component is not emphasized, so the distortion can be suppressed. In addition, the bass of the non-harmonic musical instrument sound component is emphasized, so the sense of shock and the sense of beat can be improved.

[0063] Furthermore, in the bass emphasis method according to the first embodiment, the non-harmonic instrument sound components include percussion instrument sound components.

[0064] The percussion instrument sound component has more random frequency components than the harmonic instrument sound component and is a non-continuous sound, so even if the bass of the percussion instrument sound component is emphasized, it is not easy to be recognized as distortion. Therefore, according to this method, the bass of the harmonic instrument sound component is not emphasized, and the bass of the percussion instrument sound component is emphasized, so that the sense of shock and the sense of beat can be further improved.

[0065] In the bass emphasis method according to the first embodiment, the step of extracting the percussion instrument signal b2 from the input sound signal a1 includes the steps of generating a first bass signal b1 based on the input sound signal a1, and extracting the percussion instrument signal b2 from the first bass signal b1. The first bass signal b1 is a signal in which frequency components in a higher frequency band than the frequency band of the percussion instrument sound component are reduced.

[0066] According to this method, the percussion instrument signal b2 is extracted from the first bass signal b1 after the high frequency component is reduced. Therefore, the amount of calculation involved in extracting the percussion instrument signal b2 is reduced compared to the amount of calculation in the case of extracting the percussion instrument signal b2 from the input sound signal a1 before the high frequency component is reduced, thereby reducing the calculation load.

[0067] In the bass emphasis method according to the first embodiment, the step of generating the low-frequency signal c4 based on the percussion instrument signal b2 includes the steps of generating a second bass signal c1 based on the percussion instrument signal b2, and generating the low-frequency signal c4 based on the second bass signal c1. The second bass signal c1 is a signal obtained by reducing a frequency component in a higher frequency band than a frequency band of a percussion instrument sound component.

[0068] According to this method, only the low-frequency components of the percussion instrument sound components are emphasized, so the sense of shock and the sense of rhythm can be further improved.

[0069] In the bass emphasis method according to the first embodiment, the step of generating the low-frequency band emphasis signal e1 includes the steps of generating a delayed sound signal d1, and adding the delayed sound signal d1 to the low-frequency signal c4 to generate the low-frequency band emphasis signal e1. The delayed sound signal d1 is a signal obtained by delaying the input sound signal a1 by a time until the low-frequency signal c4 is generated based on the input sound signal a1.

[0070] According to this method, the phase relationship between the low-frequency signal c4 and the input sound signal a1 can be adjusted, so that sound with less distortion and improved sense of shock and beat can be reproduced.

[0071] In addition, the bass emphasis device 20 according to the first embodiment includes an extraction unit 21, a generation unit 22, a delay unit 23, and a synthesis unit 24. The extraction unit 21 extracts a percussion instrument signal b2 from an input sound signal a1. The generation unit 22 generates a low-frequency signal c4 based on the percussion instrument signal b2. The synthesis unit 24 generates a low-frequency band emphasis signal e1 based on the low-frequency signal c4 and the input sound signal a1.

[0072] According to this aspect, the bass of the harmonic instrument sound component is not emphasized, so the occurrence of distortion can be suppressed. In addition, the bass of the percussion instrument sound component is emphasized, so the sense of shock and the sense of rhythm can be improved.

[0073] In addition, in the first embodiment, the percussion instrument sound component is an example of a "non-harmonic instrument sound component", the percussion instrument signal b2 is an example of a "non-harmonic instrument signal", the generating unit 22 is an example of a "first generating unit", and the combination of the delay unit 23 and the synthesis unit 24 is an example of a "second generating unit".

[0074] B: Deformation

[0075] The present invention is not limited to the above-mentioned embodiment, and various modifications can be adopted within the scope of the present invention. The following examples illustrate specific modifications. In addition, two or more methods arbitrarily selected from the following examples can be appropriately combined within the scope that does not contradict each other. In addition, in the following examples, for the elements whose effects and functions are equivalent to the above-mentioned embodiments, the reference numerals used in the above description are used and the respective detailed descriptions are appropriately omitted.

[0076] B1: First variant

[0077] Below, refer to Fig.10The acoustic system involved in the first variant is described. In addition, in the following description, for the sake of simplicity, the same reference numerals are used for the same structural elements as those in the first embodiment, and the description of their functions is sometimes omitted. In addition, in the following description, for the sake of simplicity, the differences between the first variant and the first embodiment are mainly described.

[0078] Fig.10 1 is a block diagram showing an example of an audio system 1A including a bass emphasis device 20A according to a first modification. The audio system 1A is installed in a vehicle such as a car, similarly to the audio system 1 according to the first embodiment. The audio system 1A includes a storage device 10A, a bass emphasis device 20A, an amplifier device 30, a speaker device 40, and an actuator 50.

[0079] The storage device 10A is a computer-readable recording medium. The storage device 10A includes a nonvolatile memory and a volatile memory. Examples of the nonvolatile memory include ROM, EPROM, and EEPROM. Examples of the volatile memory include RAM.

[0080] The storage device 10A stores a program p2 and various information. The program p2 defines the operation of the bass emphasis device 20A. The storage device 10A may store the program p2 read from a storage device of a server (not shown). In this case, the storage device of the server is an example of a computer-readable recording medium.

[0081] The bass emphasis device 20A reads the program p2 from the storage device 10A. The bass emphasis device 20A executes the program p2 to function as an extraction unit 21, a generation unit 22, a delay unit 23, a synthesis unit 24, and an output unit 25. At least one of the extraction unit 21, the generation unit 22, the delay unit 23, the synthesis unit 24, and the output unit 25 can be implemented by a circuit such as a DSP, an ASIC, a PLD, or an FPGA.

[0082] The extraction unit 21, the generation unit 22, the delay unit 23 and the synthesis unit 24 are Figure 1 The extraction unit 21, generation unit 22, delay unit 23 and synthesis unit 24 have the same structure, so their description is omitted.

[0083] The output unit 25 outputs the output sound signal f1 including the low-frequency signal c4 to the actuator 50 .

[0084] The actuator 50 is provided on a seat cushion 61 of a seat 60 of a vehicle. The actuator 50 includes, for example, a magnet fixed to a housing via a damper; a yoke directly fixed to the housing; and a coil wound around the yoke. A current corresponding to the output sound signal f1 flows through the coil. Due to the interaction between the current flowing through the coil according to the output sound signal f1 and the magnetic field generated by the magnet, a force along the axis of the coil is generated. Therefore, as the output sound signal f1 changes, the yoke and the coil vibrate relative to the magnet along the axis of the coil. According to the above structure, the actuator 50 vibrates the seat cushion 61 based on the output sound signal f1.

[0085] As described above, the bass emphasis device 20A involved in the first variant example includes an extraction unit 21, a generation unit 22, and an output unit 25. The extraction unit 21 extracts the percussion instrument signal b2 from the input sound signal a1. The input sound signal a1 is a signal containing a harmonic instrument sound component and a percussion instrument sound component. The percussion instrument signal b2 is a signal representing the percussion instrument sound component. The generation unit 22 generates a low-frequency signal c4 based on the percussion instrument signal b2. The low-frequency signal c4 is a signal having a frequency of 1 / 2 of the fundamental wave component frequency of the percussion instrument signal b2. The output unit 25 outputs the output sound signal f1 to the actuator 50. The output sound signal f1 is a signal containing the low-frequency signal c4.

[0086] According to this embodiment, the bass emphasis device 20A can provide vibration corresponding to the output sound signal f1 to the body of the passenger sitting on the seat 60 by vibrating the seat cushion 61. Therefore, the passenger can feel the shock and the beat not only from the ears of the passenger but also from the whole body. Therefore, the passenger can feel the shock and the beat more strongly.

[0087] In addition, the actuator 50 is not limited to an actuator having a damper of the above structure, and may be, for example, a speaker capable of playing bass, such as a woofer.

[0088] In addition, the actuator 50 may be provided at the backrest 62 of the seat 60 .

[0089] In addition, the sound system 1A according to the first modification is installed in a vehicle such as a car, and the actuator 50 causes the seat cushion 61 of the seat 60 to vibrate according to the output sound signal f1, but the sound system 1A can also be applied to buildings such as houses. In this case, the actuator 50 can be arranged on a sofa, a chair, a cushion, etc.

[0090] B2: Second modification

[0091] In the first modification, the low frequency signal c4 is input to the output unit 25 . However, the output unit 25 may output a low frequency band emphasis signal e1 synthesized from the low frequency signal c4 and the delayed sound signal d1 to the actuator 50 instead of the low frequency signal c4 .

[0092] B3: The third variant

[0093] In the first embodiment, HPSS is used for extracting percussion instrument sound components, but the method for extracting percussion instrument sound components is not limited to the method using HPSS, and various extraction methods can be used. For example, a well-known sound source separation technology can be used for extracting percussion instrument sound components. As a sound source separation technology, a technology for separating a lead vocal sound and each instrument sound from a music signal obtained by mixing a lead vocal sound and a plurality of instrument sounds based on deep learning realized by a neural network is known.

[0094] For example, according to the Demucs technology developed by Facebook Research, a recursive neural network based on the U-Net architecture is used to analyze the temporal structure of music signals. The analysis results are input into a convolutional neural network to separate each sound source in the frequency domain. In addition, the spectrogram of each separated sound source is inverse Fourier transformed and restored to a waveform in the time domain (https: / / github.com / facebookresearch / demucs).

[0095] By applying the above sound source separation technology, the percussion instrument sound components can be extracted.

[0096] B4: 4th variant

[0097] In the first embodiment, the extraction unit 21 is provided with a low-pass filter 211 at the front stage of the percussion instrument sound extraction unit 212. The purpose of the low-pass filter 211 is to reduce high-frequency band components that are not necessary for the calculation of the percussion instrument sound extraction unit 212, thereby reducing the amount of calculation processing of the percussion instrument sound extraction unit 212. Therefore, the low-pass filter 211 may be omitted.

[0098] B5: The fifth variant

[0099] In the generator 22 of the first embodiment, a signal having a frequency of 1 / 2 of the frequency of the fundamental wave component of the percussion instrument signal b2 is generated as the low-frequency signal c4, but the low-frequency signal c4 may be a signal having a frequency of 1 / N (N is an integer greater than or equal to 3) of the frequency of the fundamental wave component of the percussion instrument signal b2. For example, the generator of the fifth modified example generates a signal having a frequency of 1 / 4 of the frequency of the fundamental wave component of the percussion instrument signal b2 as the low-frequency signal c4.

[0100] According to this aspect, the low-frequency signal can be further emphasized, so the sense of shock and the sense of beat can be further improved.

[0101] B6: Sixth variant

[0102] Furthermore, although the audio system 1 according to the first embodiment is mounted on a vehicle such as an automobile, the audio system 1 can also be applied to the fields of home audio and professional audio.

[0103] C: Appendix

[0104] According to the above-exemplified embodiment, for example, the following configurations can be understood.

[0105] A bass emphasis method according to one embodiment of the present invention (embodiment 1) comprises the following steps: extracting a non-harmonic instrument signal representing a harmonic instrument sound component from an input sound signal comprising a harmonic instrument sound component and a non-harmonic instrument sound component as a component other than the harmonic instrument sound component; generating a low-frequency signal based on the non-harmonic instrument signal, the low-frequency signal having a frequency of 1 / N of the frequency of the fundamental component of the non-harmonic instrument signal, wherein N is an integer greater than 2; and generating a low-frequency band emphasis signal in which the low-frequency band frequency component of the input sound signal is emphasized based on the low-frequency signal and the input sound signal.

[0106] When a low-band signal having a frequency 1 / N of the fundamental wave component of a harmonic musical instrument sound component is generated in order to emphasize the bass of a harmonic musical instrument sound component and added to the original harmonic musical instrument sound component, the overtones of the low-band signal are sometimes not present in the harmonic musical instrument sound component after adding the low-band signal. In addition, the harmonic musical instrument sound component is a continuous sound, so the harmonic musical instrument sound component after adding the low-band signal is sometimes recognized as an unnaturally distorted sound. On the other hand, the non-harmonic musical instrument sound component has a random frequency component compared to the harmonic musical instrument sound component, and the continuous sound is less, so even if the bass of the non-harmonic musical instrument sound component is emphasized, it is not easy to be recognized as distortion. Therefore, according to this method, the bass of the harmonic musical instrument sound component is not emphasized, so the distortion can be suppressed. In addition, the bass of the non-harmonic musical instrument sound component is emphasized, so the sense of shock and the sense of beat can be improved.

[0107] In the bass emphasis method according to one aspect (aspect 2) of the present invention, the non-harmonic instrument sound component includes a percussion instrument sound component.

[0108] The percussion instrument sound component has more random frequency components than the harmonic instrument sound component and is a non-continuous sound, so even if the bass of the percussion instrument sound component is emphasized, it is not easy to be recognized as distortion. Therefore, according to this method, the bass of the harmonic instrument sound component is not emphasized, and the bass of the percussion instrument sound component is emphasized, so that the sense of shock and the sense of beat can be further improved.

[0109] In a bass emphasis method according to one embodiment (embodiment 3) of the present invention, the step of extracting the non-harmonic musical instrument signal from the input sound signal includes the following steps: generating a first bass signal having a frequency component in a higher frequency band than the frequency band of the non-harmonic musical instrument sound component reduced based on the input sound signal, and extracting the non-harmonic musical instrument signal from the first bass signal.

[0110] According to this aspect, the inharmonic instrument signal is extracted from the first bass signal after the high frequency component is reduced. Therefore, the amount of calculation involved in the extraction is reduced compared to the amount of calculation when the inharmonic instrument signal is extracted from the input sound signal before the high frequency component is reduced, thereby reducing the calculation load.

[0111] In a bass emphasis method according to one embodiment (method 4) of the present invention, the step of generating the low-frequency signal based on the non-harmonic musical instrument signal includes the following steps: generating a second bass signal having a higher frequency band than the frequency band of the non-harmonic musical instrument sound component reduced according to the non-harmonic musical instrument signal, and generating the low-frequency signal according to the second bass signal.

[0112] According to this aspect, only the low-frequency components of the inharmonic instrument sound components are emphasized, so that the sense of shock and the sense of rhythm can be further improved.

[0113] In a bass emphasis method involved in one embodiment (method 5) of the present invention, the step of generating the low-frequency band emphasis signal includes the following steps: generating a delayed sound signal by delaying the input sound signal for a period of time until the low-frequency signal is generated based on the input sound signal, adding the delayed sound signal and the low-frequency signal, thereby generating the low-frequency band emphasis signal.

[0114] According to this aspect, the phase relationship between the low-frequency signal and the input sound signal can be adjusted, so that sound with less distortion and improved sense of shock and beat can be reproduced.

[0115] A bass emphasis device according to one embodiment of the present invention (embodiment 6) comprises: an extraction unit, which extracts a non-harmonic instrument signal representing a harmonic instrument sound component from an input sound signal including a harmonic instrument sound component and a non-harmonic instrument sound component as a component other than the harmonic instrument sound component; a first generation unit, which generates a low-frequency signal based on the non-harmonic instrument signal, the low-frequency signal having a frequency of 1 / N of the frequency of the fundamental component of the non-harmonic instrument signal, wherein N is an integer greater than 2; and a second generation unit, which generates a low-frequency band emphasis signal in which the low-frequency band frequency component of the input sound signal is emphasized based on the low-frequency signal and the input sound signal.

[0116] According to this aspect, the bass of the harmonic instrument sound component is not emphasized, so the occurrence of distortion can be suppressed. In addition, the bass of the non-harmonic instrument sound component is emphasized, so the sense of shock and the sense of rhythm can be improved.

[0117] A bass emphasis device according to one embodiment of the present invention (embodiment 7) comprises: an extraction unit, which extracts a non-harmonic instrument signal representing a harmonic instrument sound component from an input sound signal comprising a harmonic instrument sound component and a non-harmonic instrument sound component as a component other than the harmonic instrument sound component; a generation unit, which generates a low-frequency signal based on the non-harmonic instrument signal, the low-frequency signal having a frequency of 1 / N of the frequency of the fundamental component of the non-harmonic instrument signal, wherein N is an integer greater than 2; and an output unit, which outputs an output sound signal comprising at least the low-frequency signal to an actuator that vibrates a seat.

[0118] According to this aspect, since the seat is vibrated by the signal in which the bass sound of the non-harmonic musical instrument sound component is emphasized, the sense of shock and the sense of rhythm can be further enhanced.

[0119] Description of the label

[0120] 20…bass emphasis device, 21…extraction unit, 22…generation unit, 23…delay unit, 24…synthesis unit, 25…output unit, 50…actuator, 60…seat, a1…input sound signal, b1…first bass signal, b2…percussion instrument signal, c1…second bass signal, c4…low-frequency signal, e1…low-frequency band emphasis signal, d1…delayed sound signal.

Claims

1. A method for bass emphasis, comprising the following steps: extracting a non-harmonic instrument signal representing the non-harmonic instrument sound component from an input sound signal including a harmonic instrument sound component and a non-harmonic instrument sound component as a component other than the harmonic instrument sound component; A low-frequency signal is generated based on the non-harmonic musical instrument signal, the low-frequency signal having a frequency 1 / N of the frequency of the fundamental wave component of the non-harmonic musical instrument signal, wherein: N is an integer greater than 2; and A low-frequency band emphasized signal in which the low-frequency band frequency components of the input audio signal are emphasized is generated based on the low-frequency signal and the input audio signal.

2. The bass emphasis method according to claim 1, wherein: The non-harmonic instrument sound components include percussion instrument sound components.

3. The bass emphasis method according to claim 1, wherein: The step of extracting the non-harmonic musical instrument signal from the input sound signal comprises the following steps: generating, based on the input sound signal, a first bass signal in which frequency components in a higher frequency band than the frequency band of the non-harmonic musical instrument sound component are reduced, The non-harmonic musical instrument signal is extracted from the first bass signal.

4. The bass emphasis method according to claim 1, wherein: The step of generating the low-frequency signal based on the non-harmonic musical instrument signal comprises the following steps: generating a second bass signal in which a frequency component in a higher frequency band than the frequency band of the non-harmonic musical instrument sound component is reduced based on the non-harmonic musical instrument signal, The low-frequency signal is generated based on the second bass signal.

5. The bass emphasis method according to any one of claims 1 to 3, wherein: The step of generating the low-frequency band emphasis signal comprises the following steps: generating a delayed sound signal by delaying the input sound signal by a time until the low-frequency signal is generated based on the input sound signal, The low-frequency band emphasized signal is generated by adding the delayed sound signal and the low-frequency signal.

6. A bass emphasis device, comprising: an extraction unit that extracts a non-harmonic instrument signal representing the non-harmonic instrument sound component from an input sound signal including a harmonic instrument sound component and a non-harmonic instrument sound component that is a component other than the harmonic instrument sound component; A first generating unit generates a low-frequency signal based on the inharmonic musical instrument signal, the low-frequency signal having a frequency 1 / N of a frequency of a fundamental wave component of the inharmonic musical instrument signal, wherein: N is an integer greater than 2; and A second generating unit generates a low-frequency band emphasized signal in which a low-frequency band frequency component of the input audio signal is emphasized, based on the low-frequency signal and the input audio signal.

7. A bass emphasis device, comprising: an extraction unit that extracts a non-harmonic instrument signal representing the non-harmonic instrument sound component from an input sound signal including a harmonic instrument sound component and a non-harmonic instrument sound component that is a component other than the harmonic instrument sound component; A generating unit generates a low-frequency signal based on the non-harmonic musical instrument signal, the low-frequency signal having a frequency 1 / N of the frequency of the fundamental wave component of the non-harmonic musical instrument signal, wherein: N is an integer greater than 2; and An output unit outputs an output sound signal including at least the low-frequency signal to an actuator that vibrates the seat.

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