Harmonic generation device, harmonic generation method, and program

Abstract

A harmonic generating device capable of generating harmonics having linear characteristics with respect to input amplitude is provided. [Solution] A harmonic generation device including a harmonic generation unit, which includes a first harmonic generator that squares the positive pole of a signal input to the harmonic generation unit and multiplies the negative pole by 0 and outputs the result, a high-pass filter that suppresses the DC component of the output of the first harmonic generator, and a second harmonic generator that takes the square root of the positive pole of the output of the high-pass filter and multiplies it by -1, and multiplies the negative pole by -1, takes the square root, and outputs the result.

Description

[Technical field]

[0001] The present disclosure relates to a harmonic generation device, a harmonic generation method, and a program for generating virtual bass tones. [Background technology]

[0002] Generally, small speakers have poor bass reproduction capabilities. To address this issue, a technique called "missing fundamental" is known that enhances bass by applying the phenomenon in which the pitch of a non-existent fundamental is perceived due to its overtones, even when the fundamental tone is missing (Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] NTT Communication Science Laboratories, "Missing Fundamental", [online], NTT Communication Science Laboratories, [Retrieved April 2, 2024], Internet〈 URL: https: / / illusion-forum.ilab.ntt.co.jp / missing-fndamental / index.html 〉 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, a method of generating harmonics by distorting a signal using input / output characteristics created with a polynomial has the advantage that soft clip control can be used to prevent the production of higher-order harmonics by setting the degree and coefficients of the polynomial. However, because the level of the harmonics relative to the input amplitude decreases logarithmically, the volume of the harmonics depends on the input level, and there is also the issue that this nonlinear attenuation causes large distortions (noise that is noticeable to the ear).

[0005] Therefore, an object of the present disclosure is to provide a harmonic generation device capable of generating harmonics having linear characteristics with respect to the input amplitude. [Means for solving the problem]

[0006] The harmonic generation device of the present disclosure includes a harmonic generation section.

[0007] The harmonic generation unit includes a first harmonic generator, a high-pass filter, and a second harmonic generator.

[0008] The first harmonic generator squares the positive pole of the signal input to the harmonic generation unit and multiplies the negative pole by 0 and outputs the result. The high-pass filter suppresses the DC component of the output of the first harmonic generator. The second harmonic generator calculates the square root of the positive pole of the output of the high-pass filter, multiplies it by -1, and multiplies the negative pole by -1, calculates the square root, and outputs the result. Effect of the Invention

[0009] According to the harmonic generation device of the present disclosure, it is possible to generate harmonics having linear characteristics with respect to the input amplitude. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a block diagram showing the functional configuration of the harmonic generation device of the first embodiment. [Diagram 2] 3 is a diagram illustrating an example of the characteristics of a filter included in the harmonic generation device of the first embodiment. [Diagram 3] 4 is a flowchart showing the operation of the harmonic generation device of the first embodiment. [Figure 4] FIG. 2 is a block diagram showing the functional configuration of a harmonic generation unit of the harmonic generation device according to the first embodiment. [Diagram 5] 4 is a flowchart showing the operation of a harmonic generation unit of the harmonic generation device according to the first embodiment. [Figure 6] A diagram showing the input / output characteristics of the first harmonic generator. [Figure 7] 13 is a graph showing the attenuation characteristics (linear) of each harmonic of the first harmonic generator. [Figure 8] A graph showing the input / output characteristics of the function that served as the basis for the first harmonic generator. [Figure 9] A graph showing the linear attenuation characteristics for each harmonic of the function that served as the basis for the first harmonic generator. [Figure 10] A diagram showing the input / output characteristics of the second harmonic generator. [Figure 11] A graph showing the attenuation characteristics (linear) of each harmonic of the second harmonic generator. [Figure 12] A graph showing the attenuation characteristics (linear) of each harmonic processed in the order of the first harmonic generator, high-pass filter, and second harmonic generator. [Figure 13] 13 is a graph showing the attenuation characteristics (linear) of each harmonic after fundamental tone adjustment processing. [Figure 14] 1 is a diagram showing the frequency characteristics of a small speaker to which the harmonic generation method of the present disclosure is applied. [Figure 15] 13 is a diagram showing the frequency characteristics of the output signal and the generated harmonics when white noise is input to a small speaker to which the harmonic generation method of the present disclosure is applied. [Figure 16] FIG. 13 is a diagram showing the frequency characteristics of a small speaker with and without harmonic addition. [Figure 17] FIG. 2 is a diagram showing an example of the functional configuration of a computer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described in detail. Note that components having the same functions are given the same reference numbers and redundant description will be omitted. EXAMPLES

[0012] Hereinafter, a description will be given of a harmonic generation device of Example 1. The harmonic generation device of this example is a device that aims to virtually reproduce missing low-frequency sounds by generating overtones and calculating and adding harmonics from low-frequency sounds that cannot be reproduced by small speakers.

[0013] As shown in Fig. 1, the harmonic generation device 1 of this embodiment includes a DC component suppression high-pass filter 11, a signal division section 12, a first phase correction section 13, a second phase correction section 14, a harmonic extraction low-pass filter 15, a harmonic generation section 16, a high-order harmonic suppression low-pass filter 17, and a subtraction section 18. Fig. 2 illustrates the filter characteristics of each filter (11, 15, 17).

[0014] The operation of each component will be described below with reference to FIG.

[0015] <DC component suppression high-pass filter 11> The DC component suppression high-pass filter 11 suppresses the DC component of the signal input to the overtone production device 1 (S11).

[0016] <Signal division unit 12> The signal splitter 12 splits the output from the DC component suppression high-pass filter 11 into two (S12). One of the split signals is input to the first phase corrector 13 as the original sound, and the other is input to the harmonic extraction low-pass filter 15.

[0017] <First phase correction section 13> The first phase correction unit 13 corrects the phase of one of the divided signals (S13).

[0018] <Second phase correction section 14> The second phase corrector 14 corrects the phase of one of the divided signals (S14).

[0019] The first phase correction section 13 inserted on the original sound side is provided for the purpose of correcting the phase rotated by the harmonic extraction low-pass filter 15. The second phase correction section 14 is provided for the purpose of correcting the phase rotated by the high-order harmonic suppression low-pass filter 17.

[0020] <Harmonic extraction low-pass filter 15> The harmonic extraction low-pass filter 15 extracts the band of the signal that is the source of the harmonic overtones (S15).

[0021] <Harmonic Generation Section 16> The other of the divided signals, which is the signal that has been low-pass filtered in step S15, is input to the overtone generation unit 16. The overtone generation unit 16 executes a overtone generation process, which will be described later, to generate overtones (S16). In this embodiment, the output from the overtone generation unit 16 is called a group of overtones.

[0022] <High-order harmonic suppression low-pass filter 17> The high-order harmonic suppression low-pass filter 17 suppresses unnecessary high-order harmonics (harmonics of a predetermined order or higher) from the generated harmonics (S17). The order of the high-order harmonic suppression low-pass filter 17 is selected according to its cutoff frequency.

[0023] <Subtraction section 18> The subtraction unit 18 subtracts the output of the high-order harmonic suppression low-pass filter 17 from the output of the second phase correction unit 14 after level adjustment, and outputs the result (S18).

[0024] The amplitude of the harmonics generated by polynomials is nonlinear with respect to the amplitude of the input signal. 2 ) and then multiplying it by the square root with an inverse decay rate and distorting it again, resulting in the generation of harmonics with a linear decay rate.

[0025] Hereinafter, a detailed functional configuration of the overtone generation unit 16 of the overtone generation device 1 of this embodiment will be described with reference to Fig. 4. As shown in the figure, the overtone generation unit 16 includes a first overtone generator 161, a high-pass filter 162, a second overtone generator 163, a phase rotation filter 164, a fundamental tone adjuster 165, a subtractor 166, and a DC component suppression high-pass filter 167.

[0026] As shown in the figure, a signal input to the overtone generation unit 16 is split into two, one of which is input to a first overtone generator 161 and the other to a fundamental tone adjuster 165 via a phase rotation filter 164 .

[0027] The operation of each component will be described below with reference to FIG.

[0028] <First Harmonic Generator 161> The first overtone generator 161 squares the positive polarity of the signal input to the overtone generation unit 16 and multiplies the negative polarity by 0, and outputs the result (S161). The input / output characteristics of the first overtone generator 161 are shown in FIG.

[0029] The calculation in first harmonic generator 161 is expressed by (Equation 1).

[0030] Positive pole: y=x 2 Negative pole: y=0 …(Formula 1) 7 shows the attenuation characteristics (linear) of each harmonic generated by the first harmonic generator 161. As shown in the figure, the harmonic generated by (Equation 1) decays to the square of the input amplitude (x 2 For example, if the input is reduced by 6 dB, the output is reduced by 12 dB.

[0031] <<The function that became the basis for the first harmonic generator 161>> Here, the function on which the first harmonic generator 161 is based will be explained.

[0032] Equation 1 is derived by modifying the soft clip function shown in equation 2.

[0033] Positive pole: y=-(x-1) 2 +1 Negative pole:y=+(x+1) 2 -1 where -1≦x≦1 …(Formula 2) The input / output characteristics of the soft clip function of (Equation 2) are shown in Fig. 8. Also, the attenuation characteristics (linearity) of each harmonic of (Equation 2) are shown in Fig. 9.

[0034] In this example, formula 2 was modified in the following manner.

[0035] First, to generate odd harmonics, the negative pole slope is set to 1 (y = x), and to obtain continuity at the origin, the slope is corrected (multiplied by 0.5) so that the differential value at the positive pole's origin is also 1. In addition, the input signal (x) is subtracted to suppress the fundamental component. As a result, (Equation 3) is obtained.

[0036] Positive pole: y=(-(x-1) 2 +1)*0.5-x Negative pole: y=xx …(Formula 3) Solving (Equation 3) gives (Equation 4).

[0037] Positive electrode:y=-0.5x 2 Negative pole: y=0 …(Formula 4) To simplify the calculation, the positive polarity constant "-0.5" is set to "1.0" to obtain (Equation 1). The polarity inversion is corrected by second harmonic generator 163, which will be described later.

[0038] <High-pass filter 162> The high-pass filter 162 suppresses the DC component of the output of the first harmonic generator 161 (S162).

[0039] q Since the output of the first harmonic generator 161 has a DC component, the high-pass filter 162 suppresses 0 Hz of the input signal. In this case, a second-order HPF with Q=0.5 is used due to the phase characteristic relationship with the phase shifter (first-order APF) that aligns the phase with the fundamental tone to be subtracted in the fundamental tone adjustment process described later.

[0040] <Second Harmonic Generator 163> Second harmonic generator 163 calculates the square root of the positive polarity of the output of high-pass filter 162, multiplies it by −1, and multiplies the negative polarity by −1, calculates the square root, and outputs the result (S163).

[0041] The attenuation rate of the harmonics generated by the first harmonic generator 161 has a slope of 2 dB / dB. Therefore, the second harmonic generator 163 generates harmonics again using the equation shown in (Equation 5) which has a slope of an attenuation rate of 0.5 dB / dB.

[0042] Positive pole: y=-sqrt(x) Negative pole: y=sqrt(-x) …(Formula 5) dfc

[0043] The attenuation characteristic of the harmonic generated by the second harmonic generator 163 is a square root attenuation. For example, if the input drops by 6 dB, the output drops by 3 dB.

[0044] <Square root method> Fig. 12 shows the input / output characteristics resulting from processing in the order of first harmonic generator 161 - high-pass filter 162 - second harmonic generator 163. In the state shown in Fig. 12, the DC component suppression high-pass filter 167 subsequent to the second harmonic generator 163 is assumed to be unprocessed. As shown in the figure, it can be seen that the attenuation characteristics of the input and output are linear.

[0045] <Phase rotation filter 164> The phase rotation filter 164 has the same phase characteristics as the high-pass filter 162 .

[0046] In the overtone generation section 16, since the phase is rotated by the high-pass filter 162, the phase is aligned by applying the phase rotation filter 164, which has the same phase characteristics, to the fundamental tone to be adjusted.

[0047] <Fundamental tone adjuster 165> The fundamental tone adjuster 165 performs fundamental tone adjustment processing on the signal input to the overtone generation unit 16 (S165).

[0048] By the processing of steps S161-S163, the attenuation characteristics of the harmonics become linear with respect to the fundamental tone, which is the input, so that it becomes possible to subtract the fundamental tone from the harmonics and suppress it.

[0049] The fundamental tone adjuster 165 functions as a gain (multiplier), and as a result of level control by the fundamental tone adjuster 165, if the level is adjusted to the same level as the fundamental tone in the harmonic group of the output of the second harmonic generator 163, and also adjusted by the phase shifter of the phase rotation filter 164 to the same phase as the phase of the fundamental tone in the output of the second harmonic generator 163, then as a result of subtracting the output of the fundamental tone adjuster 165 from the output of the second harmonic generator 163, only the fundamental tone is subtracted from the harmonic group including the fundamental tone, and only the harmonic tone remains.

[0050] The attenuation characteristics (linear) of each harmonic after the fundamental tone adjustment process is shown in Figure 13. By adding the adjusted fundamental tone separately at a desired level, it is possible to arbitrarily control the amount of fundamental tone included in the harmonic group.

[0051] <Subtractor 166> The subtractor 166 subtracts the output of the fundamental tone adjuster 165 from the output of the second harmonic generator 163 and outputs the result (S166).

[0052] <DC component suppression high-pass filter 167> The DC component suppression high-pass filter 167 suppresses the DC component of the signal output from the subtractor 166 (S167).

[0053] <Example of application to small speakers> An example of application of the harmonic generation method of this embodiment to a small speaker will be described below. The frequency characteristics of the small speaker of this application example are shown in FIG.

[0054] As shown in the figure, the frequency characteristics of the small speaker of this application example begin to attenuate at 250 Hz, and are about -20 dB at about 70 Hz. Based on this frequency characteristic, the harmonic LPF was set to 250 Hz, the attenuation amount was 24 dB / Oct., and the harmonic extraction LPF was set to 160 Hz.

[0055] The frequency response (spectrum of white noise) after this processing is shown in Figure 15. As shown by the dashed line graph, harmonics up to 250Hz are added to the input signal. As a result, the output signal (dashed line graph) shows an increase of about 1.5dB below 250Hz compared to the input signal (solid line graph).

[0056] Because the amplification of the output signal due to harmonic generation is thus slight, there is little margin for overflow in signal processing and little burden on the (small) speakers, resulting in audible loudness of bass.

[0057] The effect of the fundamental tone adjustment process is great in reducing the level of the harmonics that are added. For reference, the difference in frequency characteristics of the output signal from an actual speaker with and without harmonic addition is shown in Figure 16. As expected, we can see that about 1.5 dB of harmonics are added to the frequencies near the limit of bass generation.

[0058] <Additional Notes> The functions performed by the components described herein may be implemented in circuitry or processing circuitry, including general purpose processors, application specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to perform the functions described. Processors include transistors and other circuits and are considered to be circuitry or processing circuitry. A processor may be a programmed processor that executes a program stored in a memory.

[0059] In this specification, a circuitry, unit, or means is hardware that is programmed to realize or performs the described functions, which may be any hardware disclosed in this specification or any hardware known to be programmed to realize or perform the described functions.

[0060] If the hardware is a processor considered to be a type of circuitry, the circuitry, means, or unit is a combination of the hardware and software used to configure the hardware and / or processor.

[0061] The various processes described above can be implemented by loading a program for executing each step of the above method into the recording unit 10020 of the computer shown in FIG. 17, and operating the control unit 10010, input unit 10030, output unit 10040, etc.

[0062] The program describing the processing contents can be recorded on a computer-readable recording medium, which may be, for example, a magnetic recording device, an optical disk, a magneto-optical recording medium, a semiconductor memory, or any other type of recording medium.

[0063] The program may be distributed, for example, by selling, transferring, lending, etc. portable recording media such as DVDs and CD-ROMs on which the program is recorded. Furthermore, the program may be distributed by storing the program in a storage device of a server computer and transferring the program from the server computer to other computers via a network.

[0064] A computer that executes such a program, for example, first stores the program recorded on a portable recording medium or the program transferred from a server computer in its own storage device. Then, when executing a process, the computer reads the program stored in its own recording medium and executes a process according to the read program. As another execution form of the program, the computer may directly read the program from the portable recording medium and execute a process according to the program, or may execute a process according to the received program each time a program is transferred from the server computer to the computer. The server computer may not transfer the program to the computer, but may execute the process by a so-called ASP (Application Service Provider) type service that realizes the processing function only by issuing an execution instruction and obtaining the result. Furthermore, the server computer may execute the process of the terminal by using a so-called SaaS (Software as a Service) type service that allows a user to use a part of the server computer together with the program. The program in this embodiment includes information used for processing by an electronic computer that is equivalent to a program (data that is not a direct command to the computer but has a nature that specifies the processing of the computer, etc.).

[0065] In addition, in this embodiment, the present device is configured by executing a specific program on a computer, but at least a part of the processing contents may be realized by hardware.

Claims

1. A harmonic generation device including a harmonic generation unit, The harmonic generation unit includes: a first harmonic generator that squares the positive polarity of the signal input to the harmonic generation unit and multiplies the negative polarity by zero and outputs the result; a high-pass filter for suppressing a DC component of the output of the first harmonic generator; A second harmonic generator is included which performs a square root operation on the positive terminal of the output of the high-pass filter, multiplies the result by -1, and performs a square root operation on the negative terminal of the output of the high-pass filter, and outputs the result. Harmonic generator.

2. 2. The harmonic generation device according to claim 1, The harmonic generation unit includes: a fundamental tone adjuster that performs fundamental tone adjustment processing on the signal input to the harmonic generation unit; A subtractor is provided for subtracting the output of the fundamental tone adjuster from the output of the second harmonic generator and outputting the result. Harmonic generator.

3. 3. The harmonic generation device according to claim 2, The harmonic generation unit includes: Before the fundamental tone adjuster Includes a phase rotation filter with the same characteristics as the high-pass filter Harmonic generator.

4. 4. The harmonic generation device according to claim 1, A stage following the harmonic generation unit, Includes a high-order harmonic suppression low-pass filter that suppresses harmonics of a specified order or higher. Harmonic generator.

5. 4. The harmonic generation device according to claim 1, A stage preceding the harmonic generation unit, Includes a harmonic extraction low-pass filter that extracts the signal band that is the source of harmonics Harmonic generator.

6. 4. The harmonic generation device according to claim 1, a DC component suppression high-pass filter that suppresses a DC component of a signal input to the harmonic generation device; a signal splitting unit that splits an output from the DC component suppression high-pass filter into two; a phase correction unit that corrects the phase of one of the divided signals; The harmonic generation unit includes: The other of the divided signals is input, A subtraction unit that adds the output of the phase correction unit and the output of the harmonic generation unit and outputs the result. Harmonic generator.

7. A harmonic generation method executed by a harmonic generation device, comprising: a first harmonic generation step of squaring the positive polarity of the input signal and multiplying the negative polarity by zero to output the result; a high-pass filter step for suppressing a DC component of the output of the first harmonic generation step; A second harmonic generation step of performing a square root operation on the positive output of the high-pass filter step, multiplying the positive output by −1, and multiplying the negative output by −1, performing a square root operation, and outputting the result. Harmonic generation method.

8. A program that causes a computer to function as the harmonic generation device according to claim 1.

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