Overtone generation device, overtone generation method, and program

Abstract

To provide an overtone generation device capable of generating overtone having linear characteristics with respect to an input amplitude.SOLUTION: Disclosed is an overtone generation device including an overtone generation section. The overtone generation section includes: a first overtone generator by which a positive pole of a signal which is inputted to the overtone generation section is squared, a negative pole is multiplied by 0 and the result is outputted; a high-pass filter which suppresses a DC component of output of the first overtone generator; and a second overtone generator by which square root arithmetic is performed on a positive pole of output of the high-pass filter, the positive pole is multiplied by -1, a negative pole is multiplied by -1, square root arithmetic is performed and the result is outputted.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Generally, small speakers have poor bass reproduction capabilities. To address this issue, a technique known as missing fundamental technology is known that enhances bass by applying the phenomenon known as "missing fundamental," which is the perception of the pitch of a fundamental tone that does not exist due to its overtones, even when the fundamental tone is absent (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, the 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 performed to prevent the generation of higher-order harmonics by setting the degree and coefficients of the polynomial. However, because the level of the harmonics decreases logarithmically relative to the input amplitude, the volume of the harmonics depends on the input level, and there is also the issue that this nonlinear attenuation causes significant distortion (noise that is noticeable to the ear).

[0005] Therefore, an object of the present disclosure is to provide a harmonic generation device that can generate harmonics that have 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, then outputs the result. The high-pass filter suppresses the DC component of the output of the first harmonic generator. The second harmonic generator takes 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, then takes the square root, and outputs the result. [Effects of the Invention]

[0009] The harmonic generation device of the present disclosure can generate harmonics that have linear characteristics relative to the input amplitude. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing the functional configuration of a harmonic generation device according to a first embodiment. [Figure 2] 3A and 3B are diagrams illustrating the characteristics of a filter included in the harmonic generation device of the first embodiment. [Figure 3] 3 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. [Figure 5] 4 is a flowchart showing the operation of the overtone generation unit of the overtone generation device according to the first embodiment. [Figure 6] FIG. 10 is a diagram showing the input / output characteristics of the first harmonic generator. [Figure 7] FIG. 10 is a diagram showing the attenuation characteristics (linear) of each harmonic of the first harmonic generator. [Figure 8] A diagram showing the input / output characteristics of the function that served as the basis for the first harmonic generator. [Figure 9] A graph showing the attenuation characteristics (linear) of each harmonic of the function that served as the basis for the first harmonic generator. [Figure 10] FIG. 10 is a diagram showing the input / output characteristics of a second harmonic generator. [Figure 11] FIG. 10 is a diagram 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 after processing in the order of the first harmonic generator, high-pass filter, and second harmonic generator. [Figure 13] FIG. 10 is a diagram showing the attenuation characteristics (linear) of each harmonic after fundamental tone adjustment processing. [Figure 14] FIG. 10 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] 10 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. 10 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 INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail. Note that components having the same functions are assigned the same numbers, and redundant explanations will be omitted. [Example]

[0012] The following describes the harmonic generation device of Example 1. The harmonic generation device of this example is a device that generates harmonic overtones to virtually reproduce missing bass sounds that cannot be reproduced by small speakers by calculating and adding harmonics of the bass sounds.

[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 dividing unit 12, a first phase correction unit 13, a second phase correction unit 14, a harmonic extraction low-pass filter 15, a harmonic generation unit 16, a high-order harmonic suppression low-pass filter 17, and a subtraction unit 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 generating device 1 (S11).

[0016] <Signal division unit 12> The signal dividing unit 12 divides the output from the DC component suppression high-pass filter 11 into two (S12). One of the divided signals is input to the first phase correction unit 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 corrector 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 unit 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 unit 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 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 multiplying the harmonics generated by the square root with an inverse decay rate, we then distorted them again, resulting in the generation of harmonics with a linear decay rate.

[0025] The detailed functional configuration of the overtone generation unit 16 of the overtone generation device 1 of this embodiment will be described below 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, the 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 of which is input 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 electrode: 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) is proportional to the input amplitude squared (x 2 ) For example, if the input is reduced by 6 dB, the output will be reduced by 12 dB.

[0031] <<The function that became the basis for the first harmonic generator 161>> Here, the function that is the basis of first harmonic generator 161 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 However, -1≦x≦1 …(Formula 2) The input / output characteristics of the soft clip function of (Equation 2) are shown in Fig. 8. The attenuation characteristics (linearity) of each harmonic of (Equation 2) are also shown in Fig. 9.

[0034] In this example, (Formula 2) was modified in the following manner.

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

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

[0037] Positive electrode:y=-0.5x 2 Negative electrode: 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 Because the output of first harmonic generator 161 has a DC component, 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 characteristics 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 below.

[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 the result 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 first harmonic generator 161 has a slope of 2 dB / dB. Therefore, 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 characteristics of the harmonics generated by the second harmonic generator 163 are 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, and second harmonic generator 163. In the state shown in Fig. 12, the DC component suppression high-pass filter 167 subsequent to second harmonic generator 163 is assumed to be unprocessed. As shown in Fig. 12, it can be seen that the input / output attenuation characteristics 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 harmonic generation unit 16, the phase is rotated by the high-pass filter 162, so the phase is aligned by applying a phase rotation filter 164 with 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 that is the input, making it possible to subtract and suppress the fundamental tone from the harmonics.

[0049] Fundamental tone adjuster 165 functions as a gain (multiplier), and as a result of level control by fundamental tone adjuster 165, if the level is adjusted to the same level as the fundamental tone in the harmonic group output from second harmonic generator 163, and if the phase is adjusted to the same phase as the fundamental tone in the harmonic group output from second harmonic generator 163 by the phase shifter of phase rotation filter 164, then as a result of subtracting the output of fundamental tone adjuster 165 from the output of 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] Figure 13 shows the linear decay characteristics of each harmonic after the fundamental tone adjustment process. 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 tone 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 in this application example begin to attenuate at 250 Hz, reaching approximately -20 dB at approximately 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) resulting from this processing is shown in Figure 15. As shown by the dashed-dotted line, harmonics up to 250 Hz are added to the input signal. As a result, the output signal (dashed line) is increased by about 1.5 dB below 250 Hz compared to the input signal (solid line).

[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) speaker, resulting in a loud bass sound.

[0057] The ability to reduce the level of the harmonics that are added is a major benefit of fundamental tone adjustment processing. For reference, Figure 16 shows the difference in frequency characteristics of an actual speaker output signal with and without harmonic addition. As expected, we can see that harmonics are added by about 1.5 dB to 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 described functions. A processor includes transistors and other circuits and is considered to be circuitry or processing circuitry. A processor may also be a programmed processor that executes programs stored in 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 herein 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 that executes each step of the above method into the recording unit 10020 of the computer shown in Figure 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 suitable recording medium.

[0063] The program may be distributed, for example, by selling, transferring, lending, etc. a portable recording medium such as a DVD or CD-ROM on which the program is recorded. Furthermore, the program may be stored in a storage device of a server computer, and then transferred from the server computer to another computer via a network, thereby distributing the program.

[0064] A computer that executes such a program may first temporarily store the program recorded on a portable recording medium or transferred from a server computer in its own storage device. Then, when executing a process, the computer reads the program stored on its own recording medium and executes the process in accordance with the read program. Alternatively, the computer may read the program directly from a portable recording medium and execute the process in accordance with the program. Furthermore, the computer may execute the process in accordance with the program each time a program is transferred from a server computer to the computer. The server computer may not transfer the program to the computer, but may instead execute the process through a so-called ASP (Application Service Provider) service, which realizes the processing function by issuing an execution instruction and obtaining the results. Furthermore, the server computer may execute the process on a terminal using a so-called SaaS (Software as a Service) service, which allows users to use part of the server computer along with the program. In this embodiment, the program includes information used for computer processing that is equivalent to a program (such as data that is not a direct instruction to the computer but has properties that define computer processing).

[0065] Furthermore, in this embodiment, the device is configured by executing a predetermined 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 a first harmonic generator that squares the positive polarity of the signal input to the harmonic generation unit and multiplies the negative polarity by 0, and outputs the result; a high-pass filter that suppresses a DC component of the output of the first harmonic generator; A second harmonic generator is included which performs square root calculation on the positive polarity of the output of the high-pass filter, multiplies the result by -1, and performs square root calculation on the negative polarity 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 a fundamental tone adjuster that performs fundamental tone adjustment processing on the signal input to the harmonic generation unit; a subtractor that subtracts the output of the fundamental tone adjuster from the output of the second harmonic generator and outputs the result Harmonic generator.

3. 3. The harmonic generation device according to claim 2, The harmonic generation unit 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 subsequent to the harmonic generation unit; Includes a high-order harmonic suppression low-pass filter that suppresses harmonics above a specified order. 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 dividing unit that divides the 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 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 0 and outputting 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 calculating the square root of the positive polarity of the output of the high-pass filter step, multiplying the result by −1, and multiplying the negative polarity of the output of the high-pass filter step by −1, calculating the square root, 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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