Generation apparatus, generation method, and program
The system estimates sound pickup signals using spherical harmonic function expansion coefficients from error microphones at unequal intervals to enhance noise suppression performance, addressing the challenge of reduced effectiveness when error microphones are not near the user's ear.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NIPPON TELEGRAPH & TELEPHONE CORP
- Filing Date
- 2023-02-20
- Publication Date
- 2026-06-04
Smart Images
Figure 0007870012000017 
Figure 0007870012000018 
Figure 0007870012000019
Abstract
Description
Technical Field
[0001] The present invention relates to the technology of active noise control (ANC) that suppresses external noise at a specific position.
Background Art
[0002] Non-Patent Document 1 is known as a conventional active noise control technology. In active noise control, a reference microphone, an error microphone, and a cancellation speaker are generally used. FIG. 1 shows a configuration example of a conventional noise suppression device. The reference microphone 91 picks up the noise emitted by the noise source. The cancellation speaker 92 reproduces the cancellation signal generated by the suppression signal generation device 90 and emits a cancellation sound that cancels out the noise. Further, the error microphone 93 picks up and feedbacks the remaining noise. The suppression signal generation device 90 actively controls and generates a cancellation signal using the sound pickup signal of the reference microphone 91 and the sound pickup signal of the error microphone 93 so that the remaining noise becomes small. At the installation position of the error microphone 93, the cancellation speaker 92 emits a cancellation sound so that the remaining noise becomes small. Therefore, the cancellation sound suppresses the noise most efficiently at the installation position of the error microphone 93. Therefore, the error microphone 93 is installed near the user's ear.
Prior Art Documents
Non-Patent Documents
[0003]
Non-Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] However, in actual use, it may not be possible to place the error microphone 93 close to the user's ear. As the distance between the error microphone 93 and the user's ear increases, as mentioned above, the noise is most efficiently suppressed at the installation location of the error microphone 93. Closer to the user's ear, more noise remains, reducing the suppression performance and potentially preventing the user from fully benefiting from noise suppression. For example, simulations confirmed that when the distance from the noise source to the ear is 100 mm and the error microphone 93 is placed at the user's ear (0 mm), the suppression performance is -∞ dB, while when the error microphone 93 is placed at an intermediate point between the noise source and the ear, the suppression performance is -7.38 dB. Figure 2 illustrates the difference between the conventional suppression range (sweet spot) S1 and the desired sweet spot S2.
[0005] The present invention aims to provide a generation device, generation method, and program thereof that achieve high suppression performance even when the sound is picked up near the user's ear, far from the actual error microphone, by estimating the sound pickup signal obtained when sound is picked up near the user's ear from the sound pickup signal picked up at the actual placement of the error microphone, and using the estimated sound pickup signal instead of the sound pickup signal picked up at the actual placement of the error microphone in order to actively control the cancellation signal. [Means for solving the problem]
[0006] To solve the above problems, according to one aspect of the present invention, the generating device generates a cancellation signal used for active noise control. The generating device includes a sound pressure estimation unit that estimates the sound received when a virtual microphone is placed closer to the observation point than the multiple error microphones, using spherical harmonic function expansion coefficients estimated by the least squares method from the sound received signals of multiple error microphones placed at unequal intervals near the user's head, and obtains an estimated sound received signal; and a suppression signal generation unit that generates a cancellation signal for suppressing noise at the virtual microphone's installation location using the sound received signal of the noise to be suppressed and the estimated sound received signal, wherein the virtual microphone is a microphone that is virtually installed but is not actually installed, and multiple error microphones The device is installed on a spherical surface to satisfy the following conditions (i) to (iv): (i) multiple error microphones are arranged in the horizontal angular direction and multiple error microphones are arranged in the elevation angular direction; (ii) it comprises a first and second layer with at least four error microphones arranged in the horizontal angular direction and a third and fourth layer with at least two error microphones arranged in the horizontal angular direction; (iii) the first, second, third and fourth layers are arranged at different angles in the elevation angular direction; and (iv) the first and second layers are positioned above the head and the third and fourth layers are positioned to the sides of the head. [Effects of the Invention]
[0007] According to the present invention, it is possible to achieve higher suppression performance than conventional methods when it is not possible to place the error microphone near the user's ear. [Brief explanation of the drawing]
[0008] [Figure 1] A diagram illustrating conventional active noise control. [Figure 2] A diagram illustrating the suppression range of conventional technologies. [Figure 3] Functional block diagram of the noise suppression system according to the first embodiment. [Figure 4] A diagram showing an example of the processing flow of the noise suppression system according to the first embodiment. [Figure 5]A diagram illustrating estimation method 1. [Figure 6] A diagram illustrating estimation method 2. [Figure 7] A diagram illustrating estimation method 3. [Figure 8] A figure showing the simulation results of the first embodiment. [Figure 9] This figure shows the simulation of the prediction error when the direction of arrival of the noise source is changed using estimation methods 2 and 3 of the first embodiment. [Figure 10] This figure shows the simulation results when the prediction error is simulated when the direction of arrival of the noise source is changed using estimation methods 2 and 3 of the first embodiment. [Figure 11] A diagram illustrating the positional relationship of the error microphone relative to the user's head. [Figure 12] Plan and rear view showing the relative positions of the error microphones. [Figure 13] A plan view showing the configuration when the horizontal angle of the four error microphones, positioned in the elevation / depression direction, is changed. [Figure 14] Plan views showing the changes in elevation angles for the first, second, third, and fourth layers. [Figure 15] This figure shows the simulation results when the prediction error is simulated when the direction of arrival of the noise source is changed, using estimation method 2 of the first embodiment and the second embodiment. [Figure 16] A diagram showing an example of a computer configuration to which this method is applied. [Modes for carrying out the invention]
[0009] Embodiments of the present invention will be described below. In the drawings used in the following description, components with the same function or steps that perform the same processing will be denoted by the same reference numerals, and redundant explanations will be omitted. In the following description, the symbols "^" used in the text will be omitted. -Symbols such as "&" should ideally be placed directly above the following character, but due to limitations in text notation, they are placed immediately before the character. Within formulas, these symbols are written in their original positions. Furthermore, unless otherwise specified, any processing performed on individual elements of a vector or matrix shall apply to all elements of that vector or matrix.
[0010] <Key points of the first embodiment> In this embodiment, the observed sound pressure near the ear is estimated from the sound pickup signal of an error microphone placed at a distance from the ear. For example, the sound pickup signal of a virtual error microphone placed near the ear is estimated from the sound pickup signal of the actual error microphone, and in ANC, the sound pickup signal of the virtual error microphone is used as the sound pickup signal of the conventional error microphone. With this configuration, the sweet spot is changed from the installation location of the error microphone to the location of the virtual error microphone, and a sound is produced that cancels out any remaining noise near the ear.
[0011] Various methods can be considered for estimating the sound signal picked up by a virtual error microphone. For example, the sound pressure can be estimated by considering the distance attenuation and phase delay from the actual error microphone's placement to the ear. Alternatively, for example, the sound pressure at the ear can be estimated using spherical harmonics from an actual error microphone placed on a sphere.
[0012] <First Embodiment> Figure 3 shows a functional block diagram of the noise suppression system according to the first embodiment, and Figure 4 shows its processing flow.
[0013] The noise suppression system includes a reference microphone 91, a cancellation speaker 92, an error microphone 93, a suppression signal generation unit 110, and a sound pressure estimation unit 120. The device consisting of the suppression signal generation unit 110 and the sound pressure estimation unit 120 is also called a suppression signal generation device.
[0014] The suppression signal generator takes the sound pickup signal x(r) from the reference microphone 91 and the sound pickup signal x(e) from the error microphone 93 as inputs, and generates a cancellation signal (hereinafter also referred to as "suppression signal") y such that the point where the amount of noise suppression is maximum is located closer to the user than the installation position of the error microphone 93, and outputs it to the cancellation speaker 92.
[0015] A suppression signal generator is a special device configured by loading a special program into a known or dedicated computer having, for example, a central processing unit (CPU) and main memory (RAM). The suppression signal generator executes each process under the control of, for example, the central processing unit. Data input to the suppression signal generator and data obtained from each process are stored in, for example, main memory, and the data stored in main memory is read to the central processing unit as needed and used for other processes. Each processing unit of the suppression signal generator may be composed of hardware such as integrated circuits, at least in part. Each storage unit of the suppression signal generator can be composed of, for example, main memory such as RAM (Random Access Memory), or middleware such as a relational database or key-value store. However, each storage unit does not necessarily have to be located inside the suppression signal generator; it may be composed of auxiliary storage devices made of semiconductor memory elements such as hard disks, optical disks, or flash memory, and may be located outside the suppression signal generator.
[0016] The following describes each part.
[0017] <Reference Microphone 91> Reference microphone 91 picks up the sound to be suppressed (S91) and outputs the picked-up signal x(r). The sound to be suppressed picked up by reference microphone 91 will be referred to as "noise" below.
[0018] <Cancel Speaker 92> The cancellation speaker 92 receives the cancellation signal y as input and reproduces the cancellation signal y (S92). When the reproduced sound from the cancellation speaker 92 and the noise to be suppressed are in perfect opposite phase, the reproduced sound and the noise to be suppressed overlap, that is, the sound waves superimpose, causing the waves to cancel each other out, and thus the noise is suppressed.
[0019] <Error Microphone 93> The error microphone 93 picks up sounds that were not suppressed by the playback sound played back from the cancellation speaker 92, including any remaining noise (S93), and outputs a pickup signal x(e). The error microphone 93 is positioned closer to the noise source than the observation point (e.g., the user's ear). For example, as shown in Figure 5, the error microphone 93 is positioned 0.05m closer to the noise source than the user's ear.
[0020] <Sound pressure estimation unit 120> The sound pressure estimation unit 120 takes the output signal (acquired signal) x(e) of the error microphone 93 as input and calculates and outputs an estimated acquired signal x(v), which is the signal that is estimated to be acquired when the microphone 130 is placed closer to the observation point than the error microphone 93. In other words, the sound pressure estimation unit 120 estimates the acquired signal obtained when the sound that was not suppressed by the playback sound reproduced from the cancellation speaker 92 is acquired at the placement position of the microphone 130 (S120), and outputs the estimated acquired signal as the estimated acquired signal x(v). Three methods for estimating the estimated acquired signal x(v) are given below as examples. Here, the microphone 130 is not actually installed but is installed virtually, and will be referred to as the virtual microphone 130 below.
[0021] (Estimation method 1) In this estimation method, the sound pickup signal x(v) of the virtual microphone 130 is estimated from the actual sound pickup signal x(e) of the error microphone 93 based on distance attenuation and phase delay. Figure 5 is a diagram illustrating the positional relationship between the noise source, the error microphone 93, and the virtual microphone 130.
[0022] In this estimation method, the position of the noise source is assumed, and it is assumed that the noise propagates as a plane wave from the noise source to the error microphone 93 and the virtual microphone 130. From the transfer function from the noise source to the error microphone 93 and the transfer function from the noise source to the observation point (the position of the virtual microphone 130), the distance attenuation and phase shift from the error microphone 93 to the observation point are estimated, and the sound pickup signal picked up by the virtual microphone 130 is estimated. The sound pressure estimation unit 120 estimates the sound pickup signal of the virtual microphone 130 from the output signal (sound pickup signal) x(e) of the error microphone 93 according to the following formula, and the estimated sound pickup signal x(v)=[^G p1 ^G p2 is output.
[0023] ^G pn =w n x(e) (n = 1, 2) (1) Here, considering only the gain attenuation, w n is w n =|G pn | / |G e | (2) And considering only the phase shift, w n is w n =exp((arg G pn -arg G e )j) (3) That is. G e , G pn in equations (2) and (3) are calculated in advance prior to the estimation process from the assumed position of the noise source and the observation point. For example, a speaker for the noise source is arranged at the assumed position of the noise source, a predetermined signal is reproduced by the speaker for the noise source, and G e is obtained from the sound pickup signal picked up by the microphone arranged at the position of the error microphone, and G pn is obtained from the sound pickup signal picked up by the microphone arranged at the position of the observation point and set aside. (Estimation Method 2) In this estimation method, the sound pickup signal of a virtual error microphone is estimated using the spherical harmonic expansion coefficients from the sound pickup signals of a plurality of error microphones arranged at equal intervals near the head. FIG. 6 is a diagram for explaining the positional relationship of the actual error microphones.
[0024] In this estimation method, the radius r e Error microphones are placed at equal intervals on the surface of a sphere, and the sound pressure on the sphere of radius r is estimated. For example, the distance from the center to the error microphone is r. e Assuming r = 0.15m, error microphones can be placed at equal intervals by (i) placing 6 error microphones at the center of each face of a regular hexahedron (see Figure 6(i)) and (ii) placing 12 error microphones at the center of each face of a regular dodecahedron (see Figure 6(ii)). For example, the distance from the center to the observation point (position of virtual microphone 130) is estimated as r = 0.08m.
[0025] By utilizing spherical harmonic expansion, it is possible to estimate the observed sound pressure on any given sphere from the observed sound pressure on a given sphere.
[0026] radius r e Observed sound pressure values from the above L error microphones: p(θ1,φ1), p(θ2,φ2), ..., p(θ L ,φ L ) is obtained. For example, the sound pickup signals x(e) = [p(θ1,φ1), p(θ2,φ2), ..., p(θ L ,φ L )]
[0027] The sound pressure estimation unit 120 calculates the spherical harmonic function Y using the following equation. m n Radius r for (·) e The sound field coefficient P shown above nm (r e )
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[0028] The derivation of equation (5) will be explained below.
[0029] When the noise source is considered a point source and reflection from a rigid sphere of radius a is taken into account, the sound pressure at point (r,θ,φ) is:
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[0030] (N+1) 2 <L Here, the spherical harmonics Y m n The number of speakers required corresponds to each mode (·). If L=6, then N=1; if L=12, then N=2.
[0031] Furthermore, N is subject to the following constraints under which spatial aliasing does not occur.
[0032] kr <N The distance between the head and the virtual error microphone is limited. For example, with a frequency of 300Hz, when N=1, the estimable range is limited to a distance of r=0.18m from the head.
[0033] (Estimation method 3) This estimation method estimates the sound pickup signal of a virtual error microphone using spherical harmonic function expansion coefficients estimated by the least squares method from the sound pickup signals of multiple error microphones placed at unequal intervals near the head. Figure 7 is a diagram illustrating the positional relationship of the error microphones. For example, error microphones can be placed at four points behind the head (four azimuth angles (0°, 30°, 150°, 180°) × elevation angle 0°) or twelve points behind the head (four azimuth angles (0°, 30°, 150°, 180°) × three elevation angles (-30°, 0°, 30°)). The installation radius of the error microphones should be determined by the environment in which they are installed and the type of sound to be suppressed. For example, when used in a railway where running noise needs to be suppressed, the installation radius of the error microphones should be 0.13m, taking into account the size of the seats.
[0034] In this estimation method, the radius r e Error microphones are placed at non-equal intervals on a sphere, and the sound pressure on the sphere of radius r is estimated. In this estimation method, the spherical harmonic expansion cannot be directly used, so the spherical harmonic expansion coefficients are estimated using the least squares method to obtain the sound pressure on the sphere of radius r.
[0035] radius r e Observed sound pressure values p(r) from the L error microphones above. e ,θ1,φ1),p(r e ,θ2,φ2),…,p(r e ,θ L ,φ L ) is obtained. Error microphone 93's sound pickup signal x(e) = - p=[p(r e ,θ1,φ1),p(r e ,θ2,φ2),…,p(r e ,θ L ,φ L )] T Let's assume that. - p can be expressed as follows:
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[0036] The sound pressure estimation unit 120 minimizes the squared error of the absolute value. - P(r e We find the solution to be ).
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[0037] <Suppression signal generation unit 110> The suppression signal generation unit 110 takes the sound-collected signal x(r) and the estimated sound-collected signal x(v) as inputs, generates a cancellation signal y to suppress noise at the installation location of the virtual microphone 130 (S110), and outputs it.
[0038] Conventional techniques can be used for generating the cancellation signal. For example, the method described in Non-Patent Document 1 can be used. In this embodiment, feedforward ANC is realized using a sound-collected signal x(r), an estimated sound-collected signal x(v), and a cancellation signal y. The sound-collected signal that would be obtained when the interference sound between the noise from the noise source and the reproduced sound of the cancellation signal y is detected by the virtual microphone 130 is estimated, and the noise from the noise source is detected by the reference microphone 91 and input to a noise control filter realized by an adaptive digital filter to generate the cancellation signal y, which is then reproduced by the cancellation speaker 92. It is assumed that the reproduced sound of the cancellation signal y propagates through a secondary path, which is a series of transmission systems from the cancellation speaker 92 to the virtual microphone 130. The coefficients of the noise control filter are then updated by an adaptive algorithm so that the input to the virtual microphone 130 is minimized. Conventional update methods can be used for updating the coefficients of the noise control filter, so a description is omitted. In feedforward ANC, a secondary path model that estimates the secondary path is used in the adaptive algorithm to compensate for the influence of the secondary path.
[0039] <Effects> With the above configuration, higher suppression performance than conventional methods can be achieved when it is not possible to place the error microphone near the user's ear. Figure 8 shows the simulation results of the first embodiment. (A) is a 300Hz plane wave noise, and (B) is a 100Hz plane wave noise.
[0040] <Second Embodiment> This explanation will focus on the differences from the first embodiment.
[0041] Figure 9 shows the simulation of the prediction error when the direction of arrival of the noise source is changed using estimation methods 2 and 3 of the first embodiment. The left side as seen from the user is set to 0°, and the direction is changed by 15° increments, resulting in a total of 13 directions from which the noise is expected to arrive. Figure 10 shows the simulation results.
[0042] Estimation method 2 offers higher estimation accuracy compared to estimation method 3, but it requires placing multiple error microphones on the front of the user's head, which can be disruptive to the user and narrow their field of view.
[0043] On the other hand, in estimation method 3, since the error microphone is not placed in front of the user's head, it does not interfere with the user or narrow their field of view, but it cannot achieve the same level of estimation accuracy as estimation method 2.
[0044] In this embodiment, we describe a method for arranging error microphones that achieves the same level of estimation accuracy as the equally spaced arrangement in estimation method 2, while being arranged at non-equal intervals that do not interfere with the user or narrow their field of view.
[0045] In this embodiment, the sound pickup signal of a virtual error microphone is estimated using spherical harmonic function expansion coefficients estimated by the least squares method from the sound pickup signals of multiple error microphones arranged at non-equal intervals near the head.
[0046] In this embodiment, radius r e Error microphones are placed at non-equal intervals on a sphere, and the sound pressure on the sphere of radius r is estimated. In this embodiment, since the spherical harmonic expansion cannot be directly used, the spherical harmonic expansion coefficients are estimated by the least squares method, similar to estimation method 3, to obtain the sound pressure on the sphere of radius r.
[0047] The signal processing method is the same as in estimation method 3, so the explanation will be omitted. Figure 11 is a diagram illustrating the positional relationship of the error microphone relative to the user's head, and Figure 12 is a top view and a rear view showing the positional relationship of the error microphone. In Figure 12, and Figures 13 and 14 described later, the black circles in the figures represent the position of the error microphone 93. For example, the error microphone is positioned to satisfy the following conditions.
[0048] (i) Multiple error microphones are placed in the horizontal direction, and multiple error microphones are placed in the elevation direction.
[0049] (ii) The system comprises two layers, each with two error microphones arranged in the horizontal direction, and two layers, each with four error microphones arranged.
[0050] (iii) Arrange the four layers described in (ii) above at different angles in the direction of elevation and depression.
[0051] (iv) A layer with four error microphones is placed at the top of the head, and a layer with two error microphones is placed at the sides of the head.
[0052] In the example shown in Figure 12, four error microphones are placed in the horizontal direction on the first and second layers, two error microphones are placed in the horizontal direction on the third and fourth layers, four error microphones are placed in the elevation direction at horizontal angles of 0° and 180°, and two error microphones are placed in the elevation direction at horizontal angles of 90° and 270°, satisfying conditions (i) and (ii). Note that the radius r is where the error microphones are placed. e The error microphone is positioned so that the center of the sphere coincides with the center of the assumed user's head (e.g., the center of gravity). Using the cross-section passing through the center of the user's head as the reference (0°), the first, second, third, and fourth layers are planes parallel to the cross-section. The first, second, third, and fourth layers and radius r e A point on a circle formed by the intersection of two spheres and radius r e The angles between the line connecting the center of the sphere and the cross-section are called the elevation angles of the first, second, third, and fourth layers, respectively. The elevation angles of the first layer are given in descending order: first layer > second layer > third layer > fourth layer. The first, second, third, and fourth layers are positioned at elevation angles of 60°, 45°, 30°, and 0°, respectively, satisfying condition (iii). Furthermore, the first and second layers are positioned above the head, and the third and fourth layers are positioned to the sides of the head, satisfying condition (vi).
[0053] Similar to estimation method 3, the installation radius of the error microphone should be determined by the environment in which it is installed and the type of sound to be suppressed. For example, when used in a railway where the goal is to suppress running noise, the installation radius of the error microphone should be 0.13m, taking seat size into consideration.
[0054] Considering that the human field of vision is approximately 180-200 degrees horizontally and approximately 60 degrees vertically, the error microphone is positioned to ensure the desired field of view.
[0055] For example, the four error microphones positioned in the elevation and depression directions at horizontal angles of 0° and 180° in Figure 12 may also be positioned in the elevation and depression directions at horizontal angles of 30° and 150°, provided that the error microphones are allowed to be partially present at the left and right edges of the field of view (see Figure 13(A)). Alternatively, if it is required that the error microphones are not at all present in the left and right edges of the field of view, the four error microphones may be positioned in the elevation and depression directions at horizontal angles of 340° (-20°) and 200° (see Figure 13(B)).
[0056] Furthermore, for example, if it is permissible for the error microphone to be somewhat above the field of view, the second layer may be set to an elevation angle of 30° (see Figure 14 (A)). Also, if it is required that the error microphone not be at all in the field of view in the upper direction, the second layer may be set to an elevation angle of 65° (see Figure 14 (B)). The elevation angles of the first, third, and fourth layers should be changed according to the second layer. Note that the head position in condition (iv) changes according to the desired field of view, with the first and second layer error microphones positioned above the lower limit of the range in which they are permitted to be located vertically within the field of view, and the head position is such that the third and fourth layer error microphones are positioned below the lower limit of the range in which they are permitted to be located vertically within the field of view. Since the third and fourth layer error microphones are not positioned in front of the user, they do not interfere with the user and do not narrow the desired field of view.
[0057] Depending on the desired field of view, error microphones are positioned, for example, four error microphones are placed in the elevation direction in the horizontal angles of -20° to 30° and 150° to 200° (see Figure 13), and the elevation angle of the second layer is set to 30° to 65° (see Figure 14).
[0058] Figure 12 shows the straight line and radius r formed by the median sagittal plane and the first and second layers, respectively.e Two error microphones are placed on each of the two points formed by the intersection of the spherical surface and the central coronal surface, and the lines formed by the 1st, 2nd, 3rd, and 4th layers and the radius r e It can also be said that two error microphones are placed on each of the two points formed by the intersection of the spherical surface.
[0059] <Effects> Figure 15 shows a simulation of the prediction error when the direction of arrival of the noise source is changed, using estimation method 2 of the first embodiment and this embodiment (microphone arrangement in Figure 12). With the microphone arrangement of this embodiment, the same effects as the first embodiment are achieved, and furthermore, since the error microphone is not placed in front of the user's head, it does not interfere with the user, does not narrow the field of view, and can achieve estimation accuracy comparable to estimation method 2.
[0060] <Other variations> The present invention is not limited to the embodiments and modifications described above. For example, the various processes described above may not only be performed sequentially as described, but may also be performed in parallel or individually as needed, depending on the processing capacity of the device performing the processes. Other modifications can be made as appropriate without departing from the spirit of the present invention.
[0061] <Program and recording medium> The various processes described above can be carried out by loading a program that executes each step of the above method into the computer's memory unit 2020 shown in Figure 16, and then causing the control unit 2010, input unit 2030, output unit 2040, etc. to operate.
[0062] The program describing this process can be recorded on a computer-readable recording medium. Any computer-readable recording medium can be used, such as a magnetic recording device, optical disc, magneto-optical recording medium, or semiconductor memory.
[0063] Furthermore, this program may be distributed, for example, by selling, transferring, or lending portable recording media such as DVDs or CD-ROMs on which the program is recorded. Alternatively, the program may be stored in the storage device of a server computer and distributed by transferring the program from the server computer to other computers via a network.
[0064] A computer executing such a program may, for example, first store the program recorded on a portable storage medium or a program transferred from a server computer in its own storage device. Then, when processing is to be executed, the computer reads the program stored on its own storage medium and executes the processing according to the read program. Alternatively, the computer may directly read the program from the portable storage medium and execute the processing according to that program, or it may sequentially execute the processing according to the received program each time a program is transferred to it from a server computer. Furthermore, the above processing may be executed by a so-called ASP (Application Service Provider) type service, where the server computer does not transfer programs to this computer, but the processing function is realized only by execution instructions and result acquisition. In this form, the program includes information used for processing by an electronic computer that is equivalent to a program (data that is not a direct instruction to the computer but has the property of defining the processing of the computer, etc.).
[0065] Furthermore, in this configuration, the device is configured by executing a predetermined program on a computer, but at least a part of these processes may be implemented in hardware.
Claims
1. A generator for generating cancellation signals used in active noise control, A sound pressure estimation unit obtains an estimated sound signal by estimating spherical harmonic function expansion coefficients using the least squares method from the sound signals picked up by multiple error microphones placed at non-equally spaced intervals near the user's head, and using the estimated spherical harmonic function expansion coefficients to estimate the sound signal that would be picked up if a virtual microphone were placed closer to the observation point than the multiple error microphones, and obtaining an estimated sound signal. The system includes a suppression signal generation unit that generates a cancellation signal to suppress noise at the installation location of the virtual microphone using the sound pickup signal obtained from the noise to be suppressed and the estimated sound pickup signal, The aforementioned virtual microphone is a microphone that is virtually installed but is not actually installed. The aforementioned multiple error microphones are installed on a spherical surface such that the following conditions (i) to (iv) are met: (i) Multiple error microphones are arranged in the horizontal direction, and multiple error microphones are arranged in the elevation direction. (ii) comprising a first layer and a second layer having at least four error microphones arranged in the horizontal angular direction, and a third layer and a fourth layer having at least two error microphones arranged in the horizontal angular direction, (iii) The first layer, the second layer, the third layer and the fourth layer are arranged at different angles in the elevation and depression direction. (iv) The first and second layers are positioned at the upper part of the head, and the third and fourth layers are positioned at the sides of the head. generator.
2. A generating apparatus according to claim 1, Four error microphones are positioned in the elevation / depression direction at horizontal angles of 0° and 180°, and two error microphones are positioned in the elevation / depression direction at horizontal angles of 90° and 270°. The elevation angles of the first, second, third, and fourth layers are 60°, 45°, 30°, and 0°, respectively. generator.
3. A method for generating a cancellation signal used for active noise control, A sound pressure estimation step in which the spherical harmonic expansion coefficients are estimated using the least squares method from the sound signals picked up by multiple error microphones placed at unequal intervals near the user's head, and the sound signal picked up when a virtual microphone is placed closer to the observation point than the multiple error microphones is estimated using the estimated spherical harmonic expansion coefficients to obtain the estimated sound signal, The process includes a suppression signal generation step, which generates a cancellation signal for suppressing noise at the installation location of the virtual microphone, using the sound pickup signal obtained from the noise to be suppressed and the estimated sound pickup signal. The aforementioned virtual microphone is a microphone that is virtually installed but is not actually installed. The aforementioned multiple error microphones are installed on a spherical surface such that the following conditions (i) to (iv) are met: (i) Multiple error microphones are arranged in the horizontal direction, and multiple error microphones are arranged in the elevation direction. (ii) comprising a first layer and a second layer having at least four error microphones arranged in the horizontal angular direction, and a third layer and a fourth layer having at least two error microphones arranged in the horizontal angular direction, (iii) The first layer, the second layer, the third layer and the fourth layer are arranged at different angles in the elevation and depression direction. (iv) The first and second layers are positioned at the upper part of the head, and the third and fourth layers are positioned at the sides of the head. Generation method.
4. A program for causing a computer to function as a generating device according to claim 1 or claim 2.