Patent Translate Powered by EPO and Google Notice This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate, complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or financial decisions, should not be based on machine-translation output. DESCRIPTION JP2001142471 [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic technique for reproducing a sound field, and more particularly, to an apparatus for reproducing a sound field for appropriately reproducing a change in the sound field caused by the movement of an object not emitting sound. About. [0002] 2. Description of the Related Art In a virtually created environment, such as a TV (television) conference system, a virtual reality system, a multimedia game, etc., by giving appropriate stimuli artificially generated to human five senses. Technology to make the human feel like it is in development is developing. In such a system, the audio plays a great role as well as the visual stimulus. For that purpose, it is necessary to simulate what the sound field of the assumed environment will be and to properly reproduce the sound field of the assumed environment. [0003] Conventionally, such sound field reproduction methods can be roughly classified into the following three. The first method is to measure the head related transfer function in the space, for example, a music hall, at a number of places, and the sound source recorded in the anechoic music space (such as the sound recorded in the anechoic music space It is called "dry sound 09-05-2019 1 source". And the same sound field as the original space in each place. [0004] The second method simulates an echo pattern by simulating a sound field according to the shape of the room and the positional relationship of objects in the room by a method (sound ray method, virtual image method, etc.) according to geometrical modeling. It is a method to reproduce the sound field with a sense of reality. [0005] The third method is to divide the space inside the room that is the object of sound field reproduction into many small elements and perform numerical calculation according to the finite element method or the boundary element method in consideration of the wave nature of the sound. , Is a method to simulate the sound field of the room. [0006] However, all the conventional methods have problems to be solved as described below. [0007] In this first method, it is necessary to measure the transfer function many times in order to raise the S / N (signal / noise ratio) even if the head related transfer function is measured for only one point in the room. Therefore, much time is required for preparation. Also, it is very difficult to obtain a head-related transfer function for a sufficiently large number of points in the target space. Therefore, for example, when it is assumed that the position of the listener moves, it is difficult to reproduce a sufficient sound field. Also, even if head related transfer functions for a large number of points are obtained, it is necessary to store them all, and a large storage capacity is required. Furthermore, when the shape of the space, the arrangement of the object, and the shape change, it is necessary to measure all head related transfer functions again. 09-05-2019 2 [0008] After all, this first method can not be used when reproducing the sound field in real time. [0009] In the second method, there is a problem that a sound field that can not be generated in the shadow portion of the object can not be generated because the sound diffraction is ignored. In order to generate the sound field of the shadow part, it is necessary to consider the reflected wave from the wall, but in order to do so, the space of interest has to be surrounded by the wall where a sufficiently large reflected wave can be obtained . [0010] Therefore, in this second method, it is difficult to reproduce, for example, a sound field of a space in which an object that does not generate sound moves. [0011] In the third method, there is a problem that it is not possible to reproduce the sound field for one point inside the room if the calculation for the entire room is not performed. It takes a lot of time to calculate across the room. In addition, if the shape of the room changes, it is necessary to change the simulation conditions again and perform the calculation again. Furthermore, in order to accurately obtain the high frequency components contained in the auditory stimulation at a certain point, the space must be divided into extremely small elements and calculations must be performed for each of them. Therefore, the amount of calculation is enormous. [0012] Therefore, even with this third method, it is difficult to reproduce in real time the sound field in an environment where the arrangement of objects inside the space frequently changes. 09-05-2019 3 [0013] Therefore, the main object of the present invention is to provide a sound field reproducing apparatus capable of reproducing a sound field in real time which can cope with a change in the arrangement of objects inside a space. [0014] According to the invention as set forth in claim 1, the sound field reproducing apparatus comprises a sound source disposed in a predetermined space, and a rigid ball of known position disposed in the predetermined space. A sound field reproducing apparatus for reproducing a sound field in a predetermined space by a hard sphere model including a predetermined frequency range at a plurality of locations on a predetermined line having a predetermined relationship with a line connecting a sound source and the hard sphere model Transfer function supplying means for supplying the transfer function of the sound wave from the sound source, the position information determining means for determining the position information on the position to reproduce the sound field, and the position information determining means Based on the determined position information, the corresponding transfer function is supplied from the transfer function supply means, and the input sound source signal is converted according to the transfer function to synthesize and output an acoustic signal. And a force signal combining means. [0015] Depending on the position information to reproduce the sound field, a corresponding predetermined transfer function is supplied by the transfer function supply means, and the input sound source signal is converted using this transfer function. Transfer functions are obtained at a plurality of locations on a predetermined line having a predetermined relationship with a line connecting a sound source and a hard sphere in advance by the rigid sphere model, and acoustic signals at listening positions are synthesized based on the transfer function. Therefore, even if the hard sphere itself does not generate sound, it is possible to reproduce the changing sound field under the influence of the object of the hard sphere. 09-05-2019 4 [0016] According to the invention of claim 2, in addition to the constitution of the invention of claim 1, the position information determining means outputs position information corresponding to the left ear and the right ear of the listener, and an output signal combining means Based on the position information of the left ear and the right ear, the corresponding transfer functions are supplied from the transfer function supplying means, and the input sound source signals are converted according to the respective transfer functions and And means for combining and outputting the right ear acoustic signal. [0017] Since the sound signal by the transfer function at the left ear and the sound signal by the transfer function at the right ear are respectively synthesized and output, the sound signal that a human would perceive at a predetermined place is reproduced more faithfully. [0018] According to the invention described in claim 3, in addition to the configuration of the invention described in claim 2, the position information determining means changes the distance between the left ear and the right ear of the listener, whereby the listener The sound field is reproduced as if the size of the rigid sphere relative to. [0019] According to the third aspect of the invention, in addition to the effects of the invention of the second aspect, the hard sphere perceived by the listener by only a simple process of changing the parameter of the distance between the listener's ears The size of the (object) can be changed. [0020] According to the invention set forth in claim 4, in addition to the constitution of the invention set forth in claim 1, the transfer function supplying means stores the value of the transfer function previously obtained for each position and each frequency. Includes a storage device. [0021] According to the fourth aspect of the invention, in addition to the effects of the first aspect of the invention, the value of the transfer function previously obtained for each position and frequency 09-05-2019 5 is stored in the storage device. By reading from this storage device, the transfer function for each position can be easily obtained. [0022] According to the invention set forth in claim 5, in addition to the constitution of the invention set forth in claim 1, the transfer function supplying means is the largest of the autocorrelation matrix of the matrix having transfer functions for each position and each frequency. Coefficient supply means for supplying a coefficient for reconstructing a transfer function by linear combination of a plurality of eigenvectors and a plurality of eigenvectors respectively corresponding to a plurality of eigenvalues, position information A means for receiving a coefficient corresponding to positional information given from the determination means from the coefficient supply means, and using the coefficients to calculate a linear combination of a plurality of eigenvectors received from the coefficient supply means, includes means for outputting a transfer function . [0023] According to the fifth aspect of the invention, in addition to the effects of the invention of the first aspect, the transfer function can be accurately represented by linear combination of a plurality of eigenvectors respectively corresponding to the largest plurality of eigenvalues. . Since it is not necessary to store all transfer functions, storage capacity can be reduced. [0024] According to the invention set forth in claim 6, in addition to the constitution of the invention set forth in claim 5, the coefficient supply means comprises eigenvector storage means for storing a plurality of eigenvectors, and a coefficient determined for each position. Coefficient storage means for storing, and given position information, the corresponding coefficients are output from the coefficient storage means. [0025] 09-05-2019 6 According to the invention of claim 6, in addition to the effects of the invention of claim 5, in order to supply a transfer function, a finite number of eigenvectors and coefficients determined for each position are stored. Good. It is not necessary to store all of the transfer functions, and the storage capacity can be reduced. [0026] According to the invention of claim 7, in addition to the constitution of the invention of claim 5, the coefficient supply means comprises: eigenvector storage means for storing a plurality of eigenvectors; and a position given from position information determination means And means for calculating and outputting a coefficient determined for each eigenvector according to each position by polynomial approximation obtained in advance according to the information. [0027] According to the seventh aspect of the invention, in addition to the effects of the fifth aspect of the invention, in order to supply a transfer function, a finite number of eigenvectors and coefficients to be determined for each position are calculated. A polynomial approximation may be stored. A storage device for storing all of the transfer functions is unnecessary, and it is not necessary to store all the coefficients for linear combination determined for each position. Therefore, the capacity of the storage device can be reduced. [0028] According to the invention described in claim 8, in addition to the configuration of the invention described in claim 1, the transfer function supply means includes transfer function calculation means for calculating a transfer function for each position and each frequency, Among the transfer functions calculated by the transfer function calculation means, transfer function correction means for correcting a characteristic waveform caused by a hard sphere model according to a predetermined method, and the transfer function corrected by the transfer function correction means Storage device for storing the 09-05-2019 7 [0029] According to the eighth aspect of the invention, in addition to the effects of the first aspect of the invention, of the transfer function, the characteristic waveform caused by the hard sphere model is corrected according to a predetermined method. As a result, the sound field obtained according to this corrected transfer function becomes closer to the actual sound field without including the unnaturalness resulting from the characteristic waveform of the hard sphere model. [0030] According to the invention as set forth in claim 9, in addition to the constitution of the invention as set forth in claim 1, the transfer function supply means comprises transfer function calculation means for calculating a transfer function for each position and each frequency. Transfer function correction means for correcting a characteristic waveform attributable to a hard sphere model among the transfer functions calculated by the transfer function calculation means according to a predetermined method, and after correction for each position and each frequency The transfer function is reconstructed by linear combination of a plurality of eigenvectors respectively corresponding to a plurality of eigenvalues predetermined in descending order of the eigenvalues of the autocorrelation matrix of the matrix having the transfer function as an element Means for supplying coefficients corresponding to each position, and coefficients supplying means for coefficients corresponding to the information on the position given from the position information determining means. It received from, by using the supplied coefficient, and means for outputting the transfer function by computing the linear combination of the plurality of eigenvectors to receive from the coefficient supply means. [0031] According to the invention as set forth in claim 9, in addition to the operation and effect of the invention as set forth in claim 1, transfer function correction is performed according to a method in which a characteristic waveform derived from a hard sphere model among transfer functions is predetermined. The eigenvectors and the coefficients are supplied by the counting and supplying means from the corrected transfer function after being corrected by the means. 09-05-2019 8 Further, at the time of reproduction of the sound field, the original corrected transfer coefficient is restored according to the eigenvectors and coefficients thus obtained. The sound field obtained according to the transfer function after this correction is closer to an actual sound field because it does not include the unnaturalness that arises from the characteristic waveform by the hard sphere model. [0032] BEST MODE FOR CARRYING OUT THE INVENTION In the embodiment described below, as will be described later, the sum of a direct wave from a sound source and a velocity potential by a reflected wave from a surface (a hard surface) of a rigid sphere placed in a sound field. The velocity potential of the sound wave at any point in space is expressed, and the transfer function is determined for each frequency from the ratio of this to the velocity potential of the sound source, corresponding to the position on a certain straight line in space. Then, this transfer function is used to simulate and output an acoustic signal at a specific point from the acoustic signal from the sound source. The rigid ball model that is the basis of this will be described later. First Embodiment Referring to FIG. 1, a sound field reproduction device 20 according to a first embodiment of the present invention estimates a position of a listener and outputs a listener's position estimation unit 22; Transfer function storage unit for storing and supplying a hard disk 24 storing an acoustic signal as a sound source, an acoustic signal input unit 28 for reproducing the acoustic signal from the hard disk 24, and a transfer function predetermined as described later 32. Based on the listener's position information given by the listener's position estimation unit 22, the transfer function storage unit 32 obtains a transfer function that has been obtained in advance corresponding to the position, and the acoustic signal input unit 28 An output signal synthesis unit 30 for synthesizing an output signal by convoluting a transfer function corresponding to each frequency component of an acoustic signal to be supplied, and an output from the output signal synthesis unit 30 And an acoustic signal output section 34 for outputting a signal to the outside. The acoustic signal output from the acoustic signal output unit 34 is amplified by, for example, the amplifier 36 and applied to the speaker 38 to generate sound. In 09-05-2019 9 place of the sound source signal reproduced from the hard disk 24, an acoustic signal transmitted from a remote place via the communication line 26 may be given to the acoustic signal input unit 28. [0033] As a synthesis method in the output signal synthesis unit 30, a method of subjecting an input signal to Fourier transform and then multiplying the result by a transfer function and summing the result, and subjecting the result to inverse Fourier transform, performing inverse Fourier transform on the transfer function, time axis There are a method of convoluting and outputting the input signal, and a method of controlling the graphic equalizer by the transfer function to control the frequency distribution of the input signal. [0034] FIG. 2 is a flow chart showing a process of generating a transfer function of the device of the first embodiment. Referring to FIG. 2, in this system, in particular, transfer functions stored in transfer function storage unit 32 are prepared in advance through several stages. That is, first, at step 50, a transfer function in a predetermined space is simulated by a rigid ball model as described later. Subsequently, the transfer function for each frequency is determined at each point along a certain straight line (in this embodiment, a line z = 1 (z) or a line z perpendicular to the Z axis as described later) (step 52). Then, the transfer function storage unit 32 shown in FIG. 1 is prepared by storing the transfer function thus obtained in the storage device. Although the line for obtaining the transfer function is assumed to be a straight line here, another curve may be used depending on the application. [0035] The rigid ball model which is the basis of the simulation performed in step 50 will be described with reference to FIG. In FIG. 3, it is assumed that the coordinates of an arbitrary point P are represented by polar coordinates (r, θ) centering on the origin O. And, here, consider a hard sphere of radius a centered on the origin O. Consider a Z axis 64 passing horizontally through the origin O. 09-05-2019 10 [0036] In this model, an arbitrary spatial velocity is obtained as the sum of the velocity potential φi of a direct wave (plane wave) traveling parallel to the Z axis 64 from a sound source (not shown) and the velocity potential φr due to the reflected wave from the rigid sphere of the hard sphere 62. Express the velocity potential φ (r, θ, t) = φi + φr at the point. Here, t is a variable representing time. [0037] The velocity potential Φ is a variable defined by the following equation (1). [0039] The left side of the equation (1) represents the vibration velocity of the medium particle by the sound wave. “∇” represents nabra (∂ / ∂x, ∂ / ∂y, ∂ / ∂z). [0040] Assuming that .phi.i is known, the boundary condition on the surface of the hard sphere 62 determines the unknown parameter of .phi.r (and hence .phi.) described above, whereby the velocity potential .phi. at any point in space can be determined. The transfer function at each point can be determined from the ratio of φ at each point thus determined to the velocity potential at the sound source. [0041] An example of the determined transfer function is shown in FIG. In FIG. 4, a straight line 60 of z = 1 (El) in FIG. Of the transfer function determined along the In FIG. 4, “Position” is a position on the straight line 60 where the point at which the straight line 60 intersects the Z axis 64 is 0 and 09-05-2019 11 the upward direction is positive. "Frequency" indicates the target frequency for which the transfer function has been obtained, and its unit is kilohertz (kHz). The vertical axis also represents the transfer function at a certain frequency at a certain position (the ratio of the velocity potential at that point with respect to that frequency to the velocity potential with respect to that frequency at the sound source; Relative Amplitude). [0042] As apparent from FIG. 4, when a certain point (position) existing on the opposite side to the sound source with respect to the rigid sphere 62 is determined, the transfer function at that point can be expressed as a function of frequency. Therefore, by convoluting the transfer function into the original acoustic signal, it is possible to simulate the sound field at the position opposite to the sound source with respect to the hard sphere 62. In this case, since only the sound field generated in the shadows is taken into consideration, it is not necessary to obtain the transfer function for a wide range of points. [0043] The same applies to the point (position) on the sound source side with respect to the rigid ball 62. Referring to FIG. 5, the sum of the velocity potential φi of a direct wave (plane wave) traveling parallel to Z axis 64 from a sound source (not shown) and the velocity potential φr due to the reflected wave from rigid sphere 62 The velocity potential φ (r, θ, t) = φi + φr is expressed at an arbitrary point P (r, θ) of [0044] As in the case where point P is opposite to the sound source with respect to rigid sphere 62, the boundary conditions at the surface of rigid sphere 62 determine the unknown parameter of r r (and hence 上 記) mentioned above, whereby the velocity at any point in space The potential φ can be determined. The transfer function at each point located between the hard sphere 62 and the sound source can be determined from the ratio of φ at each point thus determined to the velocity potential of the sound source. [0045] 09-05-2019 12 An example of the determined transfer function is shown in FIG. FIG. 6 is a straight line 66 in which z = m in FIG. 5 (the straight line 66 is on the same side as the sound source with respect to the hard sphere 62). Of the transfer function determined along the In FIG. 6, as in FIG. 4, “Position” is a position on the straight line 66 where the point where the straight line 66 intersects the Z axis 64 is 0 and the upward direction is positive. "Frequency" indicates the frequency of interest for which the transfer function is determined, and the vertical axis indicates the transfer function (Relative Amplitude) at a certain frequency at a certain position. [0046] The transfer function storage unit 32 shown in FIG. 1 stores this transfer function. That is, in step 50 of FIG. 2, FIG. 3 or FIG. And the transfer function along z = 1 or m is determined in step 52, and the transfer function shown in FIG. 4 or 6 thus obtained is stored in the transfer function storage unit 32 in step 54. deep. [0047] The sound field reproduction device 20 set in advance in this manner operates as follows. First, the position estimation unit 22 of the listener estimates the position of the listener. For example, in a virtual reality system or the like, a relationship between a sound source and an object present in a virtual environment and a virtual position of a listener is always maintained. The listener's position estimation unit 22 estimates the position of the listener relative to the sound source (the position on the straight line 60 z = 1 in FIG. 4 or the position on the straight line 66 z = m in FIG. 6) from such information. [0048] On the other hand, an acoustic signal to be reproduced is input from the hard disk 24 or the communication line 26 through the acoustic signal input unit 28. In the case of a game or a movie, an audio signal recorded on the hard disk 24 will be reproduced, and in the case of a TV conference system, an audio signal will be transmitted from a remote place via the communication line 26. I will. Also, if the communication speed is sufficient, it is possible to receive a movie sound signal from a remote place via the communication line 26. 09-05-2019 13 [0049] The transfer function storage unit 32 stores the transfer function shown in FIG. 4 or 6 as described above. The transfer function can be determined by the position on the straight line 60 or the straight line 66 and the frequency. The output signal synthesis unit 30 synthesizes the acoustic signal by convoluting the transfer function determined from the transfer function storage unit 32 with the acoustic signal supplied from the acoustic signal input unit 28, and outputs it to the amplifier 36 via the acoustic signal output unit 34. Do. The amplifier 36 amplifies this acoustic signal and supplies it to a speaker 38, which generates an acoustic wave in accordance with this acoustic signal. This sound wave is formed by the sound wave and the hard sphere 62 when the sound wave from the sound source proceeds actually as shown in FIG. 4 or 6 at the position of the listener estimated by the position estimation unit 22 of the listener. The simulated sound field is simulated. [0050] According to this sound field reproduction device 20, for example, by changing the position of the listener on z = 1 to reproduce the sound field and giving it to the listener, the listener does not relatively change the position, and the hard sphere 62 The sound field can be reproduced as if the position of. At this time, the hard ball 62 itself is not required to generate a sound. Therefore, the change of the sound field when the silent object moves in the space can be simply reproduced. The same is true when the position of the listener on z = m is changed. [0051] For example, when a large fish (eg, a shark) moves in the sea, the conventional sound field reproduction method can reproduce a sound field that reflects the movement of the shark, unless the shark produces a sound. It was not. Therefore, for example, the listener is made aware of the movement of the shark by generating a sound that the shark is constantly generating bubbles and moving the place where the sound is generated. However, these methods have the problem that they can not reproduce the sound field in an environment where sharks move without generating sound. 09-05-2019 14 [0052] On the other hand, in the present invention, even if the shark does not make a sound, it is possible to reproduce the change of the sound field due to the movement of the shark. Therefore, it is possible to configure the virtual environment more faithfully. Moreover, the value of the transfer function stored in the transfer function storage unit 32 can be obtained in advance by simulation. Therefore, the processing in the output signal synthesis unit 30 is only mere table lookup and convolution operation. The amount of computation is small, and changes in the sound field can be reproduced in real time. [0053] As described above, it is also possible to change the relative position between the listener and the object simply by changing the position of the listener on z = 1 or z = m. It can be changed simply. The method for that is as follows. [0054] In order to make the listener perceive the position of a virtually moving object, it is necessary to generate sounds to be presented to the left ear and the right ear. This may be done by using the transfer functions at each of the left ear position 66 and the right ear position 68 shown in FIG. 7 to generate the sound for the left ear and the sound for the right ear. In the following, the case where the position of the listener is on the opposite side of the sound source with respect to the hard ball 62 will be described as an example, but the same applies to the case where the position of the listener is on the same side as the sound source with respect to the hard ball 62. [0055] Now, let k be the distance between both ears. This k is usually a constant that can be determined statistically. Here, if the distance k is increased (that is, the distance between human ears is increased), the same effect as when the size of the hard sphere 62 is relatively reduced can be obtained. Conversely, if the distance k is reduced, the same effect as when the size of the hard sphere 62 is relatively increased can be obtained. Therefore, by appropriately changing the distance k, it is possible to easily create a sound field reflecting the difference in the size of the 09-05-2019 15 object. Second Embodiment In the first embodiment described above, the transfer function is stored in the transfer function storage unit 32 as it is. In this case, since only the transfer function for a narrow range of points needs to be obtained in the first embodiment, the amount of data to be stored in the transfer function storage unit 32 is not so large, but still a certain amount of storage capacity is required. Emphasis on real-time sound field reproduction may require a large amount of high-speed storage devices. Since such an increase in storage capacity leads to an increase in the cost of the device, it is desirable to minimize the required storage capacity. In the system of this second embodiment, the storage capacity can be made smaller than that of the first embodiment. [0056] First, matters underlying the second embodiment will be described. The data of the transfer function shown in FIG. 4 is expressed in matrix form, with the position of each point as a row, the frequency as a column, and the transfer function as a value of each element. Then, a matrix (autocorrelation matrix) obtained by multiplying the conjugate transpose matrix of this matrix by itself is determined, and the eigenvalue decomposition is performed. FIG. 8 shows the eigenvalues obtained from the transfer function of FIG. Corresponding eigenvalues correspond to these eigenvalues. Each eigenvector is a vector having the same number of elements as the number of columns (number of frequencies) of the original matrix. [0057] Referring to FIG. 8, the number of eigenvalues having a large value is limited. Thus, it can be seen that the original transfer function distribution can be relatively accurately reconstructed from a small number of eigenvectors corresponding to these eigenvalues. In the second embodiment, from the eigenvectors corresponding to the indexes 1 to 4 shown in FIG. 8, the head related transfer function when the listener is located on the opposite side to the sound source with respect to the rigid ball 62 is reconstructed. The graph of FIG. 9 shows the coefficients for each eigenvector as a function of the position when the original head related transfer function is determined by multiplying each eigenvector with a coefficient for each position at this time. . [0058] Referring to FIG. 9, these coefficients correspond to the first transfer coefficient curve 72 09-05-2019 16 corresponding to the eigenvector of index 1, the second transfer coefficient curve 74 corresponding to the eigenvector of index 2, and the third corresponding to the eigenvector of index 3 A transfer coefficient curve 76 and a fourth transfer coefficient curve 78 corresponding to the eigenvector of index 4 are represented. If the values corresponding to these four curves are stored, when the position of the listener is determined opposite to the sound source with respect to the rigid ball 62, the corresponding four coefficients are determined, and these four coefficients are added to the corresponding eigenvectors By combining, the transfer function at that place can be obtained. [0059] Similarly, FIG. 10 shows the eigenvalues when the eigenvalue decomposition is performed for the transfer function shown in FIG. 6 in order from the largest value. From the eigenvectors corresponding to the indexes 1 to 4 shown in FIG. 10, the head transfer function when the listener is located between the sound source and the hard sphere 62 is reconstructed. The graph of FIG. 11 shows the coefficients for each eigenvector as a function of the position when the original head related transfer function is determined by multiplying each eigenvector with a coefficient for each position at this time. . [0060] Referring to FIG. 11, as in the case of FIG. 9, these coefficients correspond to a first transfer coefficient curve 82 corresponding to the eigenvector of index 1, a second transfer coefficient curve 84 corresponding to the eigenvector of index 2, index 3 A third transfer coefficient curve 86 corresponding to the eigenvector and a fourth transfer coefficient curve 88 corresponding to the eigenvector of index 4 are represented. If the values corresponding to these four curves are stored, when the position of the listener is determined on the same side as the sound source with respect to the hard sphere model, the corresponding four coefficients are determined, and these four coefficients are added to the corresponding eigenvectors By combining, the transfer function at that place can be obtained. [0061] When the respective curves of FIGS. 9 and 11 are stored in the form of a table, the required storage capacity is much smaller than when the transfer functions shown in FIGS. 4 and 6 are stored as they are. 09-05-2019 17 [0062] The block diagram of the system of this Embodiment 2 is shown in FIG. In FIG. 12, parts that are the same as the parts shown in FIG. 1 are given the same reference numerals. Their functions are also identical. Therefore, the detailed description about them is not repeated here. [0063] The sound field reproduction apparatus 90 shown in FIG. 12 differs from the sound field reproduction apparatus 20 shown in FIG. 1 in that the coefficient storage unit 91 for storing the coefficients for the eigenvectors of the indexes 1 to 4; A coefficient reading unit 92 for a position for reading from the coefficient storage unit 91, which is connected to the output of the position estimation unit 22 and corresponds to the listener's position obtained from the listener's position estimation unit 22, is newly included. 1, a transfer function generating vector storage unit 94 for storing the eigenvectors of the indexes 1 to 4 shown in FIG. 8 in place of the transfer function storage unit 32 shown in FIG. A transfer function synthesis unit 96 is newly included to synthesize a transfer function by multiplying the corresponding eigenvectors stored in the transfer function generation vector storage unit 94 by coefficients and taking the sum. 1 and, instead of the output signal synthesis unit 30 of FIG. 1, an output signal synthesis unit for synthesizing an acoustic signal by convoluting the transfer coefficient given from the transfer function synthesis unit 96 into the acoustic signal from the acoustic signal input unit 28 Including 98. [0064] In FIG. 12, in order to clarify the description, FIG. 9 and FIG. 9 are obtained from the transfer function calculation processing unit 100 for calculating the transfer function by simulation in advance and the transfer function calculated by the transfer function calculation processing unit 100. A coefficient calculation unit 102 for calculating the coefficient distribution as shown in 11 and storing the calculated coefficient distribution in the coefficient storage unit 91 is described. In practice, the processing blocks 100 and 102 operate not at the time of operation of the device but at preparation time, but may be included in the device itself or may be provided 09-05-2019 18 independently of the device. [0065] The coefficient storage unit 91 stores in advance a table of coefficients (corresponding to FIG. 9 or FIG. 11) obtained based on the simulation result performed in advance. In the transfer function generation vector storage unit 94, eigenvectors corresponding to the indexes 1 to 4 in FIG. 8 or 10 are stored in advance. Based on the position information estimated by the position estimation unit 22 of the listener, the coefficient readout unit 92 for the position stores coefficients based on whether the position is on the same side as the sound source or on the same side as the sound source. The coefficient to be multiplied by the vector of indexes 1 to 4 in FIG. The transfer function combining unit 96 combines the transfer function by multiplying the coefficient given from the coefficient reading unit 92 for the position and the corresponding eigenvector read out from the transfer function generation vector storage unit 94, and outputs the result to the output signal combining unit 98. give. The output signal synthesis unit 98 convolutes the transfer function with the acoustic signal supplied from the acoustic signal input unit 28, outputs the acoustic signal and supplies the acoustic signal to the acoustic signal output unit 34. The acoustic signal supplied from the acoustic signal output unit 34 to the amplifier 36 is amplified and output from the speaker 38. [0066] The flow of data and the flow of processing in the sound field reproduction device 90 of the second embodiment are shown in FIG. Referring to FIG. 13, first, on the basis of the size information 110 of the object, the calculation 112 of the distance between the left and right ears for expressing the size of the object is performed. Also, based on relative position information 114 of the head with respect to the object and distance information between the left and right ears obtained from the calculation 112 of distance between the left and right ears, position information 116 of the left and right ears is calculated. [0067] Given the positional information 116 of the left and right ears, transfer function coefficients 118 for the respective eigenvectors (indexes 1 to 4) for synthesizing the transfer functions at the positions of the respective ears are obtained from the coefficient storage unit 91. Further, the 09-05-2019 19 eigenvectors 120 of the indexes 1 to 4 are obtained from the transfer function generation vector storage unit 94. Based on the position information 116 of each of the left and right ears, the transfer function coefficient 118 and the eigenvector 120, calculation (synthesis) of the transfer function is performed (calculation of the transfer function 122). By convolving the transfer function thus obtained with the sound signal from the source sound source 124 (convolution operation 126), a single-ear signal output 128 for the left ear and the right ear is obtained. By reproducing this signal with a speaker or headphones, a sound field corresponding to the position of the head calculated by the relative position information 114 of the head to the object is reproduced. [0068] As described above, according to the apparatus of this embodiment, instead of storing all data constituting the transfer function, a relatively small number of eigenvectors and a graph of coefficients corresponding to these eigenvectors are reproduced (FIG. 9) You can store the data of The amount of data can be much smaller than in the case of storing all transfer functions shown in FIG. Therefore, the required storage capacity can be reduced. Third Embodiment The device of the second embodiment described above can significantly reduce the required storage capacity as compared with the device of the first embodiment. However, if there is a margin in processing speed, it is possible to further reduce the storage capacity. The apparatus according to the third embodiment calculates the coefficients stored in the storage device in the second embodiment by polynomial approximation. The four curves 72 to 78 and 82 to 88 shown in FIG. 9 or FIG. 11 are all relatively smooth curves. Therefore, these curves can be approximated by polynomials, respectively. Once the approximating polynomial is determined, by determining the position, it is possible to obtain the coefficient for calculating the transfer function as the value of the polynomial whose position is substituted into the variable. It is not necessary to store all the data corresponding to the curves 72-78 and 82-88 shown in FIG. 9 or FIG. Therefore, in the third embodiment, the storage capacity can be further reduced as compared with the second embodiment. [0069] FIG. 14 shows the flow of data and the flow of processing in the apparatus of the third embodiment. Referring to FIG. 14, this system differs from the system of the second embodiment shown in FIG. 13 in that coefficients are calculated from position information by polynomial approximation 140, instead of the process of calculating transfer functions 122 of FIG. And the process 144 of calculating a transfer function based on the coefficients thus obtained and the 09-05-2019 20 eigenvector 120. In other respects, the device of FIG. 14 is the same as the device of FIG. Therefore, in FIG. 14, parts that are the same as parts shown in FIG. 13 are given the same reference numerals, and the detailed description thereof will not be repeated here. [0070] In the apparatus of the third embodiment, coefficients for linear combination of eigenvectors are calculated by polynomial approximation. Therefore, there is no need to store these coefficients. Therefore, the storage capacity can be further reduced as compared with the apparatus of the second embodiment. Fourth Embodiment In the description of the first to third embodiments above, a hard sphere model as shown in FIG. 3 or FIG. 5 is assumed, and sound field reproduction is performed based on a transfer function calculated from such a model. . However, when such a sound field reproduction apparatus is used, an object assumed to be present in the sound field is not actually a hard sphere. For example, in most cases the shape is not a sphere or the object is not rigid, in particular if its surface has a different sound reflection characteristic than rigid, such as clothing, leather, fur or wood. Therefore, if a transfer function (see FIGS. 4 and 6) calculated from a rigid body model as shown in FIG. 3 or 5 is used as it is, a sound field slightly different from the actual sound field may be reproduced. [0071] Therefore, in the device according to the fourth embodiment, the transfer function (FIGS. 4 and 6) calculated from the rigid ball model as shown in FIG. 3 or 5 is corrected to more faithfully reproduce the actual sound field. It is used. FIG. 15 shows an example of a corrected transfer function (corresponding to the case where the position of the listener is on the opposite side of the sound source with respect to the rigid ball). In this transfer function, among the transfer functions shown in FIG. 4, an edge-like portion existing in a portion where the position (Position) corresponds to 0 is deleted from the vicinity of the rising portion, and instead, the portion is spline-interpolated It is [0072] The rigid sphere model is characterized in that a very sharp edge as shown in FIG. 4 is generated near position = 0, since total reflection is assumed on the object to be completely spherical. However, in an actual object, such exact reflection does not occur but scattering occurs. 09-05-2019 21 Therefore, as shown in FIG. 15, it is possible to more appropriately reproduce the actual sound field if the edge portion is deleted and the shape of the transfer function of that portion is blunted. [0073] When eigenvalues are decomposed into transfer functions shown in FIG. 15, numbers (indexes) are assigned in order from large eigenvalues, and FIG. 16 shows the relationship between the index and the magnitude of the eigenvalues. In this case, it can be seen that the value of the eigenvalue corresponding to index 1 is larger than that in the case shown in FIG. 8 or FIG. [0074] The relationship between the listening position and each coefficient when the transfer function is represented by the linear combination of the eigenvectors of the indexes 1 to 4 obtained from the transfer function shown in FIG. 15 is shown in FIG. Referring to FIG. 17, in the same manner as shown in FIG. 9, these coefficients correspond to a first transfer coefficient curve 172 corresponding to the eigenvector of index 1 and a second transfer coefficient curve 174 corresponding to the eigenvector of index 2, A third transfer coefficient curve 176 corresponding to the eigenvector of index 3 and a fourth transfer coefficient curve 178 corresponding to the eigenvector of index 4 are represented. By using the relationship shown in FIG. 17, it is possible to realize a sound field reproduction device having the same configuration as that of the second embodiment (FIG. 12). [0075] FIG. 18 shows a block diagram of the sound field reproduction device 190 according to the fourth embodiment. This sound field reproduction device 190 differs from the sound field reproduction device 90 according to the second embodiment shown in FIG. 12 in that the transfer function calculated by the transfer function calculation unit 100 according to the hard sphere model is corrected as described above This is a point that a transfer function correction unit 192 to be provided to the calculation unit 102 is newly included. The sound field reproduction apparatus 190 is the same as the sound field reproduction apparatus 90 shown in FIG. Therefore, the detailed description about them is not repeated here. 09-05-2019 22 [0076] The correction process performed by the transfer function correction unit 192 is a process of blunting the sharp edge at position = 0 shown in FIG. The shape of a typical transfer function obtained as a result is as shown in FIG. 15, but various other correction methods are conceivable. For example, instead of removing the edge portion as shown in FIG. 15 and then performing spline interpolation, the relative amplitude may be reduced by a certain coefficient only for the edge portion. Also, the upper end of the edge portion may be cut off at a specific threshold value, and spline interpolation may be performed between them. In any case, it is most preferable to correct the transfer function in the form considered to be optimal according to the acoustical characteristics of what is assumed to be the object present in the sound field to be reproduced, but it is quite difficult. The correction of the transfer function may be performed according to a predetermined correction method, regardless of the acoustic characteristics of. Also in this case, the sound field closer to the actual sound field is reproduced as compared with the case where the transfer function obtained from the hard sphere model is used as it is. [0077] Also, as already described, the process of calculating the transfer function, calculating the coefficients, and storing the calculated coefficients in the coefficient storage unit 91 is performed by another device before the operation of the sound field reproduction device 190. It is also good. In such a case, the sound field reproduction device 190 may not have the transfer function calculation unit 100, the transfer function correction unit 192, and the coefficient calculation unit 102, and eventually has the same structure as the sound field reproduction device 90 of the second embodiment. [0078] The present invention is applicable not only to the apparatus of the second embodiment but also to the apparatus of the first embodiment or the third embodiment in that the transfer function is corrected as described above. The modifications necessary for that will be apparent to those skilled in the art from the above description of the fourth embodiment. [0079] 09-05-2019 23 It should be understood that the embodiments disclosed herein are illustrative and nonrestrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all the modifications within the meaning and scope equivalent to the claims. 09-05-2019 24

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