Acoustic control device, acoustic control method, and acoustic control program

Abstract

To provide an acoustic control device, an acoustic control method, and an acoustic control program that can realize sound image localization simulating a rotating sound source with a simple configuration.SOLUTION: An acoustic control device includes a frequency characteristic calculation unit, a filter calculation unit, and a filter storage unit. The frequency characteristic calculation unit calculates the frequency characteristic of a filter to be convoluted with an acoustic signal input to a speaker from the number of point sound sources in a simulated rotation sound source represented by a plurality of point sound sources arranged on a circumference, the complex volume velocity of sound radiated from each point sound source based on the Lobe mode of the simulated rotation sound source, and the transfer function between the sound receiving point and each point sound source in a space in which the simulated rotation sound source is arranged, on the basis of the radius of the circle, the horizontal distance between the center of the circle and the sound receiving point, and the vertical distance between the center of the circle and the sound receiving point. The filter calculation unit calculates the filter from the frequency characteristic of the filter. The filter storage unit stores the filter.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to an audio control device, an audio control method, and an audio control program. [Background technology]

[0002] There is known a sound image localization technique that uses various types of audio playback devices such as speakers to localize a sound image in the space around a user. For example, the arrival time difference between sounds emitted from a group of two or more omnidirectional speakers arranged on a horizontal plane and the sound reaches both ears of the user is used for sound image localization in the azimuth direction centered on the user. On the other hand, it is desired to be able to perform sound image localization in the elevation direction centered on the user with a simple configuration.

[0003] Here, for sounds coming from aircraft with rotors such as helicopters and drones, it is easy to tell from what height the sound has come. This is thought to be because, due to the characteristics of human hearing, it is easy to localize and discriminate the elevation angle direction of sounds from rotating sound sources. Sound image localization that simulates sounds from such rotating sound sources is thought to be effective for sound image localization in the elevation angle direction of the user. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-070578 A Summary of the Invention [Problem to be solved by the invention]

[0005] The embodiments provide an acoustic control device, an acoustic control method, and an acoustic control program that can realize sound image localization that simulates a rotating sound source with a simple configuration. [Means for solving the problem]

[0006] An acoustic control device according to one aspect includes a frequency characteristic calculation unit, a filter calculation unit, and a filter storage unit. The frequency characteristic calculation unit calculates the frequency characteristic of a filter to be convoluted with an acoustic signal input to a speaker from the complex volume velocity of sound radiated from each point sound source based on the number of point sound sources in a simulated rotational sound source represented by a plurality of point sound sources arranged on a circumference and the Lobe mode of the simulated rotational sound source, and the transfer function between the sound receiving point and each point sound source in a space in which the simulated rotational sound source is arranged, based on the radius of the circle, the horizontal distance between the center of the circle and the sound receiving point, and the vertical distance between the center of the circle and the sound receiving point. The filter calculation unit calculates the filter from the frequency characteristic of the filter. The filter storage unit stores the filter. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the configuration of an audio control system according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing an example of a configuration of the acoustic control device. [Diagram 3] FIG. 3 is a diagram illustrating a hardware configuration of an example of the acoustic control device. [Figure 4] FIG. 4 is a flowchart showing a calculation process of a rotation sound source correction filter performed by the acoustic control device. [Diagram 5] FIG. 5 is a diagram showing an example of an input screen. [Figure 6A] FIG. 6A is a schematic diagram of an example rotating sound source. [Figure 6B] FIG. 6B is a schematic diagram of the simulated rotation sound source according to the embodiment. [Figure 7] FIG. 7 is a diagram showing a space in which a simulated rotating sound source is placed. [Figure 8A] FIG. 8A is a diagram showing a change in frequency characteristics caused by changing Ra / RR. [Figure 8B] FIG. 8B is a diagram showing a change in frequency characteristics caused by changing Ra / RR. [Figure 9A] FIG. 9A is a diagram showing a change in frequency characteristics due to a change in rotation mode. [Figure 9B]FIG. 9B is a diagram showing a change in frequency characteristics due to a change in the rotation mode. [Figure 10A] FIG. 10A is a diagram showing a change in frequency characteristics caused by changing the low-frequency volume balance. [Figure 10B] FIG. 10B is a diagram showing a change in frequency characteristics due to a change in the low-frequency volume balance. [Figure 11] FIG. 11 is a diagram showing the concept of calculating the frequency characteristics of a filter when there is a floor. [Figure 12A] FIG. 12A is a Bode plot showing gain characteristics calculated from the frequency characteristics of a filter with an elevation angle of 45 deg. [Figure 12B] FIG. 12B is a Bode plot showing the phase characteristic calculated from the frequency characteristic of the filter with an elevation angle of 45 deg. [Figure 12C] FIG. 12C is a diagram showing the time characteristic of a rotation sound source compensation filter for an elevation angle of 45 deg that is created from the gain characteristic in FIG. 12A and the phase characteristic in FIG. 12B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will now be described with reference to the accompanying drawings. Fig. 1 is a diagram showing the configuration of an acoustic control system according to an embodiment. An acoustic control system 1 includes a speaker 2 and an acoustic control device 3. As shown in Figs.

[0009] The speaker 2 is, for example, disposed in front of the user U, and is a sound source that radiates sound to the user U based on an acoustic signal input from the acoustic control device 3. The speaker 2 is an omnidirectional speaker.

[0010] The acoustic control device 3 is a computer configured to convolve an input acoustic signal with a rotational sound source correction filter and input the acoustic signal convolved with the filter to the speaker 2. As will be described in detail later, the rotational sound source correction filter is a filter that is generated in consideration of the characteristics of the rotational sound generated when rotors mounted on aircraft such as helicopters and drones rotate. By playing back sound from the speaker 2 based on the acoustic signal convolved with the rotational sound source correction filter, a sound image S is localized in the elevation angle direction of the user U.

[0011] 2 is a block diagram showing an example of the configuration of the acoustic control device 3. The acoustic control device 3 has a parameter acquisition unit 31, a frequency characteristic calculation unit 32, a frequency characteristic presentation unit 33, a filter calculation unit 34, and a filter storage unit 35.

[0012] The parameter acquisition unit 31 acquires various parameters necessary for calculating the rotation sound source correction filter. The rotation sound source correction filter is calculated taking into account the characteristics of the simulated rotation sound source. The simulated rotation sound source in the embodiment is a simulated sound source that is arranged in a three-dimensional space and emits a sound with characteristics similar to the rotation sound of a rotor. The parameters include the number of point sound sources constituting the simulated rotation sound source that models the rotation sound source, the radius of the simulated rotation sound source, the horizontal distance from the sound receiving point to the center of the simulated rotation sound source, the vertical distance from the sound receiving point to the center of the simulated rotation sound source, the rotation mode of the simulated rotation sound source, the blade noise frequency of the simulated rotation sound source, and the low-frequency volume balance. The radius of the simulated rotation sound source is the distance from the center of the simulated rotation sound source to the point sound source. The horizontal distance is the distance on the XY plane between the sound receiving point and the center of the simulated rotation sound source when the XYZ axes are set in the three-dimensional space. The vertical distance is the distance in the Z-axis direction between the sound receiving point and the center of the simulated rotating sound source when the XYZ axes are set in a three-dimensional space. The rotation mode is the lobe mode in the circumferential direction of the rotor blade of the simulated rotating sound source. The blade noise frequency is the angular frequency when the rotor blade of the simulated rotating sound source is assumed to rotate. However, in the design of the filter in the embodiment, since the lobe mode is assumed at all frequencies, it is not necessary to specify the rotation speed of the blade as a parameter. The filter characteristics required in this case indicate the gain and phase when there is an arbitrary blade noise frequency in each lobe mode. The low-frequency volume balance is the gain correction amount for correcting the low-frequency high-pass characteristics specific to the rotating sound source, which will be described later. These parameters will be described in detail later.

[0013] The frequency characteristic calculation unit 32 calculates the frequency characteristic of the filter based on the parameters acquired by the parameter acquisition unit 31. For example, the frequency characteristic calculation unit 32 calculates the complex sound pressure of the sound that reaches the position of the user U from the simulated rotation sound source based on the volume velocity of the sound radiated from the simulated rotation sound source and the transfer characteristic of the sound for each elevation angle, and obtains the frequency characteristic of the filter from the calculated complex sound pressure. The calculation of the frequency characteristic will be described later.

[0014] The frequency characteristic presenting unit 33 presents the frequency characteristics of the filter for each elevation angle calculated by the frequency characteristic calculating unit 32 to the user by, for example, displaying the frequency characteristics. The user can select the frequency characteristic for a desired elevation angle from the presented frequency characteristics.

[0015] The filter calculation unit 34 calculates a rotation sound source compensation filter to be convoluted with the acoustic signal from the frequency characteristics of the elevation angle selected by the user. The filter calculation unit 34 calculates an FIR (finite impulse response) filter to be convoluted with the acoustic signal, for example, by performing an inverse Fourier transform on the product of the gain characteristic and phase characteristic calculated from the frequency characteristic of the filter.

[0016] The filter storage unit 35 stores the rotation sound source correction filter calculated by the filter calculation unit 34. By convolving the rotation sound source correction filter with the acoustic signal reproduced by the speaker 2, a sound image is localized as if a rotor were rotating in the elevation angle direction of the user U.

[0017] 3 is a diagram showing an example of a hardware configuration of the acoustic control device 3. The acoustic control device 3 may be a computer having a processor 301, a memory 302, a storage 303, an input device 304, a display device 305, and a communication device 306 as hardware. The processor 301, the memory 302, the storage 303, the input device 304, the display device 305, and the communication device 306 are connected to a bus 307. The acoustic control device 3 may be mounted on a control device for the speaker 2, a personal computer, a smartphone, a tablet terminal, or the like.

[0018] The processor 301 is a processor that controls the overall operation of the acoustic control device 3. The processor 301 executes an acoustic control program 3031 stored in the storage 303, for example, to cause the acoustic control device 3 to operate as a parameter acquisition unit 31, a frequency characteristic calculation unit 32, a frequency characteristic presentation unit 33, and a filter calculation unit 34. The processor 301 is, for example, a CPU. The processor 301 may be an MPU, a GPU, an ASIC, an FPGA, or the like. The processor 301 may be a single CPU, or the like, or may be multiple CPUs, or the like.

[0019] The memory 302 includes a ROM and a RAM. The ROM is a non-volatile memory. The ROM stores a startup program for the acoustic control device 3 and the like. The RAM is a volatile memory. The RAM is used as a working memory for processing in the processor 301, for example.

[0020] The storage 303 is, for example, a storage such as a flash memory, a hard disk drive, or a solid state drive. The storage 303 stores various programs executed by the processor 301, such as an acoustic control program 3031. The storage 303 can also operate as a filter storage unit 35 that stores a rotation sound source compensation filter.

[0021] The input device 304 is an input device such as a touch panel, a keyboard, a mouse, etc. When the input device 304 is operated, a signal corresponding to the operation content is input to the processor 301 via the bus 307. The processor 301 performs various processes according to this signal. The input device 304 can be used to input the parameters described above.

[0022] The display device 305 is a display device such as a liquid crystal display, an organic EL display, etc. The display device 305 displays various images.

[0023] The communication device 306 is a communication device for allowing the audio control device 3 to communicate with an external device. The communication device 306 may be a communication device for wired communication, or may be a communication device for wireless communication.

[0024] The acoustic control method according to the embodiment will be described below. Fig. 4 is a flowchart showing the calculation process of the rotation sound source correction filter by the acoustic control device 3. In the following description, the number of point sound sources of the simulated rotation sound source is Lp, the radius of the simulated rotation sound source is Ra, the horizontal distance from the sound receiving point to the center of the rotation sound source is RR, the vertical distance from the sound receiving point to the center of the simulated rotation sound source is high, the rotation mode of the rotation sound source is M, the blade noise frequency of the simulated rotation sound source is ω (virtually set at all frequencies), and the low-frequency volume balance is Low. Furthermore, the vertical distance of the rotation sound source is high, and the number of point sound sources is Low. p The description will continue assuming that the blade noise frequency ω is predetermined.

[0025] In step S1, the parameter acquisition unit 31 acquires parameters based on, for example, an input by a user U. The parameters may be input by the user U on, for example, an input screen displayed on the display device 305. In addition, the initial values ​​of each parameter may be determined in advance.

[0026] Fig. 5 is a diagram showing an example of an input screen. The input screen shown in Fig. 5 includes, for example, a frequency characteristic display area 321, an Ra / RR input field 322, a rotation mode input field 323, a low-frequency volume balance input field 324, spatial information input fields 325a, 325b, and 325c, and a decision button 326. Here, input fields and buttons other than those shown in Fig. 5 may be provided. For example, the input screen in Fig. 5 may include an input field for high and an input field for L. p An input field for the above may be provided.

[0027] The frequency characteristic display area 321 is an area where frequency characteristics calculated according to input of parameters are displayed. As will be described later, frequency characteristics are calculated for each elevation angle of the rotating sound source. In the frequency characteristic display area 321, frequency characteristics calculated for each elevation angle are displayed in an overlapping manner. Alternatively, in the frequency characteristic display area 321, frequency characteristics calculated for each elevation angle may be displayed in a switching manner.

[0028] The Ra / RR input field 322 is an input field for the user to input the value of Ra / RR. The value of Ra / RR may be input by, for example, directly inputting a numerical value. Alternatively, the value of Ra / RR may be input by using a user interface (UI) such as a slider, or may be selected from several options displayed in a drop-down list. In addition, for example, if either the value of Ra or the value of RR is a fixed value, the value of Ra / RR may be input by inputting the non-fixed value. Although FIG. 5 shows an example in which the value is input in the form of a ratio of Ra / RR, it goes without saying that separate input fields may be provided for Ra and RR.

[0029] The rotation mode input field 323 is an input field for the user to input the value of the rotation mode M. The value of M can be input by, for example, directly inputting a numerical value. Alternatively, M can be input by selecting from among several options displayed in a drop-down list.

[0030] The bass volume balance input field 324 is an input field for the user to input a value for the bass volume balance Low. The input of Low can be performed, for example, by directly inputting a numerical value. Alternatively, the bass volume balance can be input by input using a user interface (UI) such as a slider, or can be selected from several options displayed in a drop-down list.

[0031] The space information input fields 325a, 325b, and 325c are input fields for inputting characteristic information of the space in which the sound control system 1 is used. The characteristic information of the space includes information on whether or not the space is a free space. The information on whether or not the space is a free space includes information on the presence or absence of a floor, ceiling, and walls in the space. The space information input field 325a is, for example, a radio button for selecting the presence or absence of a floor in the space. The space information input field 325b is, for example, a radio button for selecting the presence or absence of a ceiling in the space. The space information input field 325c is, for example, a radio button for selecting the presence or absence of a wall in the space. When the presence of a floor, ceiling, or wall is selected in the space information input fields 325a, 325b, and 325c, the frequency characteristics are calculated assuming that the floor, ceiling, or wall exists in the space. The positions of the floor, ceiling, and walls may be fixed. Alternatively, when the presence of a floor, ceiling, or wall is selected in the space information input fields 325a, 325b, and 325c, a display field for inputting the respective positions may be displayed, and the positions of the floor, ceiling, and wall may be set according to the input in this display field. On the other hand, when none of the floor, ceiling, and wall is selected in the space information input fields 325a, 325b, and 325c, the space is considered to be a free space, and the frequency characteristics are calculated.

[0032] The decision button 326 is a button for the user to instruct the acoustic control device 3 to execute filter calculations.

[0033] Returning now to the description of Fig. 4, in step S2, the frequency characteristic calculation unit 32 calculates the frequency characteristic based on the parameters acquired in step S1. The frequency characteristic calculation unit 32 may calculate the frequency characteristic using initial values ​​for parameters not input by the user. The calculation of the frequency characteristic will be described below.

[0034] FIG. 6A is a schematic diagram of an example of a rotary sound source. For example, FIG. 6A shows a schematic diagram of a rotary sound source having three rotor blades. The rotor blade radius of the rotary sound source in FIG. 6A is a. The blade noise frequency ω and lobe mode M when the rotor blade m of such a rotary sound source rotates in the direction r at a rotational speed Ω are respectively expressed by the following formula (1). In formula (1), B is the number of rotor blades. Also, x is the noise target order. Here, the lobe mode M in formula (1) is the lobe mode in the case where the rotary sound source does not have a stator blade. In the case where the rotary sound source has a stator blade, the lobe mode M further includes a stator blade term according to the number of stator blades.

number

[0035] 6B is a schematic diagram of a simulated rotating sound source according to the embodiment. The rotating sound source shown in FIG. 6A is a set of L 100 sq. m that are arranged at equal intervals on a circumference of a radius a from the center 0, with the rotation axis of the rotor blade as the center 0. p It is known that the sound source can be modeled by L p If there are many enough, then at position i (i=1,…,L p ) point sound source p i Complex volume velocity q pi can be expressed by the following equation (2). p is a constant that represents the complex amplitude. As shown in equation (2), the complex volume velocity of each point sound source has an amplitude component e jωt and the phase delay component e based on the arrangement angle of the point sound source -jMφpi It is expressed as the product of and.

number

[0036] Assume that the simulated rotational noise source SR modeled as in equation (2) is located at a horizontal distance RR and height high from the sound receiving point P as shown in Fig. 7. The radius Ra of the simulated rotational noise source SR is equal to the rotor blade radius a. The distance Rb from the sound receiving point P to the center of the simulated rotational noise source SR, i.e., the center O of the circle shown in Fig. 6B, can be expressed by the following equation (3).

number

[0037] Each point sound source p of the simulated rotating sound source SR i The complex sound pressure at the receiving point P when sound is radiated from the receiving point P and each point sound source p i The acoustic transfer function between i In other words, the complex sound pressure at the receiving point can be expressed by the following equation (4). i Complex volume velocity and acoustic transfer function F i The acoustic transfer function F i For example, a sound source is actually placed at a position i that is a distance Rb from the sound receiving point P, and a sound based on a random signal or a sound based on a TSP (Time stretched Pulse) signal is emitted from the sound source. This sound is collected by a microphone placed at the position of the sound receiving point P, and the sound can be calculated from the microphone acquired signal. In the proposed setting, each point sound source p i The position of can be changed by Ra, RR and high. Therefore, the acoustic transfer function F i may be calculated for each Ra, each RR, and each high. In addition, the acoustic transfer function F i may also be calculated by simulation using acoustic analysis. In this case, the acoustic transfer function F i may be calculated for each Ra, each RR and each high.

number

[0038] The frequency characteristic calculation unit 32 calculates the complex volume velocity q piand the acoustic transfer function F for each elevation angle i Then, the frequency characteristic calculation unit 32 calculates the frequency characteristic of the filter for each elevation angle based on the formula (4). At this time, the frequency characteristic calculation unit 32 performs a correction to amplify the gain below the first peak of the frequency characteristic of the filter for each elevation angle calculated based on the formula (4) by -LowdB. Specifically, the frequency characteristic calculation unit 32 selects a frequency having the first peak, and amplifies the gain below the selected frequency to (first peak-Low) dB. Then, the frequency characteristic calculation unit 32 calculates the gain characteristic and the phase characteristic from the calculated frequency characteristic.

[0039] Furthermore, as the elevation angle increases, i.e., as high increases, the distance Rb from the sound receiving point P to the center of the simulated rotational sound source SR also increases. As the distance Rb from the sound receiving point P to the center of the simulated rotational sound source SR increases, the sound pressure at the sound receiving point attenuates. In order to suppress the distance attenuation of the sound pressure at the sound receiving point, the frequency characteristic calculation unit 32 may perform a correction by multiplying the sum of the volume velocities of the respective point sound sources by Rb according to the following formula (5).

number

[0040] Returning now to the explanation of FIG. 4, in step S3, the frequency characteristic presentation unit 33 displays the frequency characteristic calculated by the frequency characteristic calculation unit 32 in the frequency characteristic display area 321 of the input screen. FIG. 5 shows an example in which the gain characteristic is displayed. The gain characteristic in FIG. 5 is a characteristic in which the rotation sound source radius Ra is 0.05 m, the horizontal distance RR is 1.0 m, the rotation mode M is 2, and the low-frequency volume balance Low is 0 dB. The height high is changed in 10 steps from 0 to RR / 4. In this case, the elevation angle (=arctan(high / RR)) of the rotation sound source with respect to the sound receiving point is 0 deg, 14 deg, 26.6 deg, 36.9 deg, 45 deg, 51.3 deg, 56.3 deg, 60.3 deg, 63.4 deg, and 66 deg. FIG. 5 shows an example in which only the gain characteristic is displayed in the frequency characteristic display area 321. As shown in Fig. 5, the frequency characteristics calculated based on the volume velocity of the rotating sound source have notch characteristics where the gain drops sharply in a specific band. Generally, the frequency band that can create a sense of up and down positioning is a notch frequency of 6 kHz-12 kHz. As shown in Fig. 5, the characteristics of the notch frequency in the range of 6 kHz-12 kHz differ depending on the elevation angle, i.e., the high value. Here, Fig. 5 is an example in which only the gain characteristics are displayed, but the phase characteristics may also be displayed in addition to the gain characteristics.

[0041] In step S4, the filter calculation unit 34 judges whether or not a group of elevation angles has been selected. The group of elevation angles here is a group of elevation angles that represents the frequency characteristics displayed in the frequency characteristic display area 321. While viewing the frequency characteristics shown in FIG. 5, the user confirms that the frequency characteristics that the user desires have been obtained and selects the decision button 326. The filter calculation unit 34 judges that a group of elevation angles has been selected in response to the selection of the decision button 326. If it is not judged in step S4 that a group of elevation angles has been selected, the process proceeds to step S5. If it is judged in step S4 that a group of elevation angles has been selected, the process proceeds to step S8. It may be judged whether or not a specific elevation angle has been selected, instead of a group of elevation angles.

[0042] In step S5, the parameter acquisition unit 31 determines whether or not the user has changed the parameters. When the content of any of the input fields shown in Fig. 5 is changed, it is determined that the parameters have been changed. If it is determined in step S5 that the user has not changed the parameters, the process returns to step S4. If it is determined in step S5 that the user has changed the parameters, the process proceeds to step S6.

[0043] In step S6, the frequency characteristic calculation unit 32 recalculates the frequency characteristic of the filter based on the changed parameters, and in step S7, the frequency characteristic presentation unit 33 displays the recalculated frequency characteristic.

[0044] Fig. 8A and Fig. 8B are diagrams showing changes in frequency characteristics due to changes in Ra / RR. Fig. 8A shows the frequency characteristics when the rotation sound source radius Ra is 0.1 m and the horizontal distance RR is 1.0 m, i.e., Ra / RR=0.1. On the other hand, Fig. 8B shows the frequency characteristics when the rotation sound source radius Ra is 0.05 m and the horizontal distance RR is 1.0 m, i.e., Ra / RR=0.05. Changing Ra or RR affects the frequency characteristics of the sound receiving point P and each point sound source p i The positional relationship between the sound receiving point P and each point sound source p i By changing the positional relationship with i This changes the notch frequency in the frequency characteristics. For example, as shown in FIG. 8B, when Ra / RR becomes smaller, the notch frequency shifts to the higher frequency side.

[0045] 9A and 9B are diagrams showing changes in frequency characteristics due to changes in rotation mode. FIG. 9A shows the frequency characteristics when the rotation mode is 2. Meanwhile, FIG. 9B shows the frequency characteristics when the rotation mode is 4. A change in rotation mode corresponds to a change in the number of rotor blades (and / or stator blades) of the rotation sound source. In other words, a change in rotation mode changes the phase distribution of the complex volume velocity. This changes the notch frequency in the frequency characteristics. For example, as the rotation mode becomes larger, the notch frequency shifts to the high frequency side as shown in FIG. 9B.

[0046] 10A and 10B are diagrams showing changes in frequency characteristics due to changes in the low-frequency sound volume balance. FIG. 10A shows frequency characteristics when the low-frequency sound volume balance is not corrected. Meanwhile, FIG. 10B shows frequency characteristics when the rotation mode is 4 and the low-frequency sound volume balance Low is -10 dB. When the low-frequency sound volume balance is not corrected, as shown in FIG. 10A, the frequency characteristics of the filter have high-pass filter characteristics in which the gain in the low frequency range is greatly reduced. Therefore, as shown in FIG. 10B, the notch characteristics specific to the rotation sound source can be emphasized by amplifying the gain below the first peak to a value obtained by lowering the gain of the first peak by -Low. The degree of emphasis of the notch characteristics changes depending on the change in the low-frequency sound volume balance.

[0047] FIG. 11 is a diagram showing the concept of calculating the frequency characteristics of a filter when there is a floor. When sound is emitted from a sound source SR in a space with a floor, the sound received at the sound receiving point includes the sound reflected by the floor in addition to the sound received directly from the sound source SR. Therefore, the calculation of the frequency characteristics of the filter must take into account the reflected sound from the floor. The reflected sound from the floor can be considered as the sound from a simulated rotational sound source SR2 that is located in a position symmetrical to the simulated rotational sound source SR with respect to the floor. For example, when the sound receiving point P is at a height of H from the floor, the simulated rotational sound source SR2 can be considered to be at a horizontal distance of RR and at a height of -H-high from the floor. FIG. 11 shows an example of a floor, but in the same way, when there is a ceiling or a wall, the frequency characteristics of the filter are calculated assuming that there is another rotational sound source in a position symmetrical to the simulated rotational sound source SR with respect to the ceiling and wall.

[0048] Returning now to the description of Fig. 4, in step S8, the filter calculation unit 34 calculates a filter using the frequency characteristics of the filter for the elevation angle selected by the user. In step S9, the filter calculation unit 34 stores the created filter in the filter storage unit 35. Thereafter, the process of Fig. 4 ends.

[0049] An example of filter calculation will be described below. In the following description, it is assumed that an elevation angle of 45 deg is selected by the user. Fig. 12A is a Bode plot showing gain characteristics calculated from the frequency characteristics of a filter with an elevation angle of 45 deg. Fig. 12B is a Bode plot showing phase characteristics calculated from the frequency characteristics of a filter with an elevation angle of 45 deg.

[0050] In calculating the filter, the filter calculation unit 34 first calculates the product of the gain characteristic and the phase characteristic. Then, the filter calculation unit 34 performs inverse FFT on the product of the gain characteristic and the phase characteristic to calculate the time response of a filter having frequency characteristics represented by the Bode diagrams of Figs. 12A and 12B, that is, an FIR filter, as a rotation sound source compensation filter. Fig. 12C is a diagram showing the time characteristics of a rotation sound source compensation filter for an elevation angle of 45 deg created from the gain characteristic of Fig. 12A and the phase characteristic of Fig. 12B. By reproducing the sound signal convoluted with the rotation sound source compensation filter having the characteristics shown in Fig. 12C from the speaker 2, the user U can perceive a sound equivalent to a rotation sound source located at an elevation angle of 45 deg. In this way, sound image localization in the elevation angle direction can be realized.

[0051] As described above, according to the embodiment, a filter reflecting the characteristics of a rotational sound source is convoluted into an acoustic signal input to an omnidirectional speaker, thereby realizing a sound image localization simulating a rotational sound source using only an omnidirectional speaker. It is easy to know from what height a sound from a rotational sound source comes, and it is considered to be effective for sound image localization in the elevation angle direction of a user. In addition, a sound from a rotational sound source can be simulated by an omnidirectional speaker. That is, in the embodiment, there is no need to place a speaker facing the elevation angle direction in order to realize sound image localization in the elevation angle direction, and sound image localization in the elevation angle direction is realized with a simple configuration.

[0052] In addition, the ratio Ra / RR of the radius Ra of the rotating sound source to the horizontal distance RR from the sound receiving point to the center of the rotating sound source, the vertical distance high from the sound receiving point to the center of the rotating sound source, and the rotation mode M of the rotating sound source can be adjusted by the user as parameters for simulating the rotating sound source. This allows sound image localization to be performed simulating rotating sound sources of various positions and / or structures.

[0053] In addition, in the case of a normal rotating sound source, the sound pressure at the sound receiving point rapidly attenuates as high increases. In contrast, the volume velocity sum is multiplied by Rb to suppress the attenuation of sound pressure due to an increase in high, i.e., an increase in Rb, so that the user hears a loud sound even if high increases.

[0054] Here, in the embodiment, high is determined in advance. As described above, high may also be set by the user. In this case, the frequency characteristic of the filter may be calculated only for the high set by the user, that is, the elevation angle.

[0055] In addition, in the embodiment, the user can select a desired parameter set while viewing the frequency characteristics of the filter displayed on the display device. In contrast, the process may be modified so that the user can select a desired parameter set while actually listening to the sound localized in the sound image. In this case, the calculation of the filter for each elevation angle is performed based on the parameters acquired in step S1, and the sound is actually reproduced by the speaker 2 based on the calculated filter. The user can select a desired parameter set while listening to this sound.

[0056] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0057] 1 Acoustic control system, 2 Speaker, 3 Acoustic control device, 31 Parameter acquisition unit, 32 Frequency characteristic calculation unit, 33 Frequency characteristic presentation unit, 34 Filter calculation unit, 35 Filter storage unit, 301 Processor, 302 Memory, 303 Storage, 304 Input device, 305 Display device, 306 Communication device, 307 Bus.

Claims

1. A frequency characteristic calculation unit that calculates the frequency characteristic of a filter to be convoluted with an acoustic signal input to a speaker from the complex volume velocity of sound radiated from each point sound source based on the number of point sound sources in a simulated rotational sound source represented by a plurality of point sound sources arranged on a circumference and the Lobe mode of the simulated rotational sound source, and the acoustic transfer function between the sound receiving point and each of the point sound sources in a space in which the sound receiving point and the simulated rotational sound source are arranged, based on the radius of the circle, the horizontal distance between the center of the circle and the sound receiving point, and the vertical distance between the center of the circle and the sound receiving point; a filter calculation unit that calculates the filter based on a frequency characteristic of the filter; a filter storage unit that stores the filter; An audio control device comprising:

2. The frequency characteristic calculation unit corrects the frequency characteristic according to the distance between the center of the circle and the sound receiving point. The acoustic control device according to claim 1 .

3. the frequency characteristic calculation unit performs a correction to amplify a gain of a frequency band equal to or lower than a first peak in the frequency characteristic to a value obtained by decreasing the gain value of the first peak by a specified value; The acoustic control device according to claim 1 .

4. A parameter acquisition unit is further provided for acquiring a lobe mode of the simulated rotating sound source, a radius of the circle, and a horizontal distance between the center of the circle and a sound receiving point based on a user's input, The frequency characteristic calculation unit calculates the frequency characteristic based on the lobe mode of the simulated rotating sound source input by the user, the radius of the circle, and the horizontal distance between the center of the circle and the sound receiving point. The acoustic control device according to claim 1 .

5. the frequency characteristic calculation unit calculates the frequency characteristic based on a plurality of vertical distances between the center of the circle and the sound receiving point, The filter calculation unit calculates the filter from the frequency characteristic corresponding to the vertical distance selected by a user. The acoustic control device according to claim 4.

6. The parameter acquisition unit further acquires characteristic information of the space, The frequency characteristic calculation unit calculates the frequency characteristic based on the spatial characteristic information. The acoustic control device according to claim 4.

7. Calculating the frequency characteristics of a filter to be convoluted with respect to an acoustic signal input to a speaker from the number of point sound sources in a simulated rotating sound source represented by a plurality of point sound sources arranged on a circumference, the complex volume velocity of sound radiated from each point sound source based on the Lobe mode of the simulated rotating sound source, and the acoustic transfer function between the sound receiving point and each of the point sound sources in a space in which the simulated rotating sound source is arranged, based on the radius of the circle, the horizontal distance between the center of the circle and the sound receiving point, and the vertical distance between the center of the circle and the sound receiving point; calculating the filter from a frequency characteristic of the filter; An acoustic control method comprising:

8. Calculating the frequency characteristics of a filter to be convoluted with respect to an acoustic signal input to a speaker from the number of point sound sources in a simulated rotating sound source represented by a plurality of point sound sources arranged on a circumference, the complex volume velocity of sound radiated from each point sound source based on the Lobe mode of the simulated rotating sound source, and the acoustic transfer function between the sound receiving point and each of the point sound sources in a space in which the simulated rotating sound source is arranged, based on the radius of the circle, the horizontal distance between the center of the circle and the sound receiving point, and the vertical distance between the center of the circle and the sound receiving point; calculating the filter from a frequency characteristic of the filter; An acoustic control program for causing a computer to execute the above.

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