JP2021183910A - Estimation method of acoustic power level - Google Patents

Abstract

To provide an estimation method of an acoustic power level that can easily calculate a correction value to be used when estimating the acoustic power level of an estimation target sound source.SOLUTION: An estimation method of an acoustic power level comprises: a positioning step (step S102) for determining setting positions of a plurality of microphones; a reproduction step (step S107) for reproducing a measurement environment of an estimation target sound source in a semi-anechoic space by using a reference sound source whose acoustic power level is known; a reproduction acquisition step (step S108) for acquiring a sound pressure level of the reference sound source that the plurality of microphones measure in the reproduced measurement environment; and a first calculation step (step S110) for calculating a correction value to be used when estimating the acoustic power level of the estimation target sound source based on the acquired sound pressure level.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for estimating sound power level.

As a method of estimating the sound power level of a sound source in a closed space, for example, as in Patent Document 1, a method using a reference sound source whose sound power level is known is known. In the method described in Patent Document 1, a plurality of sensors are installed in a closed space where the sound source to be estimated is installed, and the sound pressure level is corrected to the first average sound pressure level which is the average value of the sound pressure levels measured by those sensors. The sound power level is calculated by adding a value.

The correction value is calculated based on the sound pressure level measured by each sensor when the reference sound source is sequentially installed at a plurality of measurement points set in the closed space and the reference sound source is operated at each measurement point. .. Specifically, the second average sound pressure level, which is the average value of the sound pressure levels measured by each sensor for the reference sound source, is calculated for each measurement point. Then, an intermediate value between the maximum value and the minimum value of the second average sound pressure level is calculated, and the difference between the intermediate value and the sound power level of the reference sound source is set as the correction value.

Japanese Unexamined Patent Publication No. 2002-365127

However, in the method described in Patent Document 1, when the closed space is narrow, it is necessary to repeatedly install the reference sound source in the narrow closed space and measure with the sensor, so that the man-hours for calculating the correction value are enormous. It becomes a thing. If it is difficult to install a reference sound source at each measurement point, it is necessary to take out the estimation target sound source from the closed space. These problems are not limited to a narrow closed space, but are common when the sound source to be estimated is installed in a closed space other than an anechoic space or a semi-anechoic space.

An object of the present invention is to provide a method for estimating a sound power level that can easily calculate a correction value when estimating the sound power level of a sound source to be estimated.

The sound power level estimation method for solving the above problems is to measure the sound pressure level of the estimation target sound source with a plurality of electroacoustic converters installed around the estimation target sound source, and based on the measured sound pressure level. The sound power level of the estimation target sound source is estimated. This estimation method reproduces the positioning step of determining the installation position of the plurality of electroacoustic converters and the measurement environment of the estimation target sound source in a semi-insensitive space using a reference sound source having a known sound power level as a sound source. The sound of the estimation target sound source based on the step, the acquisition step of acquiring the sound pressure level of the reference sound source measured by the plurality of electroacoustic converters in the reproduced measurement environment, and the acquired sound pressure level. It includes a calculation step of calculating a correction value when estimating a power level.

According to the above configuration, a correction value for estimating the acoustic power level of the estimation target sound source is calculated based on the sound pressure level of the reference sound source measured by the electroacoustic converter in the measured environment of the reproduced estimation target sound source. NS. As a result, the number of times the reference sound source is installed can be reduced, and the man-hours for calculating the correction value can be reduced. Moreover, it is not necessary to extract the sound source to be estimated from the closed space. As a result, the correction value when estimating the sound power level of the sound source to be estimated can be easily calculated.

In the sound power level estimation method having the above configuration, the sound power level of the estimation target sound source is estimated by the average value of the partial sound power levels of each of the plurality of estimation surface elements divided based on the shape of the estimation target sound source. The value. At least one of the plurality of electroacoustic transducers is associated with each of the plurality of estimation surface elements. The partial acoustic power level is a value obtained by correcting the average sound pressure level, which is the average value of the sound pressure levels measured by the associated electroacoustic converter. In the acquisition step, the sound pressure level of the reference sound source measured by the associated electroacoustic transducer is acquired for each estimated surface element. In the calculation step, the difference between the average value of the sound pressure level acquired in the acquisition step and the sound power level of the reference sound source is calculated as a correction value for correcting the average sound pressure level for each estimation surface element. ..

According to the above configuration, since the area information necessary for estimating the partial acoustic power level can be acquired, the accuracy of the calculated partial acoustic power level can be improved.
In the method for estimating the acoustic power level having the above configuration, the measured sound pressure level is a value obtained by correcting the measured value of the electroacoustic converter. Further, this estimation method further includes a reference sound source acquisition step of acquiring the sound pressure level of the reference sound source measured by each of the plurality of electroacoustic converters in the measurement environment of the estimation target sound source. In the calculation step, for each of the plurality of electroacoustic converters, the difference between the sound pressure level acquired in the reference sound source acquisition step and the sound pressure level acquired in the reproduction acquisition step is a correction value for correcting the measured value. Calculate as.

According to the above configuration, the influence of the reflected wave, diffraction, and transmission of the estimation target sound source in the closed space can be eliminated by the correction value. As a result, the accuracy of the partial acoustic power level and, by extension, the accuracy of the acoustic power level of the estimation target sound source can be improved.

The method for estimating the acoustic power level having the above configuration includes a division step of dividing the frequency of the sound pressure level measured by the plurality of electroacoustic converters into a plurality of frequency bands, and the acoustic power for each of the plurality of frequency bands. It may further include a selection step of selecting a correction method when calculating the level.

The inventors have found that the appropriate correction method differs depending on the frequency band. According to the above configuration, the error between the estimated sound power level and the actual sound power level can be reduced.

The figure which shows the installation state of the estimation target sound source schematically. The figure which shows the schematic structure of the estimation system which estimates the sound power level. The flowchart which shows the estimation method of the acoustic power level in 1st Embodiment. The figure which shows typically the reference sound source acquisition process in 1st Embodiment. In the first embodiment, (a) a diagram schematically showing a state in which a reference sound source is installed in a semi-anechoic space, and (b) a diagram schematically showing a state in which a measurement environment using a microphone is reproduced. The graph which shows an example of the comparison result of the acoustic power level in 1st Embodiment. The graph which shows an example of the comparison result of the acoustic power level in 2nd Embodiment. The graph which shows an example of the comparison result of the acoustic power level in 3rd Embodiment. The flowchart which shows a part of the sound power level estimation method in the modification. The graph which shows an example of the comparison result of the acoustic power level in the modification example.

(First Embodiment)
A first embodiment of the method for estimating the sound power level will be described with reference to FIGS. 1 to 6.

As shown in FIG. 1, in the sound power level estimation method, the sound power level Lw ([dB]) of the estimation target sound source 10 is estimated. The estimation target sound source 10 is installed in the closed space 12, and the sound power level Lw is unknown.

The estimation target sound source 10 is divided into a plurality of estimation surface elements Zi (i is a natural number) based on its shape. Specifically, the estimation target sound source 10 is simplified into a polyhedron based on its shape, and each surface constituting the polyhedron is set in the estimation surface element Zi. For example, if the simplified polyhedron of the estimation target sound source 10 is a rectangular parallelepiped, each surface constituting the rectangular parallelepiped is set in the estimation surface element Zi. The sound power level Lw of the estimation target sound source 10 is obtained by averaging the partial sound power level Lwi ([dB]) for each of the estimated surface elements Zi. "I" is a symbol used when specifying the estimation surface element Zi. For example, the partial sound power level Lw1 indicates the partial sound power level of the estimated surface element Z1.

A plurality of microphones M are installed in the closed space 12. The microphone M is an electroacoustic transducer. At least one of the plurality of microphones M is associated with each of the plurality of estimation surface elements Zi. The j-th (j is a natural number) microphone M associated with the estimation surface element Zi is referred to as microphone Mij. Further, the measured value of the microphone Mij is referred to as a measured value Lmij. The partial sound power level Lwi is calculated based on the measured value Lmij of the associated microphone Mij. The total number of estimated surface elements is N, and the total number of microphones for each estimated surface element is Xi. Note that FIG. 1 shows only the four microphones M11, M12, M13, and M14 associated with the estimation surface element Z1.

An example of the closed space 12 is an engine room of an automobile, and an example of the estimation target sound source 10 is an engine installed in the engine room. Although the closed space 12 and the estimation target sound source 10 are shown in a simplified manner in FIG. 1, obstacles such as a bonnet and auxiliary equipment are installed in the vicinity of the engine in the actual engine room. In such a case, the microphone Mij is installed in a narrow space around the engine in consideration of the positional relationship between the engine and obstacles.

The estimation system 20 for estimating the sound power level Lw of the estimation target sound source 10 will be described with reference to FIG. 2.
The estimation system 20 includes a microphone Mij, an input unit 21, and an estimation device 25.

Each microphone Mij inputs each measured value Lmij to the estimation device 25.
The input unit 21 is, for example, a keyboard or a mouse, and is configured to be able to input various information to the estimation device 25 by being operated by an operator. Further, the input unit 21 is configured to be able to instruct the processing to be executed by the estimation device 25. The input unit 21 switches the handling of the correspondence information indicating the correspondence relationship between the microphone Mij and the estimation surface element Zi, the reference sound source information indicating the acoustic power level Lw of the reference sound source 34 described later, and the measured value Lmij in the estimation device 25. Mode information, etc. can be input. The mode information is one of the reproduction environment mode, the reference sound source mode, and the measurement mode.

The estimation device 25 executes various processes based on various information from the microphone Mij and the input unit 21, instructions from the input unit 21, a program stored in the memory, and various data. The estimation device 25 may be configured as a circuit including one or more dedicated hardware circuits such as an ASIC, one or more processors operating according to a computer program (software), or a combination thereof. The processor includes a CPU and a memory such as a RAM and a ROM, and the memory stores a program code or a command configured to cause the CPU to execute a process. Memory or computer-readable media includes any available medium accessible by a general purpose or dedicated computer.

The estimation device 25 has an acquisition unit 26, a first correction value calculation unit 27, a second correction value calculation unit 28, an estimation unit 29, and a storage unit 30 as various functional units.
The acquisition unit 26 acquires various information and stores the data indicating the acquired various information in a predetermined area of the storage unit 30.

The first correction value calculation unit 27 calculates a correction value (first correction value) Ai ([dB]), which is a correction value when calculating the partial sound power level Lwi of the estimation surface element Zi, for each estimation surface element Zi. do.

The second correction value calculation unit 28 calculates a correction value (second correction value) Bij ([dB]) for correcting the measured value Lmij of the microphone Mij for each microphone Mij.
The estimation unit 29 calculates the partial sound power level Lwi of each estimated surface element Zi, and estimates the sound power level Lw of the estimation target sound source 10 based on the calculated partial sound power level Lwi.

An example of a method for estimating the sound power level Lw using the above-mentioned estimation system 20 will be described with reference to FIGS. 2 to 5.
As shown in FIG. 3, first, a surface element setting step is performed (step S101). In the surface element setting step, a plurality of estimation surface elements Zi are set for the estimation target sound source 10 based on the shape of the estimation target sound source 10.

Next, a positioning step is performed (step S102). In the positioning step, the installation position of each microphone M in the closed space 12 is determined and installed in the closed space 12. The installation position of each microphone M is determined in consideration of the positional relationship of the estimation target sound source 10 with each estimation surface element Zi, the positional relationship with obstacles around the estimation target sound source 10, and the like. The installation position of each microphone M can be indicated by, for example, a three-dimensional coordinate system having a reference point in the closed space 12 as an origin. The reference point is, for example, a specific position (for example, a center position) in the estimation target sound source 10 or a position of a specific microphone M.

Further, in the positioning step, the microphone M and the estimation surface element Zi are also associated with each other. In the association, each microphone M is associated with any of the plurality of estimated surface elements Zi, and at least one microphone M is associated with each estimated surface element Zi. The j-th microphone M associated with the estimation surface element Zi in this way is expressed as microphone Mij. The association between the microphone Mij and the estimation surface element Zi is input to the estimation device 25 as the association information through the input unit 21. The correspondence information is acquired by the acquisition unit 26 and stored as the association data 31 in a predetermined area of the storage unit 30.

Next, the measurement step (step S103) is performed. In the measurement step, the sound pressure level of the estimation target sound source 10 is measured by each microphone Mij. Specifically, mode information indicating the measurement mode is input to the estimation device 25 through the input unit 21. After that, the estimation target sound source 10 is operated, and the estimation device 25 is instructed to start measurement through the input unit 21. In the measurement mode, the acquisition unit 26 acquires the measured value Lmij of each microphone Mij, and stores the estimation measurement data 43 based on the acquired measured value Lmij of each microphone Mij in a predetermined area of the storage unit 30. Hereinafter, the measured value Lmij constituting the estimation measurement data 43 is referred to as an estimation measurement value Lrig.

The estimated measured value Lrig may be configured to be measured at the same time for all the estimated surface elements Zi by performing the measuring step after installing all the microphones Mij in the closed space 12. Further, the estimated measured value Lrig may be configured to be measured for each estimated surface element Zi by repeating the surface element setting step, the positioning step, and the measuring step.

When the estimation measurement value Lrig is measured for all the estimation surface elements Zi (step S104: YES), the reference sound source acquisition step (step S105) is performed.
At the start of the reference sound source acquisition process, the microphone Mij associated with each estimation surface element Zi is in a state of being installed in the closed space 12. In the reference sound source acquisition step, the sound pressure level of the reference sound source 34 measured by the associated microphone Mij is acquired for each estimation surface element Zi. The reference sound source 34 is, for example, a point sound source having a known sound power level LwK. The reference sound source information indicating the known sound power level LwK of the reference sound source 34 is input to the estimation device 25 through the input unit 21. The reference sound source information input to the estimation device 25 is acquired by the acquisition unit 26 and stored in a predetermined area of the storage unit 30 as the reference sound source data 35.

With reference to FIG. 4, the reference sound source acquisition process will be specifically described using the estimation surface element Z1 as an example.
As shown in FIG. 4, when the sound pressure level of the reference sound source 34 is acquired by the microphone M1j associated with the estimation surface element Z1, the reference sound source 34 is installed at the position of the center of gravity of the estimation surface element Z1 or the like.

Next, the mode information indicating the reference sound source mode and the information indicating the estimation surface element Z1 are input to the estimation device 25 through the input unit 21. After that, the reference sound source 34 is operated, and the estimation device 25 is instructed to start measurement through the input unit 21. In the reference sound source mode at this time, the acquisition unit 26 acquires the measured value Lm1j of the microphone M1j associated with the estimation surface element Z1, and stores the data indicating the acquired measured value Lm1j of the microphone M1j in the predetermined storage unit 30. Store in the area.

In the reference sound source acquisition step, the sound pressure level of the reference sound source 34 described above is measured for each of the estimation surface elements Z1, Z2, ..., Zi. When the measurement for all the estimated surface elements Zi is completed (step S106: YES), the storage unit 30 stores the reference sound source measurement data 41 composed of the measured values Lmij acquired in the reference sound source acquisition step. ing. The reference sound source measurement data 41 is measurement data used when calculating the correction value Bij. Hereinafter, the measured value Lmij constituting the reference sound source measurement data 41 is referred to as a reference sound source measurement value Ltij.

Next, a reproduction step (step S107) and a reproduction acquisition step (step S108) are performed for each estimation surface element Zi.
With reference to FIG. 5, the reproduction step (step S107) and the reproduction acquisition step (step S108) will be specifically described by taking the estimation surface element Z1 as an example.

In the reproduction step, the measurement environment of the estimation target sound source 10 by the microphone M1j associated with the estimation surface element Z1 is reproduced in the semi-anechoic space having the floor surface with the reference sound source 34 as the measurement target.

Specifically, first, as shown in FIG. 5A, a reference sound source 34 is installed on the floor surface 32 of the semi-anechoic space 33, and a part of the floor surface 32 based on the reference sound source 34 is estimated. It is assumed that the surface element Z1. The positional relationship between the reference sound source 34 and the estimated surface element Z1 expresses the positional relationship between the reference sound source 34 and the estimated surface element Z1 in the reference sound source acquisition step (step S105).

Next, as shown in FIG. 5B, the microphone M1j is arranged with reference to the reference sound source 34 based on the positional relationship between the reference sound source 34 and the microphone M1j in the reference sound source acquisition process. As a result, the measurement environment of the estimation target sound source 10 by the microphone M1j is reproduced in the semi-anechoic space 33 for the estimation surface element Z1.

In the reproduction acquisition step (step S108), the sound pressure level of the reference sound source 34 measured by the microphone M1j in the measurement environment reproduced in the reproduction step (step S107) is acquired.
Specifically, the mode information indicating the reproduction environment mode and the information indicating the estimation surface element Z1 are input to the estimation device 25 through the input unit 21. After that, the reference sound source 34 is operated, and the estimation device 25 is instructed to start measurement through the input unit 21. In the reproduction environment mode at this time, the acquisition unit 26 acquires the measured value Lm1j of the microphone M1j associated with the estimation surface element Z1, and stores the data indicating the acquired measured value Lm1j of the microphone M1j in the predetermined storage unit 30. Store in the area.

The reproduction step (step S107) and the reproduction acquisition step (step S108) are performed for each of the estimation surface elements Z1, Z2, ..., Zi. When the measurement for all the estimated surface elements Zi is completed (step S109: YES), the storage unit 30 stores the reproduction environment measurement data 36 composed of the measured values Lmij acquired in the reproduction acquisition step. In the following, the measured value Lmij constituting the reproduction environment measurement data 36 is referred to as a reproduction environment measurement value Lcij. The reproduction environment measurement data 36 is measurement data used when calculating the correction value Ai and the correction value Bij.

Next, the first calculation step (step S110) is performed. In the first calculation step, the correction value Ai, which is the correction value when calculating the partial sound power level Lwi, is calculated for each estimated surface element Zi. The correction value Ai is a correction value indicating the area information necessary for estimating the partial sound power level Lwi of each estimated surface element Zi.

Specifically, the calculation instruction of the correction value Ai is input to the estimation device 25 through the input unit 21. When the calculation instruction of the correction value Ai is input, the first correction value calculation unit 27 extracts the reproduction environment measurement value Lcij of the microphone Mij associated with the estimation surface element Zi to be calculated from the reproduction environment measurement data 36. do. Then, as shown in the equation (1), the first correction value calculation unit 27 subtracts the average value of the extracted reproduction environment measurement value Lcij from the known sound power level LwK of the reference sound source 34 to obtain the correction value Ai. calculate. In addition, Si is the area of the arrangement portion of the microphone Mij associated with the estimation surface element Zi to be calculated.

The first correction value calculation unit 27 calculates the correction value Ai for each estimated surface element Zi, and stores the first correction data 37 in which the calculated correction value Ai and the estimated surface element Zi are associated with each other in a predetermined area of the storage unit 30. Store in.

Next, the second calculation step (step S111) is performed. In the second calculation step, a correction value Bij that corrects the measured value Lmij of the microphone Mij is calculated for each microphone Mij. The correction value Bij is a correction value that excludes the influence of the reflected wave, diffraction, and transmission of the target sound source in the closed space from the measured value Lmij.

Specifically, the calculation instruction of the correction value Bij is input to the estimation device 25 through the input unit 21. When the calculation instruction of the correction value Bij is input, the second correction value calculation unit 28 measures the reference sound source from the reproduction environment measurement data 36 to the reproduction environment measurement value Lcij and the reference sound source measurement data 41 for the microphone Mij to be calculated. Extract the value Ltij. Then, as shown in the equation (2), the second correction value calculation unit 28 calculates the correction value Bij by subtracting the reproduction environment measurement value Lcij from the extracted reference sound source measurement value Ltij.

The second correction value calculation unit 28 calculates the correction value Bij for each microphone Mij, and stores the second correction data 42 in which the calculated correction value Bij and the microphone Mij are associated with each other in a predetermined area of the storage unit 30.

Next, the estimation step (step S112) is performed. In the estimation process, the sound power level Lw of the estimation target sound source 10 is estimated.
Specifically, the estimation instruction of the sound power level Lw of the estimation target sound source 10 is input to the estimation device 25 through the input unit 21. When the estimation instruction is input, the estimation unit 29 corrects each microphone Mij from the estimation measurement value Lrig based on the estimation measurement data 43 and the second correction data 42, as shown in the equation (3). The value obtained by subtracting the value Bij is calculated as the estimated sound pressure level Lij, which is the sound pressure level measured by the microphone Mij. Then, as shown in the equation (4), the estimation unit 29 calculates the average value of the estimation sound pressure level Lij of the associated microphone Mij for each estimation surface element Zi. As shown in the equation (5), the estimation unit 29 calculates the partial sound power level Lwi for each estimated surface element Zi by adding the correction value Ai to the calculated average value. The estimation unit 29 estimates the average value of the partial sound power level Lwi calculated for each estimation surface element Zi as the sound power level Lw of the estimation target sound source 10.

FIG. 6 is an example of the results of a comparative experiment performed on the sound power level Lw of the estimation target sound source 10 estimated by the above estimation method. The estimation target sound source 10 is an engine installed in the engine room of an automobile.

As shown in FIG. 6, it was confirmed that the estimated sound power level Lw has a smaller error with respect to the true value of the sound power level Lw than in the case where the correction by the correction value Ai and the correction value Bij is not performed. That is, according to the estimation method described above, even if the estimation target sound source 10 is installed in a narrow closed space 12 such as an engine installed in an engine room, the estimation target sound source 10 is not taken out from the closed space 12. It was confirmed that the acoustic power level Lw can be estimated accurately.

The operation and effect of the first embodiment will be described.
(1-1) In the above-mentioned sound power level Lw estimation method, the measurement environment of the estimation target sound source 10 by the microphone Mij is reproduced in the semi-anechoic space 33 with the reference sound source 34 as the measurement target. Then, the correction value Ai for each estimation surface element Zi is calculated based on the known sound power level LwK of the reference sound source 34 and the reproduction environment measurement value Lcij of each microphone Mij in the reproduced measurement environment.

Further, the measurement environment of the estimation target sound source 10 by the microphone Mij is reproduced with the reference sound source 34 as the measurement target. Then, the correction value Bij is calculated based on the above-mentioned reproduction environment measurement value Lcij and the reference sound source measurement value Ltij of each microphone Mij in the reproduced measurement environment.

Then, the sound power level Lw of each estimation target sound source 10 is estimated based on the correction value Ai, the correction value Bij, and the estimation measurement value Lrig.
According to this configuration, since the number of times the reference sound source 34 is installed can be reduced, the correction value when estimating the sound power level Lw of the estimation target sound source 10 can be calculated with less man-hours. As a result, the correction value can be easily calculated.

(1-2) According to the above configuration, even when the estimation target sound source 10 is arranged in the narrow closed space 12, the estimation target sound source 10 is taken out from the closed space 12 and the sound of the estimation target sound source 10 is taken out. There is no need to measure the pressure level. Therefore, the sound power level Lw of the estimation target sound source 10 can be estimated by a simple method.

(1-3) According to the above configuration, since the correction value Ai can be acquired as the area information of each estimated surface element Zi necessary for estimating the partial sound power level Lwi, the partial sound power level Lwi of each estimated surface element Zi can be acquired. The accuracy, and thus the accuracy of the sound power level Lw of the estimation target sound source 10, can be improved.

(1-4) According to the above configuration, the estimation sound pressure level Lij is a value obtained by excluding the influence of the reflected wave, diffraction, and transmission of the estimation target sound source 10 in the closed space 12 from the estimation measurement value Lrig by the correction value Bij. Can be. As a result, the accuracy of the partial acoustic power level Lwi, and by extension, the accuracy of the acoustic power level Lw of the estimation target sound source 10 can be improved.

(Second Embodiment)
A second embodiment of the method for estimating the sound power level will be described with reference to FIG. 7. The method for estimating the sound power level of the second embodiment is different from the method for estimating the sound power level of the first embodiment and the method for calculating the correction value Ai. Therefore, in the second embodiment, the calculation method of the correction value Ai'will be described in detail.

In the first calculation step (step S110) of the second embodiment, the actual area Si of each estimated surface element Zi set in the surface element setting step (step S101) is calculated, and the actual area Si is calculated based on the area Si. The correction value Ai'is calculated.

Specifically, the surface element information indicating the shape of the estimated surface element Zi divided based on the shape of the estimation target sound source 10 is input to the estimation device 25 through the input unit 21. The surface element information may be, for example, information indicating the coordinates of each vertex or information indicating the length of each side or the size of each internal angle for each estimated surface element Zi.

When the surface element information is input, the acquisition unit 26 acquires the input surface element information. The first correction value calculation unit 27 calculates the area Si of the estimated surface element Zi based on the surface element information acquired by the acquisition unit 26, and substitutes the calculated area Si into the equation (6) to obtain a value. It is calculated as the correction value Ai'of the estimated surface element Zi.

FIG. 7 is an example of the results of a comparative experiment performed on the sound power level Lw of the estimation target sound source 10 estimated using the correction value Ai'calculated in this way and the above-mentioned correction value Bij. The estimation target sound source 10 is an engine installed in the engine room as in the first embodiment.

As shown in FIG. 7, it was confirmed that the estimated sound power level Lw has a smaller error with respect to the true value of the sound power level Lw than when the correction by the correction value Ai'and the correction value Bij is not performed. .. In particular, in this estimation method, it was confirmed that the error is small at a frequency lower than the specific frequency F1 (1000 Hz in this comparative experiment).

The effect of the second embodiment will be described.
(2-1) Even with the above configuration, it is possible to obtain an effect similar to the effect described in (1-1) to (1-4) of the first embodiment.

(Third Embodiment)
A third embodiment of the method for estimating the sound power level will be described with reference to FIG. The sound power level estimation method of the third embodiment differs from the sound power level estimation method of the first embodiment in the correction value calculated by using the reference sound source measurement value Ltij. Therefore, with respect to the third embodiment, a method of calculating the correction value will be described in detail.

In the second calculation step (step S111) of the third embodiment, for each estimated surface element Zi by the second correction value calculation unit 28 based on the reference sound source measurement value Ltij acquired in the reference sound source acquisition step (step S106). The correction value (third correction value) Ci is calculated.

Specifically, the surface element information indicating the shape of the estimated surface element Zi divided based on the shape of the estimation target sound source 10 is input to the estimation device 25 through the input unit 21. The surface element information may be, for example, information indicating the coordinates of each vertex or information indicating the length of each side or the size of each internal angle for each estimated surface element Zi.

When the surface element information is input, the acquisition unit 26 acquires the input surface element information. The second correction value calculation unit 28 calculates the correction value Ci as shown in the equation (7) for each estimation surface element Zi. Specifically, the second correction value calculation unit 28 first calculates the partial sound power level based on the reference sound source measurement value Ltij, as in the first and second terms on the right side in the equation (7). Si is the area of the estimated surface element Zi calculated based on the surface element information acquired by the acquisition unit 26. Then, the second correction value calculation unit 28 subtracts the known acoustic power level LwK from the partial acoustic power level by subtracting the partial acoustic power level based on the reproduced environment measurement value Lcij from the partial acoustic power level. The correction value Ci is calculated by.

In the estimation step (step S112), as shown in the equation (8), the estimation unit 29 relates to the area of the estimation surface element in the average value (first term on the right side) of the estimation measurement value Lrig for each estimation surface element Zi. The partial sound power level Lwi is calculated by subtracting the correction value Ci from the value obtained by adding the value (second term on the right side). Then, the estimation unit 29 estimates the average value of the partial sound power level Lwi calculated for each estimation surface element Zi as the sound power level Lw of the estimation target sound source 10 according to the equation (9).

FIG. 8 is an example of the results of a comparative experiment performed on the sound power level Lw of the estimation target sound source 10 calculated in this way. As shown in FIG. 8, it was confirmed that the estimated sound power level Lw has a smaller error with respect to the true value of the sound power level Lw than in the case where the correction by the correction value Ci is not performed. In particular, in this estimation method, it was confirmed that the error is small at a frequency higher than the specific frequency F1 (1000 Hz in this comparative experiment).

The effect of the third embodiment will be described.
(3-1) Even with the above configuration, it is possible to obtain an effect similar to the effect described in (1-1) to (1-3) of the first embodiment.

This embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
-Measurements for obtaining various measurement data 36, 41, 43 may be performed in any order as long as the installation position of the microphone Mij is determined. Further, the various correction values may be calculated after the measurement data required for the calculation of the correction values is obtained, and may be calculated in any order.

The estimation device 25 may be configured to calculate at least one of various correction values and estimate the sound power level Lw using the calculated correction values.
-As described above, the present inventors have a small error with respect to the true value at a frequency lower than the specific frequency F1 in the estimation method of the second embodiment, and the specific frequency F1 in the estimation method of the third embodiment. We have found that the error with respect to the true value is small at higher frequencies. That is, it was found that the appropriate correction method differs depending on the frequency band. Further, the present inventors have different values for the specific frequency F1 depending on the shape of the estimation target sound source 10, and based on the results of experiments and simulations conducted in advance using the reference sound source 34, for each shape of the estimation target sound source 10. Found that it is possible to set to. From this, the sound power level Lw of the estimation target sound source 10 may be estimated by a correction method different for each frequency band based on the shape of the estimation target sound source 10.

In the estimation method described above, as shown in FIG. 9, a division step (step S100-1) for dividing the frequency band is performed prior to the surface element setting step (step S101). Further, a selection step (step S100-2) for selecting a correction method for each frequency band is performed between the surface element setting step (step S101) and the calculation step for calculating the correction value (for example, step S110).

In the division step (step S101-1), first, the reference sound source 34 is regarded as a virtual polyhedron, and the microphone Mij is installed with each surface constituting the polyhedron as the estimated surface element Zi. Next, the sound pressure level of the reference sound source 34 is measured in a semi-anechoic space or a closed space using the microphone Mij, and the sound power level Lw is calculated using various correction methods. Next, the calculated sound power level Lw is compared with the known sound power level LwK of the reference sound source 34, and a frequency band suitable for various correction methods is specified.

By identifying the frequency band by simulating the reference sound source 34 as a polyhedron having various shapes, it is possible to associate various correction methods and an appropriate frequency band for the correction method with respect to the shape of the estimation target sound source 10. Then, the appropriate information, which is the associated information, is stored in advance in the storage unit 30 of the estimation device 25. It should be noted that such appropriate information may be composed of a model constructed by machine learning in which the shape of the polyhedron is input, the correction method and the frequency band appropriate for the correction method are output after a certain amount of sample is taken. ..

In the selection step (step S100-2), shape information indicating the shape of the estimation target sound source 10 is input to the estimation device 25 through the input unit 21. The estimation unit 29 selects an appropriate correction method, that is, an appropriate correction value calculation method by the correction value calculation unit for each frequency band, based on the shape information and the appropriate information stored in the storage unit 30.

According to this configuration, for example, as shown in FIG. 10, the estimation method of the second embodiment is used at a frequency lower than the specific frequency F1, and the estimation method of the third embodiment is used at a frequency higher than the specific frequency F1. Can be used to calculate the sound power level Lw. As a result, the error between the estimated value of the sound power level Lw and the true value of the sound power level Lw can be further reduced. The sound power level Lw at the specific frequency F1 is any of a value calculated by using the estimation method of the second embodiment, a value calculated by using the estimation method of the third embodiment, and an intermediate value between these values. May be.

The reproduction step (step S107) and the reproduction acquisition step (step S108) may be performed by computer simulation. In this case, in the reproduction step, the measurement environment by the microphone M is reproduced based on the coordinates of the installation position determined in the positioning step. Further, in the reproduction acquisition step, the sound pressure level of the reference sound source measured by each microphone M is estimated by numerical simulation by, for example, the boundary element method or the finite element method. Since this numerical simulation is performed for each estimation surface element Zi, a large computational load is not applied to the computer.

M ... Microphone, 10 ... Estimated sound source, 12 ... Closed space, 20 ... Estimate system, 21 ... Input unit, 25 ... Estimator, 26 ... Acquisition unit, 27 ... First correction value calculation unit, 28 ... Second correction value Calculation unit, 29 ... estimation unit, 30 ... storage unit, 31 ... associated data, 32 ... floor surface, 33 ... semi-insensitive space, 34 ... reference sound source, 35 ... reference sound source data, 36 ... reproduction environment measurement data, 37 ... 1st correction data, 41 ... Reference sound source measurement data, 42 ... 2nd correction data, 43 ... Measurement data for estimation.

Claims (4)

Sound power of the estimation target sound source is measured by a plurality of electroacoustic converters installed around the estimation target sound source, and the sound power level of the estimation target sound source is estimated based on the measured sound pressure level. It ’s a level estimation method.
The positioning step of determining the installation position of the plurality of electroacoustic converters and
A reproduction process that reproduces the measurement environment of the estimation target sound source in a semi-anechoic space using a reference sound source with a known sound power level as a sound source.
A reproduction acquisition step of acquiring the sound pressure level of the reference sound source measured by the plurality of electroacoustic converters in the reproduced measurement environment, and a reproduction acquisition step.
A calculation step of calculating a correction value when estimating the sound power level of the estimation target sound source based on the acquired sound pressure level, and a calculation step.
A method of estimating sound power level. The sound power level of the estimation target sound source is a value estimated by the average value of the partial sound power levels of each of the plurality of estimation surface elements divided based on the shape of the estimation target sound source.
Each of the plurality of estimation surface elements is associated with at least one of the plurality of electroacoustic transducers.
The partial acoustic power level is a value obtained by correcting the average sound pressure level, which is the average value of the sound pressure levels measured by the associated electroacoustic converter.
In the reproduction acquisition step, the sound pressure level of the reference sound source measured by the associated electroacoustic transducer is acquired for each estimated surface element.
In the calculation step, the difference between the average value of the sound pressure level acquired in the reproduction acquisition step and the sound power level of the reference sound source is calculated as a correction value for correcting the average sound pressure level for each estimated surface element. The method for estimating the sound power level according to claim 1. The measured sound pressure level is a value obtained by correcting the measured value of the electroacoustic converter.
Further provided with a reference sound source acquisition step of acquiring the sound pressure level of the reference sound source measured by each of the plurality of electroacoustic converters in the measurement environment of the estimation target sound source.
In the calculation step, for each of the plurality of electroacoustic converters, the difference between the sound pressure level acquired in the reference sound source acquisition step and the sound pressure level acquired in the reproduction acquisition step is a correction value for correcting the measured value. The method for estimating the acoustic power level according to claim 1 or 2. A division step of dividing the frequency of the sound pressure level measured by the plurality of electroacoustic converters into a plurality of frequency bands, and a division step.
The method for estimating a sound power level according to any one of claims 1 to 3, further comprising a selection step of selecting a correction method for calculating the sound power level for each of the plurality of frequency bands.

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