JP7478710B2 - Noise source contribution analysis device, noise source contribution analysis method, and noise source contribution analysis program - Google Patents

Description

The present invention relates to a noise source contribution analysis device, a noise source contribution analysis method, and a noise source contribution analysis program, and in particular to a noise source contribution analysis device, a noise source contribution analysis method, and a noise source contribution analysis program that analyze how the sound pressure of multiple noise sources contributes to the sound pressure of noise in a location where noise control measures should be taken.

When implementing noise control measures, it is effective to take measures against the noise source that contributes most to the sound pressure of the noise at the observation point among multiple noise sources. Noise source contribution analysis devices have been known as devices that analyze the degree of contribution of the sound pressure of a noise source to the sound pressure of the noise at the observation point (see, for example, Patent Document 1).

In conventional noise source contribution analysis devices, the sound pressure of the noise at an observation point was calculated by adding up the sound pressure energy of multiple noise sources at the observation point, and the degree of contribution of multiple noise sources at the observation point was analyzed based on this calculated sound pressure of the noise at the observation point.

It is known that the sound pressure of noise at an observation point calculated using the above method generally matches the sound pressure actually measured at the observation point in the high frequency range, but deviates significantly in the low frequency range. This means that with conventional noise source contribution analysis devices, it may be difficult to accurately analyze the degree of contribution of multiple noise sources at an observation point.

Japanese Patent Application Laid-Open No. 5-26722

The present disclosure therefore aims to provide a noise source contribution analysis device, a noise source contribution analysis method, and a noise source contribution analysis program that can accurately estimate the total sound pressure at an observation point, which is necessary to more accurately analyze the degree of contribution of multiple noise sources at the observation point.

That is, the noise source contribution analysis device according to the first aspect is a noise source contribution analysis device that analyzes the degree of contribution of the noise source sound pressure of each of the multiple noise sources to the total sound pressure at an observation point to which the multiple noise sources contribute, and includes a noise source sound pressure acquisition unit that acquires the noise source sound pressure detected in the vicinity of each of the multiple noise sources, a transfer function acquisition unit that acquires, for each of the multiple noise sources, a transfer function that indicates the transfer characteristics of the noise from each of the multiple noise sources to the observation point, and a noise source sound pressure corresponding to the transfer function acquired for each of the multiple noise sources by the transfer function acquisition unit. The system includes an observation point sound pressure calculation unit that receives each of the noise sources and outputs the respective outputs as observation point sound pressures, a high frequency band extraction unit that extracts the high frequency band of the observation point sound pressures calculated by the observation point sound pressure calculation unit as high frequency band sound pressures, a low frequency band extraction unit that extracts the low frequency band of the observation point sound pressures calculated by the observation point sound pressure calculation unit as low frequency band sound pressures, and a total sound pressure calculation unit that calculates the total sound pressure at the observation point based on the sum of the squares of the high frequency band sound pressures of each of the multiple noise sources and the sum of the low frequency band sound pressures of each of the multiple noise sources.

In a second aspect, the vibration source contribution analysis device according to the first aspect may further include a contribution calculation unit that calculates the degree of contribution of each of a plurality of noise sources to the calculated total sound pressure.

In a third aspect, in the vibration source contribution analysis device according to the first or second aspect, the cutoff frequency that is the boundary between the high frequency band and the low frequency band may be set based on the distance between the noise source and the observation point.

In a fourth aspect, in the vibration source contribution analysis device according to the third aspect, the cutoff frequency may be a frequency at which the distance between the noise source and the observation point is one wavelength.

In a fifth aspect, in the vibration source contribution analysis device according to the first or second aspect, the cutoff frequency may be set based on the dimensions of the surface on which the noise source is present.

In a noise source contribution analysis method according to a sixth aspect, in a noise source contribution analysis method for analyzing the degree of contribution of a noise source sound pressure for each of a plurality of noise sources to a total sound pressure at an observation point to which the plurality of noise sources contribute, a computer used in a noise source contribution analysis device includes a noise source sound pressure acquisition step for acquiring a noise source sound pressure detected in the vicinity of each of the plurality of noise sources, a transfer function acquisition step for acquiring, for each of the plurality of noise sources, a transfer function indicating the transfer characteristics of the noise from each of the plurality of noise sources to the observation point, and a noise source sound pressure corresponding to the transfer function acquired for each of the plurality of noise sources in the transfer function acquisition step. The system executes an observation point sound pressure calculation step in which each of the sound pressures is input and the output is output as the observation point sound pressure, a high frequency band extraction step in which high frequency band sound pressures from the observation point sound pressures calculated in the observation point sound pressure calculation step are extracted as high frequency band sound pressures, a low frequency band extraction step in which low frequency band sound pressures from the observation point sound pressures calculated in the observation point sound pressure calculation step are extracted as low frequency band sound pressures, and a total sound pressure calculation step in which a total sound pressure at the observation point is calculated based on the sum of the squares of the high frequency band sound pressures of each of the multiple noise sources and the sum of the low frequency band sound pressures of each of the multiple noise sources.

In a noise source contribution analysis program according to a seventh aspect, which analyzes the degree of contribution of the noise source sound pressure of each of a plurality of noise sources to the total sound pressure at an observation point to which the plurality of noise sources contribute, a computer used in the noise source contribution analysis device includes a noise source sound pressure acquisition function for acquiring the noise source sound pressure detected in the vicinity of each of the plurality of noise sources, a transfer function acquisition function for acquiring, for each of the plurality of noise sources, a transfer function indicating the transfer characteristics of the noise from each of the plurality of noise sources to the observation point, and a transfer function for each of the plurality of noise sources acquired by the transfer function acquisition function, It performs an observation point sound pressure calculation function that inputs the corresponding noise source sound pressures and outputs the output as the observation point sound pressure, a high frequency band extraction function that extracts the high frequency band of the observation point sound pressures calculated by the observation point sound pressure calculation function as high frequency band sound pressure, a low frequency band extraction function that extracts the low frequency band of the observation point sound pressures calculated by the observation point sound pressure calculation function as low frequency band sound pressure, and a total sound pressure calculation function that calculates the total sound pressure at the observation point based on the sum of the squares of the high frequency band sound pressures of each of the multiple noise sources and the sum of the low frequency band sound pressures of each of the multiple noise sources.

The present disclosure provides a noise source contribution analysis device, a noise source contribution analysis method, and a noise source contribution analysis program that can accurately estimate the total sound pressure at an observation point, which is necessary to more accurately analyze the degree of contribution of multiple noise sources at the observation point.

1 is a diagram for explaining noise inside the automobile according to the present embodiment. FIG. 1 is a diagram illustrating noise at an ear position (observation point) according to an embodiment of the present invention. FIG. 1 is a diagram illustrating noise at an ear position (observation point) according to an embodiment of the present invention. FIG. 5 is a diagram illustrating the relationship between the frequency and phase difference of noise according to the embodiment. FIG. 1A to 1C are diagrams for explaining characteristics of acoustic wave interference due to a phase difference according to the present embodiment. 1 is a diagram for explaining the discrepancy between the actual measured sound pressure value of noise at the ear position (observation point) according to the present embodiment and the calculated value according to the conventional method. FIG. 5 is a diagram for explaining an example of a calculated value of the noise source contribution analysis device according to the embodiment. FIG. FIG. 2 is a block diagram for explaining an example of a mechanical configuration of the noise source contribution analysis device according to the present embodiment. 1 is a block diagram for explaining an example of a functional configuration of a noise source contribution analysis device according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the flow of processing inside the noise source contribution analysis device according to the present embodiment. 1 is a diagram for explaining why an accurate total sound pressure at the ear position (observation point) is required according to the present embodiment. FIG. 1 is a diagram for explaining why an accurate total sound pressure at the ear position (observation point) is required according to the present embodiment. FIG. 4 is a flowchart of a noise source contribution analysis program according to the present embodiment.

A noise source contribution analysis device 50 according to this embodiment will be described with reference to FIGS.
The noise source contribution analysis device 50 analyzes the degree of contribution of the noise source sound pressure of each noise source to the total sound pressure at an observation point to which the multiple noise sources contribute. Hereinafter, an example of noise radiated toward the interior of the living space of an automobile 10 will be described. Note that the noise source contribution analysis device 50 according to this embodiment is not limited to automobiles 10, and can also be applied to noise that penetrates into the interior of vehicles other than automobiles, such as trains, ships, and airplanes, or buildings such as buildings and houses.

Noise in the living space of an automobile 10 will be described with reference to Fig. 1. Fig. 1 is a diagram for explaining noise inside an automobile 10 according to this embodiment.
Noises felt inside the living space of the automobile 10 include engine noise, wind noise, road noise, muffled noise, etc. These noises become noise sources when the wall surfaces (panels 12) constituting the living space of the automobile 10 vibrate, and are radiated into the living space of the automobile 10 and reach the ears of the passengers as noise.

Engine sound is vibration and noise originating from the engine 14 installed in the engine room of the automobile 10, which is transmitted to the panel 12 via solid propagation 21 and air propagation 22. Wind noise is caused by air 20 flowing along the outer surface of the body 11 of the automobile 10 vibrating the panel 12. Road noise is vibration and noise generated between the road surface and the tires 13 while the automobile 10 is traveling, which is transmitted to the panel 12 via solid propagation 21 and air propagation 22. Booming sound is vibration and noise caused by the propeller shaft 16 which is transmitted to the panel 12 via solid propagation 21 and air propagation 22.

When multiple noise sources occur on the panel 12, the noise heard at the passenger's ear position (observation point) is a mixture of noises radiated from the multiple noise sources.
As a means for noise control within the living space of the automobile 10, it is effective to identify the vibrations of the panels 12 that have a large effect on the noise heard at the ear position (observation point) of the passengers and suppress the vibrations. Therefore, in order to effectively identify and take measures against the panels 12 that have a large effect on the noise heard at the ear position (observation point), a noise source contribution analysis is performed to calculate the percentage to which the vibration of each panel 12 contributes to the noise at the ear position (observation point).

Next, the superposition of two noises radiated from different noise sources at ear position (observation point) 24 will be described with reference to Figures 2 to 7. The superposition of high-frequency band noises will be described with reference to Figure 2. Figure 2 is a diagram explaining noises at ear position (observation point) according to this embodiment.

In FIG. 2, there are a first noise source 28 and a second noise source 29. The sound pressures of the first noise source 28 and the second noise source 29 are detected by a first microphone 32a and a second microphone 32b installed near the respective noise sources. The first microphone 32a and the second microphone 32b are PU probes of an acoustic particle velocity sensor.

Let the sound pressures measured near the first noise source 28 and the second noise source 29 be sound pressures a1 and a2, respectively. Let the transfer functions from the first noise source 28 and the second noise source 29 to the ear position (observation point) be transfer functions (f1) and (f2), respectively. If the calculated sound pressures at the ear position (observation point) of the noise radiated from the first noise source 28 and the second noise source 29 are defined as sound pressures b1 and b2, respectively, then the following equations (1) and (2) hold.

耳位置（観測点）の音圧を（ｃ）と定義すると以下の式（３）が成立する。

If the sound pressure at the ear position (observation point) is defined as (c), the following equation (3) holds.

Equation (3) comes from the fact that in the high frequency band, the sound pressure energy at the ear position (observation point) is approximately equal to the sum of the energy of the contributing sounds. Equation (3) can be further expanded to the following equation (4).

Equation (4) means that the sound pressure energy at the ear position (observation point) in the high frequency band is approximately equal to the sum of the contributing sound pressure energies. This is because sounds in the high frequency band have little interference with each other and can be considered independent.

Next, the superposition of low-frequency band noise will be described with reference to Figs. 3 to 7. Fig. 3 is a diagram for explaining noise at ear position (observation point) according to this embodiment, Fig. 4 is a diagram for explaining the relationship between noise frequency and phase difference according to this embodiment, Fig. 5 is a diagram for explaining the characteristics of sound wave interference due to phase difference according to this embodiment, Fig. 6 is a diagram for explaining the deviation between the actual measured value of the sound pressure of the noise at ear position (observation point) according to this embodiment and the calculated value using a conventional method, and Fig. 7 is a diagram for explaining an example of a calculated value of the noise source contribution analysis device according to this embodiment.

When the distance between the first noise source 28 and the second noise source 29 is short, these two noise sources can be regarded as one noise source 33 (see FIG. 3). In this case, the sound pressure (c) of the noise at the ear position (observation point) can be calculated by the following formula (5).

Pcont(yi) in equation (5) is the calculated sound pressure at the ear position (observation point) of the noise radiated from noise source yi, and is the value obtained by multiplying the transfer function described above by the sound pressure near noise source yi. Pref(x) is the actual measured sound pressure at the ear position (observation point x).

In the low-frequency band, the sound pressure at ear position (observation point) must take into account the interference between the sounds that contribute to the sound in question, and is calculated as the sum of the amplitudes if the noises are in phase, and as the difference in amplitudes if they are out of phase.

Furthermore, even when the wavelength of the noise is long relative to the distance between the first noise source 28 and the second noise source 29 and the ear position (observation point) (i.e., in the case of a low frequency band), the sound pressure (c) of the noise at the ear position (observation point) can be calculated using formula (5).

It is known that the effect of phase shift due to differences in path length is greater in the high frequency band than in the low frequency band (see Figure 4). Furthermore, it is known that the degree of mutual interference between two noises is greater in the low frequency band than in the high frequency band (see Figure 5).

The problems with the conventional calculation method will be explained with reference to FIG. 6. As shown in FIG. 6, the divergence between the calculation result (c) 39 and the actual measurement value (d) 38 of the conventional calculation method increases below 1400 Hz. In the conventional calculation method, (c) is calculated using equation (4) in all bands including the high-frequency band and the low-frequency band. Equation (4) does not take into account interference between noises in the low-frequency band, and the inventors of the present disclosure have found that this is the cause of the divergence between the calculation result (c) 39 and the actual measurement value (d) 38.

The inventors of the present disclosure investigated conventional calculation methods and found that the calculation methods are based on the premise that noises caused by vibrations of each noise source interfere with each other in an uncorrelated manner at the ear position (observation point). Because noises caused by vibrations of each noise source have different path lengths to reach the ear position (observation point), there is a phase difference between each noise at the ear position (observation point) (see Figure 4). Furthermore, because the phase difference between each noise is small in the low frequency band, the degree of interference between each noise at the ear position (observation point) becomes strong due to the principle of wave superposition, and conversely, the degree of interference becomes weaker in the high frequency band (see Figure 5).

Therefore, we modified the calculation method (equation (5)) to obtain the measured values of acoustic particle velocity and sound pressure at each noise source as complex numbers and calculate the contribution by retaining the phase difference generated between the noise sources. As a result, the maximum deviation between the calculated value 71 and the actual measured value 70 could be reduced from 12 dB to 6 dB, and accuracy was improved (see Figure 7). As a result, the deviation between the measured value 72 and the actual measured value 70, which occurred with the conventional analysis method, could be reduced by approximately 6 dB, and accuracy was improved.

Next, a mechanical configuration of the noise source contribution analysis device 50 will be described with reference to Fig. 8. It is a block diagram for explaining an example of the mechanical configuration of the noise source contribution analysis device 50 according to the present embodiment. The noise source contribution analysis device 50 may be connected to a communication network 51.
The noise source contribution analysis device 50 includes a Read Only Memory (ROM) 50a, a Random Access Memory (RAM) 50b, a storage unit 50c, a Central Processing Unit (CPU) 50d, an input/output interface 50e, a communication interface 50f, etc. The noise source contribution analysis device 50 also includes an input device 50g and an output device 50h as its external devices.

The memory unit 50c can be used as a storage device, and stores the noise source contribution analysis program (described below) required for the operation of the noise source contribution analysis device 50, various applications, and various data used by the applications.

The input/output interface 50e transmits and receives data to and from the input device 50g and the output device 50h. The input device 50g includes a keyboard 52, a mouse 53, a web camera 54, etc., and the output device 50h includes a monitor 55, a speaker 56, a printer 57, etc., which are so-called peripheral devices of the information processing device.

The functional configuration of the noise source contribution analysis device 50 will be described with reference to Fig. 9. Fig. 9 is a block diagram for explaining an example of the functional configuration of the noise source contribution analysis device 50 according to this embodiment.
The noise source contribution analysis device 50 stores a noise source contribution analysis program required for operation in a ROM 50a or a storage unit 50c, and loads the noise source contribution analysis program into a main memory constituted by a RAM 50b etc. The CPU 50d accesses the main memory into which the noise source contribution analysis program has been loaded, and executes the noise source contribution analysis program.

By executing the noise source contribution analysis program, the noise source contribution analysis device 50 provides the CPU 50d with a noise source sound pressure acquisition unit 60, a transfer function acquisition unit 61, an observation point sound pressure calculation unit 62, a high frequency band extraction unit 63, a low frequency band extraction unit 64, a total sound pressure calculation unit 65, and a contribution degree calculation unit 66 as functional units.

The noise source sound pressure acquisition unit 60 acquires the noise source sound pressure detected in the vicinity of each of the multiple noise sources.
The noise source sound pressure is detected by microphones installed near each of the multiple noise sources. The noise source sound pressure acquisition unit 60 acquires the noise source sound pressure from the microphones.

The transfer function acquisition unit 61 acquires, for each of the plurality of noise sources, a transfer function that indicates the transfer characteristics of noise from each of the plurality of noise sources to the observation point.
The transfer function is a function that indicates how noise emitted from a noise source changes before it is transmitted to an observation point.

The observation point sound pressure calculation unit 62 inputs the noise source sound pressure corresponding to each transfer function acquired by the transfer function acquisition unit 61 for each of the multiple noise sources, and outputs the output as the observation point sound pressure.

The high frequency band extraction unit 63 extracts, from the observation point sound pressures calculated by the observation point sound pressure calculation unit 62, those in the high frequency band as high frequency band sound pressures.
The cutoff frequency for extracting the high-frequency band sound pressure varies depending on the sound field environment. Therefore, it is necessary to investigate in advance the cutoff frequency at which the deviation between the calculation result of the total sound pressure calculation unit 65 and the actual measurement value of the observation point sound pressure is the smallest, and set the cutoff frequency. The cutoff frequency may be set based on the distance between the noise source and the ear position (observation point), or may be set to a frequency that takes the distance as one wavelength.

The cutoff frequency may further be set based on the dimensions of the surface on which the noise source resides.

The low-frequency band extraction unit 64 extracts low-frequency band sound pressures from the observation point sound pressures calculated by the observation point sound pressure calculation unit 62 as low-frequency band sound pressures.
The cutoff frequency for extracting the low-frequency band sound pressure is the same as the cutoff frequency for extracting the high-frequency band sound pressure.

The total sound pressure calculation unit 65 calculates the total sound pressure at the observation point based on the sum of the squares of the high-frequency band sound pressures of each of the multiple noise sources and the sum of the low-frequency band sound pressures of each of the multiple noise sources.

The total sound pressure calculation unit 65 calculates the total sound pressure in the high frequency band using equation (4) and calculates the total sound pressure in the low frequency band using equation (5).

The contribution degree calculation unit 66 calculates the degree of contribution of each of the multiple noise sources to the calculated total sound pressure.
The contribution calculation unit 66 calculates the degree of contribution of the sound pressure measured near each noise source based on the ratio of each sound pressure to the total sound pressure at the ear position (observation point).

Next, the flow of processing by the noise source contribution analysis device 50 will be described with reference to FIG.
For ease of explanation, four noise sources are shown in Fig. 10. A first microphone 32a, a second microphone 32b, a third microphone 32c, and a fourth microphone 32d are installed near the four noise sources, respectively, to detect the sound pressure of the four noise sources. In the embodiment, the high frequency band and the low frequency band are distinguished by the wavelength. Sounds with wavelengths of approximately 1 m or more are considered to be in the low frequency band. This is based on the fact that the distance from the noise source to the driver's ear in the vehicle interior space (see Fig. 1) is 1 m.

The wavelength length that separates the high frequency band from the low frequency band may be set based on the dimensions of the surface (panel 12) on which the noise source is present. As an example, if the surface on which the noise source is present is rectangular (including square), the wavelength length that separates the high frequency band from the low frequency band may be the length of the long side of the surface on which the noise source is present. As a second example, the wavelength length that separates the high frequency band from the low frequency band may be set based on the diameter of the surface on which the noise source is present, or may be set to the same length as the diameter. Here, the "diameter" of a figure refers to the longest distance between two parallel lines that contact the figure from both sides, and is a concept that is defined not only for circles and ellipses but also for convex figures in general. Note that a convex figure refers to a figure in which a point on a line segment connecting any two points on the figure is also on the figure.

The detected sound pressures near the four noise sources are input to the CPU 50d by the noise source sound pressure acquisition unit 60. Next, the observation point sound pressure calculation unit 62 multiplies the detected sound pressures near the four noise sources by transfer functions f1 to f4 (67a to 67d) to calculate the sound pressures at the observation points of the noise radiated from the four noise sources.

The four sound pressure values calculated by the observation point sound pressure calculation unit 62 are sent to the high frequency band extraction unit 63, which consists of HPF (High Pass Filter) 1 to HPF 4 (63a to 63d), and the low frequency band extraction unit 64, which consists of LPF (Low Pass Filter) 1 to LPF 4 (64a to 64d).

The total sound pressure calculation unit 65 includes a high frequency band addition unit 65a and a low frequency band addition unit 65b.
The high frequency band adder 65a substitutes the high frequency band sound pressures extracted from HPF1 to HPF4 (63a to 63d) as (b1 to b4) into equation (4) to calculate the sound pressure (c) at the observation point in the high frequency band.

The low-frequency band addition unit 65b substitutes the low-frequency band sound pressures extracted from LPF1 to LPF4 (64a to 64d) as (Pcont(y1) to Pcont(y4)) into equation (5) to calculate the sound pressure (c) at the observation point in the low-frequency band.

The sound pressure P(t), which is the calculation result of the total sound pressure calculation unit 65, is obtained by adding together the sound pressure (c) at the observation point in the high frequency band and the sound pressure (c) at the observation point in the low frequency band.

Next, the concept of contribution analysis will be described with reference to FIGS.
11 and 12 are diagrams for explaining the reason why an accurate total sound pressure at the ear position (observation point) according to this embodiment is necessary.

Noise source contribution analysis does not only require finding the ratio of the sound pressure of each noise source to the total sound pressure at the ear position (observation point), but also requires the following viewpoints. That is, if the sound pressures of the noise reaching the ear position (observation point) from each noise source are b1, b2, and the total sound pressure is c, it is necessary to know the change in the total sound pressure c when sound pressure b1 or b2 is eliminated. The above-mentioned conventional calculation method and the calculation method of the present disclosure calculate the effect on the total sound pressure c differently. Figures 11 and 12 show an example in which there is not much difference between the conventional method and the present disclosure in sound field 1, while an example in which there is a large difference between the conventional method and the present disclosure in sound field 2.

In sound field 1 (see FIG. 11), a cosine wave with an amplitude of 1.0 at t=0 is radiated from first noise source 28, and a cosine wave with an amplitude of 0.5 at t=0 is radiated from second noise source 29.

In sound field 2 (see Figure 12), a cosine wave with an amplitude of 1.0 at t = 0 is radiated from the third noise source 30, and a cosine wave with an amplitude of -0.5 at t = 0 is radiated from the fourth noise source 31.

The analysis results of the sound field 1 using the above-mentioned conventional calculation method will be described below.
The maximum amplitude of the total sound pressure c is 1.12 according to formula (4). When the first noise source 28 is removed, the maximum amplitude of the total sound pressure c becomes 0.5 (a decrease of 0.62). Therefore, by removing the first noise source 28, the maximum amplitude of the total sound pressure c becomes 0.45 times, a decrease of -7 dB. When the second noise source 29 is removed, the maximum amplitude of the total sound pressure c becomes 1.0 (a decrease of 0.12). Therefore, by removing the second noise source 29, the maximum amplitude of the total sound pressure c becomes 0.89 times, a decrease of -1 dB.

The change in the maximum amplitude of the total sound pressure c when the first noise source 28 is removed is a decrease of 0.62 (1.12-0.5). The change in the maximum amplitude of the total sound pressure c when the second noise source 29 is removed is a decrease of 0.12 (1.12-1.0). Therefore, the contributions of the first noise source 28 and the second noise source 29 at the ear position (observation point) may be calculated as follows.
Contribution of first noise source 28=100×0.62/(0.62+0.12)=83.8%
Contribution of second noise source 29=100×0.12/(0.62+0.12)=16.2%

Next, the analysis results of the sound field 1 using the calculation method of the present disclosure will be described below.
The maximum amplitude of the total sound pressure c is 1.5 according to formula (5). When the first noise source 28 is removed, the maximum amplitude of the total sound pressure c is 0.5 (a decrease of 1.0). Therefore, by removing the first noise source 28, the maximum amplitude of the total sound pressure c becomes 0.33 times, a decrease of -9.6 dB. When the second noise source 29 is removed, the maximum amplitude of the total sound pressure c is 1.0 (a decrease of 0.5). Therefore, by removing the second noise source 29, the maximum amplitude of the total sound pressure c becomes 0.7 times, a decrease of -3.1 dB.

The change in the maximum amplitude of the total sound pressure c when the first noise source 28 is removed is a decrease of 1.0 (1.5--0.5). The change in the maximum amplitude of the total sound pressure c when the second noise source 29 is removed is a decrease of 0.5 (1.5-1.0). Therefore, the contributions of the first noise source 28 and the second noise source 29 at the ear position (observation point) may be calculated as follows.
Contribution of first noise source 28=100×1.0/(1.0+0.5)=66.7%
Contribution of second noise source 29=100×0.5/(1.0+0.5)=33.3%

In sound field 1, both the results of the conventional calculation method and the calculation method disclosed herein show that noise control measures are effective for both the first noise source 28 and the second noise source 29. Furthermore, both the results of the conventional calculation method and the calculation method disclosed herein suggest that measures for the first noise source 28 have a greater effect. However, on the other hand, in the case of sound field 2 shown below, the results of the calculation method disclosed herein are more appropriate than those of the conventional calculation method.

Next, the analysis results for the sound field 2 using the above-mentioned conventional calculation method will be described below.
The maximum amplitude of the total sound pressure c is 1.12 according to formula (4). When the third noise source 30 is removed, the maximum amplitude of the total sound pressure c becomes 0.5 (a decrease of 0.62). Therefore, by removing the third noise source 30, the maximum amplitude of the total sound pressure c becomes 0.45 times, a decrease of -7 dB. When the fourth noise source 31 is removed, the maximum amplitude of the total sound pressure c becomes 1.0 (a decrease of 0.12). Therefore, by removing the fourth noise source 31, the maximum amplitude of the total sound pressure c becomes 0.89 times, a decrease of -1 dB.

The change in the maximum amplitude of the total sound pressure c when the third noise source 30 is removed is a decrease of 0.62 (1.12-0.5). The change in the maximum amplitude of the total sound pressure c when the fourth noise source 31 is removed is a decrease of 0.12 (1.12-1.0). Therefore, the contributions of the third noise source 30 and the fourth noise source 31 at the ear position (observation point) may be calculated as follows.
Contribution of third noise source 30=100×0.62/(0.62+0.12)=83.8%
Contribution of fourth noise source 31=100×0.12/(0.62+0.12)=16.2%

Next, the analysis results for sound field 2 using the calculation method of the present disclosure will be described below.
The maximum amplitude of the total sound pressure c is 0.5 according to formula (5). When the third noise source 30 is removed, the maximum amplitude of the total sound pressure c is 0.5 (a decrease of 0.0). Therefore, by removing the third noise source 30, the maximum amplitude of the total sound pressure c becomes 1.0 times, and there is no effect. When the fourth noise source 31 is removed, the maximum amplitude of the total sound pressure c becomes 1.0 (an increase of 0.5). Therefore, by removing the fourth noise source 31, the maximum amplitude of the total sound pressure c becomes double, an increase of 6.0 dB.

The change in the maximum amplitude of the total sound pressure c when the third noise source 30 is removed is a decrease of 0.0 (0.5-0.5). The change in the maximum amplitude of the total sound pressure c when the fourth noise source 31 is removed is a decrease of -0.5 (0.5-1.0), that is, an increase of 0.5. Therefore, the contributions of the third noise source 30 and the fourth noise source 31 at the ear position (observation point) may be calculated as follows.
Contribution of third noise source 30=100×0.0/(0.0+0.5)=0.0%
Contribution of fourth noise source 31=100×(−0.5)/(0.0+0.5)=−100.0%

In reality, in sound field 2, taking measures against the third noise source 30 has no effect, and taking measures against the fourth noise source 31 actually increases the noise. The results of the calculation method disclosed herein represent the actual results and are appropriate. On the other hand, the conventional calculation method gives a result in which measures against both the third noise source 30 and the fourth noise source 31 are effective, and furthermore, measures against the third noise source 30 have a greater effect, which gives an erroneous suggestion.

The calculation of the contribution of each noise source described above can be expanded as follows.
That is, there are first to N noise sources that contribute to the total sound pressure c, and the change in the maximum amplitude of the total sound pressure c when the nth noise source (n is any integer from 1 to N) is removed is denoted as an. In this case, the contribution of the nth noise source can be calculated by equation (6). an is considered positive when the maximum amplitude of the total sound pressure c decreases, and is considered negative when the maximum amplitude of the total sound pressure c increases.

Next, the noise source contribution analysis method according to this embodiment will be described together with the noise source contribution analysis program with reference to FIG. 13. FIG. 13 is a flowchart of the noise source contribution analysis program according to this embodiment.

As shown in FIG. 13, the noise source contribution analysis program includes a noise source sound pressure acquisition step S60, a transfer function acquisition step S61, an observation point sound pressure calculation step S62, a high frequency band extraction step S63, a low frequency band extraction step S64, a total sound pressure calculation step S65, and a contribution degree calculation step S66.

The noise source contribution analysis device 50 loads the noise source contribution analysis program stored in the ROM 50a or the memory unit 50c into the main memory, and executes the noise source contribution analysis program using the CPU 50d.

The noise source contribution analysis program enables the CPU 50d of the noise source contribution analysis device 50 to realize functions such as a noise source sound pressure acquisition function, a transfer function acquisition function, an observation point sound pressure calculation function, a high frequency band extraction function, a low frequency band extraction function, a total sound pressure calculation function, and a contribution degree calculation function.

These functions are illustrated as being processed in the order shown in the flowchart of Figure 13, but this is not limiting, and the noise source contribution analysis program may be executed by changing the order as appropriate.

The above-mentioned functions overlap with the explanations of the noise source sound pressure acquisition unit 60, transfer function acquisition unit 61, observation point sound pressure calculation unit 62, high frequency band extraction unit 63, low frequency band extraction unit 64, total sound pressure calculation unit 65, and contribution calculation unit 66 of the noise source contribution analysis device 50 described above, so detailed explanations thereof will be omitted.

The noise source sound pressure acquisition function acquires the noise source sound pressure detected in the vicinity of each of the multiple noise sources (S60: noise source sound pressure acquisition step).

The transfer function acquisition function acquires a transfer function for each of the multiple noise sources that indicates the transfer characteristics of the noise from each of the multiple noise sources to the observation point (S61: transfer function acquisition step).

The observation point sound pressure calculation function inputs the noise source sound pressure corresponding to each transfer function acquired by the transfer function acquisition unit 61 for each of the multiple noise sources, and outputs the output as the observation point sound pressure (S62: Observation point sound pressure calculation step).

The high frequency band extraction function extracts the high frequency band of the observation point sound pressures calculated by the observation point sound pressure calculation unit 62 as high frequency band sound pressures (S63: high frequency band extraction step).

The low-frequency band extraction function extracts the low-frequency band from the observation point sound pressures calculated by the observation point sound pressure calculation unit 62 as low-frequency band sound pressures (S64: low-frequency band extraction step).

The total sound pressure calculation function calculates the total sound pressure at the observation point based on the sum of the squares of the high-frequency band sound pressures of each of the multiple noise sources and the sum of the low-frequency band sound pressures of each of the multiple noise sources (S65: total sound pressure calculation step).

The contribution calculation function calculates the degree of contribution of each of the multiple noise sources to the calculated total sound pressure (S66: contribution calculation step).

According to the present embodiment described above, different formulas are used to calculate the total sound pressure at ear position (observation point) for the high frequency band and the low frequency band. When calculating the total sound pressure in the low frequency band, the effect of interference between noises is taken into account. This reduces the discrepancy between the total sound pressure at ear position (observation point) and the calculated value by approximately 6 dB, improving accuracy.

The present disclosure is not limited to the noise source contribution analysis device 50, the noise source contribution analysis method, and the noise source contribution analysis program according to the above-described embodiments, and can be implemented by various other modified examples or application examples without departing from the gist of the present disclosure described in the claims.

10 Automobile 11 Body 12 Panel 13 Tire 14 Engine 15 Seat 16 Propeller shaft 17 Windshield 18 Rear window 20 Wind flow 21 Solid propagation 22 Air propagation 23 Sound radiation 24 Ear position (observation point)
28 First noise source 29 Second noise source 30 Third noise source 31 Fourth noise source 32a First microphone 32b Second microphone 32c Third microphone 32d Fourth microphone 33 Noise source 34 First panel 35 Second panel 36 Low frequency 37 High frequency 38 Actual measurement value (d)
39 Calculated value (c)
50 Noise source contribution analysis device 50a Read Only Memory (ROM)
50b Random Access Memory (RAM)
50c Memory unit 50d Central Processing Unit (CPU)
50e Input/Output interface 50f Communication interface 50g Input device 50h Output device 51 Communication network 52 Keyboard 53 Mouse 54 Web camera 55 Monitor 56 Speaker 57 Printer 60 Noise source sound pressure acquisition unit 61 Transfer function acquisition unit 62 Observation point sound pressure calculation unit 63 High frequency band extraction unit 63a High frequency band extraction unit 63b High frequency band extraction unit 63c High frequency band extraction unit 63d High frequency band extraction unit 64 Low frequency band extraction unit 64a Low frequency band extraction unit 64b Low frequency band extraction unit 64c Low frequency band extraction unit 64d Low frequency band extraction unit 65 Total sound pressure calculation unit 65a High frequency band addition unit 65b Low frequency band addition unit 66 Contribution degree calculation unit 67a Transfer function f1
67b Transfer function f2
67c Transfer function f3
67d Transfer function f4
70 Actual measurement value 71 Current calculation value 72 Previous calculation value 75 Noise source

Claims (7)

A noise source contribution analysis device that analyzes the degree of contribution of a noise source sound pressure of each of a plurality of noise sources to a total sound pressure at an observation point to which the noise sources contribute,
a noise source sound pressure acquisition unit that acquires the noise source sound pressure detected in the vicinity of each of the plurality of noise sources;
a transfer function acquisition unit that acquires, for each of the plurality of noise sources, a transfer function that indicates a transfer characteristic of noise from the each of the plurality of noise sources to the observation point;
an observation point sound pressure calculation unit that inputs the noise source sound pressure corresponding to each of the transfer functions acquired for each of the plurality of noise sources by the transfer function acquisition unit, and outputs the outputs as observation point sound pressures;
a high frequency band extraction unit that extracts, as a high frequency band sound pressure, a high frequency band sound pressure from the observation point sound pressures calculated by the observation point sound pressure calculation unit;
a low-frequency band extraction unit that extracts, as a low-frequency band sound pressure, a low-frequency band sound pressure from the observation point sound pressures calculated by the observation point sound pressure calculation unit;
a total sound pressure calculation unit that calculates the total sound pressure at the observation point based on a sum of squares of high-frequency band sound pressures of each of the plurality of noise sources and a sum of low-frequency band sound pressures of each of the plurality of noise sources;
A noise source contribution analysis device comprising: a contribution calculation unit that calculates a degree of contribution of each of the plurality of noise sources to the calculated total sound pressure;
The noise source contribution analysis device according to claim 1, further comprising: The noise source contribution analysis device according to claim 1 or 2, characterized in that the cutoff frequency that is the boundary between the high frequency band and the low frequency band is set based on the distance between the noise source and the observation point. The noise source contribution analysis device according to claim 3, characterized in that the cutoff frequency is a frequency in which the distance between the noise source and the observation point is one wavelength. The noise source contribution analysis device according to claim 1 or 2, characterized in that the cutoff frequency that is the boundary between the high frequency band and the low frequency band is set based on the dimensions of the surface on which the noise source exists. A noise source contribution analysis method for analyzing the degree of contribution of each noise source to a total sound pressure at an observation point to which a plurality of noise sources contribute, comprising:
The computer used in the noise source contribution analysis device is
a noise source sound pressure acquisition step of acquiring the noise source sound pressure detected in the vicinity of each of the plurality of noise sources;
a transfer function acquisition step of acquiring, for each of the plurality of noise sources, a transfer function indicating a transfer characteristic of noise from each of the plurality of noise sources to the observation point;
an observation point sound pressure calculation step of inputting the noise source sound pressure corresponding to each of the transfer functions acquired for the plurality of noise sources in the transfer function acquisition step, and outputting the outputs as observation point sound pressures;
a high frequency band extraction step of extracting, as a high frequency band sound pressure, a high frequency band sound pressure from the observation point sound pressures calculated in the observation point sound pressure calculation step;
a low-frequency band extraction step of extracting, as a low-frequency band sound pressure, a low-frequency band sound pressure from the observation point sound pressures calculated in the observation point sound pressure calculation step;
a total sound pressure calculation step of calculating the total sound pressure at the observation point based on a sum of squares of high-frequency band sound pressures of each of the plurality of noise sources and a sum of low-frequency band sound pressures of each of the plurality of noise sources;
A noise source contribution analysis method that performs the above. In a noise source contribution analysis program that analyzes the degree of contribution of each noise source to the total sound pressure at an observation point to which multiple noise sources contribute,
The computer used in the noise source contribution analysis device is
a noise source sound pressure acquisition function for acquiring the noise source sound pressure detected in the vicinity of each of the plurality of noise sources;
a transfer function acquisition function that acquires, for each of the plurality of noise sources, a transfer function that indicates a transfer characteristic of noise from each of the plurality of noise sources to the observation point;
an observation point sound pressure calculation function that inputs the noise source sound pressure corresponding to each of the transfer functions acquired for each of the plurality of noise sources by the transfer function acquisition function, and outputs the outputs as observation point sound pressures;
a high frequency band extraction function for extracting, as a high frequency band sound pressure, a high frequency band sound pressure from the observation point sound pressures calculated by the observation point sound pressure calculation function;
a low-frequency band extraction function for extracting, as a low-frequency band sound pressure, a low-frequency band sound pressure from the observation point sound pressures calculated by the observation point sound pressure calculation function;
a total sound pressure calculation function that calculates the total sound pressure at the observation point based on the sum of squares of the high-frequency band sound pressures of each of the plurality of noise sources and the sum of the low-frequency band sound pressures of each of the plurality of noise sources;
A noise source contribution analysis program that demonstrates

Images