JP5390447B2 - Method for estimating noise countermeasure effect - Google Patents

Description

  The present invention relates to a method for estimating in advance an effect amount when measures are taken against specific noise such as road traffic and factories by a beamforming method using a sound source exploration apparatus.

  A beam forming method is known as one of sound source visualization methods using a sound source exploration apparatus. When implementing this method, first, a plurality of microphones constituting the sound source exploration device are arranged at predetermined intervals in a vertical direction at a certain distance from the sound source to be searched, and the sound waves generated from the sound source. Is input to each microphone, and the sound pressure value of the sound wave input to each microphone is converted into an electrical signal and output. Next, the output signals are integrated after correcting and adding the time difference by a delay circuit, and calculation processing is performed to calculate the volume (sound pressure), frequency, and vector quantity of the sound generated from the sound source.

  Then, an arbitrary range (analysis target range) of a virtual vertical plane including a sound source (a plane that can be superimposed and matched with an image captured from the position of the sound source exploration device with the sound source in the viewing angle) at an arbitrary interval Divide into vertical and horizontal meshes, calculate the sound pressure level for each mesh based on the above calculated data, and create an isoline map color-coded for each range of sound pressure level based on those calculated data Visualize.

  According to the beam forming method using this sound source exploration device, it is possible to accurately grasp the position and size of the sound source, so when noise countermeasures such as road traffic are to be implemented, the cause of noise generation is specified. Is used in preliminary surveys.

WO2004 / 021031

  By the way, there are often a plurality of noise sources in the noise that is considered for countermeasures in road traffic and the like. In such a case, if noise countermeasures are to be implemented for all noise sources, a great deal of cost and labor is required, which is inefficient. Therefore, by using the beam forming method using the sound source exploration device, if it is possible to grasp in advance the effect amount (noise countermeasure effect amount) when noise countermeasures are implemented for individual noise sources, the minimum necessary It is considered that the noise countermeasure plan can be efficiently formulated and executed with the cost and labor of However, if the beam forming method is simply used, the position and size of the noise source can be accurately grasped, but the noise countermeasure effect amount cannot be grasped for each noise source.

  From this point of view, the present invention provides a method for grasping a noise countermeasure effect amount with sufficient accuracy in advance based on information obtained by using a beam forming method using a sound source search device. With the goal.

  The noise countermeasure effect amount estimation method according to the present invention includes a first step of measuring a noise to be countermeasured by a sound source exploration device and calculating a sound pressure level, a frequency, and a vector amount of the noise, and an analysis target range. For each mesh obtained by dividing the analysis target range in the second step based on the data calculated in the second step and the data calculated in the first step. A third step for calculating the overall sound pressure level value, a fourth step for calculating the total energy amount of the noise within the analysis target range set in the second step, and the data calculated in the first step. In addition, the sound pressure level value for each mesh divided within the analysis target range in the second step is calculated for each frequency, and among these, the contribution of noise that is the countermeasure target The mesh data of the highest frequency is selected, and in the mesh data of the selected frequency, the countermeasure target is based on the attenuation width value (for example, 3 dB) determined in advance based on the directivity characteristics of the sound source search device to be used. The fifth step for setting the noise range, the sixth step for calculating the total energy amount of noise within the countermeasure target noise range set in the fifth step, and the total energy amount of noise within the analysis target range in the fourth step The seventh step of calculating the contribution degree of the total energy amount of the noise within the countermeasure target noise range in the sixth step is performed.

  In this noise countermeasure effect estimation method, the integrated value of the sound pressure level in the range indicated as the sound source in the mesh data of the sound pressure level acquired for a certain sound source matches the sound power level of the sound source. A width value from the sound source center for defining the mesh range to be calculated is calculated in advance based on the directivity characteristics of the sound source exploration device to be used, and this is calculated as the countermeasure target noise range in the fifth step. The noise width used when determining the noise range, and the noise range for which the sound pressure level is reduced from the mesh of the highest sound pressure level in the mesh data of the frequency selected in the fifth step It is preferable to set it as the range.

  In addition, the noise countermeasure effect amount estimation method according to the present invention can be executed for single-shot noise (point sound source noise), and also can be executed for moving sound source noise (linear sound source noise). You can also

  According to the method of the present invention, when noise countermeasures are taken under a road overpass or along a road where a large number of sound sources exist, or a factory, etc., by utilizing noise measurement data at the site boundary line Before taking actual noise countermeasures, it is possible to quantitatively estimate the noise countermeasure effect amount at each individual location. The method according to the present invention can also be applied to a moving sound source, and it is possible to quantitatively estimate a countermeasure effect amount by a sound insulation wall against road traffic noise.

FIG. 1 is a conceptual diagram relating to “setting of countermeasure target noise range” of the fifth step in the noise countermeasure effect estimation method according to the present invention.

Hereinafter, an embodiment for carrying out the “method for estimating the noise countermeasure effect amount” according to the present invention will be described. First, the outline will be described. The noise countermeasure effect estimation method according to the present invention is implemented by sequentially executing the following steps.
1st step Measurement of sound pressure level 2nd step Setting analysis target range 3rd step Calculation of overall sound pressure level value for each mesh 4th step Calculation of total energy amount of noise in analysis target range 5th step Analysis by frequency Setting of the target noise range based on the results Step 6 Calculation of the total amount of noise within the target noise range Step 7 Calculation of the noise countermeasure effect

  Next, details of each step will be described.

First step (measurement of sound pressure level)
A plurality of microphones constituting the sound source exploration device are arranged at predetermined intervals in the vertical direction at a certain distance from the sound source of the noise to be analyzed, and the noise is measured and an electrical signal is output and output. The signals are integrated after correcting and adding the time difference by a delay circuit, and calculation processing is performed to calculate the sound pressure level, frequency, and vector amount of noise.

Second step (setting of analysis target range)
An analysis target range is set in a virtual vertical plane including a noise source (a plane that can be superimposed and matched with an image captured by placing the sound source in the viewing angle from the position of the sound source search device). Then, the set analysis target range is divided into meshes vertically and horizontally at arbitrary intervals.

Third step (calculation of overall sound pressure level for each mesh)
Based on the data (sound pressure level, frequency, vector quantity) calculated in the first step, the overall sound pressure level value (sound pressure at each frequency) for each mesh divided within the analysis target range in the second step. Calculate the total level).

Fourth step (calculation of the total amount of noise within the analysis target range)
The total energy amount of noise within the analysis target range set in the second step (overall synthesized sound pressure level value of the analysis target range) is calculated by the following equation.
L: Total energy amount of noise within the analysis target range L1, L2, L3 ...: Overall sound pressure level value in each mesh

5th step (setting of the noise range for countermeasures based on the analysis result by frequency)
Based on the data (sound pressure level, frequency, vector amount) calculated in the first step, the sound pressure level value for each mesh obtained by dividing the analysis target range in the second step is calculated for each frequency. And the mesh data of the frequency with the highest contribution of the noise used as countermeasure object are selected from them.

  Next, a countermeasure target noise range is set in the mesh data of the selected frequency. Specifically, a range (attenuation width P) from the highest sound pressure level in the mesh data of the selected frequency to a sound pressure level several dB lower than that is set as the countermeasure target noise range.

  The value of the attenuation width P (unit: dB) is determined in advance based on the directivity characteristics of the sound source exploration device used for the measurement of the sound pressure level in the first step. When an isoline diagram (mesh-like plan view visualizing a sound source) is created by the beamforming method, the value obtained by integrating the sound pressure levels of all meshes within the range (spatial width) indicated as the sound source The sound power level of the sound source does not necessarily match, and the directivity characteristics of the beamforming method vary depending on the sound source exploration device used. Therefore, the integrated value and sound power level of all sound pressure levels in the sound source range This is because the shift width of the sound source also varies depending on the sound source exploration device to be used. Therefore, of the range indicated as the sound source in the mesh data of the sound pressure level, the range of the mesh in which the integrated value of the sound pressure level matches the sound power level of the sound source, and such a range are specified. Value (width value from the center of the sound source), that is, how much width is extracted from the center of the sound source and the sound pressure level is integrated to match the sound power level of the sound source This is calculated in advance based on the directivity characteristics of the sound source exploration device to be used, and this is set as the attenuation width P.

6th step (calculation of the total amount of energy of noise within the target noise range)
The total energy amount of noise within the countermeasure target noise range set in the fifth step (overall synthesized sound pressure level value of the countermeasure target noise range) is calculated by the following equation.
J: Total energy amount of noise within the target noise range J1, J2, J3 ...: Overall sound pressure level value for each mesh within the target noise range

7th step (calculation of noise countermeasure effect)
The contribution of the total energy amount J of noise within the target noise range of the sixth step to the total energy amount L of noise within the fourth step analysis target range is calculated by the following formula, and this is calculated as the noise countermeasure effect. Consider quantity.
K: Noise reduction effect (J's contribution to L)
L: Total amount of noise within the analysis target range J: Total amount of noise within the target noise range

  Here, regarding the estimation method of the noise countermeasure effect amount according to the present invention, the results of tests conducted by the inventors of the present invention will be described as examples of the present invention.

  With respect to the attenuation width P (unit: dB) set in the fifth step of the present invention, an indoor measurement test was performed to confirm the accuracy of the theoretical value.

  A speaker (sound source) and a Spectris Co., Ltd. sound source exploration device (product name: long-distance sound source exploration device using optimized beam forming method) are installed in a semi-anechoic room at a predetermined distance. Output sound (pink noise) was measured with a sound source probe. The directivity characteristic of this sound source exploration device is theoretically designed to match the sound power level by integrating a space (range) that is 3 dB lower than the highest sound pressure level (sound source center). Therefore, as a result of setting the attenuation width P to 3 dB and integrating the range from the sound source center down to 3 dB, the sound power level was 83.8 dB. On the other hand, the result of measuring the sound pressure level with a precision sound level meter installed at a position 3 m away from the sound source was 65.9 dB. When the sound power level was estimated from the measured value of the sound pressure level using the distance attenuation formula, it was 83.4 dB. When these were compared, the error was 0.4 dB, and it was confirmed that the accuracy was sufficiently high with respect to the maximum error tolerance (± 2.0 dB) indicated by “JIS Z 8732”.

  Next, using the sound source exploration device of Example 1, the noise countermeasure effect amount estimation method according to the present invention is implemented, and the noise level before and after the actual noise countermeasure is measured using a precision sound level meter. The accuracy was confirmed.

  First, as a first step, a sound source exploration device is installed at a position some distance away from the noise source to be analyzed (the road viaduct joint), and the noise of the joint (noise generated when the vehicle passes through the joint) Measurements were made.

  Next, as a second step, an analysis target range is set in a virtual vertical plane including a road viaduct joint that is a direct noise source, and the set analysis target range is vertically and horizontally spaced at an arbitrary interval. It was divided into meshes. It should be noted that when setting the analysis target range, it is desirable to include not only a direct noise generation source but also a portion assumed to be an indirect noise generation source by reflection, diffraction, or the like.

Moreover, it is desirable that the interval between the meshes when the set analysis target range is divided vertically and horizontally is smaller than the reference mesh interval C calculated by the following equation.
C = (λ / 2) × (D / R)
C: Reference mesh interval λ: Wavelength D: Distance from sound source to measurement position (installation point of microphone of sound source search device) R: Diameter of microphone array of sound source search device (3 m in this embodiment)

  Subsequently, as a third step, an overall sound pressure level value was calculated for each mesh obtained by dividing the analysis target range based on the data calculated in the first step. By using this beam forming method, the position and size of the sound source can be visualized, so that the position of the noise generation source that is the countermeasure target can be specified. In this embodiment, the sound source is one place.

  Next, as the fourth step, the total energy amount of the noise within the analysis target range set in the second step was calculated using the above equation (1). In this example, the total energy amount of noise within the analysis target range was 105.4 dB.

  Next, as a fifth step, based on the data calculated in the first step, the sound pressure level value for each mesh obtained by dividing the analysis target range in the second step is calculated for each frequency, and the calculated data is Based on this, an isoline map was created for each frequency. Then, data having a frequency of 400 Hz with the highest sound pressure level of the mesh that is the center of the sound source is selected from among them, the attenuation width P is set to 3 dB, and the countermeasure target noise range is set. That is, the range of noise that was reduced by 3 dB from the highest sound pressure level (sound source center) in the selected frequency data was taken as the countermeasure target noise range.

  FIG. 1 is a conceptual diagram regarding the setting of the countermeasure target noise range. In this figure, A indicates the analysis target range, B indicates the countermeasure target noise range, P indicates the attenuation width, and X indicates the mesh having the highest sound pressure level in the range indicated as the sound source. In this figure, the display of the sound pressure level for each mesh is omitted.

  Subsequently, as a sixth step, the total energy amount of the noise within the countermeasure target noise range set in the fifth step was calculated using the above-described equation (2). As a result, the total energy amount of the noise within the countermeasure target noise range was 101.8 dB.

  Finally, as the seventh step, the degree of contribution (noise countermeasure effect amount) of the total noise amount within the target noise range to the total noise amount within the analysis target range is calculated using the above equation (3). As a result, it was 2.5 dB. On the other hand, the noise level difference before and after the implementation of noise countermeasures measured using a precision sound level meter was 2.0 dB. From this result, it was confirmed that the noise countermeasure effect amount can be estimated with sufficient accuracy according to the method of the present invention.

  In the present embodiment, the sound source is one place as described above. However, when there are a plurality of sound sources, the countermeasure target noise range of the fifth step is set for each sound source, and each countermeasure target is set. By performing the processes of the sixth step and the seventh step on the noise range, the contribution degree of each sound source can be calculated.

  Furthermore, for the other noise generation sources, the noise countermeasure effect amount estimation method according to the present invention is implemented using the sound source exploration device according to the first embodiment as in the second embodiment, and a precision sound level meter is used. The noise levels before and after actual noise countermeasures were measured to confirm the accuracy.

  First, as a first step, a sound source survey device was installed at a certain distance from the noise generation source (highway) to be analyzed, and the noise of automobiles traveling on the highway (so-called road traffic noise) was measured. .

  Next, as a second step, an analysis target range is set in a virtual vertical plane including a highway that is a direct noise generation source, and the analysis target range is meshed vertically and horizontally at arbitrary intervals within the set analysis target range. Divided into

  Subsequently, as a third step, an overall sound pressure level value was calculated for each mesh obtained by dividing the analysis target range based on the data calculated in the first step.

  Next, as the fourth step, the total energy amount of the noise within the analysis target range set in the second step was calculated using the above equation (1). In this example, the total energy amount of noise within the analysis target range was 114.7 dB.

  Next, as a fifth step, based on the data calculated in the first step, the sound pressure level value for each mesh obtained by dividing the analysis target range in the second step is calculated for each frequency, and the calculated data is Based on this, an isoline map was created for each frequency. Then, data of a frequency of 2000 Hz assumed to be a noise generation source was selected from them, the attenuation width P was set to 3 dB, and the countermeasure target noise range was set.

  Subsequently, as the sixth step, the total energy amount of the noise within the countermeasure target noise range set in the fifth step was calculated using the above “Equation 2”. In the present embodiment, among the total energy amount of noise within the countermeasure target noise range, the noise energy amount of the direct sound (diffracted sound) is 110.2 dB, and the energy amount of the noise of the reflected sound from the elevated back surface of the direct bridge is 110. .3 dB.

  Finally, as a seventh step, the degree of contribution (noise countermeasure effect amount) of the total noise amount within the target noise range to the total noise amount within the analysis target range is calculated using the above “Equation 3”. As a result, the direct sound (diffracted sound) was 1.9 dB, and the direct reflected viaduct of the viaduct was 2.0 dB, which was 3.9 dB in total. On the other hand, the noise level difference before and after the implementation of noise countermeasures measured using a precision sound level meter was 3.0 dB. From this result, it was confirmed that the noise countermeasure effect amount can be estimated with sufficient accuracy according to the method of the present invention.

A: Analysis target range,
B: Countermeasure noise range,
P: attenuation width,
X: Mesh with the highest sound pressure level

Claims (4)

A first step of measuring the noise to be countermeasured by the sound source exploration device and calculating the sound pressure level, frequency, and vector quantity of the noise;
A second step of setting an analysis target range and dividing the range into a mesh shape vertically and horizontally at an arbitrary interval;
A third step of calculating an overall sound pressure level value for each mesh obtained by dividing the analysis target range of the second step based on the data calculated in the first step;
A fourth step of calculating a total energy amount of noise within the analysis target range set in the second step;
Based on the data calculated in the first step, the sound pressure level value for each mesh obtained by dividing the analysis target range in the second step is calculated for each frequency. Select the mesh data of the frequency with the highest contribution, and in the selected mesh data of the selected frequency, determine the noise range to be countermeasures based on the value of the attenuation width determined in advance based on the directivity characteristics of the sound source exploration device to be used. A fifth step to set,
A sixth step of calculating a total energy amount of noise within the countermeasure target noise range set in the fifth step;
And a seventh step of calculating a contribution degree of the total energy amount of noise within the countermeasure target noise range of the sixth step to the total energy amount of noise within the analysis target range of the fourth step. To estimate the noise countermeasure effect.   Among the ranges shown as sound sources in the mesh data of the sound pressure level acquired for a certain sound source, the value obtained by integrating the sound pressure level to specify the mesh range that will match the sound power level of the sound source, The value of the width from the sound source center is calculated in advance based on the directivity characteristics of the sound source exploration device to be used, and this is set as the attenuation width used when the countermeasure target noise range is determined in the fifth step. The range is a range from a mesh having the highest sound pressure level to a mesh having a reduced sound pressure level corresponding to the attenuation width in the mesh data of the frequency selected in the fifth step. The method for estimating the noise countermeasure effect amount according to 1.   3. The noise countermeasure effect amount estimation method according to claim 2, wherein the attenuation width value is 3 dB.   The noise countermeasure effect amount estimation method according to any one of claims 1 to 3, wherein the noise countermeasure effect amount according to any one of claims 1 to 3 is targeted for a point sound source noise generated in a single shot or a line sound source noise caused by a moving sound source.