JP3046535B2 - Continuous monitoring of factory noise - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously monitoring noise generated in a factory separately from noise generated outside the factory.

[0002]

2. Description of the Related Art The noise generated in factories has a standard value determined by the Noise Control Law and the like as one of the factors that adversely affect the living environment in the surrounding residential area. Therefore, in a specific factory or the like having a specific facility that generates noise, it is necessary to measure factory noise. Since the noise regulation value is determined by the noise level at the boundary of the factory premises, the measurement of factory noise is usually performed at the boundary of the factory premises. In manned factory noise measurement, noise generated from outside the factory can be identified and removed, and only the factory noise can be evaluated. However, in unmanned factory noise measurement, noise generated from outside the factory is measured in the same manner as factory noise, and it is difficult to evaluate factory noise regulation values.

In the measurement of a moving sound source such as traffic noise, as a method of identifying a moving sound source by a spatial correlation method, two microphones are installed at a distance from each other, a time difference between incident noises is calculated by a cross-correlation method, and the moving sound source is calculated. A method of identifying and measuring (Proceedings of the Acoustical Society of Japan, pp. 293-294, April 1977) has been proposed.

Some noise measurement methods have been proposed for the purpose of improving the measurement accuracy of factory noise. For example, noise energy in a region where the noise level is small in a state where background noise in which the noise level fluctuates and stationary noise in which the noise level is almost constant is obtained, and the noise energy in the region where the noise level of the background noise is small is obtained from this noise energy. A method of obtaining the noise level of the stationary sound from the energy obtained by subtracting the energy (JP-A-58-191934)
Japanese Patent Application Laid-Open No. H10-157, the noise acoustic signal generated at a sound source to be measured by a unidirectional microphone is converted into a first measurement signal, and the acoustic signal including the noise acoustic signal is converted to a second measurement signal by a non-directional microphone. And the first and second measurement signals are Fourier transformed to obtain first and second measurement Fourier transform signals, and the first measurement Fourier transform signal is conjugated to obtain the second measurement Fourier transform A method of obtaining a noise measurement signal by multiplying the signal and dividing the result by the square operation result of the first measurement Fourier transform signal, and averaging the division operation result (Japanese Patent Publication No. 5-4).
3979).

[0005]

The above-mentioned various measuring methods cannot be directly applied to factory noise in which there are a plurality of target sound sources, the target sound sources are distributed over a wide range, and starting and stopping cannot be easily performed. Have difficulty.

That is, the moving sound source identification method based on the spatial correlation method can determine the moving sound source and measure its noise. However, since only the moving sound source is to be measured, factory noise is continuously monitored. It does not have a function of removing disturbances, and does not have a function of discriminating and removing fixed sound sources generated outside the factory, and cannot be directly applied to measurement of factory noise.

In the method disclosed in Japanese Patent Application Laid-Open No. 58-191934, it is necessary to stop a target sound source in a factory in order to measure noise outside the factory, that is, background noise.
In a factory having a plurality of sound sources, if the sound source cannot be stopped, this method cannot be applied.

Further, the method disclosed in Japanese Patent Publication No. 5-43979 measures a target sound source using a unidirectional microphone, and is therefore applicable to measurement of factory noise where the target sound source covers a wide area. Have difficulty.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the prior art, arbitrarily designate the direction of a sound source to be measured, discriminate and remove noise generated from other directions, and pass near a measurement point. It is an object of the present invention to provide a method of continuously monitoring factory noise that can accurately and accurately measure factory noise by recognizing and removing noise from an automobile or the like as a disturbance due to a moving sound source.

[0010]

Means for Solving the Problems The present inventors have conducted various tests and studies to achieve the above object. As a result, the direction of the target sound source, that is, the range of the factory is arbitrarily specified by the azimuth, and the noise within the specified azimuth from the outside of the factory such as road traffic noise, human voice, dog squeal, etc. By eliminating the generated noise, it was determined that the factory noise could be measured with high precision, and it was possible to evaluate the regulated value of the factory noise, and the present invention was reached.

That is, the present invention relates to a method of unmanned continuous monitoring of factory noise, in which a range of a factory to be measured at a measuring point is designated by an azimuth angle, and a noise level measured by an omnidirectional microphone and a sound level meter is used. Input the signal of the azimuth angle at which noise is generated from the direction identification probe with the sound intensity microphone installed in the axial or triaxial direction to the analysis unit, and use the least squares method of the direction of the sound source and the time at that time in the analysis unit From the results of the regression analysis, it is determined whether or not the sound source is moving and whether or not the sound source is generated from the factory side, and after removing moving sound sources such as road traffic noise and noise generated from outside the factory, A method for continuously monitoring factory noise, wherein the factory noise is obtained by an index to be evaluated.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below in connection with the case of identifying the directions of two axes. As shown in FIG. 1, the omnidirectional microphone 1 and the sound level meter 2 measure the noise level at the measurement point, and the A / D converter 3
To convert the analog signal into a digital signal and input it to the analysis unit 4. At the same time, the sound intensity in the X-axis and Y-axis directions is measured by the sound intensity microphones 11, 12, and 13 of the direction identification probe 5. The sound intensity is a ratio (W / m ² ) of energy flow per unit area of sound at a certain measurement point, and can be represented by a vector quantity having a magnitude and a direction. In sound intensity measurement, the amount of sound energy flowing perpendicularly to the microphone is measured. Therefore, by using a two-axis sound intensity microphone, the direction of the sound source, the noise Can be obtained. By arranging the two axes horizontally with respect to the measurement point, the azimuth of the sound source is represented by an azimuth.
When three-axis direction identification is performed, it is possible to obtain the elevation angle of the sound source by giving an angle in the vertical direction in addition to the horizontal direction.

In this case, the sound intensity in the X-axis direction is measured using the sound intensity microphones 11 and 12 as a pair of microphones. The sound intensity in the Y-axis direction is measured using the sound intensity microphones 12 and 13 as a pair of microphones. The sound intensity microphones 11 and 12 and the sound intensity microphones 12 and 13 are arranged at a certain angle, for example, as shown in FIG.
90 ° as shown in FIG. 2A, 4 ° as shown in FIG.
5 °, and 135 ° as shown in FIG. 2 (c). By arranging the two axes horizontally, the direction of the synthesized vector, that is, the azimuth θ of the sound source with respect to the measurement point can be obtained from the synthesis result of the vectors of the two horizontal axes. The sound intensity microphones 11 and 12 and the sound intensity microphone 1
The signals from 2 and 13 are passed through analyzers 6 and 7 to determine the sound intensity, and are converted from analog signals to digital signals by the A / D converter 3 and input to the analyzer 4.
In addition, the direction of the target sound source, that is, the range of the factory is arbitrarily specified and set in the analysis unit 4 by an azimuth.

In the analysis unit 4, as shown in FIG. 3, first, the noise level is reduced by 90% from a noise level of a past fixed period, for example, about 3 minutes.
The lower end value of the range is calculated, and a value obtained by adding an arbitrary level, for example, 4 dB to this value is set as a background noise value. This 4dB is
Since the level difference between the upper end value and the lower end value of the 90% range at this measurement point is almost 4 dB, it is set to 4 dB. Next, in the analysis unit 4, the azimuth of noise is calculated from the sound intensity in the X-axis and Y-axis directions. The azimuth θ of the noise is obtained by θ = tan ⁻¹ {(sound intensity in the Y-axis direction / sound intensity in the X-axis direction × sin α) − (1 / tan α)} when α is 90 °. In the case of α = 90 ° in FIG. 2A, it can be calculated as θ = tan ⁻¹ (sound intensity in the Y-axis direction / sound intensity in the X-axis direction). The analysis unit 4 determines whether or not the noise value is higher than the background noise value with respect to the processed noise value. If the noise value is lower than the background noise value, the noise is regarded as factory noise. When it is determined that the noise value is higher than the background noise value, it is determined whether the time during which the noise value exceeds the background noise value is longer than an arbitrary set time, for example, 4 seconds. The four seconds in this case is a time required for an object that generates noise such as a traffic vehicle to move, and is set according to the situation of the measurement point.

If it is determined that the time during which the noise value exceeds the background noise value is longer than 4 seconds, the noise value is determined to be transient noise. The transient noise is a loud noise generated temporarily by a fixed sound source such as a moving noise of a traffic vehicle, a human voice, a dog squeal and the like. The noise value determined as transient noise determines whether the sound source is a moving sound source. In this case, the determination conditions are obtained by regression analysis of the duration of the transient noise and the azimuth of the noise value at that time by the least squares method. The determination as to whether the sound source is a moving sound source is made based on the slope of the obtained regression line, that is, the amount of change in the azimuth per time and the correlation coefficient between the noise azimuth and the time regression line. The criterion for determining whether or not the sound source is a moving sound source is set according to the situation of the measurement point.
For example, when the moving speed of the moving sound source is considered to be fast, if the slope of the regression line is 6 ° / sec or more and the correlation coefficient is 0.4 or more, it is determined that the moving sound source is moving, and the moving speed of the moving sound source is considered to be slow. In this case, if the slope of the regression line is 2.5 ° / sec or more and the correlation coefficient is 0.6 or more, it is determined as a moving sound source.
It is necessary to set the conditions according to the entity.

If the sound source is determined to be a moving sound source, the noise is generated from outside the factory, such as road traffic noise. If it is determined that the sound source is not a moving sound source, it is determined whether the azimuth of the noise is on the factory side. In this case, the direction in which the factory is located is specified in advance using the azimuth. If it is determined that the azimuth of the noise is not on the factory side, it is determined that the noise is outside the factory.

When it is determined whether the time during which the noise value exceeds the background noise value is longer than 4 seconds, if the noise value is shorter than 4 seconds, it is determined whether the noise value is higher than an arbitrary set level, for example, 55 dB. I do. The noise in this case is considered to be generated from a fixed sound source. The set level of 55 dB is a level of noise that does not normally occur in a factory. If the noise value of the fixed sound source is lower than an arbitrary set level, this noise value is regarded as factory noise. If the noise value of the fixed sound source is higher than an arbitrary set level, it is determined whether or not the azimuth of the noise is on the factory side. In this case, the abnormal sound is directed toward the factory. Next, the analysis unit 4 calculates, for example, the upper end value and the median value of the 90% range using the noise value of the fixed sound source lower than the arbitrary set level and determined to be the factory noise.

As shown in FIG. 4, in addition to the X and Y axes, the sound intensity microphone 1
5, the direction identification of the noise is added to the azimuth θ of the two axes (X axis and Y axis) of the horizontal plane as shown in FIG. 5, and the sound intensity microphones 12 and 14 are used as a pair of microphones. The elevation angle δ can be obtained by measuring the sound intensity in the Z-axis direction (vertical direction). This is because the transient noise is determined in both the direction and the height with respect to the measurement point by combining the three-axis vectors, so that the identification accuracy is further improved.

When the sound intensity microphones are installed in the directions of three axes, the elevation angle as shown in FIG. Since the range can be designated from the site boundary 22 of the factory 21 by δ, the designated range can be further limited. Therefore, the noise caused by the traffic vehicle 23 distant from the site boundary 22 becomes noise outside the factory 21 and is discriminated and removed. In the analysis unit in the case of three axes, the signal from the direction identification probe is increased by one axis, and the synthesis of the vectors is performed only on three axes. Therefore, the analysis unit can be easily changed to three axes.

The above analysis makes it possible to identify the moving sound source and the azimuth of the fixed sound source. The noise from the moving sound source and the noise from the fixed sound source that is not on the factory side are used for the calculation of the factory noise. As a result, high-precision continuous monitoring of factory noise is possible.

The factory noise regulation value is a value determined by the Noise Regulation Law and the like. Factory noise measurement is JIS Z87
The measurement is performed in accordance with the method for measuring environmental noise specified in 31 and is represented by a time rate noise level. The time rate noise level is the ratio of the time when the noise level is a certain level or more to the actual measurement time. The 5% time rate noise level is the upper limit of the 90% range, and the 50% time rate noise level is the median value. is there.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG.
1. Acoustic intensity microphone at X-axis and Y-axis at 9
A direction identification probe 32 composed of an acoustic intensity microphone set at 0 ° is moved from a factory 33 to a park 34.
And the location of the measurement point at a location corresponding to the site boundary of the factory 33 across the road 35, the factory 33 side is 90 ° vertically, 0 ° to 180 ° horizontally, and the omnidirectional microphone 31 and the direction The identification probe 32 was installed at a height of 15 m. In the direction identification, in order to identify only the horizontal component based on the two-axis acoustic intensity, the X-axis and the Y-axis were set horizontally to determine the azimuth. The range of the azimuth angle of the factory 33 was set in the range of 30 ° to 150 °. Therefore, the traffic noise of the vehicle traveling on the road 35, the voice of a person or the noise of a dog emitted in the park, and the like are included in this angle range. Therefore, the factory noise to be measured has an azimuth of 3
The result is that disturbance is removed with noise in the range of 0 ° to 150 °.

FIGS. 8 to 10 show examples of the results of actual measurement of factory noise by the method of the present invention with the above arrangement. FIG. 8 shows the result of identifying the road traffic noise of the vehicle traveling on the road 35 as a moving sound source. At this time, the azimuth of the noise is moving from 25 ° to 140 °, and the duration of the noise is 8 seconds. The result of this regression analysis is Y = 2
It was represented by a regression linear equation of 4.4X + 11.5, and the correlation coefficient was 0.96. Therefore, the road traffic noise of the vehicle traveling on the road 35 is accurately identified as a moving sound source.

FIG. 9 shows the result of discriminating a voice intentionally uttered by a person in the park 34 as fixed noise. At this time, the azimuth of the noise is about 100 ° and the duration of the noise is 5 hours.
Seconds. The result of this regression analysis is Y = 0.4X + 1
It was represented by a regression linear equation of 06.0, and the correlation coefficient was 0.10. Therefore, the voice of the person uttered in the park 34 is correctly identified as a fixed sound source.

FIG. 10 shows 90% of factory noise per hour.
The calculation result of the upper end value of the range is shown. The broken line is the calculation result from the measurement result before the disturbance is removed, and the solid line is the calculation result from the measurement result after the disturbance is removed. As shown by the solid line in FIG. 10, it is clear that noise caused by traffic vehicles, which is particularly common in the daytime, is removed, and the measurement accuracy of factory noise is improved as compared with the case shown by the broken line in FIG. 10.

[0026]

As described above, according to the method of the present invention, it is possible to identify the moving sound source and the azimuth of the fixed sound source. Since the noise measurement value from which the noise from the fixed sound source is removed is used, it is possible to continuously monitor the factory noise with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of a flow of a measurement signal according to the method of the present invention.

FIGS. 2A and 2B are explanatory diagrams illustrating a combination of an installation angle of an acoustic intensity microphone and a vector in an X-axis direction and a Y-axis direction used for sound intensity measurement, FIG. 2A being 90 °, FIG. c) The figure is for 135 °.

FIG. 3 is a flowchart of a calculation in an analysis unit.

FIG. 4 shows the X axis and Y used for sound intensity measurement.
FIG. 6 is an explanatory diagram of vector synthesis when acoustic intensity microphones are installed in the axis and Z-axis directions.

FIG. 5 is an explanatory diagram of an azimuth angle and an elevation angle centered on a direction identification probe.

FIG. 6 is an explanatory diagram showing an example of an elevation angle designation in a target noise range designation.

FIG. 7 is a plan view showing an installation position of the noise measuring device in the embodiment.

FIG. 8 is a chart showing the relationship between time, noise level, and azimuth as a result of identifying traffic noise of a vehicle traveling on a road as a moving sound source.

FIG. 9 is a chart showing the relationship between time, noise level, and azimuth as a result of identifying a human voice emitted in a park as a fixed sound source.

FIG. 10: 9 per hour before and after disturbance removal of factory noise
FIG. 9 is a chart illustrating a relationship between a time of a calculation result of an upper end value of a 0% range and a noise level.

[Explanation of symbols]

1, 31 omnidirectional microphone 2 sound level meter 3 A / D converter 4 analysis unit 5, 32 direction identification probe 6, 7 analyzer 11, 12, 13, 14 sound intensity microphone 21, 33 factory 22 site boundary 23 traffic Vehicle 34 Park 35 Road α Installation angle θ Azimuth δ Elevation

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kunihiko Otsuka 1850 Minato, Wakayama City, Wakayama Prefecture Sumitomo Metal Industries, Ltd. Wakayama Works (72) Inventor Yu Yu Tomoi 3- 25-13 Tarumicho, Suita-shi, Osaka Matsushita (56) References JP-A-58-191934 (JP, A) JP-A-6-249704 (JP, A) JP-A 60-378 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) G01H 3/00-3/14 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A method for unmanned and continuous monitoring of factory noise, wherein a range of a factory to be measured at a measurement point is designated by an azimuth angle, and a noise level measured by an omnidirectional microphone and a sound level meter is compared with two axes or three axes. The signal of the azimuth angle where noise is generated from the direction identification probe with the acoustic intensity microphone installed in the direction of the axis is input to the analysis unit, and the regression analysis by the least squares method of the direction of the sound source and the time at the analysis unit in the analysis unit From the results of the above, it is determined whether the sound source is moving and whether the sound source is generated from the factory side, and after removing the moving sound source such as road traffic noise and noise generated from outside the factory, A method for continuous monitoring of factory noise, characterized in that noise is determined by an index to be evaluated.