JPS58191934A - Method for measuring stationary sound under existence of background noise - Google Patents

Abstract

PURPOSE:To obtain the noise level of stationary sounds, by obtaining the energy difference of sounds between the level of a background noise and each state of a region having a lower noise level in the state where the background noise and stationary sounds are mixed. CONSTITUTION:The first measuring point P1 is provided in the place where the traffic noise of a road 10 and the factory noise of a factory 12 are mixed, and the noise level is measured; and the second measuring point P2 is provided near a residence section 14,where the factory noise can be ignored, separated sufficiently from the factory 12, and the noise level is measured. At the measuring point P2, there are no noise sources except the traffic noise. The level of the background noise measured at the measuring point P2 is subtracted from the noise level measured at the measuring point P1 to obtain accurately the noise level of stationary sounds generated from the factory 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the noise level of stationary sound in a place where it is difficult to eliminate background noise where the noise level fluctuates.

The Noise Control Law and other regulations set standard values for noise levels in order to prevent many temples from setting up loud noises that destroy the living environment. Therefore, it is important to know the noise level generated from a specific noise source for mf ISh countermeasures.1 However, in general, noise generated from multiple noise sources exists at the same time, and it is important to know the noise level generated from a specific noise source. It is difficult to measure just the amount of noise generated from the noise source. Therefore, the noise level z df3 of the noise generated from a specific noise source (hereinafter referred to as target sound) is measured by a noise measuring device at the measurement point & the noise level is x df4,
When the noise level of the lIt@ sound (sound other than the target sound) at the measurement point is 2yd13, it is estimated by the following equation.

5yZ=10og(10I0-10) ・・・・・・
・・・・・・・・・・・・ (1) That is, measure the noise level X in a state where the target sound and background noise are mixed, and then stop the generation of the target sound. The noise level 2 of the target sound is estimated from equation (1) by measuring the level y and finding the sound energy difference from x Even if the noise level is constant, X also changes as y changes, so it is not possible to estimate the noise level 2 of the stationary sound by applying equation (1).

One example of this is estimating the noise generated from a factory or the like whose premises are in contact with a road. In this case, background noise is
Traffic noise that continuously fluctuates in volume level,
Steady noise refers to noise, such as factory noise, that remains at a constant volume level for a relatively long period of time compared to dark wi II sound.

In other words, although steady noise also changes depending on the direction of the wind, the difference between daytime and nighttime, and the operating status of the factory, it is estimated that the volume level remains at a constant level at least during the noise measurement (1 to 2 hours). This is Mf.

The present invention was made in order to eliminate the drawbacks of the conventional hIJ arrangement technology, and provides a method for measuring steady sound that can estimate the noise level of the foot if even if the noise level of background noise changes greatly. The purpose is to

The present invention eliminates background noise such as traffic noise at the Kennego fixed point.
Because it is strongly influenced by large special vehicles, etc., when looking at the distribution of approximately 1000 measured noise levels, the average value and median value fluctuate significantly, so the noise level of stationary sound at that time is estimated from the entire data. This is based on the discovery that the distribution of background noise does not maintain a nearly constant value in areas where the level of background noise is low, although it is difficult to do so.

The present invention measures the noise level in a state where background noise and steady sound are mixed, measures the noise level of the background noise in a state where the steady I can be ignored, and calculates the level of noodle flavor from these measured noise levels. The device is configured to determine the energy difference between the sounds in each state marked # in a small area, and determine the noise level of the stationary sound from the results.Next, measurements using the stationary sound measurement method according to the present invention. Directly bend JIA theory.

FIG. 1 is a diagram showing a 911 degree distribution of traffic noise measured at 5 second intervals at measurement points where there is no stationary sound such as factory noise. The horizontal axis shows the level in dB, and the vertical axis shows the level of noise generation. In addition, the actual MA is the distribution measured from midnight to 2 a.m. when traffic volume is low, and - straight chain #B is the distribution measured from 2 a.m. when traffic volume is high.
This is the distribution measured between midnight and 4 a.m.

As shown in FIG. 1, the distribution curves of the solid line A and the straight chain line B in the region of low noise level match well.

However, in an area with a high noise level, there is a difference between the solid line A and the straight chain @B due to the influence of large special vehicles that generate large noises, although the number of passing vehicles is small.

Note that the noise level is the logarithm of sound energy, so when the noise level distribution in FIG. 1 is converted into an energy distribution, it becomes as shown in FIG. 2. When the M sound level is 50 dB and 60 dB, the energy is 1
There is a difference of 0 times, 50dB and 70dB and -rhioo
There is a 1000 times difference between 50 dB and 80 dB, and the difference between real MA and single-chain MA in areas with high noise levels.
It can be seen that the energy difference between B and B is very large. However, in a region where the noise level is low (a portion smaller than a in FIGS. 1 and 2), the two also match well in energy distribution. That is, the frequency of noise occurrence in areas where the noise level of traffic noise is low is not affected by the amount of traffic or the amount of traffic.

Therefore, even if the noise level of ll1t noise varies greatly, if the noise level of background noise can be measured in an area where the noise level is small, the noise level of stationary sound can be estimated using equation (1). .

A preferred embodiment of the method for measuring steady sound in the presence of background noise according to the present invention will be described below with reference to the accompanying drawings.
FIG. 3 is a diagram showing the vicinity of till1 foot point ti when measured according to an embodiment of the present invention.

In FIG. 3, the factory 12 is located at 1411 on one side facing the road 10, and the area on the opposite side of the road 100 facing the factory 12 is a residential area 14. Vehicles passing on the road 10 do not change day and night, and traffic noise, which is background noise, cannot be excluded. Therefore, it is difficult to measure only factory noise, which is stationary noise.

Therefore, first, the noise level is measured at a place where traffic noise and factory noise coexist, that is, at the first measurement point P1 facing the road of the factory 12. In addition, a second measurement site facing the road 10 is located at a location sufficiently far away from the factory 12 on the road 10 where the factory 12 is located, where factory noise can be ignored (for example, a location 500 shoulders or more away from the factory 12). The noise level is also measured at point P. Note that the second measurement point P is
There are no major noise sources nearby other than traffic noise.

An example of the frequency distribution of the noise level at the first measurement point P is shown in FIG. 4, and an example of the frequency distribution of the noise level at the second measurement point P is shown in FIG. Since Figure 4 is the sum of traffic noise and factory noise, generally the sound energy is calculated from the average value of the noise level in Figure 4, and the energy of the sound is calculated from the average value of the noise level in Figure 5. The noise level of the factory noise can be obtained by subtracting the energy of the bamboo and considering the value as the sound energy of the factory noise. As the average value of the noise level at fixed point P, which is calculated as the sum of traffic noise and factory noise, changes, the average value of the noise level at the 1st I11 fixed point P, which is calculated as the sum of traffic noise and factory noise, also changes. 1, so the traffic noise is
As mentioned above, the area with low noise level shows a constant distribution regardless of the traffic volume or the type of passing vehicle.
The area where the noise level is small at the first fill fixed point A P and the second fill fixed point P (?+1, for example,
, the following areas and the area below y6 in Figure 5), the noise level of the factory can be determined by determining the energy level of both sounds.1, Therefore, the cumulative frequencies of the measured noise levels are equal. 'I,'N... in Figure 4
...X.

From the fifth factor Yt, Vt...y, the factory noise is calculated using the second equation, where VCi = 1.2...6.

Next, at the first measurement point P1 and the second measurement point P, 5
The noise level was measured 1000 times at second intervals for 5000 seconds, and the results of the factory noise are shown in Table 1 Table 1 At the first measurement point P1, the noise level was 50.6 dB.
50 times (5 arrogance), the same < 50.8d
There were 100 times (10%) when B or higher was achieved. Also, the second
At measurement point P, the noise level is 472d13 or higher)
There were 50 times (5 fights) and the same (48,0d13 and above)
There were 100 times (10 chis), and when the cumulative frequency was 30 chis or less, zt was almost constant and
It was 7 to 48 dB. Therefore.

The noise level in the field can be estimated to be 47 to 48 dB. In addition, in a region where the cumulative frequency is 35 or more, an inconvenient result occurs in that the noise level is lower at the first measurement point P, where there is a lot of field noise, than at the second measurement point P, where there is no factory noise. In some cases.

- It can be verified that the constant value Kl is factory noise as follows.

That is, dummy sounds with a known amount of sound energy are generated randomly over time, and traffic noise and dummy sounds are mixed (4E).
Measure the touch B-level xi in the state of
! ! It is sufficient to measure the noise level ya of only the 1tIlk sound and confirm that zl obtained from equation (2) is equal to the dummy sound at a certain cumulative frequency α- or less.

By the way, the - sound i+ is subject to measurement errors due to the influence of wind speed, etc., and in order to check the energy of the target sound, it is necessary to actually generate f (dummy f) with known energy. Also, know the energy of the target at the source of the target (
The best way to confirm this is to generate a dummy sound at the source of the logarithmic sound. Then, by detecting randomly generated dummy sounds and calculating the difference in sound energy between the presence and absence of the dummy sound and performing statistical analysis, we found that It was found that the Illll method for the target sound was good.
The energy of the obtained target sound can be detected.

Therefore, it was verified using the apparatus shown in FIG. 6 that the level of the stationary sound determined in the above embodiment was correct.

The dummy sound generator 120 consists of a general noise V generator 22 that generates a sound of 20 to 20,000 Hz and a low frequency sound generator 24 that generates a sound of 5 to 10 ax. It consists of wave sound and audible noise. The nine dummy sounds randomly generated in the dummy sound generator 20 are simultaneously measured by the low frequency microphone 26 and the noise needle 28 in the presence of background noise, and the measured values are generally used in microcomputers and the like. The data is input to the data processing device 30 located therein. Based on the input measurement values, the data processing device 30 classifies the low-frequency sound into cases where the low-frequency sound is above the one-step level (background noise + dummy sound) and the case where the low-frequency sound is below the one-step level (background noise only). Collecting 1000 measurement data, 5% value of cumulative frequency, 10 chronological value...
Calculate the 95 fight value. The respective 5-chi values, 10-chi values, . . . 95-ch values obtained by classifying whether there is a dummy sound or not are displayed on a display device 32 such as a printer. Thereafter, as described above, the cumulative frequency range α in which zl is equal to the level of the dummy sound is determined. Next, as mentioned above, we collected data for the case of Z1'# and no sound, and calculated the level of the target sound below αC, which was determined by the presence or absence of the dummy sound (2
) is used to verify the steady-state f measurement method described above.

A second measurement point P, where only the aforementioned traffic noise exists.

In Ayurai, a dummy sound of 48 dB was generated, and the level of the dummy sound was measured from the noise levels measured by classifying whether the dummy was present or not. : Shown in Table 2.

Table 2 If the background noise that fluctuates as shown in Table 2 is traffic noise, the level of the dummy sound can generally be measured with relative certainty when the cumulative frequency is 30% or less. . If
.

In the above embodiment, the case where the fluctuating background noise is traffic noise is explained, but even if it is other than traffic noise, the target sound can be measured in the same manner. In addition, it was confirmed that the distribution of background noise in areas with low noise levels was even.
When the above “sff” is
j may be determined.

As explained above, according to the present invention, the noise level is measured in a place where the target sound is present and a place where it is not present,
The noise level of the target sound can be determined from the difference in sound energy in these low noise level regions.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the frequency distribution of traffic noise, Figure 2 is a diagram showing the noise level in Figure 1 converted into noise energy, and Figure 3 is a diagram showing the steady sound measurement force coloring according to the present invention. 1], FIG. 4 is a noise frequency distribution diagram at point P1 in FIG. 3, and FIG. 5 is P in FIG. 3. FIG. 6 is a diagram illustrating the distribution of noise frequency at points, and is a diagram illustrating one example of an apparatus for verifying an embodiment of the steady sound measuring method according to the present invention. 10...road, 12...factory, PI...first measurement point, P...second measurement point. Agent: Tatsuyuki Unuma (and 2 others) Fig. 1 Fig. 2 Noise egg lefc” (7-7) yz y4ys P21: A'1 Suru l & sound level (d8) 181 Figure 6

Claims (1)

[Claims] In a method for measuring steady sound in the presence of background noise, which measures the noise level of a steady sound whose noise level is approximately constant in the presence of background noise whose noise level fluctuates, in a state where the background noise and the steady sound are mixed. The noise level of the stationary sound is determined by determining the noise energy in a region where the noise level is low, and from the energy obtained by subtracting the noise energy in the region where the noise level is low in the previous noise energy. A method for measuring W normal sound in the presence of W & noise.