JP7529618B2 - Test method for predicting and evaluating pipe flow noise - Google Patents

Description

The present invention relates to a test method for predicting and evaluating the sound of running water generated by water flowing through a pipe.

Pipes such as drainage pipes and storm drains that run indoors can cause problems if the noise generated by the running water inside them is transmitted to living spaces.
Patent Document 1 discloses a sound insulation countermeasure support system for implementing sound insulation countermeasures efficiently, rationally, and at low cost based on noise factors of a drainage vertical pipe.
However, as a prerequisite for taking such soundproofing measures, it is necessary to grasp in advance the sound pressure level of the sound of running water through the pipes.
Non-Patent Document 1 discloses that in an actual existing building, a soundproof box is installed on the piping, water is supplied to the rooftop drain, and the sound pressure level is measured.
Non-Patent Documents 2 and 3 disclose that vibrations are applied to the inside of a tubular member in a laboratory using a speaker, a steel ball, or the like, and the sound pressure level is measured outside the tubular member.

JP 2005-292971 A

"Experimental Study on the Sound of Flowing Water in Stormwater Pipes," Toda Construction Technology Research Institute, Technical Research Report, No. 46, pp. 6-11, 2020 Hiroto Yasuoka et al., "Study on the measurement method of noise generated and sound insulation performance of drainage pipes in a laboratory," Architectural Institute of Japan, "Academic Lectures Abstracts", 2008, D-1, pp. 251-256, 2008 Hajime Shinagawa et al., "Study on the measurement method of noise generated by drainage pipes and sound insulation performance in a laboratory," Architectural Institute of Japan, "Academic Lectures Abstracts," 2009, D-1, pp. 253-254, 2009 Japan Industrial Standards "Z8734:2021 Acoustics - Measurement method for sound power level of noise source by sound pressure method - Precision measurement method in reverberation room" Yuzo Tsuchiya et al., "Acoustic Characteristics of the Toda Construction New Acoustic Experimental Facility," Acoustic Technology, Vol. 42, No. 1, pp. 59-63, Japan Acoustic Materials Association, 2013

The method of Non-Patent Document 1 makes it possible to measure actual piping flowing water sounds. However, there are restrictions on pumping, adjusting the flow rate, changing the pipe diameter, etc., and it is difficult to obtain data that can be used to predict and examine the flowing water sounds of large diameter pipes in a series. The same is true when using a drainage tower or the like instead of an actual existing building.
The methods of Non-Patent Documents 2 and 3 have fewer restrictions than field experiments and can acquire sequential data. However, the correlation with actual pipe flow sounds is small, and actual pipe flow sounds cannot be predicted correctly.
The present invention has been made to solve such problems, for example, and has an object to make it possible to obtain sequential data in a laboratory that can correctly predict actual pipe flow sounds.

The test method for predicting and evaluating piping flowing water sounds involves injecting water into a straight pipe member to be tested that is to be used as piping, blocking both ends of the pipe member, and then holding the pipe member approximately horizontally and vibrating it up and down, and measuring the sound generated by the vibration.
The tube member may be vibrated in a reverberation chamber, and the sound may be measured in the reverberation chamber.
The frequency at which the tubular member is vibrated may be between 2 and 3 times per second.
The amount of water injected into the pipe member may be 2% or more and 50% or less of the capacity of the pipe.
The width by which the pipe member is vibrated may be 200 mm or more and 400 mm or less.
The length of the tube member may be between 500 mm and 1000 mm.

This test method makes it possible to measure sounds that have frequency characteristics that correlate very well with the frequency characteristics of the sound pressure level of the sound of flowing water generated by actual water flowing through pipes. Therefore, by analyzing this, it is possible to accurately predict the actual sound of flowing water.

Schematic diagram showing the experimental method. FIG. A frequency characteristic diagram showing the experimental results, comparing different pipe types. FIG. 11 is a frequency characteristic diagram showing the results of a comparative experiment. 4 is a graph showing correlations of experimental results, in which the horizontal axis indicates the sound power level in the experimental results of FIG. 3 and the vertical axis indicates the sound pressure level in the experimental results of FIG. FIG. 11 is a frequency characteristic diagram showing the results of a reference experiment. 6 is a graph showing correlations of experimental results, in which the horizontal axis indicates the sound power level in the experimental results of FIG. 6 and the vertical axis indicates the sound pressure level in the experimental results of FIG. FIG. 11 is a frequency characteristic diagram showing the results of a comparative experiment. 9 is a diagram showing correlations of experimental results, in which the horizontal axis indicates the sound power level in the experimental result of FIG. 8 and the vertical axis indicates the sound pressure level in the experimental result of FIG. Frequency response diagram showing the experimental results, comparing different amounts of water. A frequency characteristic diagram showing the experimental results, comparing the amplitudes. A frequency characteristic diagram showing the experimental results, comparing the difference in vibration frequency. A frequency characteristic diagram showing the experimental results, comparing the results with different tube lengths.

As shown in FIG. 1, one end of the straight tubular member 11 to be tested is blocked with a cap 12, water 14 is poured into the tubular member 11, and the other end is blocked with a cap 13 to seal the inside, creating a test specimen 10. Next, in a reverberation chamber that meets the requirements described in Non-Patent Document 4, the test specimen 10 is held on its side so that the tubular member 11 is approximately horizontal, and shaken up and down. The sound generated at this time is picked up and recorded by a microphone also installed in the reverberation chamber. The reverberation chamber has sufficient reflectivity and diffusion properties, so a constant sound can be recorded even if the distance between the test specimen 10 and the microphone changes when the test specimen 10 is shaken.

Experiments were conducted under the conditions shown in Figure 2 in the acoustic laboratory (reverberation chamber) described in Non-Patent Document 5. The pipe type "VP" stands for rigid polyvinyl chloride pipe, and "SGP" stands for carbon steel pipe for piping. The nominal diameter of all pipe members is 100A. For each experiment, the test piece 10 was swung for 15 seconds, and the sound was recorded for 10 seconds from 3 seconds after the start of the swing to 13 seconds after the start of the swing, and the frequency characteristics (1/3 octave band) of the sound power level [decibel (dB)] were calculated. This was done according to the method described in Non-Patent Document 4. Five experiments were conducted under the same conditions, and the average of the calculated sound power levels was calculated. The experimental results are shown in Figure 3 and Figures 10 to 13. Note that "A" indicates the overall value of the A characteristic.

For comparison, Figure 4 shows the frequency characteristics of sound pressure levels measured using the method described in Non-Patent Document 1. The pipe members are of two types, VP and SGP, with a nominal diameter of 100A and a flow rate of running water of 500 [liters per minute (L/min)]. Note that BGN indicates background noise. For frequencies where the difference between VP and SGP and BGN is small, the effect of noise is large, so it is possible that the sound pressure level due to running water is not being measured correctly.

Comparing Figure 3 and Figure 4, it can be seen that the sound power level measured by this test method corresponds very well to the sound pressure level measured by actually running water through a pipe. Also, as shown in Figure 5, the sound pressure level in Figure 4 correlates very well with the sound power level in Figure 3. As mentioned above, for the frequency range below 400 [Hertz (Hz)], the background noise contained in the sound pressure level in Figure 4 is large, and there is a possibility that the sound pressure level due to running water is not measured correctly, so the correlation is calculated using only the frequency range of 400 [Hz] or more.
Therefore, by analyzing the data recorded by this type of test method to obtain the sound power level, it is possible to correctly predict the sound pressure level due to the actual sound of running water, without using large-scale facilities such as an actual existing building or a drainage tower.

Figure 6 shows the frequency characteristics (1/3 octave band) of the sound pressure level difference measured using a method based on the "Speaker tube radiation - Near-field sound pressure method (sound absorbing/sound insulating box)" described in Non-Patent Document 2. As shown in Figure 7, the sound pressure level difference in Figure 6 does not correlate well with the sound pressure level in Figure 4. There is a deviation from the actual sound of running water, and it is difficult to predict the sound pressure level due to the actual sound of running water from the sound pressure level difference measured using this method, making it impossible to make an evaluation that corresponds to the sound of running water.

Figure 8 shows the frequency characteristics (1/3 octave band) of the maximum sound pressure level measured using a method similar to the "steel ball impact method inside a pipe (sound absorbing/sound insulating box)" described in Non-Patent Document 3. As shown in Figure 9, the maximum sound pressure level in Figure 8 does not correlate well with the sound pressure level in Figure 4. There is a deviation from the actual sound of running water, and it is difficult to predict the sound pressure level due to the actual sound of running water from the sound pressure level difference measured using this method, making it impossible to make an evaluation that corresponds to the sound of running water.

As described above, the test method disclosed herein can obtain data that is highly correlated with the sound pressure level of the actual sound of running water, compared to the methods described in Non-Patent Documents 2 and 3, and this makes it possible to correctly predict the actual sound of running water.

Next, we will consider optimal test conditions.

According to Figure 10, the more water is injected into the pipe, the higher the acoustic power level becomes. The correlation with the actual sound of running water is highest at 1 L, followed closely by 0.5 L, and lowest at 2 L. The pipe in this experiment has a nominal diameter of 100A and a length of 500 mm, so the volume inside the pipe is approximately 3.9 L. Therefore, it is preferable to inject the amount of water at least 2% and no more than 50% of the volume inside the pipe.

According to FIG. 11, the greater the amplitude of the vibration of the pipe member, the greater the acoustic power level, but because it only moves in parallel overall, there is almost no change in correlation with the actual sound of running water. In other words, there is no point in vibrating it too much. Considering that a person will be holding it in their hand and shaking it, it is preferable that the amplitude of the vibration of the pipe member be between 100 mm and 400 mm.

According to Figure 12, if the number of times the pipe member is swung per second is too small, the water hardly separates from the pipe, the generated sound becomes small, and the correlation with the actual sound of running water becomes small. Therefore, it is preferable to swung the pipe member more than twice per second. If swung more than twice per second, the higher the vibration frequency, the higher the acoustic power level will be, but since the overall movement is simply parallel, the correlation with the actual sound of running water remains almost unchanged. In other words, there is no point in swung too fast. Considering a person holding it in their hand and waving it, it is preferable to swung it less than three times per second.

According to Figure 13, the length of the tube member has almost no effect on the acoustic power level. Considering that a person will hold it in their hand and shake it, if it is too long it will be difficult to handle, so it is preferable for it to be between 500 mm and 1000 mm.

In the above experiment, the test was performed five times under the same conditions and the average was calculated, but the variation in the obtained data was small. For this reason, it is not necessary to perform the test multiple times under the same conditions; performing the test two or three times is sufficient.

According to the test method disclosed herein, it is possible to obtain data that is systematic and corresponds well to the actual sound of flowing water, using a small-scale test method performed in a laboratory, and based on this, it is possible to correctly predict the frequency characteristics of the sound pressure level of the actual sound of flowing water. It is possible to measure sounds that are similar to those of flowing water in piping, to obtain systematic data for the pipes, to perform measurements in a laboratory with few constraints on measurement preparation and time, and because the scale of the experiment and the pipes being measured are small, it is possible to reduce the cost of the experiment.

For example, as described in Non-Patent Document 1, an experiment is performed in an actual existing building, and the coefficients of the approximation formula (for example, the slope and intercept of the approximation line) are calculated by correlating the data obtained by the test method according to the present disclosure for the same piping. Then, the actual sound pressure level of the running water sound is estimated from the data obtained by the test method according to the present disclosure for other piping using the coefficients calculated in this way.
It is known that the sound pressure level of the actual sound of running water increases by about 3 dB when the flow rate of water doubles (Non-Patent Document 1, etc.). For this reason, experiments in existing buildings need only be performed for a specific flow rate of water, and the sound pressure level at any flow rate of water can be estimated from the sound pressure level estimated using the coefficient calculated for that specific flow rate.

Alternatively, if one only wishes to compare the magnitude relationship of the sound pressure levels of multiple pipes, the data obtained using the test method disclosed herein may be compared as is without being converted to the sound pressure level of the actual sound of running water.

The above-described embodiment is an example for facilitating understanding of the present invention. The present invention is not limited thereto, and includes various modifications, changes, additions, or deletions without departing from the scope defined by the appended claims. This can be easily understood by a person skilled in the art from the above description.

For example, instead of a person holding the test specimen by hand and shaking it, the test specimen can be set on a vibration device and subjected to vibrations similar to those experienced when a person holds the specimen by hand and shakes it.

10 Test specimen, 11 Pipe member, 12, 13 Cap, 14 Water.

Claims (6)

In the test method for predicting and evaluating the sound of running water from pipes,
Injecting water into a straight tubular member to be tested, which is used as a pipe, and closing both ends of the tubular member;
Thereafter, the pipe member is held substantially horizontally and vibrated up and down.
Measure the sound generated by the vibration.
Test method. The tubular member is vibrated in a reverberation chamber;
The sound is also measured in the reverberation chamber.
The test method of claim 1. The frequency of vibration of the tubular member is 2 or more and 3 or less per second.
The test method according to claim 1 or 2. The amount of water injected into the pipe member is 2% or more and 50% or less of the volume of the pipe member.
The test method according to any one of claims 1 to 3. The width of the vibration of the pipe member is 200 mm or more and 400 mm or less.
5. The test method according to claim 1 . The length of the tube member is 500 mm or more and 1000 mm or less.
6. The test method according to any one of claims 1 to 5.

Images