JP3904733B2 - Road drainage measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a road surface drainage measuring device for measuring drainage of a road surface.
[0002]
[Prior art]
The surface of drainage pavement is increasing. The reason is to increase safety during rainy weather by increasing drainage. It is well known that slip accidents may occur due to the hydroplane phenomenon caused by the accumulation of water on the road surface. In addition, the possibility of an accident increases due to freezing of pool water in winter.
[0003]
Another reason why drainage is being reviewed is that drainage pavement has the effect of reducing running noise. Most road traffic noise during high-speed driving is noise caused by contact between the road surface and tires. It is known that tire noise is reduced by several dB by increasing drainage. This is because drainage pavement has water permeability, so that sound also enters the road surface and is absorbed, and the degree of air compression / expansion at the hollow part of the tire is reduced. It has been.
[0004]
However, drainage pavement has a water-permeable structure and is soft and has a drawback that it is easily painful due to running of the vehicle. The frequency of repairs will increase compared to conventional pavements. Paving the entire road every time is expensive and inconvenient due to prolonged repairs. Therefore, if there is a measurement method for locally finding a place where pain is severe, it is possible to repair only that part. In addition, it is a very effective method if measurement can be performed without hindering normal traffic.
[0005]
[Problems to be solved by the invention]
As mentioned above, paying attention to the fact that drainage pavement has both aspects of good drainage and reduction of running noise, by measuring the local sound absorption coefficient of each part of the road surface, the sound absorption coefficient is It is conceivable to detect that the drainage is deteriorated due to the low noise, that is, the noise at that portion is large, that is, the damage is severe.
[0006]
Conventionally, the following methods are known as methods for measuring the sound absorption coefficient.
[0007]
(1) Method for obtaining normal incidence sound absorption coefficient using acoustic tube This is the most commonly used method for obtaining normal incidence sound absorption coefficient (specified in JIS standard). Although it is necessary to cut the material into a circle, it is a highly reliable measurement method. Since it is necessary to cut out a sample in order to measure the sound absorption coefficient of the road surface, it cannot be used for real-time measurement. (2) Method of obtaining a random incident sound absorption coefficient from the reverberation time with the road surface as one surface of the reverberation box Sound absorption coefficient measurement using a reverberation chamber is also a standard method standardized by JIS. Measure the reverberation time before and after bringing the sound absorbing material into the room, and calculate the sound absorption rate from these values.
[0008]
The method using a reverberation box has disadvantages such as handling a large box, the need to measure the reverberation time twice between the complete reflection surface and the road surface, and the influence of outside air temperature easily appear. Measurement of is impossible.
[0009]
(3) Method using impulse A method for obtaining a sound absorption coefficient from the ratio of the magnitude of the reflected wave on the surface to be measured and the magnitude of the reflected wave on the surface to be measured (the magnitude of the reflected wave on the completely reflecting surface) An example of the configuration of the measuring device is shown in Fig. 5. The signal generator 10 generates a pulse signal having a finite bandwidth centered on a specified frequency, and the amplifier 20 appropriately amplifies the pulse signal. Then, the sound is converted into a pulse sound by the speaker 30, and the pulse sound is sequentially incident on the surface to be measured and the hard floor surface.
[0010]
The reflected waves from the surface to be measured or the hard floor surface are collected by the microphone 40, and the collected sound signal is amplified by the amplifier 50 and sent to the signal analyzer 60. In the signal analyzer, the sound absorption rate is measured from the ratio of the magnitudes of the sound signals. The sound absorption coefficient α is obtained by the following equation.
[0011]
α = 1−P1 / P2
Where P1: energy of the reflected wave on the surface to be measured,
P2: energy of the reflected wave on the hard floor,
It is. Even in this case, it is necessary to measure twice the actual road surface and the state where the hard floor surface is placed on the same place. Even with this method, it is impossible to measure the sound absorption coefficient during traveling, that is, to measure drainage during traveling.
[0012]
As described above, in the conventional sound absorption coefficient measuring method, there is no suitable method that can measure the sound absorption coefficient in real time during traveling.
[0013]
In view of the above circumstances, an object of the present invention is to provide a road surface drainage measuring device that can be mounted on an inspection vehicle and can measure the drainage of a road surface during traveling.
[0014]
[Means for Solving the Problems]
The road surface drainage measuring device of the present invention that achieves the above-mentioned object,
A signal generator for generating a predetermined pulse signal;
A speaker that converts a pulse signal generated by a signal generator into a pulse sound emitted toward a road surface;
A sound sensor that detects both the direct sound emitted from the speaker before reaching the road surface and the reflected sound emitted from the speaker and reflected by the road surface, and the direct sound and the reflected sound detected by the sound sensor A signal analyzer for determining the drainage performance of the road surface based on the above is provided.
[0015]
Here, in the road surface drainage measuring device according to the present invention, the signal analyzer determines the drainage of the road surface based on the signals in the frequency band of 15 kHz or more of the direct sound and the reflected sound detected by the sound sensor. It is preferable.
[0016]
In this case, the signal generator may generate a band pulse signal within a frequency band of 15 kHz or more and a frequency width within one octave, or there is no limitation on the signal generator side. In addition, in other words, the signal generator generates a short pulse signal, that is, a pulse signal including a signal component in a somewhat wide frequency band, and the signal analyzer has a frequency of 15 kHz or higher between the direct sound and the reflected sound detected by the sound sensor. A signal having a frequency width within a band and within one octave may be extracted, and the drainage of the road surface may be obtained based on the extracted signal.
[0017]
The road surface drainage measuring device according to the present invention includes a plurality of sound sensors distributed as the sound sensor, and directly detects a sound with at least one of the plurality of sound sensors. The reflected sound may be detected by a plurality of all or some of the sound sensors.
[0018]
Further, the road surface drainage measuring device of the present invention includes a position detector for detecting a position on the road surface, and the road surface drainage measuring device obtains drainage information corresponding to the position on the road surface. Is preferred.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The basic idea of the present invention is to utilize the fact that drainage pavement has a large sound absorption (that is, less reflection) although there is a difference depending on the frequency. However, here, it does not stick to obtaining the quantity defined by acoustic engineering called “sound absorption coefficient”. In addition, the frequency at which the sound absorption rate is usually a problem is the audible frequency band, but it may be in the ultrasonic region if the frequency band has the highest correlation between drainage and sound absorption performance. On the other hand, here, it is required to obtain drainage in real time during traveling. Real-time measurement is related to travel speed, but it is necessary to obtain a measurement result for each predetermined distance. For example, to obtain results at intervals of 0.5 m at a traveling speed of 100 km / h, it is necessary to obtain results every 18 ms. For this purpose, it is necessary to use an acoustic pulse having a width of several ms or less. In consideration of such restrictions, here, the relationship between drainage and sound absorption was investigated in a frequency band including the ultrasonic region.
[0020]
FIG. 1 is a diagram showing a measurement system for investigating the relationship between drainage and sound absorption, and corresponds to an embodiment of the road surface drainage measurement device of the present invention. The road surface drainage measuring apparatus shown in FIG. 1 has the same operation as the block constituting the sound absorption coefficient measurement system by the impulse method shown in FIG. 5, which is given as an example of a conventional sound absorption coefficient measurement method for ease of understanding. 5 are shown with the same reference numerals as those shown in FIG. 5. However, the detailed operation of each block is not the same as that shown in FIG. Both are detected, and the signal analyzer 60 requires drainage based on the direct sound and the reflected sound.
[0021]
In the road surface drainage measuring device shown in FIG. 1, a position detector 70 is shown as a new element not shown in the configuration shown in FIG. The position detector 70 is a position detector 70 that uses a GPS (global positioning system) used for a so-called car navigator, and can receive a radio wave from an artificial satellite to know the current position.
[0022]
In the road surface drainage measuring apparatus shown in FIG. 1, position information representing the current position from the position detector 70, that is, a position on the road surface if the road surface is being measured while running on the road surface. Is output, and the signal analyzer 60 outputs drainage information indicating the drainage performance of the portion currently being measured on the road surface, which is obtained as described below. Output information consisting of sex information is generated. That is, in the road surface drainage measuring device shown in FIG. 1, drainage information corresponding to the position on the road surface is obtained.
[0023]
Here, as described above, with one microphone 40, a pulse sound (hereinafter referred to as "direct sound") generated from the speaker 30 and reflected from the road surface, and a pulse sound after reflection (hereinafter referred to as reflected sound). ) Is measured. Here, it was examined how these ratios change depending on the state of the reflecting surface 100. The distance from the speaker 30 to the road surface is 0.5 m, and the distance from the microphone 40 to the road surface is 0.3 m.
[0024]
FIG. 2 is a diagram showing an example of waveforms of the direct sound (A) and the reflected sound (B).
[0025]
It can be seen that the magnitude of the reflected sound (B) decreases with respect to the direct sound (A).
[0026]
These direct sound and reflected sound pulses include signal components in a wide frequency band from low frequency components to high frequency components exceeding 30 kHz.
[0027]
FIG. 3 is a diagram showing the degree of reduction in the spectrum of reflected sound with respect to the direct sound by performing frequency analysis of those pulses using Fourier transform on different road surfaces. The horizontal axis shows the range up to 35 kHz in frequency. The vertical axis represents the power ratio between the direct sound and the reflected sound in decibels, and the larger the dB, the greater the attenuation rate. The solid line is when drainage asphalt is the object of measurement, and the dotted line is when the drainage asphalt is damaged by stuffing clay into the joint of the drainage asphalt and that is the object of measurement. . On the road surface (solid line) of drainage pavement, frequencies with higher sound absorption are seen in some places compared to the road surface (dotted line) simulating a damaged state. In addition, this high sound absorbing frequency appears remarkably in the portion of 15 kHz or higher. When the frequency is higher than 30 kHz, it is difficult to produce sound even with a speaker, and the attenuation during propagation in the air becomes severe, so a frequency of 30 kHz or less is considered preferable. By using such a frequency band, it is possible to measure the drainage of the road surface by measuring the ratio of the reflected sound power to the direct sound. In addition, according to the measurement results shown in FIG. 3, since the sound absorption is repeated so as to vibrate along the frequency axis, the drainage is obtained based on a signal having a certain narrow frequency width, for example, a frequency width within one octave. Is preferred. The frequency width within one octave may be realized by generating a pulse signal that originally contains only a signal component within one octave on the signal generator side, or on the signal generator side, for example, It may be realized by generating a short pulse including a signal component of a frequency band that is somewhat wide and extracting only a signal component within one octave on the signal analyzer side.
[0028]
FIG. 4 is a plan view (A) and a front view (B) showing an arrangement form of speakers and microphones in another embodiment of the road surface drainage measuring device of the present invention.
[0029]
When actually evaluating the reflectivity of the road surface, the direction in which the reflected wave arrives may change depending on the inclination and roughness of the road surface. Therefore, as shown in FIG. 4, it is preferable to obtain an average power attenuation amount using a plurality of microphones 40 for one speaker 30. Thus, by disposing a plurality of microphones 40 in a distributed manner, a wide range of reflected sounds can be detected.
[0030]
In the example shown here, the frequency analysis is performed in the signal analyzer 60 as shown in FIG. 3, but the band is limited to within one octave, for example, after being received on the signal generator side or by the microphone. In this case, it is not always necessary to perform frequency analysis in the signal analyzer 60, and the sound absorption is obtained by comparing the power of the direct sound and the reflected sound within the limited band, and the discharge performance is obtained from the sound absorption. Can be sought.
[0031]
In the example shown in FIG. 4, five microphones 40 are dispersedly arranged for one speaker 30, and a direct sound is detected by a central microphone 40 a among the five microphones 40, and the remaining four microphones are detected. Reflected sound is detected by 40b or all five microphones. The reflected sounds detected by the plurality of microphones are detected by the signal analyzer 60 (see FIG. 1) and then added to each other, and the added signals are treated as reflected sound signals as a whole.
[0032]
【The invention's effect】
As described above, according to the present invention, it is possible to measure the sound absorption of the road surface in real time and to measure the drainage of the road surface from the sound absorption.
[Brief description of the drawings]
FIG. 1 is a diagram showing a measurement system for examining the relationship between drainage and sound absorption.
FIG. 2 is a diagram illustrating an example of waveforms of a direct sound (A) and a reflected sound (B).
FIG. 3 is a diagram showing the degree of reduction in the spectrum of reflected sound with respect to direct sound by performing frequency analysis of those pulses on different road surfaces using Fourier transform.
FIG. 4 is a plan view (A) and a front view (B) showing an arrangement of speakers and microphones in another embodiment of the road surface drainage measuring device of the present invention.
FIG. 5 is a diagram illustrating a configuration example of a conventional sound absorption coefficient measuring device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Signal generator 20 Amplifier 30 Speaker 40, 40a, 40b Microphone 50 Amplifier 60 Signal analyzer 70 Position detector 100 Reflecting surface

Claims (5)

A signal generator for generating a predetermined pulse signal;
A speaker that converts the pulse signal generated by the signal generator into a pulse sound emitted toward a road surface;
A sound sensor that detects both a direct sound emitted from the speaker before reaching the road surface and a reflected sound emitted from the speaker and reflected by the road surface; and the direct sound detected by the sound sensor; A road surface drainage measuring device comprising a signal analyzer for determining drainage of a road surface based on a signal within a frequency band of 15 kHz or more with reflected sound. The road surface drainage measuring device according to claim 1, wherein the signal generator generates a band pulse signal having a frequency width within a frequency band of 15 kHz or more and within one octave. The signal analyzer extracts a signal having a frequency band of 15 kHz or more and a frequency width within one octave of the direct sound and the reflected sound detected by the sound sensor, and based on the extracted signal, The road surface drainage measuring device according to claim 1, wherein the drainage of the road surface is obtained. A plurality of sound sensors distributed as the sound sensor are provided, and at least one of the plurality of sound sensors detects a direct sound, and a plurality of all or some of the plurality of sound sensors are detected. The road surface drainage measuring device according to claim 1, wherein the reflected sound is detected by a sound sensor. The road surface drainage according to claim 1, further comprising a position detector for detecting a position on the road surface, wherein the road surface drainage measuring device obtains drainage information corresponding to the position on the road surface. measuring device.

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