JP3805084B2 - Inundation state inspection method and inspection apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inundation state inspection technique for detecting the occurrence state or position of inundation generated in piping in a state concealed by a covering layer such as soil or a wall of a house.
[0002]
[Prior art]
Conventionally, for example, the following method has been employed for detecting inundation generated in city gas pipes buried in the soil.
1 Method of inserting a camera into the pipe, imaging the inside of the pipe, and confirming this by visual inspection, etc. 2 Method of opening and inspecting a water removal device previously installed at a predetermined location of the piping system 3 End of the ground supply pipe Inspecting and confirming in-pipe noise from the head, identifying whether sandblasting, etc. has occurred and checking the inundation status [0003]
[Problems to be solved by the invention]
However, the conventional techniques as described above have the following problems.
Although the method shown in 1 above is the most powerful method at present, it is necessary to perform normal excavation in order to perform the camera insertion operation. Furthermore, in this method, it is only possible to detect one of the so-called inundation boundaries, and it is necessary to detect again from the opposite side in order to specify the inundation range.
Since the method shown in the above 2 depends on the water catcher, the place where the infiltration can be confirmed is limited to the place where this is disposed. That is, in general, the water removing device is installed at a place where water is easily generated, but in reality, whether or not water is generated centering on the position is not clear. In addition, it is necessary to install a large number of water removal devices to specify the range of flooding, and the distance between the positions where the water removal devices are installed is limited in its lower limit. It is impossible to obtain sexual information.
In the method shown in 3 above, it is possible to detect the occurrence of sandblasting, but it is practically impossible to specify the location and cannot be used after the sandblasting has subsided.
The object of the present invention is to enable the inspection of all the routes along the pipe, which can minimize the insertion of the equipment into the pipe, and to confirm the presence or absence of water in a relatively limited detection operation. In addition, it is to obtain a flooded state inspection technique capable of confirming the position of the flooded boundary and the flooded range.
[0004]
[Means for Solving the Problems]
In order to achieve this object, the characteristic means of the inundation state inspection method for detecting the inundation state in the pipe concealed by the coating layer according to the present invention generates a sound at a predetermined place of the pipe and generates a sound wave in the pipe. A sound propagation step for propagating the sound wave and a reception step for receiving the sound wave propagating in the pipe at a plurality of locations along the pipe arrangement direction, and depending on the frequency of the sound wave received in the reception step, The purpose is to determine whether there is water in the pipe or the location of the water .
In this way, in the case of inspecting the inundation state, in the reception process, the sound wave is received at a plurality of locations along the piping arrangement direction, and depending on the frequency of the reception sound, the presence or absence of inundation or the It is preferable to determine the position.
Furthermore, when inspecting the flooded state, sound waves are received at a plurality of locations along the piping arrangement direction in the receiving process, and depending on the sound pressure level of the received sound, the presence or absence of flooding or It is preferable to specify.
Furthermore, in the receiving step, it is preferable to receive the sound wave reflected from the pipe at the sound generation position for the propagating sound wave, and determine the flooded boundary position from the relationship between the sound generation time and the sound reception time.
[0005]
In the present application, the method as described above is adopted, but with reference to FIG. 2, for example, when there is a flooded place in a pipe buried in the ground, this flooded place and a place where there is no flooded A description will be given of how the reception status of sound waves changes at a position corresponding to.
In FIG. 2, (a) shows the status of the piping, and (b) shows the frequency of the received sound. Here, the frequency of the received sound is a resonance frequency that resonates in the pipe and leaks out of the pipe. (C) shows the sound pressure level of received sound received at a plurality of positions on the ground side along the pipe, and (D) shows the state of received sound received at the oscillation position.
[0006]
As shown in (b), since the density of the material filled in the pipe differs depending on whether there is water in the pipe or not, the frequency of the sound wave received on the ground side corresponding to the pipe position Is different. Therefore, by detecting such a frequency, it is possible to determine the presence or absence of flooding, and when moving along the pipe, the position where the frequency changes can be identified as the flooding boundary. Further, by detecting the pair of the inundation boundaries at a position along the pipe, a portion where the sound reception frequency between these inundation boundaries is a frequency corresponding to the inundation is determined as the inundation portion. be able to.
[0007]
Next, as shown in (c), the sound attenuation state due to the influence of water differs depending on whether or not there is water in the pipe. That is, the attenuation of sound is small in gas, but the attenuation is large in water.
Therefore, if the sound pressure level of the received sound is measured at a plurality of locations along the piping direction, the sound pressure level of the received sound wave changes. And, for example, when moving from the sound source and gas side to the other gas part through the submerged part, a region where the sound pressure is relatively high and the attenuation rate is low continues temporarily, and the sound pressure is low and the attenuation rate is low. Is followed by a relatively large region, and then a position where the attenuation rate of the sound pressure is relatively low appears.
Therefore, by detecting the sound pressure level, it is possible to determine whether or not the sound pressure level is attenuated by determining that the portion where the sound pressure level is greatly attenuated is a flooded portion. A position where the pressure changes suddenly can be identified as a flooded boundary. Furthermore, by detecting the pair of the inundation boundaries at a position along the pipe, it is possible to determine the inundation part between these inundation boundaries.
In FIG. 2 (c), the change state of the sound pressure level when there is a flooded part is indicated by a mark x, and the change state of the sound pressure level when there is no flooded part is indicated by a mark.
[0008]
Furthermore, if there is water in the pipe and a pair of water intrusion boundaries are formed between the gas part and the water infiltration part, these water ingress boundaries reflect the sound waves that propagate in the pipe. Will act as a boundary. Of course, at this reflection boundary, a part of the sound wave propagates downstream.
Furthermore, if there is a bend, for example, in the pipe, this bend is also a sound wave reflection source. For example, as shown in FIG. 2 (a), when a speaker is provided at the open end of a gas pipe stand pipe and an impulse wave is propagated from the speaker into the pipe, the pipe observed at this sounding position. The reflected waves returning from the inside are as shown in (d) according to the piping situation. Therefore, in the figure, the fourth signal represents the first inundation boundary, the fifth signal represents the second inundation boundary, and in a general sense, the piping situation has been confirmed ( For example, if the number and position of pipe bends are known by radar exploration etc.), the position of the inundation boundary can be specified. As a result, the presence or absence of inundation, the position of the inundation boundary, the inundation part, etc. Can be determined.
That is, in this way, the sound propagating through the pipe is received, and the state of water immersion in the pipe can be determined from the state of the sound received in this receiving step.
[0009]
Therefore, in the case of these methods described above, since water that has entered the pipe is detected using the sound propagating in the pipe as a medium, the insertion of equipment into the pipe is minimized. However, it is possible to inspect the entire route along the pipe. Furthermore, it is possible to obtain an inundation state inspection technique that can confirm the presence or absence of inundation, confirm the position of the inundation boundary, confirm the inundation range, and the like with relatively limited detection operations.
[0010]
Now, as an inspection apparatus using the above-described inundation state inspection method, it is preferable to take the following configuration when the inundation part is specified by the frequency of the propagation sound propagating through the pipe.
That is, the inspection apparatus is configured by providing a speaker capable of generating sound having at least a plurality of frequency components in the tube and a microphone capable of receiving sound generated by the speaker and propagating through the tube.
Propagation comprising frequency analysis means for obtaining the frequency of the propagation sound received by the microphone, and determining the state of the propagation site of the received propagation sound based on a comparison between the frequency obtained by the frequency analysis means and a predetermined threshold value It is provided with a part determination means.
[0011]
When using this apparatus, for example, first, a plurality of microphones are arranged along the tube so that each microphone can receive a propagation sound propagating in each corresponding part in the tube. And the sound which has a several frequency component from a speaker is generated, and this is propagated to propagation in a pipe | tube. In this state, when a sound having a plurality of frequency components propagates through the tube, resonance occurs in the tube according to the state, and the sound corresponding to the state of each part is detected by a microphone disposed at the corresponding part. Is done.
Now, these detected sounds are analyzed by the frequency analysis means, and their frequencies are specified. This specified frequency is compared with a predetermined threshold value that is known in advance in the propagation site determination means. For example, if it is larger than this threshold value, the inside of the tube is filled with a high density (specifically, water). If the possibility is high or small, it is judged as a situation where there is a high possibility that the inside of the pipe is filled with a low density (specifically, gas). Therefore, by using this inspection device, according to the frequency of the sound received by the microphone, the state of the sound propagation part in the tube (not reverted, this part is a sound generation part from the inside of the tube to the microphone) Can be judged.
[0012]
Now, as an inspection device that uses the inundation state inspection method as described above, the propagation sound propagating in the underground pipe is used to judge the situation inside the pipe based on the sound wave propagating to the ground side, and to generate sound. In the case of a configuration in which the situation inside the tube is to be grasped based on the reflected sound returning to the side, it is preferable to employ the following configuration.
That is, the configuration of the inspection apparatus includes a speaker that can generate sound having at least a plurality of frequency components in the underground pipe, and a plurality of propagation sounds that are generated by the speaker and propagate through the underground pipe. This is configured with a microphone,
As the plurality of microphones, the sound waves leaking from the underground tube to the surface side are propagated through the underground tube and reflected at the position of the speaker, and the ground side microphone capable of receiving the sound wave leaking at multiple locations on the underground side. It is assumed that a sound source side microphone capable of receiving reflected sound is provided when returning to the speaker position (hereinafter, the configuration of the present inspection apparatus is referred to as configuration ( A )) .
With this configuration ( A ) , the sound propagating through the pipe is detected on the surface side outside the pipe, the situation inside the pipe is grasped from the ground side, and the reflected sound received at the sound source is generated by the sound source section. Detecting with the side microphone and grasping the state of the sound that propagates in the direction away from the sound source part with respect to the buried pipe, and grasping the position of the reflecting part in the pipe from the state of the reflected sound, both From the above data, the situation inside the buried pipe can be estimated.
Further, in addition to the configuration ( A ), the frequency analysis means for determining the frequency of the sound received by each microphone and the frequency received by the microphone based on a comparison between the frequency obtained by the frequency analysis means and a predetermined threshold value. If the inspection apparatus comprises a propagation site judgment means for judging the state of the propagation site of the transmitted sound, the sound propagating through the pipe is detected on the outer surface of the tube, and the detected sound is analyzed by the frequency analysis means. Thus, the frequency of the detected sound is specified, and the frequency is compared with a predetermined threshold value that is known in advance in the propagation site determination means, so that the situation inside the pipe can be grasped from the ground surface side.
On the other hand, in addition to the above configuration ( A ), the frequency analysis means for calculating the frequency of the sound received by each microphone, the sound pressure level deriving means for determining the sound pressure level of the sound received by each microphone, and each microphone are received. And a data processing means for associating and organizing the frequency and sound pressure level of the sound with the position of the microphone, the sound propagating through the pipe is detected on the outside surface of the pipe, and the detected sound is frequency analysis means. The frequency of the detected sound is specified by analyzing the sound pressure, and the sound pressure level of the detected sound is determined by deriving the detected sound by the sound pressure level deriving unit. By arranging the frequency and the sound pressure level by the data processing means for associating and organizing the frequency and the sound pressure level, it is possible to grasp the situation in the pipe from the surface side.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present application will be described with reference to the drawings.
FIG. 1 shows a state in which the flooded part A generated in the gas pipe 1 buried in the ground is being searched by applying the flooded state inspection method of the present application.
In this method, sound waves propagating in the pipe 1 are used for searching for the flooded part A.
[0014]
In the inundation state inspection of the present application, an inspection apparatus 2 having a configuration unique to the present application is used. First, the outline of the inspection apparatus 2 will be described. The inspection device 2 includes an inspection device body 3, a speaker 4, and a microphone 5 as main components.
Here, the speaker 4 is an explosion-proof type and is configured to be attachable to the tube end portion 6 exposed to the ground. The speaker 4 is configured to receive a sound generation command from the inspection apparatus main body side and be driven to generate a predetermined sound wave. A sound having at least a plurality of frequency components (specifically, a Qingdao pulse) is to be inspected. Can be generated in the tube.
Next, a description will be given of the main microphone 5. A plurality of microphones 5 are prepared. The microphone 5 is arranged on the tube end together with the ground-side microphone 5 a that is disposed on the ground surface and picks up the sound propagating from the ground, and the speaker 4. And a sound source side microphone 5b that picks up reflected sound from the inside of the tube at this position. In the example shown in FIG. 1, seven ground surface side microphones 5a and a single sound source side microphone 5b are provided, and sound reception information picked up by these devices is sent to the inspection apparatus main body side. A configuration provided for later use is employed.
[0015]
Next, the configuration of the inspection apparatus body 3 will be described.
The apparatus main body 3 includes a Qingdao pulse generating means 31 storing predetermined information for generating a Qingdao pulse from the speaker 4, a frequency analyzing means 32 for determining the frequency of the sound received by each microphone 5, and a sound pressure for determining the sound pressure level. Intra-tube propagation received by the microphone corresponding to each frequency based on a comparison between the level obtained by the level deriving unit 33 and the frequency analyzing unit 32 and a predetermined threshold set in advance by an external input or the like. Propagation site determination means 34 for determining the state of the propagation site of sound, and further, the position of the ground surface side microphone 5a (this position is separately input from the input device 35), and the frequency of sound received by each microphone 5a And data processing means 36 for organizing the sound pressure levels in association with each other.
[0016]
Based on FIG. 1, the basic principle of the flooded state inspection method of the present application will be described below with respect to a case where a gas pipe 1 (an example of an embedded pipe) embedded in a front road of each home 7 is targeted.
FIG. 1 shows a city gas piping system B for supplying city gas to each home 7. That is, a low-pressure gas pipe 9 embedded in the front road 8 is provided for each home 7, and is drawn into the premises of each home 7 through the lead-in pipe 10 from the low-pressure gas pipe 9. After the pipe is once taken out as a stand pipe 11 on the ground, it is piped to a gas supply position (not shown) in each household. A so-called gas meter (not shown) is disposed at a predetermined position of the standing tube 11.
In the figure, a situation is shown in which inundation has occurred in the overlying portion of the low-pressure gas pipe 9 and inundation A has occurred.
In the exploration work, in order to use the above-described standing tube 11, a gas meter (not shown) is removed from the standing tube 11, and the speaker 4 is attached to the tube end portion 6 of the standing tube 11. The speaker 4 can generate a Qingdao pulse in the tube by receiving information from the Qingdao pulse generating means 31 described above and receiving a control command.
Here, the Qingdao pulse is a pulse for obtaining an impulse response of the target acoustic system. 12-4 pp. 35-43 (1984).
[0017]
The speaker 4 is provided with a sound source side microphone 5b, and the microphone 5b can receive a sound wave reflected from the inside of the tube.
[0018]
On the other hand, a plurality of ground-side microphones 5a are arranged on the ground based on a pre-prepared map (not shown) of the gas pipe 1. Therefore, these microphones 5a can pick up sound waves leaking into the ground from the inside of the tube corresponding to each sound receiving area.
Information from the front-side microphones 5 a is collected in the inspection apparatus body 3, the frequency is obtained by the frequency analysis means 32, and the sound pressure level is calculated by the sound pressure level deriving means 33.
Such information is organized by the data processing means 36 as sound reception frequency and sound pressure level data corresponding to the position of the local microphone 5a. Here, the position information of the local microphone 5a is input in advance from an input device 35 provided in the device. That is, the data is arranged on the main body side so as to correspond to FIGS. 2B and 2C. That is, they are organized as spatial position-frequency data and spatial position-sound pressure level data.
On the other hand, the information obtained by the sound source side microphone 5b is arranged in relation to the elapsed time from the time when the sound wave is generated, and is arranged as information as shown in FIG. That is, it is organized as time-reflected sound pressure level data.
The information obtained in this way is received by the ground surface side microphone 5a based on a comparison between the obtained frequency and a predetermined threshold value set in advance by an external input or the like by the propagation site determination means 34. It is determined as information on the status of the in-pipe propagation site 100 that emits the in-pipe propagation sound, and is determined as the status of the in-pipe propagation site 100, and the result is output. For example, when the detection frequency is higher than the threshold frequency, it is determined that there is water in the pipe, and when the detection frequency is lower than the threshold, it is determined that there is no water in the pipe. For example, in a pipe having an inner diameter of 200φ, the resonance frequency when gas (specifically, air or methane gas) is present in the pipe is 1013 Hz in air and 1335 Hz in methane, and the resonance frequency when water is present is about 4413 Hz. If 1500 Hz is set as the threshold value, the inundation state can be specified depending on whether the resonance frequency is higher than this.
[0019]
Furthermore, a configuration is adopted in which the sound source side microphone 5b is disposed at the speaker mounting portion. Therefore, in the sound source side microphone 5b, a reflected wave from the inside of the tube of the Qingdao pulse sound generated from the speaker 4 can be detected. A plurality of reflected sounds are returned from the inside of the tube depending on the position of the reflection part. Now, the information related to the reflected sound is also organized by the data processing means 36 in a state as shown in FIG.
The above is the basic configuration when the submerged state inspection method is performed using the present inspection device 2.
[0020]
Hereinafter, the work procedure will be described.
1 The worker 12 arrives at a work site 13 as shown in FIG. At this time, an embedment map showing the burial position of the gas pipe 1 near the site is prepared. Therefore, the buried position and direction of the pipe 1 are known in advance. If it is difficult to obtain such information, the position of the pipe 1 is confirmed using a ground radar (not shown) or the like, and at least above the buried pipe on the ground side.
2 A gas meter (not shown) of a specific home 7 is removed from the standpipe 11 and the speaker 4 is attached to the end 6. At this time, as the speaker 4 is attached, the sound source side microphone 5b for detecting the reflected sound returning from the inside of the pipe together with the speaker 4 is also arranged so that the sound receiving area thereof is in the pipe. .
3 On the other hand, a plurality of ground surface side microphones 5a are arranged at positions on the buried pipe, which are known in advance. This positional relationship (specifically, the distance from the vertical tube) is input into the inspection apparatus main body from the input device 35 and is subjected to processing by the data processing means 36.
4. After completing such a preparation stage, the Qingdao pulse generating means 31 operates to propagate the Qingdao pulse sound from the speaker 4 into the tube (sound propagation process).
5. The Qingdao pulse sound that propagates in the pipe propagates sequentially in a direction away from the speaker 4 on the sounding side, and for example, if there is a bend 14 or a flooded boundary as described above, the speaker Return to the side as reflected sound.
In this state, on the ground side, the signal is received by the surface-side microphone 5a arranged along the arrangement direction at a position on the pipe. That is, a propagation wave propagating in the pipe is received, and this wave emphasizes a resonance frequency representing the state of the propagation portion of the pipe 1. On the other hand, the sound source side microphone 5b sequentially receives the reflected waves described above.
6 As described above, the reception signal received by the ground-side microphone 5a and the sound source-side microphone 5b is sent to the inspection apparatus body 3, and the reception information in the ground-side microphone 5a includes its frequency and sound. The pressure level is specified in relation to the microphone position, and the sound pressure level of the received signal of the sound source side microphone is specified in the time domain with the origin when the sound wave is generated.
Such data information typically takes the form shown in FIGS. 2B and 2C.
7. The information arranged as described above is sent to the display device 37 provided in the inspection apparatus body 3 and can be visually confirmed by the operator.
As a result, based on the method described in the section of the means for solving the problem of the present application, the worker makes a determination such as the presence or absence of flooding, the presence or absence and location of the flooded boundary, and the identification of the flooded position.
8 Further, in the inspection apparatus main body 3, the resonance frequency of the sound wave determined by the relationship between the diameter of the pipe 1 and the substance type (specifically, gas or water) in the pipe is stored. In each local microphone 5a, it is determined whether the frequency of the detected received sound is close to the resonance frequency for gas or close to that of water, and the determination result according to the frequency of each received sound is, for example, a color-coded state Is configured to display. By adopting such a configuration, the inspection device 2 of the present application can automatically identify the flooded part A.
9 Further, the inspection apparatus 2 is configured to derive a change tendency of the sound pressure level of the received sound when viewed from the sound source side, and the operator can observe the change of the inundation boundary while observing the change tendency. The position can be detected.
10 On the other hand, on the display device 37 side, the elapsed time and the state of reflected waves (FIG. 2 (d)) with the origin at the time of occurrence of the Qingdao pulse are shown. Therefore, the position of the reflected sound on the time axis can be specified, and the structure of the pipe 1 (information on the pipe diameter, the number of bends, the position, etc.) that is known to some extent, The reflection source can be specified to some extent. At the same time, since the sound velocity of the sound wave propagating in the gas and the sound velocity of the sound wave propagating in the water are known, the position of each reflected signal from the sound source can be estimated. Through these steps, the reflection source of the reflected signal is tracked, and at the same time, the position of the inundation boundary can be finally identified by referring to and comparing the result of the position inspection of the inundation part based on the aforementioned frequency. .
[0021]
[Another embodiment]
As described above, in the submerged state inspection method of the present application, mainly by receiving sound waves propagating in the pipe outside the covering layer such as soil and walls, the frequency state is used, for example, in the pipe. It is possible to estimate the inundation position in the area.
In the above embodiment, a plurality of microphones 5 are arranged on the ground surface side, sound is received at each position, and the state in the pipe is determined from the received sound, but a plurality of microphones 5 is prepared. It is also possible to provide a single microphone and receive sound while an operator moves along the direction in which the buried pipe is arranged, and determine the flooding situation from such a reception result.
Furthermore, a self-propelled vehicle that automatically performs such a movement operation may be provided, and the self-propelled vehicle may be provided with a microphone.
In the above embodiment, the buried pipe buried in the ground is targeted. However, the method of the present application is applied to the pipe in the covered state when the property of the inside is greatly changed. It can be used for indexing.
In the above embodiment, the Qingdao pulse is used to obtain the impulse response of the acoustic system, but the so-called impulse sound may be generated and sent as it is, and further the sound that can obtain the impulse response is generated.・ You may send it in. In this way, a similar effect can be obtained if the sound has a plurality of wave number components.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a state in which a flooded portion in a gas pipe is being explored using the inundation state inspection method of the present application. FIG. 2 is an explanatory view of inspection results.
DESCRIPTION OF SYMBOLS 1 Gas piping 2 Inspection apparatus 4 Speaker 5 Microphone 5a Ground surface side microphone 5b Sound source side microphone 32 Frequency analysis means 34 Propagation site judgment means

Claims (6)

A flooded state inspection method for detecting a flooded state in a pipe concealed by a coating layer,
A sound propagation step of generating a sound at a predetermined location of the pipe and propagating a sound wave in the pipe, and a reception step of receiving the sound wave propagating in the pipe at a plurality of locations along the arrangement direction of the pipe are performed. A flooded state inspection method for judging the presence or absence of flooding in the pipe or the position of the flooded location according to the frequency of the sound wave received in the receiving step. The inundation state inspection method according to claim 1 , wherein the presence or absence of inundation or the position of the inundation location is determined according to the sound pressure level of the received sound together with the frequency of the sound wave received in the reception step .   2. In the receiving step, a sound wave reflected from the pipe is received at the sounding position of the propagating sound wave, and the inundation boundary position of the flooding is determined from a relationship between sounding time and sound receiving time. The inundation state inspection method described. An inspection apparatus provided with a speaker capable of generating sound having at least a plurality of frequency components in a tube, and a microphone capable of receiving propagation sound generated by the speaker and propagating through the tube,
Frequency analysis means for obtaining a frequency of the propagation sound received by the microphone is provided, and based on a comparison between the frequency obtained by the frequency analysis means and a predetermined threshold, the propagation sound received by the microphone An inspection apparatus provided with a propagation part judging means for judging the state of the propagation part. A speaker capable of generating a sound having at least a plurality of frequency components in the underground tube, and a plurality of microphones capable of receiving a propagation sound generated by the speaker and propagating through the underground tube;
As the plurality of microphones, a sound wave leaking from the underground tube to the surface side can be received at a plurality of locations on the ground side, and the speaker is propagated through the underground tube and reflected at the position of the speaker. A sound source side microphone capable of receiving a reflected sound when returning to the speaker position, and a frequency analysis means for determining a frequency of the sound received by each microphone, and the frequency obtained by the frequency analysis means, An inspection apparatus comprising propagation part determination means for determining a state of a propagation part of the propagation sound received by the microphone based on a comparison with a predetermined threshold . A speaker capable of generating a sound having at least a plurality of frequency components in the underground tube, and a plurality of microphones capable of receiving a propagation sound generated by the speaker and propagating through the underground tube;
As the plurality of microphones, a sound wave leaking from the underground tube to the surface side can be received at a plurality of locations on the ground side, and the speaker is propagated through the underground tube and reflected at the position of the speaker. And a sound source side microphone capable of receiving a reflected sound when returning to the speaker position, and a frequency analysis means for determining a frequency of the sound received by each microphone, and a sound pressure of the sound received by each microphone An inspection apparatus comprising: sound pressure level deriving means for determining a level; and data processing means for associating and organizing the frequency and sound pressure level of sound received by each microphone by the position of the microphone .

Images