JP2020071186A - Buried object survey device and sonic speed estimation method for buried object survey - Google Patents

Abstract

To provide a buried object survey device that can accurately estimate sonic speed in a concrete body.SOLUTION: A buried object survey device performs the following: performing ultrasonic wave transmission and reception between a plurality of probes in which a probe transmits ultrasonic wave to a concrete body and another probe receives reflection wave from the bottom surface of the concrete body; averaging reflection waves with the same distance between the probes; extracting the maximum value time and the minimum value time of the averaged waveform for each distance between the probes; creating a maximum value time graph and a minimum value time graph indicating the maximum value time and the minimum value time for each distance between the probes on a coordinate whose axes are the distance between the probes and time; determining a delay time from the minimum value time graph; converting the maximum value time graph into a graph on a coordinate that incorporates the thickness of the concrete body and the delay time; and estimating sonic speed based on the converted graph.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an embedded object exploration apparatus for exploring an embedded object using ultrasonic waves, and more particularly to an embedded object exploration apparatus and an embedded object exploration sound velocity estimation method for estimating the speed of sound in a medium such as concrete.

  A buried object exploration device using ultrasonic waves and radar is known for exploring buried objects and targets such as reinforcing bars and gas pipes buried in media such as the ground, walls, and floors (for example, patents Reference 1 etc.). This buried object exploration device is provided with a sensor unit composed of a transmission / reception circuit, a transmission / reception antenna, and the like, and a monitor unit (display) in the device body, and four wheel wheels for moving in the front-back direction are arranged in the device body. It is set up. Then, a pulsed radar wave generated at a predetermined repetition period is radiated from the transmitting antenna to the ground or the wall, the reflected wave returning from the ground or the wall is received by the receiving antenna, and based on the reflected wave. The analysis processing is performed and the inside information of the ground and the wall is displayed on the monitor unit.

  In order to obtain a clear image in such a buried object exploration device, it is necessary to know the sound velocity (ultrasonic wave propagation velocity) in the medium, and an ultrasonic nondestructive measurement device equipped with a function of measuring the sound velocity is known. (For example, refer to Patent Document 2). This device radiates ultrasonic waves from the first probe to the concrete structure, receives the reception signal reflected by the bottom surface of the concrete structure with the second probe, and receives the signals at different probe intervals. The sound velocity is determined from the arrival time of the reflected wave calculated correspondingly.

Japanese Patent Laid-Open No. 2000-019257 JP, 2011-242332, A

  By the way, in the device described in Patent Document 2, since the sound velocity is calculated and determined only from the pair of reflected wave arrival times having different probe intervals, it is not possible to grasp the variation in the sound velocity value, and the sound velocity accuracy is deteriorated. There is a risk. In addition, the received signal is frequency analyzed to determine whether it is a single frequency, and the reflected wave arrival time is specified and known. Therefore, not only the configuration is complicated, but also an error may occur in specifying the reflected wave arrival time. is there.

  Therefore, an object of the present invention is to provide an embedded object exploration apparatus and an embedded object exploration sound velocity estimation method that can more accurately estimate the acoustic velocity in a medium.

  In order to achieve the above object, the invention according to claim 1 radiates ultrasonic waves from a plurality of probes to a medium, receives reflected waves from the medium by the plurality of probes, and performs an analysis process. By doing so, a buried object exploration device for exploring an embedded object in the medium, wherein ultrasonic waves are transmitted from a certain probe to the medium and reflected waves from the bottom surface of the medium are detected by another probe. Ultrasonic transmission and reception of receiving is performed between the plurality of probes, and the reflected waves having the same inter-probe distance are averaged to generate an average waveform for each inter-probe distance, and the average The maximum value time, which is the time of the peak portion of the waveform, and the minimum value time, which is the time of the valley portion of the average waveform, are extracted for each inter-probe distance, and the maximum value for each inter-probe distance. A maximum value time graph showing time on a coordinate with the distance between the probes and time as an axis, and the distance between the probes And the minimum value time, and to create a minimum value time graph showing on the coordinates with the distance between the probe and time as an axis, and the ultrasonic wave is actually transmitted to the medium after the ultrasonic wave transmission processing is performed. The delay time until being incident is calculated from the minimum value time graph, and the coordinates of the known thickness of the medium and the delay time are incorporated into the coordinates, and the maximum value time graph is coordinate-converted, and the maximum value is coordinate-converted. The sound velocity is estimated based on a time graph.

  According to a second aspect of the present invention, ultrasonic waves are radiated from a plurality of probes to a medium, reflected waves from the medium are received by the plurality of probes, and analysis processing is performed. An embedded object exploration device for exploring an embedded object, wherein ultrasonic waves are transmitted and received by transmitting ultrasonic waves from a certain probe to the medium and receiving reflected waves from the bottom surface of the medium by another probe. It is performed between the plurality of probes, and the reflected waves having the same inter-probe distance are averaged to generate an average waveform for each inter-probe distance, which is the time of the peak portion of the average waveform. The maximum value time and the minimum value time that is the time of the valley portion of the average waveform are extracted for each inter-probe distance, and the maximum time for each inter-probe distance is calculated as the inter-probe distance. And a maximum value time graph shown on a coordinate with time as an axis, and the minimum value time for each distance between the probes. Creating a minimum value time graph shown on the coordinates with the inter-child distance and time as an axis, and the delay time from when the ultrasonic wave is actually transmitted to the medium after performing the ultrasonic wave transmission process, Determining from the minimum value time graph, the coordinates incorporating the assumed value of the medium and the delay time, coordinate conversion of the maximum value time graph, to estimate the speed of sound based on the coordinate converted maximum value time graph, This estimation process is performed on a predetermined number of hypothetical values, and the final sound velocity is estimated based on the estimated plurality of sound velocities.

  According to a third aspect of the present invention, ultrasonic waves are radiated from a plurality of probes to a medium, reflected waves from the medium are received by the plurality of probes, and analysis processing is performed. In a buried object exploration, which is a method for estimating a sound velocity in a buried object for estimating a sound velocity in the medium, ultrasonic waves are transmitted from a certain probe to the medium, and reflected from the bottom surface of the medium. Receiving a wave with another probe, ultrasonic wave transmission / reception between the plurality of probes is performed, the reflected waves having the same inter-probe distance are averaged, and each inter-probe distance is increased. An average waveform is generated, and a maximum value time that is the time of the peak portion of the average waveform and a minimum value time that is the time of the valley portion of the average waveform are extracted for each inter-probe distance, and the probe The maximal value indicating the maximal time for each inter-child distance on a coordinate system with the inter-probe distance and time as axes. Between the probe and the minimum value time for each distance between the probes, a minimum value time graph showing on the coordinates with the distance between the probes and time as an axis is created, and ultrasonic wave transmission processing is performed. The delay time from when the ultrasonic wave is actually incident on the medium is calculated from the minimum value time graph, and the maximum value time graph is plotted on the coordinates incorporating the known thickness of the medium and the delay time. Is subjected to coordinate conversion, and the sound velocity is estimated based on the coordinate-converted maximum value time graph.

  According to a fourth aspect of the present invention, ultrasonic waves are radiated from a plurality of probes to a medium, reflected waves from the medium are received by the plurality of probes, and analysis processing is performed. In a buried object exploration, which is a method for estimating a sound velocity in a buried object for estimating a sound velocity in the medium, ultrasonic waves are transmitted from a certain probe to the medium, and reflected from the bottom surface of the medium. Receiving a wave with another probe, ultrasonic wave transmission / reception between the plurality of probes is performed, the reflected waves having the same inter-probe distance are averaged, and each inter-probe distance is increased. An average waveform is generated, and a maximum value time that is the time of the peak portion of the average waveform and a minimum value time that is the time of the valley portion of the average waveform are extracted for each inter-probe distance, and the probe The maximal value indicating the maximal time for each inter-child distance on a coordinate system with the inter-probe distance and time as axes. Between the probe and the minimum value time for each distance between the probes, a minimum value time graph showing on the coordinates with the distance between the probes and time as an axis is created, and ultrasonic wave transmission processing is performed. The delay time from when the ultrasonic wave is actually incident on the medium is calculated from the minimum value time graph, and the maximum value time graph is coordinated with the assumed value of the medium thickness and the delay time. Coordinate conversion, estimating the sound velocity based on the coordinate-converted maximum value time graph, performing an estimation process for a predetermined number of assumed values, and estimating the final sound velocity based on a plurality of estimated sound velocity, It is characterized by

  According to the inventions of claims 1 and 3, a maximum value time graph and a minimum value time graph are created based on an average waveform of a plurality of distances between the probes, and a delay time is calculated from the minimum value time graph, Since the sound velocity is estimated based on the maximum value time graph, which is a coordinate that incorporates the thickness of the medium and the delay time, even if the bottom surface reflected wave is difficult to find due to the influence of aggregates, etc. It is possible to find a characteristic curve and estimate the speed of sound in the medium more accurately.

  Moreover, since the averaged waveforms are generated by averaging the reflected waves with the same probe-to-probe distance, the amount of calculation can be reduced, and the effect of thermal noise can be expected to be reduced. It becomes possible to extract the minimum value time more accurately, and as a result, it becomes possible to more accurately estimate the sound velocity in the medium.

  According to the inventions of claims 2 and 4, the characteristic of the curve changes depending on the thickness of the medium, so that the speed of sound in the medium can be more accurately estimated even if the thickness of the medium is unknown.

It is a schematic block diagram which shows the buried object exploration apparatus which concerns on embodiment of this invention. FIG. 2 is a plan view (a) and a front view (b) showing the positional relationship between the probe and the concrete body of the buried object exploration apparatus of FIG. 1. 6 is a first flowchart showing a sound velocity estimation method in the buried object exploration apparatus of FIG. 1. It is a 2nd flowchart following FIG. It is a figure which shows the waveform which averaged the received waveform in the buried object search apparatus of FIG. 1, (a) shows the waveform of the 1st inter-probe distance, (b) shows the waveform of the 2nd inter-probe distance. .. It is the figure which plotted the average waveform for every distance between probes in the buried object exploration apparatus of FIG. It is a figure which shows the maximum value time graph created based on the graph of FIG. It is a figure which shows the method of extracting the maximum value time from the average waveform of a certain inter-probe distance in the buried object search apparatus of FIG. It is a figure (maximum value time graph) which shows the maximum value time extracted by the method of FIG. 8 for every distance between probes. It is a figure which shows the method of calculating delay time from the minimum value time graph in the buried object search apparatus of FIG. It is a figure explaining the coordinate parameter which incorporated the thickness and delay time of a concrete body in the buried object exploration apparatus of FIG. It is a figure which shows the method of estimating sound velocity based on the maximum value time graph which carried out coordinate conversion in the buried object exploration apparatus of FIG. It is a figure which shows the method of acquiring an appropriate straight line in the buried object search apparatus of FIG. It is a figure which shows the relationship between the thickness of a concrete body and the square residual by the buried object exploration apparatus of FIG. It is a figure which shows the relationship between the thickness of a concrete body and estimated sound velocity by the buried object exploration apparatus of FIG. It is a figure which shows the theoretical value (a) of the sound velocity in embodiment of this invention, and the estimated value (b) by the buried object search apparatus of FIG.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

  1 to 16 show an embodiment of the present invention, and FIG. 1 is a schematic block diagram showing a buried object exploration apparatus 1 according to this embodiment. The buried object exploration apparatus 1 is an apparatus for exploring an embedded object / target such as a reinforcing bar or a gas pipe, which is buried in a medium such as a concrete wall, floor, ceiling, or underground, and has a speed of sound ( The method of estimating the ultrasonic wave propagation velocity) is different from the conventional method, and other configurations and functions are the same as those of the conventional method. That is, ultrasonic waves are radiated into the medium from the plurality of probes (probes) 2, reflected waves from the medium are received by the plurality of probes 2, analyzed by the measurement unit 3, and the result is displayed on the display. ..

In the buried object exploration apparatus 1 as described above, a method for estimating the sound velocity for buried object exploration for estimating the sound velocity in the medium will be described below. Here, in this embodiment, as shown in FIG. 2, at equal intervals of 64 probe 2 ₁ to 2 ₆₄ are arranged in 16 horizontal Retsutate 4 columns lattice, concrete having a thickness h ( It is assumed that the buried object exploration apparatus 1 is arranged so as to be in contact with the surface 101a of the medium 101. Then, the sound velocity unit 4 estimates the sound velocity in the concrete body 101 as follows while controlling the probes 2 ₁ to 2 ₆₄ . Here, the case where the thickness h of the concrete body 101 is known and the case where it is unknown will be described together.

As shown in FIG. 3, first, as an ultrasonic wave transmission / reception step, the probe 2 group of the buried object exploration apparatus 1 is brought into contact with the surface 101a of the concrete body 101, and bottom surface reflected waves are transmitted / received between all the probes 2 (step S1). That is, ultrasonic wave transmission / reception is performed between all probes 2 such that ultrasonic waves are transmitted from a certain probe 2 into the concrete body 101 and reflected waves from the bottom surface 101b of the concrete body 101 are received by another probe 2. Specifically, by transmitting ultrasonic waves from the first probe 2 ₁ received by the second probe 2 _2, received by the third probe 2 ₃ transmits the ultrasonic wave from the first probe 2 ₁ 4032 (= 64 × 63) ultrasonic transmissions and receptions are performed.

  Next, as a waveform averaging step, all received waveforms having the same probe distance are averaged (step S2). That is, all the reflected waves having the same probe distance are overlapped and averaged to generate an average waveform for each probe distance. Here, in this embodiment, there are 56 types of inter-probe distances, and a reflected wave averaged for each of the 56 inter-probe distances is generated. For example, the received waveform having the smallest inter-probe distance is averaged to generate an average waveform of the first inter-probe distance d1 as shown in FIG. 5A, and the received waveform having the second smallest inter-probe distance is averaged. Then, the average waveform of the second inter-probe distance d2 as shown in FIG. 5B is generated. Generation of such an average waveform is performed for all 56 inter-probe distances.

  Subsequently, as a graph creating step, the maximum value time and the minimum value time of each average waveform are graphed (step S3). That is, first, as shown in FIG. 6, an average waveform of each inter-probe distance is shown (as if the waveform of FIG. 5 is arranged vertically) on a coordinate where the horizontal axis is the inter-probe distance and the vertical axis is time.・ Make a graph. Next, the maximum value time that is the time of the peak portion of the average waveform and the minimum value time that is the time of the valley portion of the average waveform are extracted for each average waveform of the inter-probe distance. Then, as shown in FIG. 7, a maximum value time graph is shown in which a column of maximum value times for each inter-probe distance is shown on a coordinate with the inter-probe distance and time as axes, and similarly, for each inter-probe distance. A minimum value time graph is shown in which the minimum value time column of is shown on the coordinates with the inter-probe distance and time as axes.

  More specifically, as shown in FIG. 8, all the maximum value times which are the time of the peak portion P of the average waveform of a certain inter-probe distance are extracted, and as shown in FIG. 9, the horizontal axis represents the inter-probe distance. A column of the extracted maximum value times is plotted on the corresponding inter-probe distance on the coordinate whose vertical axis is time. By performing such a plot of the maximum value time on the average waveform of all the inter-probe distances, and also performing the minimum value time, a maximum value time graph (a graph of the probe distance vs. the maximum value time) and a minimum value A time graph (graph of distance between probes vs. minimum value time) is created.

  Then, as a delay time indexing step, the delay time is acquired from the minimum value time graph (step S4). That is, the delay time is the time from the ultrasonic wave transmitting process in the buried object exploration apparatus 1 until the ultrasonic wave is actually incident on the concrete body 101 (may include the time required for the receiving process. ), The reception of the reflected wave will be delayed by this delay time. On the other hand, the arrival time of the direct wave reflected from the surface 101a of the concrete body 101 is proportional to the inter-probe distance, and if the minimum value time due to the direct wave of each inter-probe distance is connected, a straight line L1 (y = Αx + β). The intercept β of the straight line L1 with respect to the time axis is the delay time. Therefore, while changing the two parameters of the slope α and the intercept β, the straight line L1 that is most fitted (the square residual is small) is searched for on the minimum value time graph, and the delay time is calculated from this straight line L1.

  Here, the delay time is calculated from the minimum value time graph because the reflected wave (maximum value time graph) is reflected on the bottom surface 101b (boundary with air) of the concrete body 101 so that the amplitude has a minus sign. On the other hand, since the direct wave does not involve reflection, the amplitude does not have a negative value. Therefore, the direct wave applies the minimum time, and the reflected wave applies the maximum time. Further, although FIG. 7 is a maximum value time graph, lines are connected by the maximum value time so that the difference between the straight line L1 and the hyperbola L2 can be easily compared. However, in practice, the straight line L1 should be calculated from the minimum value graph.

  Next, if the thickness h of the concrete body 101 is known (in the case of “Y” in step S5), the process proceeds to step S6, and if it is unknown (in the case of “N” in step S5), the process proceeds to step S8. move on. Here, for example, when the thickness h of the concrete body 101 is input to the input unit of the buried object exploration apparatus 1, the thickness h is stored in the storage unit of the buried object exploration apparatus 1 and becomes known.

  In step S6, as a coordinate conversion step, the maximum value time graph is subjected to coordinate conversion into coordinates incorporating the thickness h of the concrete body 101 and the delay time. That is, as shown in FIG. 11, a time t from the transmission of an ultrasonic wave from a certain probe 2 to the concrete body 101 and the reception of the ultrasonic wave by another probe 2 is represented by Expression 1. Here, d is the inter-probe distance, and δt is the delay time. Next, the time parameter T is defined as in Equation 2, and the distance parameter D is defined as in Equation 3. Then, the delay time calculated in step S4 is substituted into the delay time δt, the known thickness is substituted into the thickness h, and as shown in FIG. 12, the horizontal axis represents the distance parameter D and the vertical axis represents the coordinate of the time parameter T. Then, coordinate conversion of the maximum value time graph is performed.

  Then, as a sound velocity estimation step, the sound velocity is estimated based on the maximum value time graph coordinate-converted in step S6 (step S7). That is, in the maximum value time graph coordinate-converted as described above, the maximum value time (peak time) of the wave reflected from the bottom surface 101b of the concrete body 101 having the thickness h is connected by a straight line (T = αD) passing through the origin. Since it should be, find the straight line from the origin to which the sequence of maximum values fits best. Then, as shown in FIG. 12, when the straight line L11 is searched for, the inverse number (1 / α) of the inclination α of the straight line L11 is calculated and estimated as the sound velocity.

  Here, in order to find a straight line to be fitted, as shown in FIG. 13, while changing the inclination α of the straight line little by little, a straight line (T = αD) extending from the origin is created and the squared residual is calculated. Then, the straight line with the smallest squared residual is selected as the best fitting straight line. For example, FIG. 13A shows a straight line having the smallest slope and its square residual Ra, FIG. 13B shows a straight line having the second smallest slope and its square residual Rb, and FIG. ) Shows a straight line with a moderate slope and its squared residual Rc, FIG. 13D shows a straight line with the second largest slope and its squared residual Rd, and FIG. The largest straight line and its squared residual Re are shown. In this case, the squared residual Rc is the smallest, and the straight line in FIG. 13C is selected.

  On the other hand, when the thickness h of the concrete body 101 is unknown, first, the thickness h is assumed (step S8), and then the coordinate conversion step is performed in the same manner as in step S6, and the assumed thickness (assumed value) h Then, the maximum value time graph is coordinate-converted into the coordinates including the delay time and the delay time (step S9). Subsequently, as a sound velocity estimation step, the sound velocity is estimated based on the coordinate-converted maximum value time graph in the same manner as in step S7 described above (step S10).

  After that, when the predetermined number of sound velocity values are not obtained (“N” in step S11), the process returns to step S8, the thickness h is set to the next assumed value, and the same processing is performed. In this way, the estimation process of performing the coordinate conversion step and the sound velocity estimation step assuming the thickness h is performed for a predetermined number of assumed values. Here, the predetermined number is set to a value large enough to obtain a desired speed of sound in the next step S12.

  Then, when a predetermined number of sound velocity values are obtained (“Y” in step S11), the final sound velocity is estimated based on the estimated sound velocity values as the final sound velocity estimation step (step S12). ). That is, the square residual of each sound velocity value (straight line) estimated in step S10 is compared with the assumed value of the thickness h, and the sound velocity value with the smallest square residual is specified and estimated as the final sound velocity. For example, when the square residual of each sound velocity value (each assumed value of the thickness h) estimated in step S10 is obtained as shown in FIG. 14, 150 mm that is the thickness h having the smallest square residual is selected. Then, for example, when the sound velocity value with respect to the assumed value of the thickness h is obtained as shown in FIG. 15, 4032 m / s which is the sound velocity value of the thickness h of 150 mm is specified and estimated as the final sound velocity.

  Thus, according to the buried object exploration apparatus 1 and the method for estimating the sound velocity for buried object exploration, the maximum value time graph and the minimum value time graph are created based on the average waveform of a plurality of inter-probe distances, and the delay time δt Is estimated from the minimum value time graph, and the sound velocity is estimated based on the maximum value time graph which is a coordinate incorporating the thickness h of the concrete body 101 and the delay time δt. Therefore, the sound velocity in the concrete body 101 is more accurately estimated. It becomes possible.

  Moreover, since the averaged waveforms are generated by averaging the reflected waves with the same probe distance, it is not necessary to perform the frequency analysis, which simplifies the configuration and more accurately extracts the maximum value time and the minimum value time. As a result, it becomes possible to more accurately estimate the speed of sound in the concrete body 101. Furthermore, even if there is a buried object such as an aggregate, the sound speed is estimated based on the maximum value time and the minimum value time of the total average waveform including the reflection from the buried object, so the sound speed can be estimated more accurately. It will be possible.

  Further, since the sound velocity is estimated by assuming the thickness h of the concrete body 101 to be a predetermined number, it is possible to more accurately estimate the sound velocity in the concrete body 101 even if the thickness h of the concrete body 101 is unknown. ..

  Here, we will introduce an example of actual estimation using this sound velocity estimation method for buried object exploration. FIG. 16A shows a delay of the concrete body 101 having no aggregate and a thickness h of 150 mm, the concrete body 101 having aggregate and a thickness h of 150 mm, and the concrete body 101 having an aggregate and a thickness h of 100 mm. The theoretical values of time (time delay) δt, sound velocity and thickness are shown. 16B shows a concrete body 101 having no aggregate and a thickness h of 150 mm, a concrete body 101 having aggregate and a thickness h of 150 mm, and a concrete body 101 having aggregate and a thickness h of 100 mm. The estimated values of the delay time (time delay) δt, the speed of sound, and the thickness by this method are shown. From this result, it was confirmed that the present method can estimate the sound velocity close to the theoretical value even when there is no aggregate.

  Although the embodiments of the present invention have been described above, the specific configuration is not limited to the above-mentioned embodiments, and even if there is a design change or the like within the scope not departing from the gist of the present invention, Included in the invention. For example, in the above-described embodiment, the ultrasonic wave transmission / reception step is performed between all the probes 2, but the ultrasonic wave transmission is performed between the probes 2 specified according to a predetermined rule (for example, every time several probes are skipped). You may make it perform a transmission / reception step. Furthermore, after removing the thermal noise from the averaged waveform averaged in the waveform averaging step, the process may proceed to the graph creating step. Although the delay time is estimated from the minimum value and the sound velocity is estimated from the maximum value, the roles of the minimum value and the maximum value may be exchanged.

1 buried object exploration device 2 probe (probe)
3 Measuring part 4 Sound velocity part 101 Concrete body (medium)
101a front surface 101b bottom surface

Claims (4)

An embedded object exploration apparatus for exploring an embedded object in the medium by radiating ultrasonic waves from a plurality of probes to a medium and receiving reflected waves from the medium by the plurality of the probes for analysis processing. And
Performing ultrasonic wave transmission / reception between the plurality of probes by transmitting an ultrasonic wave from a certain probe to the medium and receiving a reflected wave from the bottom surface of the medium by another probe,
Averaging the reflected waves having the same inter-probe distance to generate an average waveform for each inter-probe distance,
The maximum value time, which is the time of the peak portion of the average waveform, and the minimum value time, which is the time of the valley portion of the average waveform, are extracted for each of the inter-probe distances, and for each of the inter-probe distances, Maximum value time, the maximum value time graph showing on the coordinates with the distance between the probe and the time axis, the minimum value time for each distance between the probes, the distance between the probe and the time Create a minimum value time graph shown on the axis coordinate,
Determining the delay time from performing the ultrasonic wave transmission process until the ultrasonic wave is actually incident on the medium from the minimum value time graph,
To the coordinates incorporating the known thickness of the medium and the delay time, coordinate conversion of the maximum value time graph,
An embedded object exploration device, which estimates a sound velocity based on a coordinate-converted maximum value time graph. An embedded object exploration apparatus for exploring an embedded object in the medium by radiating ultrasonic waves from a plurality of probes to a medium and receiving reflected waves from the medium by the plurality of the probes for analysis processing. And
Performing ultrasonic wave transmission / reception between the plurality of probes by transmitting an ultrasonic wave from a certain probe to the medium and receiving a reflected wave from the bottom surface of the medium by another probe,
Averaging the reflected waves having the same inter-probe distance to generate an average waveform for each inter-probe distance,
The maximum value time, which is the time of the peak portion of the average waveform, and the minimum value time, which is the time of the valley portion of the average waveform, are extracted for each of the inter-probe distances, and for each of the inter-probe distances, Maximum value time, the maximum value time graph showing on the coordinates with the distance between the probe and the time axis, the minimum value time for each distance between the probes, the distance between the probe and the time Create a minimum value time graph shown on the axis coordinate,
Determining the delay time from performing the ultrasonic wave transmission process until the ultrasonic wave is actually incident on the medium from the minimum value time graph,
Coordinate conversion of the assumed value of the thickness of the medium and the delay time, coordinate conversion of the maximum value time graph, the sound speed is estimated based on the coordinate converted maximum value time graph, an estimation process of a predetermined number. Do it for the hypothetical value,
A buried object exploration device, characterized in that a final sound velocity is estimated based on a plurality of estimated sound velocities. In the embedded object exploration for exploring the embedded object in the medium, by radiating ultrasonic waves to the medium from the plural probes and receiving the reflected waves from the medium by the plural probes to perform analysis processing. A sound velocity estimation method for buried object exploration for estimating the sound velocity in the medium,
Performing ultrasonic wave transmission / reception between the plurality of probes by transmitting an ultrasonic wave from a certain probe to the medium and receiving a reflected wave from the bottom surface of the medium by another probe,
Averaging the reflected waves having the same inter-probe distance to generate an average waveform for each inter-probe distance,
The maximum value time, which is the time of the peak portion of the average waveform, and the minimum value time, which is the time of the valley portion of the average waveform, are extracted for each of the inter-probe distances, and for each of the inter-probe distances, Maximum value time, the maximum value time graph showing on the coordinates with the distance between the probe and the time axis, the minimum value time for each distance between the probes, the distance between the probe and the time Create a minimum value time graph shown on the axis coordinate,
Determining the delay time from performing the ultrasonic wave transmission process until the ultrasonic wave is actually incident on the medium from the minimum value time graph,
To the coordinates incorporating the known thickness of the medium and the delay time, coordinate conversion of the maximum value time graph,
A method for estimating the speed of sound for buried object exploration, which comprises estimating the speed of sound based on a coordinate-converted maximum value time graph. In the embedded object exploration for exploring the embedded object in the medium, by radiating ultrasonic waves to the medium from the plural probes and receiving the reflected waves from the medium by the plural probes to perform analysis processing. A sound velocity estimation method for buried object exploration for estimating the sound velocity in the medium,
Performing ultrasonic wave transmission / reception between the plurality of probes by transmitting an ultrasonic wave from a certain probe to the medium and receiving a reflected wave from the bottom surface of the medium by another probe,
Averaging the reflected waves having the same inter-probe distance to generate an average waveform for each inter-probe distance,
The maximum value time, which is the time of the peak portion of the average waveform, and the minimum value time, which is the time of the valley portion of the average waveform, are extracted for each of the inter-probe distances, and for each of the inter-probe distances, Maximum value time, the maximum value time graph showing on the coordinates with the distance between the probe and the time axis, the minimum value time for each distance between the probes, the distance between the probe and the time Create a minimum value time graph shown on the axis coordinate,
Determining the delay time from performing the ultrasonic wave transmission process until the ultrasonic wave is actually incident on the medium from the minimum value time graph,
Coordinate conversion of the assumed value of the thickness of the medium and the delay time, coordinate conversion of the maximum value time graph, the sound speed is estimated based on the coordinate converted maximum value time graph, an estimation process of a predetermined number. Do it for the hypothetical value,
A sound velocity estimation method for exploring buried objects, comprising estimating a final sound velocity based on a plurality of estimated sound velocities.

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