Underground cavity nondestructive detection method and system using mobile terminal

Abstract

The invention provides an underground cavity nondestructive detection method and system using a mobile terminal. The method comprises the following steps: generating a sound wave signal with a preset frequency through the mobile terminal; the sound wave signals are collected and preprocessed; analyzing the frequency spectrum of the sound wave signal, and extracting the frequency spectrum characteristic of the sound wave signal; and carrying out resonance frequency shift detection and cavity depth estimation based on the frequency spectrum characteristics. According to the invention, underground cavity rapid detection without extra hardware is realized; the method disclosed by the invention is extremely low in deployment cost and suitable for large-scale popularization; the method is high in detection precision, and meets the requirements of complex scenes such as urban roads and culverts.

Description

Technical Field

[0001] This invention relates to the field of underground cavity detection technology, and in particular to a non-destructive detection method and system for underground cavities using a mobile terminal. Background Technology

[0002] Current methods for detecting underground cavities mainly rely on specialized equipment such as ground-penetrating radar (GPR), seismic wave detectors, and resistivity imagers. These devices are large, expensive, and require highly skilled operators, making them difficult to deploy rapidly in emergency scenarios and meet the needs of widespread public adoption.

[0003] In recent years, smartphones and other mobile terminals have integrated multiple high-performance microphones and speakers, possessing certain acoustic detection capabilities, and have become widely adopted across all levels of society. Among these, multi-microphone array technology can be used for spatial sound source localization and waveform feature acquisition, possessing beamforming, signal enhancement, and direction awareness capabilities, and is widely applied in fields such as speech recognition and sound source localization. By emitting high-frequency sound waves and receiving the echo signals reflected from different media interfaces (such as soil and cavities), the identification of interface features can be achieved by combining the resonant frequency shift phenomenon.

[0004] Resonant frequency shift technology is based on the natural resonance characteristics of a medium's structure. At the soil-cavity interface, when the incident sound wave frequency approaches the structural resonant frequency, a significant change in the spectral response occurs. This frequency shift is related to the size, depth, and material of the cavity and has been studied and applied in fields such as underground pipeline inspection and medical ultrasound. However, currently, there is no complete method or device that combines a smartphone as both a sound wave source and a receiving array with resonant frequency shift analysis to achieve non-destructive detection of underground cavities, indicating a significant technological gap and application potential. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a method and system for non-destructive detection of underground cavities using a mobile terminal.

[0006] In a first aspect, embodiments of the present invention provide a method for non-destructive detection of underground cavities using a mobile terminal, comprising:

[0007] Using a mobile terminal to generate sound wave signals at a preset frequency;

[0008] The acoustic signal is acquired and preprocessed;

[0009] The spectrum of the acoustic signal is analyzed to extract its spectral features;

[0010] Based on the aforementioned spectral characteristics, resonant frequency shift detection and void depth estimation are performed.

[0011] Furthermore, the mobile terminal is used to generate a sound wave signal of a preset frequency. Specific steps include:

[0012] The system emits a sinusoidal sound wave signal of a specified frequency from the mobile terminal's speaker, sets the sound wave sampling rate, and calculates the number of samples to be generated based on the duration of the sound wave. A sinusoidal function is used to generate a simulated sound wave signal of the target frequency. The simulated sound wave signal is then converted into 16-bit PCM audio data. The AudioTrack interface is used to load and play the PCM audio data in static mode, achieving accurate output of high-frequency sound waves.

[0013] A microphone array is used for synchronous sampling, and the microphone of the mobile terminal is controlled to enable synchronous recording function, so as to collect the sound wave reflection signal from the ground while transmitting sound waves.

[0014] Furthermore, while transmitting sound waves, the method of acquiring sound wave reflection signals from underground includes: first, initializing the audio recording object and setting the same sampling rate and audio format as the transmission; then creating a buffer for receiving audio data in real time; starting the recorder and recording sound wave data for a preset time in a loop; and writing the sound wave data into a local audio file in the original PCM format.

[0015] Furthermore, the acoustic signal is acquired and preprocessed. The specific methods include: loading the recorded audio file using the librosa library, removing the DC offset component by subtracting the mean; filtering low-frequency signals below a preset frequency using a 4th-order Butterworth high-pass filter, and normalizing the processed signal to scale its amplitude range to the [-1, 1] interval.

[0016] Furthermore, the spectrum of the acoustic signal is analyzed to extract its spectral features. Specific methods include: performing a short-time Fourier transform on the signal to convert the time-domain signal into a time-frequency two-dimensional matrix; converting the amplitude spectrum into decibel units and displaying the spectrum using a heatmap; the spectrum shows the energy changes of different frequency components of the acoustic wave as it propagates over time, and the presence of abnormal frequency band responses can be visually observed through the spectrum.

[0017] Furthermore, based on the aforementioned spectral characteristics, a resonant frequency shift detection algorithm is employed for resonant frequency shift detection. The specific method includes: averaging the frequency dimensions of the short-time Fourier transform to obtain the overall power spectrum; identifying the dominant frequency peak with prominent energy in the power spectrum; comparing the detected dominant frequency peak with the reference frequency value to calculate the frequency offset; and comparing the offset with a preset offset threshold to determine whether an offset exists.

[0018] Furthermore, after calculating the frequency offset, the cavity depth is estimated based on the preset frequency offset. The specific estimation method includes: obtaining a frequency offset and cavity depth correspondence table based on expert experience or experiments. The frequency offset and cavity depth correspondence table is used to record the relationship between the frequency offset and the corresponding cavity depth. The calculated frequency offset is substituted into the frequency offset and cavity depth correspondence table to obtain the cavity depth.

[0019] Furthermore, it also includes: acquiring location information while collecting acoustic signals, constructing a location information and depth list, drawing a two-dimensional heat map or cross-sectional view based on the location information and depth list, and visually displaying the cavity information through the two-dimensional heat map or cross-sectional view.

[0020] Secondly, this invention also discloses a non-destructive detection system for underground cavities using a mobile terminal, comprising: an acoustic signal generation unit, an acoustic signal acquisition and preprocessing unit, a spectrum analysis unit, and a resonant frequency shift detection and cavity depth estimation unit; wherein:

[0021] A sound wave signal generating unit is used to generate a sound wave signal of a preset frequency using a mobile terminal.

[0022] The acoustic signal acquisition and preprocessing unit is used to acquire and preprocess the acoustic signal;

[0023] The spectrum analysis unit is used to analyze the spectrum of the acoustic signal and extract the spectral features of the acoustic signal.

[0024] The resonant frequency shift detection and hole depth estimation unit is used to perform resonant frequency shift detection and hole depth estimation based on the spectral characteristics.

[0025] Thirdly, the present invention also discloses an electronic device, characterized in that it comprises:

[0026] One or more processors;

[0027] Memory, used to store one or more programs;

[0028] When the one or more programs are executed by the one or more processors, the one or more processors implement the non-destructive testing method.

[0029] This invention provides a non-destructive detection method for underground cavities using a mobile terminal. The method involves generating an acoustic signal at a preset frequency via the mobile terminal; acquiring and preprocessing the acoustic signal; analyzing the spectrum of the acoustic signal to extract its spectral features; and performing resonance frequency shift detection and cavity depth estimation based on the spectral features. This invention enables rapid detection of underground cavities without additional hardware; the method has extremely low deployment costs, making it suitable for large-scale deployment; and the method offers high detection accuracy, meeting the needs of complex scenarios such as urban roads and culverts. Attached Figure Description

[0030] Figure 1 A flowchart illustrating a non-destructive detection method for underground cavities using a mobile terminal, provided as an embodiment of the present invention;

[0031] Figure 2 A structural block diagram of a non-destructive detection system for underground cavities using a mobile terminal, provided in an embodiment of the present invention;

[0032] Figure 3 This is a structural block diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solutions of the present invention, exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0034] Where there is no conflict, the various embodiments of the present invention and the features thereof may be combined with each other.

[0035] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0036] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded. Terms such as “connected” or “linked” are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect.

[0037] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art and the invention, and will not be interpreted as having an idealized or overly formal meaning unless expressly so defined herein.

[0038] In the technical solution of this invention, the collection, storage, use, processing, transmission, provision, and disclosure of user personal information all comply with relevant laws and regulations and do not violate public order and good morals. The use of user data in this technical solution follows relevant national laws and regulations (e.g., the "Information Security Technology - Personal Information Security Specification"). For example: appropriate measures are taken for personal information access control; restrictions are imposed on the display of personal information; the purpose of using personal information does not exceed the scope of direct or reasonable association; and explicit identity targeting is eliminated when using personal information to avoid precisely locating a specific individual.

[0039] To address at least one of the technical problems existing in the aforementioned related technologies, the present invention provides a method and system for non-destructive detection of underground cavities using a mobile terminal.

[0040] This embodiment discloses a non-destructive detection method for underground cavities using a mobile terminal, such as... Figure 1 ,include:

[0041] S100. Generating a sound wave signal of a preset frequency using a mobile terminal; In S100 of this embodiment, generating a sound wave signal of a preset frequency using a mobile terminal includes the following steps:

[0042] S101. Based on the mobile terminal speaker emitting a sinusoidal sound wave signal of a specified frequency (e.g., 18kHz to 20kHz), set the sound wave sampling rate, preferably 44100Hz, and calculate the number of samples to be generated according to the duration of the sound wave; use a sine function to generate an analog sound wave signal of the target frequency; convert the analog sound wave signal into 16-bit PCM audio data; use the AudioTrack interface to load and play the PCM audio data in static mode to achieve accurate output of high-frequency sound waves;

[0043] Specifically, on the Android platform, this can be achieved by writing code using Android's AudioTrack class. First, sine wave data of the specified frequency must be generated. This can be done using a sine function to calculate the sine wave value based on the wave length and the total length of the sound wave. Then, the AudioTrack object is initialized, setting parameters such as sampling rate, channel configuration, and encoding format. The generated sine wave data is then passed to the AudioTrack's write method. Finally, the play method is called to play the sound. By modifying the specified frequency parameters, sound wave signals of different frequencies can be generated.

[0044] S202. A microphone array is used for synchronous sampling, and the microphone of the mobile terminal is controlled to enable synchronous recording function, so as to collect the sound wave reflection signal from the ground while transmitting sound waves.

[0045] In some preferred embodiments, sound wave reflection signals from underground are acquired simultaneously with the emission of sound waves. The specific method includes: first, initializing the audio recording object and setting the same sampling rate and audio format as the emission; then creating a buffer for receiving audio data in real time; starting the recorder and recording sound wave data in a loop for a preset time; and writing the sound wave data into a local audio file in the original PCM format.

[0046] Specifically, the mobile terminal's microphone is controlled to enable synchronous recording, simultaneously transmitting sound waves and collecting reflected sound wave signals from underground. First, the audio recording object is initialized, setting the same sampling rate (44100Hz) and audio format (16-bit single-channel PCM) as the transmission. A buffer is created for real-time audio data reception. The recorder is started and loops recording approximately 3 seconds of sound wave data. The recorded data is then written to a local audio file in raw PCM format.

[0047] S200. Acquire and preprocess the acoustic signal; In S200 of this embodiment, the acoustic signal is acquired and preprocessed, and the specific methods include: loading the recorded audio file using the librosa library, removing the DC offset component by subtracting the mean; filtering low-frequency signals below a preset frequency using a 4th-order Butterworth high-pass filter, and normalizing the processed signal to scale its amplitude range to the [-1, 1] interval.

[0048] Specifically, Python is used for spectrum analysis and image display. The recorded audio file is loaded using the librosa library. The DC offset component is removed by subtracting the mean (y = y - np.mean(y)). Then, a 4th-order Butterworth high-pass filter is used to filter out low-frequency components below 15kHz. Finally, the processed signal is normalized (y = y / np.max(np.abs(y)) to scale its amplitude range to the [-1, 1] interval.

[0049] S300. Analyze the spectrum of the sound wave signal and extract its spectral features. In S300 of this embodiment, the specific method for analyzing the spectrum of the sound wave signal and extracting its spectral features includes: performing a short-time Fourier transform on the signal to convert the time-domain signal into a time-frequency two-dimensional matrix; converting the amplitude spectrum into decibel units and displaying the spectrum using a heatmap method; the spectrum shows the energy changes of different frequency components of the sound wave as it propagates over time, and the presence of abnormal frequency band responses can be observed intuitively through the spectrum.

[0050] Specifically, a Short-Time Fourier Transform (STFT) is performed on the signal to convert the time-domain signal into a two-dimensional time-frequency matrix; the amplitude spectrum is converted into decibels (dB) and displayed as a heatmap; the visualization results show the energy changes of different frequency components of the sound wave as it propagates over time. The spectrum allows for direct observation of any abnormal frequency responses (such as resonant amplification). Using this method, the spatiotemporal distribution of frequency components in a sound wave signal can be analyzed intuitively, and potential anomalies can be automatically detected.

[0051] S400. Based on the aforementioned spectral characteristics, resonant frequency shift detection and hole depth estimation are performed. Specifically, based on the aforementioned spectral characteristics, a resonant frequency shift detection algorithm is used for resonant frequency shift detection. The specific method includes: averaging the frequency dimensions of the short-time Fourier transform to obtain the overall power spectrum; identifying the dominant frequency peak with prominent energy in the power spectrum; comparing the detected dominant frequency peak with the reference frequency value to calculate the frequency offset; and comparing the offset with a preset offset threshold to determine whether an offset exists.

[0052] After calculating the frequency offset, the cavity depth is estimated based on the preset frequency offset. The specific estimation method includes: obtaining a frequency offset and cavity depth correspondence table based on expert experience or experiments. The frequency offset and cavity depth correspondence table is used to record the relationship between the frequency offset and the corresponding cavity depth. The calculated frequency offset is substituted into the frequency offset and cavity depth correspondence table to obtain the cavity depth.

[0053] For example, each 100Hz shift corresponds to a depth of 0.2 meters. Input the shift into the model: depth = 0.2 * (freq_shift / 100) to obtain the estimated value.

[0054] In some preferred embodiments, location information is acquired while collecting acoustic signals, a location information and depth list is constructed, and a two-dimensional heat map or cross-sectional view is drawn based on the location information and depth list; the cavity information is visualized through the two-dimensional heat map or cross-sectional view.

[0055] In some preferred embodiments, three main buttons, "Start Launch," "Synchronous Recording," and "Analysis Results," are also provided on the front end; a spectrum diagram, a cavity heat map, and a depth bar chart are displayed; and the charts can be exported as images or uploaded to the cloud.

[0056] This embodiment provides a non-destructive detection method for underground cavities using a mobile terminal. The method involves generating an acoustic signal at a preset frequency via the mobile terminal; acquiring and preprocessing the acoustic signal; analyzing the spectrum of the acoustic signal to extract its spectral features; and performing resonance frequency shift detection and cavity depth estimation based on the spectral features. This invention enables rapid detection of underground cavities without additional hardware; the method disclosed in this invention has extremely low deployment costs, making it suitable for large-scale deployment; and the method disclosed in this invention has high detection accuracy, meeting the needs of complex scenarios such as urban roads and culverts.

[0057] Based on the same inventive concept, embodiments of the present invention also provide a non-destructive detection system for underground cavities using a mobile terminal, such as... Figure 2 It includes: a sound wave signal generation unit, a sound wave signal acquisition and preprocessing unit, a spectrum analysis unit, and a resonant frequency shift detection and cavity depth estimation unit; wherein:

[0058] A sound wave signal generating unit is used to generate a sound wave signal of a preset frequency using a mobile terminal.

[0059] The acoustic signal acquisition and preprocessing unit is used to acquire and preprocess the acoustic signal;

[0060] The spectrum analysis unit is used to analyze the spectrum of the acoustic signal and extract the spectral features of the acoustic signal.

[0061] The resonant frequency shift detection and hole depth estimation unit is used to perform resonant frequency shift detection and hole depth estimation based on the spectral characteristics.

[0062] The specific working methods of the acoustic signal generation unit, acoustic signal acquisition and preprocessing unit, spectrum analysis unit, and resonance frequency shift detection and cavity depth estimation unit have been described in detail in Embodiment 1, and will not be repeated here.

[0063] Based on the same inventive concept, embodiments of the present invention also provide an electronic device. Figure 3 This is a structural block diagram of an electronic device provided in an embodiment of the present invention. Figure 3 As shown, an embodiment of the present invention provides an electronic device including: one or more processors 101, a memory 102, and one or more I / O interfaces 103. The memory 102 stores one or more programs, which, when executed by the one or more processors, enable the one or more processors to implement any of the non-destructive testing methods described in the above embodiments; the one or more I / O interfaces 103 are connected between the processor and the memory, configured to enable information interaction between the processor and the memory.

[0064] The processor 101 is a device with data processing capabilities, including but not limited to a central processing unit (CPU); the memory 102 is a device with data storage capabilities, including but not limited to random access memory (RAM, more specifically SDRAM, DDR, etc.), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), and flash memory (FLASH); the I / O interface (read / write interface) 103 is connected between the processor 101 and the memory 102, and can realize information interaction between the processor 101 and the memory 102, including but not limited to a data bus (Bus).

[0065] In some embodiments, the processor 101, memory 102, and I / O interface 103 are interconnected via bus 104, and thus connected to other components of the computing device.

[0066] In some embodiments, the one or more processors 101 include a field-programmable gate array.

[0067] This invention also provides a computer-readable medium. The computer-readable medium stores a computer program, which, when executed by a processor, implements the steps of any of the non-destructive testing methods described in the above embodiments. The computer-readable storage medium can be volatile or non-volatile.

[0068] This invention also provides a computer program product, including computer-readable code, or a non-volatile computer-readable storage medium carrying computer-readable code. When the computer-readable code is run in the processor of an electronic device, the processor in the electronic device executes the above-described non-destructive testing method.

[0069] Those skilled in the art will understand that all or some of the steps, systems, and apparatuses disclosed above, and their functional modules / units, can be implemented as software, firmware, hardware, or suitable combinations thereof. In hardware implementations, the division between functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all physical components may be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit (ASIC). Such software can be distributed on a computer-readable storage medium, which may include computer storage media (or non-transitory media) and communication media (or transient media).

[0070] As is known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information, such as computer-readable program instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), static random access memory (SRAM), flash memory or other memory technologies, portable compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, it is known to those skilled in the art that communication media typically contain computer-readable program instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0071] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0072] The computer program instructions used to perform the operations of this invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing state information from the computer-readable program instructions. This electronic circuitry can execute the computer-readable program instructions to implement various aspects of the invention.

[0073] The computer program product described herein can be implemented specifically through hardware, software, or a combination thereof. In one alternative embodiment, the computer program product is specifically embodied in a computer storage medium; in another alternative embodiment, the computer program product is specifically embodied in a software product, such as a software development kit (SDK), etc.

[0074] Various aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0075] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0076] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0077] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction, which contains one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0078] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in conjunction with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as set forth in the appended claims.

Claims

1. A method for non-destructive detection of underground cavities using a mobile terminal, characterized in that, include: Using a mobile terminal to generate sound wave signals at a preset frequency; The acoustic signal is acquired and preprocessed; The spectrum of the acoustic signal is analyzed to extract its spectral features; Based on the aforementioned spectral characteristics, resonant frequency shift detection and void depth estimation are performed.

2. The method according to claim 1, characterized in that, Generating a sound wave signal of a preset frequency using a mobile terminal involves the following steps: The system emits a sinusoidal sound wave signal of a specified frequency from the mobile terminal's speaker, sets the sound wave sampling rate, and calculates the number of samples to be generated based on the duration of the sound wave. A sinusoidal function is used to generate a simulated sound wave signal of the target frequency. The simulated sound wave signal is then converted into 16-bit PCM audio data. The AudioTrack interface is used to load and play the PCM audio data in static mode, achieving accurate output of high-frequency sound waves. A microphone array is used for synchronous sampling, and the microphone of the mobile terminal is controlled to enable synchronous recording function, so as to collect the sound wave reflection signal from the ground while transmitting sound waves.

3. The method according to claim 2, characterized in that, The method for collecting sound wave reflection signals from underground while transmitting sound waves includes: first, initializing the audio recording object and setting the same sampling rate and audio format as the transmission; then creating a buffer for receiving audio data in real time; starting the recorder and recording sound wave data for a preset time in a loop; and writing the sound wave data into a local audio file in the original PCM format.

4. The method according to claim 1, characterized in that, The acoustic signal is acquired and preprocessed. The specific methods include: loading the recorded audio file using the librosa library, removing the DC offset component by subtracting the mean; filtering low-frequency signals below a preset frequency using a 4th-order Butterworth high-pass filter, and normalizing the processed signal to scale its amplitude range to the [-1, 1] interval.

5. The method according to claim 1, characterized in that, The spectrum of the acoustic signal is analyzed to extract its spectral features. Specific methods include: performing a short-time Fourier transform on the signal to convert the time-domain signal into a time-frequency two-dimensional matrix; converting the amplitude spectrum into decibel units and displaying the spectrum using a heatmap; the spectrum shows the energy changes of different frequency components of the acoustic wave as it propagates over time, and the presence of abnormal frequency band responses can be observed intuitively through the spectrum.

6. The method according to claim 1, characterized in that, Based on the aforementioned spectral characteristics, a resonant frequency shift detection algorithm is used for resonant frequency shift detection. The specific method includes: averaging the frequency dimensions of the short-time Fourier transform to obtain the overall power spectrum; finding the dominant frequency peak with prominent energy in the power spectrum; comparing the detected dominant frequency peak with the reference frequency value to calculate the frequency shift; and comparing the shift with a preset shift threshold to determine whether a shift exists.

7. The method according to claim 6, characterized in that, After calculating the frequency offset, the cavity depth is estimated based on the preset frequency offset. The specific estimation method includes: obtaining a frequency offset and cavity depth correspondence table based on expert experience or experiments. The frequency offset and cavity depth correspondence table is used to record the relationship between the frequency offset and the corresponding cavity depth. The calculated frequency offset is substituted into the frequency offset and cavity depth correspondence table to obtain the cavity depth.

8. The method according to claim 6, characterized in that, Also includes: While collecting acoustic signals, location information is acquired, and a list of location information and depth is constructed. A two-dimensional heat map or cross-sectional view is drawn based on the location information and depth list. The cavity information is visualized through the two-dimensional heat map or cross-sectional view.

9. A non-destructive detection system for underground cavities using a mobile terminal, employing the method described in any one of claims 1-8, characterized in that, include: The system comprises an acoustic signal generation unit, an acoustic signal acquisition and preprocessing unit, a spectrum analysis unit, and a resonant frequency shift detection and cavity depth estimation unit; wherein: A sound wave signal generating unit is used to generate a sound wave signal of a preset frequency using a mobile terminal. The acoustic signal acquisition and preprocessing unit is used to acquire and preprocess the acoustic signal; The spectrum analysis unit is used to analyze the spectrum of the acoustic signal and extract the spectral features of the acoustic signal. The resonant frequency shift detection and hole depth estimation unit is used to perform resonant frequency shift detection and hole depth estimation based on the spectral characteristics.

10. An electronic device, characterized in that, include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in any one of claims 1 to 8.

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