Acoustic Method Research Articles

A complex boundary wave superposition method for solving external acoustic problems

This paper proposes a complex boundary wave superposition method with a unique solution of full wavenumber based on the similarity between the acoustic wave superposition method (WSM) and the external excitation response of dynamic systems and combined with the idea that a damping system has a unique solution in dynamic theory. By placing the virtual equivalent source on the virtual boundary of complex space, the conventional WSM acquires damping properties comparable to those of the dynamical system. This approach successfully addresses the non-uniqueness of the solution at the eigenfrequency and is more efficient than the conventional combined layer potential method. The paper presents a comprehensive description of the proposed method, with a focus on theory, modeling, and parameter selection. The effectiveness of this method is evaluated by applying it to two types of acoustic problems, namely, radiation and scattering. The numerical results indicate that this method effectively addresses the non-unique problems encountered in conventional WSM. Furthermore, the proposed method is as accurate and efficient as the conventional WSM.

Improving Acoustic Methods of Pipeline Leak Location with Distributed Sensing

Improving Acoustic Methods of Pipeline Leak Location with Distributed Sensing

Development of the recording device to reduce an overlook of a defect for the impact acoustic method

Several concrete structures in Japan built during a period of high economic growth—including bridges (40%) and tunnels (25%)—are now at least 40 years old and are withering. Recent years have witnessed several accidents caused by falling concrete debris from these structures. To ensure safety, these buildings are regularly inspected with non-destructive tests such as the impact acoustic method (IAM). In this method, the surface of the concrete structure under inspection is impacted by a hammer and the resulting sound vibrations are used to detect defects. According to the current inspection standard, inspection records only contain information of detectable defects, because the method relies on the physical capabilities and expertise of the professional. Consequently, there are no records of imperceptible defects. In this study, we developed a recording device that consists of an accelerometer and a microphone and connected it to an impact hammer. The device saves the output from the two components in a single file. A set of concrete specimens were then tested using the IAM with the new device and hammer. Furthermore, the contact time and striking power of the hammer were estimated using a load sensor.

Capillary wave tweezer

Precise control of microparticle movement is crucial in high throughput processing for various applications in scalable manufacturing, such as particle monolayer assembly and 3D bio-printing. Current techniques using acoustic, electrical and optical methods offer precise manipulation advantages, but their scalability is restricted due to issues such as, high input powers and complex fabrication and operation processes. In this work, we introduce the concept of capillary wave tweezers, where mm-scale capillary wave fields are dynamically manipulated to control the position of microparticles in a liquid volume. Capillary waves are generated in an open liquid volume using low frequency vibrations (in the range of 10–100 Hz) to trap particles underneath the nodes of the capillary waves. By shifting the displacement nodes of the waves, the trapped particles are precisely displaced. Using analytical and numerical models, we identify conditions under which a stable control over particle motion is achieved. By showcasing the ability to dynamically control the movement of microparticles, our concept offers a simple and high throughput method to manipulate particles in open systems.

Technologıcal Methods of Increasıng Bearıng Performance

The tribological characteristics of bearing shells manufactured using various technologies have been studied. The results obtained allow us to determine the most technologically advanced method. One of the main requirements for load-bearing shells is the absence of macrostresses in the surface layers of the load-bearing shells, leading to their destruction. The studies were carried out only in near-surface areas. The results obtained show that there are no macrostresses in antifriction coatings obtained by ion-plasma and galvanic methods. An important feature is the high adhesion strength of the antifriction layers to the base. Adhesion tests were carried out on samples cut from liners obtained by the acoustic method. The greatest adhesion strength is observed with ion plasma coating, it is 22 MPa.

Comparative Analysis of Acoustic Emission Signals from On-Load Tap-Changers for Potential Detecting of Non-Simultaneous Operations

The research reported in this paper deals with the potential of detecting non-simultaneous operation in on-load tap-changer (OLTC) using an acoustic emission method. Tests conducted under laboratory conditions were carried out using an OLTC model. Three transducers with different characteristics were used: WD 17 AH, D9241A, and R15α, alongside oscillography as the reference method. The use of two new descriptors in the time domain was proposed. The feasibility of detecting the defect with different piezoelectric transducers was investigated. As a result of the analysis of the results, it was found that each piezoelectric transducer can identify nonsimultaneous operation of the switch. The most significant changes in descriptor values occurred in the time domain, and the most effective transducer turned out to be R15α.

Spatial acoustic emission localization method for damage to prestressed steel strands of girders using special-shaped waveguide rods

As an essential load-bearing member of post-tensioned prestressed girders, prestressed steel strands will inevitably reduce the safety and durability of the bridge if damaged. However, traditional damage localization methods for the steel strand require numerous acoustic emission (AE) sensors with a complex arrangement in the prestressed girder. This study proposes a spatial AE localization method using a dual-sensor array with the assistance of special-shaped waveguide rods. The spatial damage localization is achieved by combining the time difference of arrival (TDOA) of the AE wave with the propagation attenuation law. Transverse and longitudinal damage localization for prestressed steel strands are verified on a simplified platform containing different special-shaped waveguide rods. For transverse damage localization, the TDOA of the maximum AE amplitudes is superior to that of the first waves. For longitudinal damage localization, the relative localization accuracy reaches 94%. With this method, only two AE sensors are required to localize the three-dimensional damage to the prestressed steel strands in a girder.

Information model of acoustic string musical instrument and method of automated professional tuning of instruments

Information model of acoustic string musical instrument and method of automated professional tuning of instruments

Innovative acoustic emission method for monitoring the quality and integrity of ferritic steel gas pipelines

Abstract This article presents a comprehensive improvement in the experimental analysis of cracking processes in smooth and sharp V-notched samples taken from gas transport pipelines, utilizing the acoustic emission (AE) method. The research aimed to establish a robust correlation between the failure mechanisms of uni-axially tensile samples and the distinct characteristics of AE signals for enhanced quality management in pipeline integrity. The study encompassed materials from two different straight pipe sections, encompassing both long-term used materials and new, unused materials. Through the application of the k-means grouping method to AE signal analysis, we achieved the identification of AE signal parameters characteristic of various stages of the material destruction process. This advancement introduces a significant improvement in monitoring and managing the operational safety of pipeline networks, offering a methodology that leverages advanced acoustic emission signal analysis. The outcomes present significant implications for the pipeline industry by proposing methods to enhance safety systems and more effectively manage the integrity and quality of gas infrastructure.

Frequency-selective acoustic micromanipulation platform

Acoustic micromanipulation methods offer versatile tools ranging from lab-on-chip diagnostic platforms to mobile microrobots. Acoustically oscillating bubble-powered microsystems are gaining increased attention owing to their low cost and convenient operation. To date, no studies have reported on the controllability of the driving frequency on acoustic micromanipulation platforms using Helmholtz resonators. Here, we introduce a Helmholtz resonant cavity into a bubble-powered microsystem to reveal the function of the oscillation modes and frequency selectivity. The Su–Schrieffer–Heeger (SSH) model was utilized to construct a topological interfacial state and bubble-powered working location. We experimentally observed that the microparticles were captured by the oscillation bubble and underwent orbital rotation at the topological frequency. However, the microparticles were tightly bound close to the oscillation bubble area when the driving frequency was outside the topological frequency range. Our acoustic micromanipulation platform implements multiple microparticle manipulation modes based on frequency selectivity that are independent of optical or magnetic properties, which can enrich the micromanipulation toolbox and exhibit enormous application potential in the biomedical field.

A depth-variant wavelet extraction method based on the orthogonal matching pursuit for direct inversion

The results of pre-stack depth migration reflect subsurface structures directly. However, it is an urgent geophysical problem that how to deal with this non-stationarity exhibited by depth-domain seismic data and achieve high precision reservoir prediction. To address this issue, we develop a depth-variant wavelet extraction method based on the orthogonal matching pursuit and attain direct inversion of the depth-domain acoustic impedance using the depth-variant wavelets. First, the parameters of source wavelets estimated by complex seismic trace analysis are utilized to construct the overcomplete dictionary. Secondly, the overcomplete dictionary is used to decompose the depth-domain seismic traces by orthogonal matching pursuit. Thirdly, we extract the depth-variant Ricker wavelets from the decomposed optimal atoms. Test of examples demonstrates that the proposed depth-variant wavelet method has high accuracy. The synthetic seismogram obtained by the proposed method has high Pearson correlation coefficients of 99%, which verifies that our method is feasible and accurate. Next, a depth-domain impedance trend constraint is introduced into the objective function of the conventional basis pursuit inversion to enhance the lateral continuity. Finally, the objective function with impedance trend constraint is solved by basis pursuit for depth-domain acoustic impedance. We test the direct depth-domain acoustic impedance inversion method on the synthetic and field data, which indicates that our method has high accuracy and robustness. The mean relative error of its inversion result is only 0.9% for the noise-free example and about 5% for the strong noisy example. Therefore, our method can be effectively applied to the seismic-well calibration and seismic impedance inversion in the depth domain. And it has powerful potential in reservoir characterization, fluid prediction and attribute extraction in the depth domain. Additionally, the energy distribution features of the Ricker wavelet are derived and analyzed, which can guide the application of the Ricker wavelet in seismic signal analysis.

Monitoring warning criterion of acoustic emission active waveguide system based on loess deformation and failure.

The construction of acoustic emission criterion system is crucial for monitoring and providing early warning of geological hazards. In the current soil acoustic emission monitoring methods, the signal generated by soil deformation and failure is weak and experiences high attenuation, resulting in a low level of the monitored signal. One approach to enhance the quality of monitoring data is by utilizing the active waveguide model. However, the current research on the active waveguide model system is not extensive. To address these issues, a set of active waveguide system was designed to improve the data quality of acoustic emission monitoring and early warning. The deformation and failure process of loess monitored by acoustic emission was divided into stages, and the precursor information of acoustic emission for geological disasters in loess areas was comprehensively deconstructed. The data quality advantage of the active waveguide model was verified through comparative experiments of with the passive waveguide model. This study investigates the AE signal characteristics of the active waveguide model. It explores various aspects such as the AE waveform parameter characteristics, the discrimination method for failure mode based on RA-AF value, the AE r-value characteristics, the AE b-value characteristics, and the frequency-amplitude characteristics. The study reveals the evolution law of AE signals in the active waveguide model, including early warning signs and failure morphological characteristics. Furthermore, it constructs a warning criterion for the active waveguide system. The development of this criterion system is of great importance in guiding the monitoring and early warning of geological disasters in loess areas.

Monitoring degradation in alkaline-activated slag materials

This paper deals with determining degradation changes in alkaline-activated slag-based building materials. It describes methods for determining dynamic elastic moduli obtained by acoustic non-destructive methods, including the ultrasonic pulse method and the resonance method. A finegrained mortar was chosen as the initial mix for the implementation of the experiment, the binder part of which was sodium hydroxide-activated blast-furnace granulated slag. Beams with dimensions of 40 × 40 × 160 mm were chosen as test bodies, for which acoustic non-destructive methods monitored changes in the material structure during degradation processes.

Acoustic emission technology-based waveguide localization method for damaged internal tendons of in-service post-tensioned hollow slab bridges

Prestressing tendons are crucial load-bearing elements in post-tensioned hollow slab bridges. Damage to these tendons significantly reduces the safety, functionality, and longevity of the bridge. Regular monitoring of prestressing tendons is essential for bridge operation. Acoustic emission technology, known for its high accuracy and sensitivity to minor vibrations, is a key technique for monitoring bridge cables. This study proposes a novel dual-sensor acoustic emission localization method for detecting tendon damage in post-tensioned hollow slab bridges, utilizing waveguide technology. The effectiveness of this method is confirmed through hammering tests that simulate acoustic emission damage on operational hollow slab bridges. The proposed method, requiring only two sensors, offers a cost-effective alternative for monitoring the entire span of post-tensioned hollow slab bridges, so that effectively reduces the cost of bridge health monitoring and is easy to be promoted in actual engineering projects.

Sound event detection in traffic scenes based on graph convolutional network to obtain multi-modal information

Sound event detection involves identifying sound categories in audio and determining when they start and end. However, in real-life situations, sound events are usually not isolated. When one sound event occurs, there are often other related sound events that take place as co-occurrences or successive occurrences. The timing relationship of sound events can reflect their characteristics. Therefore, this paper proposes a sound event detection method for traffic scenes based on a graph convolutional network, which considers this timing relationship as a form of multimodal information. The proposed method involves using the acoustic event window method to obtain co-occurrences or successive occurrences of relationship information in the sound signal while filtering out possible noise relationship information. This information is then represented as a graphical structure. Next, the graph convolutional neural network is improved to balance relationship weights between neighbors and itself and to avoid excessive smoothing. It is used to learn the relationship information in the graph structure. Finally, the convolutional recurrent neural network is used to learn the acoustic feature information of sound events, and the relationship information of sound events is obtained by multi-modal fusion to enhance the performance of sound event detection. The experimental results show that using multi-modal information with the proposed method can effectively improve the performance of the model and enhance the perception ability of smart cars in their surrounding environment while driving.

Acoustic wind tunnel experimental study of aerodynamic noise distribution in high-rise buildings

Wind-induced aerodynamic disturbance has become a major noise source affecting residents in super high-rise buildings. To investigate the distribution characteristics of aerodynamic noise on high-rise building surfaces in strong wind conditions and the impact of wind speed and direction, this paper pioneers the application of the acoustic wind tunnel method based on microphone array localization to the experimental study of the surface acoustic pressure field of a high-rise building model, the far-field noise spectrum of which is obtained using the microphone array sensor. The beamforming calculation method was used to obtain the spectrum and localization cloud. By comparing the spectra and cloud diagrams under different process conditions and based on existing building wind pressure reports, it is concluded that: the noise source is always located at the height of the connecting corridor where there is large wind pressure pulsation in the two building models; the aerodynamic noise is more pronounced around building gaps where the airflow is more disturbed and also in the oncoming wind trailing direction where the wind pressure pulsation is more pronounced. An increase in wind speed increased noise source amplitude from 30 dB to 60 dB, and the location of the noise source shifted backwards to the tail of the incoming wind. This paper shows that the acoustic wind tunnel method based on microphone array localization technology can obtain the aerodynamic noise intensity on the surfaces of super high-rise buildings and reasonably predict the location of the sound source. This article puts forward suggestions to reduce noise in high-rise buildings based on experimental results.

Acoustic Resonance Tuning by High-Order Lorentzian Mixing.

Nanoscale mechanical resonators have attracted a great deal of attention for signal processing, sensors, and quantum applications. Recent progress in ultrahigh-Q acoustic cavities in nanostructures allows strong interactions with various physical systems and advanced functional devices. Those acoustic cavities are highly sensitive to external perturbations, and it is hard to control those resonance properties since those responses are determined by the geometry and material. In this paper, we demonstrate a novel acoustic resonance tuning method by mixing high-order Lorentzian responses in an optomechanical system. Using weakly coupled phononic-crystal acoustic cavities, we achieve coherent mixing of second- and third-order Lorentzian responses, which is capable of the fine-tunability of the bandwidth and peak frequency of the resonance with a tuning range comparable to the acoustic dissipation rate of the device. This novel resonance tuning method can be widely applied to Lorentzian-response systems and optomechanics, especially active compensation for environmental fluctuation and fabrication errors.

Numerical Simulation Analysis of the Correlation between Hydrodynamic Noise of Hydraulic Turbines and Defects in Runner Blades

To investigate the hydrodynamic noise characterization of hydraulic turbines with runner blade defects, this article establishes the intact machine model and three kinds of models with runner blade defects. Using the Computational Fluid Dynamic (CFD) and Computational Acoustic (CA) hybrid simulation computational methods, the hydrodynamic noise field of the hydraulic turbine is numerically simulated, and the results of the acoustic near field and acoustic far field are shown. 1. The double-row leaf grille and the runner are the primary sound source areas of the hydraulic turbine, and the intensity of sound radiation from these areas is positively correlated with the degree of runner blade defects. 2. As the runner blade defects develop, the sound power level (SWL) increases more significantly in the guide vanes near the nose of the spiral case in the double-row leaf grille. The most pronounced increase in the SWL is observed at the defective craters on the runner blades. 3. The frequency of the defective noise signal is primarily concentrated in the low-frequency band. The dominant frequency amplitude associated with runner blade defects increases and rises after the occurrence of defects. Secondary frequency changes are also observed, and the location of these changes varies at different receiving points.

Designing a software system to ensure the operation of the spectral acoustic method for dust control in construction

Designing a software system to ensure the operation of the spectral acoustic method for dust control in construction

Calibration of commercial fisheries echo sounders using seabed backscatter for the estimation of fishery resources.

Acoustic methods are often used for fisheries resource surveys to investigate fish stocks in a wide area. Commercial fisheries echo sounders, which are installed on most small fishing vessels, are used to record a large amount of data during fishing trips. Therefore, it can be used to collect the basic information necessary for stock assessment for a wide area and frequently. To carry out the quantification for the fisheries echo sounder, we devised a simple method using the backscattering strength of the seabed to perform calibration periodically and easily. In this study, seabed secondary reflections were used instead of primary reflection because the fisheries echo sounders were not equipped with a time-varied gain (TVG) function, and the primary backscattering strength of the seabed was saturated. It was also necessary to use standard values of seabed backscattering strength averaged over a certain area for calibration to eliminate some of the effects of differences in seabed sediment and vessel motions. By using standard values of the seabed secondary reflections, the fisheries echo sounder was calibrated accurately. Our study can provide a reliable framework to calibrate commercial fisheries echo sounders, to improve the estimation and management of fishery resources.