Acoustic Signal Acquisition Research Articles

Self-Contained High-SNR Underwater Acoustic Signal Acquisition Node and Synchronization Sampling Method for Multiple Distributed Nodes.

Aiming at the application demand in underwater noise monitoring, observation of marine animal, antisubmarine and underwater target localization, a high-SNR underwater acoustic signal acquisition (UASA) node that combines a self-contained acquisition system and floating platform is designed to improve the acquisition performance of a single UASA node, and a high-accuracy synchronization sampling method among multiple distributed UASA nodes based on master-slave dual phase-locked loops (MSDPLL) is proposed to improve the synchronization sampling accuracy. According to the equivalent model of hydrophone and application requirements, low noise signal conditioning circuit and large-capacity data storage modules are designed. Based on the long-term monitoring requirements for underwater acoustic signal and distributed positioning requirements for underwater targets, the structure of a single UASA node is designed and MSDPLL is developed for high-accuracy synchronization sampling among multiple UASA nodes. Related experimental results verified the performance of the UASA node and the synchronization sampling method.

Assessment of the technical condition of prefabricated elements using the acoustic emission method

he article presents the results of tests using the acoustic emission method during the formation process of T-27 prestressed concrete beams. The studies included two stages. The first – testing the compressive strength of the cubic samples taken from the trial batch used for the production of beams together with the acquisition of acoustic emission signals. The second – measurements by acoustic emission, on the actual construction element during accelerated maturation of concrete caused by heating. The undertaking of the above subject results from the fact that this issue is of great importance when assessing the durability of reinforced concrete and pre-compressed elements in the aspect of the analysis of these structures in terms of durability. The impact of material degradation on the durability of the structure is difficult to appraise due to the lack of reliable results needed to estimate the durability of the selected statistical approach. However, the use of the acoustic emission method based on the identification of destructive processes creates the possibility of locating, identifying and monitoring the emerging and developing destructive processes affecting the durability of concrete elements.

Bubble dynamics and cavitation intensity in milli-scale channels under an ultrasonic horn.

Under a vibrating ultrasonic horn device, intense cavitation occurs but is restricted to a small volume due to strong attenuation effects. In this study, milli-scale channels were introduced under the horn. The effect of this on the cavitation development and intensity within the channels were explored. High speed videography of up to 100,000 fps and acoustic signal acquisition through hydrophone were conducted. Cavitation intensity was observed to increase within the channels as compared to free field condition. Bubble density increased with a decrease in channel diameter and a rise in ultrasonic amplitude. Furthermore, an intriguing phenomenon of large bubble cluster formation near the channel exit (20 mm away from the horn surface) was detected. The oscillation behaviour of these clusters is dependent on both channel diameter and ultrasonic amplitude. At the maximum ultrasonic amplitude, the clusters reached maximum radiuses exceeding 3 mm and collapsed violently. Repetitive transient collapses near the exit region suggest that the introduction of milli-scale channels could extend the effective cavitation zone length and enhance the overall cavitation intensity under an ultrasonic horn.

Design and Implementation of Universal Acoustic Signal Processing Platform

Acoustic signal processing has been widely used in many fields. In order to meet the demand of engineering applications, a universal acoustic signal processing platform based on DSP+ARM has been proposed to realize acquisition, processing and output of two-channel acoustic signals. The hardware and software realization methods have been discussed. At the same time, the acoustic signal acquisition performance and impulse response of acoustic signal output module have been measured. The results show that the acquisition sensitivity is 86 mV/Pa, the output response is changed by different loudspeakers.

Continuous Health Monitoring With Resonant-Microphone-Array-Based Wearable Stethoscope

This paper reports the implementation and evaluation of an array-based recognition system for the detection of wheezing in breathing. We describe the design and fabrication of a resonant microphone array for pre-filtered acoustic signal acquisition, and outline a novel signal classification algorithm that benefits from its properties. The use of a resonant-transducer array at the input simplifies several of the required digital processing steps necessary for performing spectral filtering and wheezing recognition. The recognizer system is evaluated and compared against a traditional approach, and the experimental results show that recognition processing time (and power consumption) can be reduced 11 times, specifically from 5.11 to 0.46 s. Classification experiments also indicate a robustness in recognition accuracy to low-frequency-dominated background noises such as those emitted by the heart. The findings suggest that this technique has wide-ranging applicability to low-power and self-powered wireless sensing and detection systems.

Experimental investigations of monolithic IGBT transistor acoustic emission phenomena

Many recent researches are focused on the diagnostic methods allowing determination of the condition of working semiconductor components (power transistors, diodes etc.). As any solid material under stresses (mechanical, temperature and electrical) the semiconductors are generating elastic waves in the case of changing conductivity state. Based on the results of experimental research, a correlation can be observed between the transition between the on and off states of a single IGBT transistor and the emitted acoustic signal. Acquisition of acoustic emission signals was obtained with use of a wide band acoustic emission sensor. The received signal initially was prepared by AD input card with amplifier and then were recorded by means of a computer software. Acquired data were exported the to a file, which enabled further processing of the measured signals. The aim of the study was to determine the acoustic emission background signal coming from switching IGBT transistor and preparation of frequency response. The results of analysis will be used as a reference point for a further investigation of early-stage faults of semiconductors elements.

3D Vertical Seismic Profiling Acquired Using Fibre-Optic Sensing Das – Results From The CO2CRC Otway Project

Distributed Acoustic Sensing (DAS) is an optical interferometric method for acquisition of acoustic and seismic signals. It uses laser pulses that travel along the length of a fibre-optic cable and backscatter as they encounter small inconsistencies in the fibre. Impinging seismic waves cause strain on the cable, resulting in differences in phase of the backscattered light. Interest in DAS has increased significantly in the past decade as it is particularly suited for VSP acquisitions, including for permanent reservoir monitoring. Fibre-optic cables can be installed permanently in the well, cemented behind the casing or attached to tubing; they offer a relatively cheaper and efficient solution when compared to conventional borehole sensors. This study is part of the CO2CRC Otway Project. The Otway Project site is located approximately 240 km south-west of Melbourne, Australia. The Stage 2C of the project aims to monitor a small injection (15 kt) of CO2/CH4 gas mixture at a depth of approximately 1500 m. Here, we show the results of a 3D VSP survey acquired using DAS cable deployed on production tubing in the injector well. The DAS up-going wavefield shows a high level of noise. However, DAS is able to record the main reflections, including at the injection depth. After 3D migration of the data, noise levels reduce significantly. Events on DAS inline match with events on a corridor stack produced from a geophone check-shot data. Due to the directionality pattern, DAS was only able to image up to approximately 300 m radius from the well.

Acoustic Emission of Monolithic IGBT Transistors

Abstract Due to the increasing number of applications of power semiconductor devices, more and more attention is being paid to diagnostic methods to determine the condition of working semiconductor components. On the basis of the results of experimental research, a correlation can be observed between the transition between the on/off states of a single IGBT transistor in operation and the acoustic signal emitted by it. Acquisition of acoustic emission signals was obtained using a specialized sensor from Vallen. To record the received signal, a high resolution digital oscilloscope was used, which exported the recorded signal to a file, which enabled further digital processing of the acquired signals. The aim of the study was to determine the usefulness of acoustic emission detection methods to determine the possibility of damage to an element based on the recorded acoustic signal.

Development of a multisensor array for localizing bats in space

We present a novel multisensor array to track flight paths of bats in space. Our array is designed to be portable and, thus, field applicable. Eight microphones are employed to localize each echolocation call, whereas two cameras provide continuous information on the flight path between the calls. To reduce costs and, thus, make it available for low-budget research the array was developed from scratch including a novel acoustic signal recording and processing hardware. Our developed acoustic hardware is the first system to sample eight microphone channels synchronously at 1 MS/s/CH with 16 Bit resolution without the necessity of computers or laptops. All eight signals from the ultrasonic microphones are not only recorded but also processed in real time in the frequency as well as time domain to determine the existence of echolocation calls. Only relevant acoustic signal are recorded which enables long term deployments of the array. During the acoustic signal acquisition, the system records images of two infrared cameras at 12 Hz and, in addition, several environmental factors such as temperature, humidity and illumination. Recorded datasets can be associated with a global position and time-stamp through a GPS module and matched to the GPS coordinate system with a three-axis accelerometer. The overall system (microphones, cameras and sensors) was designed to be affordable, easy to use in the field on battery power and without the necessity of an additional laptop. Without cost optimization and only small quantity we reached a prize below 1000 EUR for a complete system.

Designing ocean acoustic waveguide remote sensing for target detecting and tracking

Acoustic sensor used sound wave to transmit pulses into the underwater in order to gain underwater environment information. We developed Ocean Acoustics Waveguide Remote Sensing (OAWRS) instrument. The acoustic signal acquisition system has been designed which used to record the direct, reflected, scattered or echoed signals originated from transmitter transducer, targets or underwater objects. The acquisition system compose of interconnected hardware and software with a simple working principles. The software, which is written under Windows™ and Matlab, controlled the hardware by sending commands to the Transmitter Module located somewhere to generate a sound pulse and the Receiver Module to be ready to receive sound signals. The received sound data may be recorded for further analysis to developed OAWRS algorithm.

A HYBRID NUMERICAL/EXPERIMENTAL STUDY OF THE AERODYNAMIC NOISE PREDICTION

An accurate noise prediction is important in order to reduce noise emission significantly and to prevent expensive after-design treatments. This study aims to examine the aerodynamics and aeroacoustics performance of an open system consisting of an axial fan and a heat exchanger where hybrid method incorporating CFD (Computational Fluid Dynamics) and CAA (Computational Aeroacoustics) is used to predict the noise behavior. The hybrid model method used consists of three steps. Firstly, the flow is computed by means of flow-computed fluids and the pressure fluctuations are obtained. This is followed by the acquisition of acoustic signals from these fluctuations and the attainment of a sound pressure level approach with the FW-H (Ffowcs Williams & Hawkings) model.  Unsteady flow field of the air channel case was obtained by using different turbulence models. The SAS model is capable of resolving largescale turbulent structures without the time and grid-scale resolution restrictions of LES (Large Eddy Simulations), often allowing the use of existing grids created for URANS simulations. For this reason, two different turbulence models, namely URANS (Unsteady Reynolds Averaged Navier Stokes) model, SAS (Scale Adaptive Simulations) model have been applied. Acoustic sources were computed based on the pressure fluctuations and sound pressure level and frequency dependent graphics were plotted with Fast Fourier Transform. On the other hand, acoustic measurements were performed in a semi-anechoic chamber for both of them. When the experimental and numerical results were compared with the previously determined receiver points, the accuracy rate was obtained as SAS, URANS respectively.

Mitigating Wind Induced Noise in Outdoor Microphone Signals Using a Singular Spectral Subspace Method

Wind induced noise is one of the major concerns of outdoor acoustic signal acquisition. It affects many field measurement and audio recording scenarios. Filtering such noise is known to be difficult due to its broadband and time varying nature. In this paper, a new method to mitigate wind induced noise in microphone signals is developed. Instead of applying filtering techniques, wind induced noise is statistically separated from wanted signals in a singular spectral subspace. The paper is presented in the context of handling microphone signals acquired outdoor for acoustic sensing and environmental noise monitoring or soundscapes sampling. The method includes two complementary stages, namely decomposition and reconstruction. The first stage decomposes mixed signals in eigen-subspaces, selects and groups the principal components according to their contributions to wind noise and wanted signals in the singular spectrum domain. The second stage reconstructs the signals in the time domain, resulting in the separation of wind noise and wanted signals. Results show that microphone wind noise is separable in the singular spectrum domain evidenced by the weighted correlation. The new method might be generalized to other outdoor sound acquisition applications.

Research on Acoustic Emission Signal Acquisition and Acoustic Source Identification of Tank Floor Corrosion

Based on the acoustic emission source location theory of tank bottom, the sensor located among the medium inside the tank is put forward, which could identify the acoustic source of tank bottom corrosion defects together with the sensors which are arranged on tank outside wall near tank bottom, and thus the reliability of acoustic emission source location technology on the tank bottom can be increased. Location experiment of simulative tank bottom, attenuation characteristic experiment of simulative tank and acoustic source identification experiment of simulative tank bottom corrosion have been conducted. The results present that the method of acoustic source identification and location could enhance the identification of acoustic source in arbitrary triangle location, increase the area of the tank bottom zone location, decrease the missing signals caused by acoustic attenuation, at the same time, the sensors inside tank are more sensitive to acoustic source of corrosion than that outside tank, and reduce the influence caused by weather and other factors on acoustic source location. So the method can improve the reliability of acoustic emission source identification and location on tank bottom, provide theory and experiment foundation for acoustic emission testing evaluation of tank bottom. Key words: Tank bottom; Acoustic emission; Positioning; Identification

Algorithm for heart rate extraction in a novel wearable acoustic sensor.

Phonocardiography is a widely used method of listening to the heart sounds and indicating the presence of cardiac abnormalities. Each heart cycle consists of two major sounds – S1 and S2 – that can be used to determine the heart rate. The conventional method of acoustic signal acquisition involves placing the sound sensor at the chest where this sound is most audible. Presented is a novel algorithm for the detection of S1 and S2 heart sounds and the use of them to extract the heart rate from signals acquired by a small sensor placed at the neck. This algorithm achieves an accuracy of 90.73 and 90.69%, with respect to heart rate value provided by two commercial devices, evaluated on more than 38 h of data acquired from ten different subjects during sleep in a pilot clinical study. This is the largest dataset for acoustic heart sound classification and heart rate extraction in the literature to date. The algorithm in this study used signals from a sensor designed to monitor breathing. This shows that the same sensor and signal can be used to monitor both breathing and heart rate, making it highly useful for long-term wearable vital signs monitoring.

Acoustic Emission Signal Acquisition and Analysis on Tool Wear

In the field of machinery manufacture, broken state at the time of the cutting tool in cutting metal, recognition has always been a study is of great significance. Currently, for the state of tool wear and collapse edge damage identification method already has a mature experience. However the existing condition monitoring methods are often used in accuracy and convenience has limitations, this paper USES the acoustic emission technology, as a kind of integrated online test sys tem design lay the foundation. This paper aimed at the sensor in the wireless transmission module, the performance characteristics of tool condition monitoring system of the main structure was designed, and then by acoustic emission signal from the cutting tool in cutting process as the research object, studies the cutting tool characteristics of acoustic emission signal under different damage state, for the on-line monitoring system design and calibration to provide theoretical support.

The Research of Shaoguo Tunnel Failure Characteristics of Triaxial and Acoustic Emission Characteristics

This is accomplished by a variety of indoor rock mechanics experiments and experimental sound emission, taking Chengde area of Hebei Province the tunnel rock made of rock as research object to simulate various loading rock failure process. To analysis the data obtained of acoustic emission and Dynamics in the process obtaining the characteristic parameters of rock failure process in order to Monitor and Forecast. Through the three axial compression test and the process of acoustic emission signal acquisition discussed the relation between the mechanical parameters of rock acoustic emission parameters of stress. The characteristic parameters of acoustic emission signals with stress and time change through analyzing the acoustic Emission characteristics of each stage in the process of rock failure provide the basis for the prediction of rock burst.

A Design of Underwater Acoustic Signal Acquisition Module

This paper introduced a underwater acoustic signal acquisition module which used preamplifier, filter plate and the digital circuit board collect original data for 20 Hz to 1K Hz frequency data through acoustic vector hydrophone .It could send the collected data to the PC on the coast through wireless data transmission radio station and store the collected original data d into the SD card as well.

Crack Position Recognition of Metal Deep Drawing Parts Based on BP Neural Network

Crack position of metal drawing parts molding was analyzed by the BP neural network. First analysis of the drawing parts forming process may crack in different position. The BP neural network location identification was introduced in the basic process. 11 characteristic parameters from the drawing parts may crack position were gathered by acoustic emission signal acquisition system of deep drawing process. Then the BP neural network was designed rational, and carried out appropriate conduct to train and test. Establishing deep drawing parts of the relations between the different positions crack acoustic emission characteristic parameters and the corresponding position. Crack location was identified, in order to achieve the purpose of positioning the work piece forming process. The better method of acoustic emission location issues are resolved, metal deep drawing forming of crack location identification for basis. Provide the basis for metal drawing parts forming crack location identification.

Self-similarity property of acoustic data acquired in shallow water environment

Abstract Underwater acoustic modeling in shallow water environment is difficult since sound waves reflect several times between the surface and the water bottom. This article discusses an underwater acoustic characteristics analysis method based on self-similarity. It is found that acoustic signal has good self-similarity in shallow water. The actual towed hydrophone linear array was established and it was used for underwater acoustic signal acquisition experiment in Qilihai Reservoir which is located in the suburb of Tianjin, China. It can be derived that the signals acquired by hydrophones have self-similarity by the analysis of the variance of m-aggregated time series. It is proved that the characteristics of self-similarity can be used for the sound pulse propagation in shallow water.

Acoustic Signal Acquisition and Analysis System Based on Digital Signal Processor

Leak detection and calibration of pipe internal roughness in a water distribution network are significant issue for environment pollution around the world. In recent years the problem of leak detection in pipelines, tanks, and process vessels has been the focus of many man-hours of effort. Acquisition the acoustic signal around the leakage to determine the location and size of leaks is emerging as an important tool. A double acoustic data acquisition and signal processing system based on the TI digital signal processor TMS320VC5410 and analog to digital converter TLC320AD50C is presented in this paper. The system design is introduced, with emphasis on the digital signal processor minimal system and TMS320VC5410 interface circuit which consists of two chips of A/D TLC320AD50C. The software development of the data acquisition and signal analysis is introduced. The system can be used in the application of real-time acoustic signal acquisition and leak location.