scholarly journals Air Ultrasonic Signal Localization with a Beamforming Microphone Array

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Ali Movahed ◽  
Thomas Waschkies ◽  
Ute Rabe
Keyword(s):  
Nondestructive Testing ◽  
Array Signal Processing ◽  
Microphone Array ◽  
Signal Frequency ◽  
Ultrasonic Frequency ◽  
Sound Waves ◽  
Frequency Range ◽  
Sound Sources ◽  
Ultrasonic Sound ◽  
Processing Techniques

Nondestructive testing methods are used to inspect and test materials and components for discontinuities or differences in mechanical characteristics. Phased array signal processing techniques have been widely used in different applications, but less research has been conducted on contactless nondestructive testing with passive arrays. This paper presents an application of beamforming techniques analysis using a passive synthetic microphone array to calculate the origin and intensity of sound waves in the ultrasonic frequency range. Acoustic cameras operating in the audible frequency range are well known. In order to conduct measurements in higher frequencies, the arrangement of microphones in an array has to be taken into consideration. This arrangement has a strong influence on the array properties, such as its beam pattern, its dynamics, and its susceptibility to spatial aliasing. Based on simulations, optimized configurations with 16, 32, and 48 microphones and 20 cm diameter were implemented in real experiments to investigate the array resolution and localize ultrasonic sources at 75 kHz signal frequency. The results show that development of an ultrasonic camera to localize ultrasonic sound sources is beneficial.

Concealed Weapon Detection Using Acoustic Spectral Characterisation

2009 ◽  
Author(s):  
George A. Vadakkel ◽  
S. Olutunde Oyadiji
Keyword(s):  
Acoustic Signal ◽  
Acoustic Waves ◽  
Natural Frequencies ◽  
Sound Waves ◽  
Frequency Range ◽  
Ultrasonic Sound ◽  
Audible Frequency ◽  
Spectral Characterisation ◽  
Concealed Weapon Detection ◽  
Experimental Trials

This paper focuses on showing how one could identify a component by using acoustic waves within the audible frequency range. The purpose of this study is to incorporate the findings from this paper in concealed weapon detection (CWD) where objects hidden behind a person’s clothing could be detected using acoustic or ultrasonic sound waves. Experimental trials are carried out using a directional speaker which generates a highly directional acoustic beam. This can then be pointed at any target and the sound reflected from it analyzed. Initially, a sound source is selected based on the maximum frequency range. The characteristic of the acoustic signal produced by the source is then recorded to be used as reference. Different objects are selected to be used as targets. The sound reflected from these objects is recorded. The spectrograms from these targets reveal that the incident sound waves have been modulated. By taking the ratio of the reflected and the incident sound signals one could obtain the natural frequencies of the object and the spectrogram of the reflected acoustic signal could give indication of the object’s shape.

Optimal Design and Implementation of an Omnidirectional Panel Speaker Array Using the Genetic Algorithm

2004 ◽  
Vol 126 (4) ◽  
pp. 553-560 ◽  
Author(s):  
Mingsian R. Bai ◽  
Jihting Kuo
Keyword(s):  
Genetic Algorithm ◽  
Radiation Pattern ◽  
Digital Signal Processor ◽  
Array Signal Processing ◽  
Low Frequency ◽  
Digital Signal ◽  
Design Stage ◽  
Frequency Range ◽  
Sound Beam ◽  
Processing Techniques

A panel speaker array with omnidirectional radiation pattern is presented in this paper. Array signal-processing techniques are utilized to manipulate the sound beam electronically such that wide-angle radiation can be maintained over a large frequency range. In order to achieve this purpose without sacrificing the array efficiency, the genetic algorithm (GA) is employed in the design stage to calculate the optimal array coefficients. The GA proved to be an effective technique in searching for the array coefficients that maximize the efficiency with desired flatness of radiation pattern. In addition, a modified design is also proposed to further enhance the efficiency in the low frequency range. The resulting designs are implemented on a digital signal processor platform and experimentally verified by using a small 5×1 panel speaker array and a large 3×3 panel speaker array.

scholarly journals Direction of arrival estimation of partial sound sources of vehicles with a two-microphone array

Acta Acustica ◽  
2021 ◽  
Vol 5 ◽  
pp. 18
Author(s):  
Gabriela Dantas Rocha ◽  
Julio Cesar B. Torres ◽  
Mariane Rembold Petraglia ◽  
Michael Vorländer
Keyword(s):  
Microphone Array ◽  
Direction Of Arrival ◽  
Urban Environments ◽  
Average Error ◽  
Vehicle Speed ◽  
Source Characterization ◽  
Sound Sources ◽  
Moving Vehicles ◽  
Processing Techniques ◽  
Intermediate Value

The generalized cross-correlation with phase transform (GCC-PHAT) algorithm has proved to be useful for blindly estimating the direction of arrival of compact sound sources from microphone array recordings. In applications with distributions of partial sources, such as the tires of vehicles in urban environments, the GCC-PHAT needs to be improved, otherwise the detected sound directions change values between directions of the main sources or correspond to an intermediate value between these directions. This paper presents an extension of the GCC-PHAT, based on post-processing of the output delay matrix and on image processing techniques, in order to separately identify directions of the sound produced by the front and rear tires of moving vehicles. The proposed approach can be extended to identify the tire noise directions produced by vehicles with multiple axles. The algorithm performance is analyzed using pass-by measurements of two-axle vehicles, acquired by a two-microphone array. The experiments were conducted with passenger vehicles of four distinct models, running at different speeds. The experimental results show that the proposed method is able to estimate the vehicle speed with an average error of 10.8 km/h and the vehicle wheelbase with 26 cm on average. A possible application is multiple source characterization for parametric vehicle sound synthesis in auralization.

scholarly journals Microphone Arrays as a Leakage Detection Tool in Industrial Compressed Air Systems

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Petr Eret ◽  
Craig Meskell
Keyword(s):  
Best Practice ◽  
Microphone Array ◽  
Leak Detection ◽  
Microphone Arrays ◽  
Compressed Air ◽  
Handheld Devices ◽  
Ultrasonic Frequency ◽  
Noisy Environment ◽  
Frequency Range ◽  
Industrial Manufacturing

Compressed air energy is expensive, but common in industrial manufacturing plant. However, a significant part of the generated compressed air energy is lost due to leakage. Best practice requires ongoing leak detection and repair. Leak detection in the ultrasonic frequency range using handheld devices is possible only over short distances as associated high-frequency sound is rapidly attenuated by atmospheric absorption. Pressurized air escaping to ambience also generates frequencies below 20 kHz. In this paper beamforming—a well known method for generating noise maps—is tested as a tool for localization of compressed air leaks at larger distances in the audible frequency range. Advanced beamforming methods in both time domain (broadband) and frequency domain (narrowband) have been implemented in a variety of situations on a laboratory experimental rig with several open blows representing leakage in a noisy environment similar to a factory setting. Based on the results achieved it is concluded that the microphone array approach has the potential to be a robust leak identification tool. The experience gained here can also provide useful guidance to the practitioner.

scholarly journals Acoustic source localization using the open spherical microphone array in the low-frequency range

2019 ◽  
Vol 283 ◽  
pp. 04001
Author(s):  
Boquan Yang ◽  
Shengguo Shi ◽  
Desen Yang
Keyword(s):  
Source Localization ◽  
Generalized Inverse ◽  
Microphone Array ◽  
Low Frequency ◽  
Poor Performance ◽  
Microphone Arrays ◽  
Three Dimension ◽  
Frequency Range ◽  
Array Aperture ◽  
Regularization Matrix

Recently, spherical microphone arrays (SMA) have become increasingly significant for source localization and identification in three dimension due to its spherical symmetry. However, conventional Spherical Harmonic Beamforming (SHB) based on SMA has limitations, such as poor resolution and high side-lobe levels in image maps. To overcome these limitations, this paper employs the iterative generalized inverse beamforming algorithm with a virtual extrapolated open spherical microphone array. The sidelobes can be suppressed and the main-lobe can be narrowed by introducing the two iteration processes into the generalized inverse beamforming (GIB) algorithm. The instability caused by uncertainties in actual measurements, such as measurement noise and configuration problems in the process of GIB, can be minimized by iteratively redefining the form of regularization matrix and the corresponding GIB localization results. In addition, the poor performance of microphone arrays in the low-frequency range due to the array aperture can be improved by using a virtual extrapolated open spherical array (EA), which has a larger array aperture. The virtual array is obtained by a kind of data preprocessing method through the regularization matrix algorithm. Both results from simulations and experiments show the feasibility and accuracy of the method.

Design of Control System for Hydraulically Vibrated Processing Tomato Fruit Seedling Separation Device

2014 ◽  
Vol 651-653 ◽  
pp. 693-696
Author(s):  
Li Hong Wang ◽  
Rong Qing Liang ◽  
Cheng Song Li ◽  
Za Kan ◽  
Jin Wei Qin
Keyword(s):  
Tomato Fruit ◽  
Simulation Software ◽  
Signal Frequency ◽  
System Control ◽  
Frequency Range ◽  
Hydraulic Simulation ◽  
Separation Device ◽  
Processing Tomato ◽  
Input Signal Frequency ◽  
Set Up

Eccentric style processing tomato fruit seeding separation device exist high machining and assembly precision or other issues. In order to solve this problem, the mode of vibration of hydraulic replaced the eccentric style to drive the fruit seedling separation roller to separate processing tomato effectively. To facilitate adjustment of the hydraulic system, a kind of control circuit PLC as the core was designed according to the actual production requirements. PLC and other elements were selected. The system control signal frequency was initially set up as 1~5 HZ, within the frequency range hydraulic simulation software was used to simulate and analyze the hydraulic vibration system. The result shows that the system rams steady when the input signal frequency range was 1~5HZ.

Hypersonic Velocity, Absorption and Relaxation in Molten CSNO3

1977 ◽  
Vol 32 (1) ◽  
pp. 57-60 ◽  
Author(s):  
H. E. Gunilla Knape ◽  
Lena M. Torell
Keyword(s):  
Relaxation Time ◽  
High Frequency ◽  
Viscosity Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Ultrasonic Velocities ◽  
Hypersonic Velocity ◽  
Frequency Shifts ◽  
Bulk Viscosity Coefficient ◽  
Good Agreement

Abstract Brillouin spectra of molten CSNO3 were investigated for scattering angles between 40 and 140° and in a temperature interval of 420-520 °C. An Ar+ singlemode laser was used for excitation and the total instrumental width was ~265 MHz. The measured frequency shifts and linewidths of the Brillouin components were used to determine velocities and attenuations of thermal sound waves in the frequency range 2.3-7.0 GHz. A dispersion of 4-5% was found between the present hyper­ sonic velocities and reported ultrasonic velocities. A considerable decrease in attenuation with frequency was observed in the investigated frequency range, with the value at high frequency ap­ proaching the classical attenuation. The results are in good agreement with Mountain's theory of a single relaxation time. The relaxation time of the bulk viscosity coefficient was calculated to 1.2×10-10S.

Locating and tracking sound sources on a horizontal axis wind turbine using a compact microphone array based on beamforming

2019 ◽  
Vol 146 ◽  
pp. 295-309 ◽  
Author(s):  
Cui Qing Zhang ◽  
Zhi Ying Gao ◽  
Yong Yan Chen ◽  
Yuan Jun Dai ◽  
Jian Wen Wang ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Microphone Array ◽  
Horizontal Axis ◽  
Horizontal Axis Wind Turbine ◽  
Sound Sources
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