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.

Flexibly guiding of acoustic waves by one-dimensional sonic crystal with omnidirectional bandgap

2015 ◽  
Vol 29 (28) ◽  
pp. 1550193 ◽  
Author(s):  
Hai-Long He ◽  
Shi-Liang Ou-Yang ◽  
Zhaojian He ◽  
Ke Deng ◽  
Heping Zhao
Keyword(s):  
Numerical Simulations ◽  
Crystal Structures ◽  
Acoustic Waves ◽  
High Efficiency ◽  
Wide Frequency Range ◽  
Sound Waves ◽  
Frequency Range ◽  
Bending Angle ◽  
One Dimensional ◽  
Sonic Crystal

An acoustic waveguide based on the omnidirectional reflection of one-dimensional (1D) sonic crystal (sc) is designed to realize the flexible guiding of sound waves. Numerical simulations indicate that high-efficiency transmission can be achieved at arbitrary bending angle and over a wide frequency range. Moreover, flexible waveguide branches can also be easily constructed by introducing more crystal structures into the waveguides. Owing to its designing flexibility, this waveguide would be very useful in various integrated applications based on SCs.

Implantation of Poly(ethyl acrylate) in Mesoporus Poly(styrene-co-divinylbenzene) Microspheres as a Particulate Sound Absorbent

2004 ◽  
Vol 856 ◽  
Author(s):  
Yeap Hung Ng ◽  
Liang Hong
Keyword(s):  
Acoustic Waves ◽  
Pore Radius ◽  
Suspension Polymerization ◽  
Ethyl Acrylate ◽  
Sound Waves ◽  
Frequency Range ◽  
Attenuation Level ◽  
Polymerization Reactor ◽  
The Individual ◽  
Individual Particles

ABSTRACTPorous microspheres of poly(styrene-co-divinylbenzene) (SD) have been synthesized by suspension polymerization. They present a narrow porosity gap (21–24%) and a mean pore-radius range (106–117 Å). The mesoporous voids are then made use as the polymerization reactor for ethyl acrylate (EA), and as a result of the embedded polymerization, linear EA formed is trapped inside the individual particles (SD-EA), and its Tg is brought up to as high as the ambient temperature. Two specific loadings of EA were attained: 11% and 28% by weight. The acoustic absorption behaviors of SD-EA and SD microspheres are assessed by the attenuation coefficient (a = IAttenuated/IIncidence), in which the incident acoustic waves are two arbitrary audio frequency bands, 100–1000 Hz and 4000–5000Hz. In contrast to porous SD microspheres, SD-EA microspheres apparently relax the incident frequencies and attenuate more effectively the higher frequency sound waves. The maximum attenuation level (a) of SD-EA absorbent is about 80% (dB). It was found that the higher EA loading could improve rather slightly the attenuation level in the higher frequency range.

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.

Simulation of Fabry-Perot Resonance for 3D Printable Complex Holey Acoustic Metamaterials

2020 ◽  
Author(s):  
Sanjay Ravichandran ◽  
Xin Wu ◽  
Yutai Su ◽  
Jing Shi
Keyword(s):  
Resonance Condition ◽  
Simulation Method ◽  
Complex Structures ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Frequency Range ◽  
Acoustic Metamaterial ◽  
Fabry Perot ◽  
Audible Frequency ◽  
Sub Wavelength

Abstract An acoustic metamaterial is a kind of material that is artificially designed in such a way that it can manipulate, control and direct sound waves. To date, various designs for acoustic metamaterials in the imaging applications have been proposed. However, these designs are generally simple due to the restriction from conventional manufacturing methods. By taking advantage of the additive manufacturing (AM) techniques, many complex acoustic metamaterials could be realized. However, the research on the complex structures for imaging applications has been very limited. In this paper, various 3D printable holey structured metamaterials with only one aperture are proposed, and the application possibility for sub-wavelength acoustic imaging in the audible frequency range is investigated. By using numerical simulation method, the effect of transmission properties of incident evanescent waves is analyzed to see whether these waves can completely transmit through the metamaterial. The phenomenon of Fabry-Perot resonances (FPR) that occur inside the hole for five different aperture shapes which are air-filled is studied, and the possibility of operating in a broadband resonance condition for the five designs are analyzed. These results can also be used to obtain valuable information for realizing a broadband acoustic hyperlens, which is an emerging application of 3D printable acoustic metamaterials.

Transmission control of acoustic metasurface with dumbbell-shaped double-split hollow sphere

2020 ◽  
Vol 34 (33) ◽  
pp. 2050386
Author(s):  
Yibao Dong ◽  
Yuanbo Wang ◽  
Jianxiang Sun ◽  
Changlin Ding ◽  
Shilong Zhai ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
Simple Structure ◽  
Negative Refraction ◽  
Hollow Spheres ◽  
Complex Structures ◽  
Sound Waves ◽  
Large Size ◽  
Audible Frequency ◽  
Potential Applications ◽  
Focusing Lens

Complex structures, large size and limited manipulation of acoustic waves are the problems that restrict the development of acoustic metasurfaces. Here, we report a transmission-type acoustic metasurface based on local resonance mechanism, which is composed of meta-atomic units called dumbbell-shaped double-split hollow spheres (DSDSHS). This metasurface with subwavelength scale has the advantage of simple structure and easy preparation, and can realize the full manipulation of sound waves. Negative refraction with different transmission angles and high intensity plate focusing lens are realized in the air environment of audible frequency. The proposed metasurface has potential applications in the miniaturization and integration of sound transmission and sound energy collection, opening a new opportunity for manipulation of acoustic wavefront.

Microcontroller Device for Conductor Identification Using Acoustic Signal

2020 ◽  
Vol 67 (1) ◽  
pp. 28-34
Author(s):  
Aleksandr V. Vinogradov ◽  
Aleksey V. Bukreev
Keyword(s):  
Acoustic Signal ◽  
Acoustic Waves ◽  
Theoretical Calculations ◽  
Poor Quality ◽  
Electrical Circuit ◽  
Research Purpose ◽  
Electrical Wiring ◽  
The Right ◽  
The Cost ◽  
Technical Solutions

When repairing and replacing electrical wiring in enterprises, the main difficulty is the lack or poor quality of documentation, plans for conductors laying. Distinguishing wires (cables) and their cores by the color of the shells or using tags attached to the ends is difficult if the shells have the same color and there are no tags. Devices and technical solutions used to identify wires and cables do not allow recognizing conductors without breaking the electrical circuit, removing insulation, and de-energizing the network. Searching for the right conductor is a time-consuming operation. (Research purpose) The research purpose is developing a new microcontroller device for identifying wires using an acoustic signal. (Materials and methods) Literature sources has been searched for devices for conductors identifying. (Results and discussion) The article proposes a method that involves feeding an acoustic signal to a wire at one point and capturing it at another, in order to recognize the desired wire. The article presents results of comparison of the developed microcontroller device for identifying conductors using an acoustic signal with known devices and methods for conductors recognizing. (Conclusions) The article reveals the shortcomings of existing methods and means of identifying wires and cables. Authors performed a theoretical calculation of the sound pressure in the conductor at a given distance. The article presents the calculation of speed of acoustic waves in conductors with different types of insulation. Authors designed a microcontroller device for identifying conductors using an acoustic signal and tested it. It was determined that the device increases the safety of work, reduces the cost of operating internal wiring and identification time; eliminates the violation of wire insulation, the need to disable electrical receivers. The convergence of theoretical calculations and experimental data was shown.

scholarly journals Aspects of Strength Testing of Tank Containers in Compliance with the Requirements of the UN Navigation Rules and Regulations

2021 ◽  
Vol 9 (3) ◽  
pp. 349
Author(s):  
Andrii Sulym ◽  
Pavlo Khozia ◽  
Eduard Tretiak ◽  
Václav Píštěk ◽  
Oleksij Fomin ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Response Spectrum ◽  
Experimental Curve ◽  
Bulk Liquid ◽  
Frequency Range ◽  
Test Configuration ◽  
Shock Response ◽  
Shock Response Spectrum ◽  
Spectrum Curve ◽  
The Impact

This article deals with the method of computer-aided studies of the results of tank container impact tests to confirm the ability of portable tanks and multi-element gas containers to withstand the impact in the longitudinal direction on a specially equipped test rig or using a railway flat car by impacting a flat car with a striking car, in compliance with the requirements of the UN Navigation Rules and Regulations. It is shown that the main assessed characteristic of the UN requirements is the spectrum of the shock response (accelerations) for the interval natural frequencies of the shock pulse. The calculation of the points of the shock response spectrum curve based on the test results is reproduced in four stages. A test configuration of the impact testing of the railway flat car with a tank container is presented, and the impact is performed in such a way that, under a single impact, the shock spectrum curve obtained during the tests for both fittings subjected to impact repeats or exceeds the minimum shock spectrum curve for all frequencies in the range of 2 Hz to 100 Hz. Formulas for determining the relative displacements and accelerations for the interval natural frequencies of the shock wave are given. The research results are presented in graphical form, indicating that the experimental values of the shock response spectrum exceed the minimum permissible values; the equation of the experimental curve of the shock response spectrum in the frequency range 0–100 Hz is described by power-law dependence. The coefficients of the equation were determined by the statistical method of maximum likelihood with the determination factor being 0.897, which is a satisfactory value; a comparative analysis showed that the experimental curve of the impact response spectrum in the frequency range 0–100 Hz exceeds the normalized curve, which confirms compliance with regulatory requirements. A new test configuration is proposed using a tank car with a bulk liquid, the processes in which upon impact differ significantly from other freight wagons under longitudinal impact loads of the tank container. The hydraulic impact resulting from the impact on the tank container and the platform creates an overturning moment that causes the rear fittings to be unloaded.

scholarly journals Detection and localization of multiple small damages in beam

2021 ◽  
Vol 13 (1) ◽  
pp. 168781402098732
Author(s):  
Ayisha Nayyar ◽  
Ummul Baneen ◽  
Syed Abbas Zilqurnain Naqvi ◽  
Muhammad Ahsan
Keyword(s):  
Frequency Response ◽  
Natural Frequencies ◽  
Signal To Noise Ratio ◽  
Moving Average ◽  
A Priori ◽  
Damage Index ◽  
High Signal ◽  
Frequency Range ◽  
Spatial Locality ◽  
System Frequency

Localizing small damages often requires sensors be mounted in the proximity of damage to obtain high Signal-to-Noise Ratio in system frequency response to input excitation. The proximity requirement limits the applicability of existing schemes for low-severity damage detection as an estimate of damage location may not be known  a priori. In this work it is shown that spatial locality is not a fundamental impediment; multiple small damages can still be detected with high accuracy provided that the frequency range beyond the first five natural frequencies is utilized in the Frequency response functions (FRF) curvature method. The proposed method presented in this paper applies sensitivity analysis to systematically unearth frequency ranges capable of elevating damage index peak at correct damage locations. It is a baseline-free method that employs a smoothing polynomial to emulate reference curvatures for the undamaged structure. Numerical simulation of steel-beam shows that small multiple damages of severity as low as 5% can be reliably detected by including frequency range covering 5–10th natural frequencies. The efficacy of the scheme is also experimentally validated for the same beam. It is also found that a simple noise filtration scheme such as a Gaussian moving average filter can adequately remove false peaks from the damage index profile.

Simulation of multiwavelength conditions in laser picosecond ultrasonics

SIMULATION ◽  
2021 ◽  
pp. 003754972199645
Author(s):  
Philippe Babilotte
Keyword(s):  
Numerical Simulations ◽  
Acoustic Signal ◽  
Acoustic Waves ◽  
Bulk Material ◽  
Deformation Field ◽  
Optical Pump ◽  
Pump And Probe ◽  
Oriented Object ◽  
Numerical Approaches ◽  
Picosecond Ultrasonics

Complete numerical simulations are given under SciLab® and MATLAB® coding environments, concerning propagative acoustic wavefronts, for laser picosecond ultrasonics under multiwavelength conditions. Simulations of the deformation field and its propagation into bulk material are given under different wavelength configurations for optical pump and probe beams, which are used to generate and to detect the acoustic signal. Complete insights concerning the dynamics of the acoustic waves are given, considering the absence of carrier diffusions into the material. Several numerical approaches are proposed concerning both the functions introduced to simulate the wavefront ( Heaviside or error) and the coding approach (linear/vectorized/ Oriented Object Programming), under the pure thermo-elastic approach.

SIMP for Complex Structures

2016 ◽  
Vol 846 ◽  
pp. 535-540
Author(s):  
David J. Munk ◽  
David W. Boyd ◽  
Gareth A. Vio
Keyword(s):  
Natural Frequencies ◽  
Dynamic Loads ◽  
Topology Optimisation ◽  
Complex Structures ◽  
Structural Failure ◽  
Frequency Range ◽  
Aerodynamic Loading ◽  
Frequency Excitation ◽  
Wing Structure ◽  
Lifting Surfaces

Designing structures with frequency constraints is an important task in aerospace engineering. Aerodynamic loading, gust loading, and engine vibrations all impart dynamic loads upon an airframe. To avoid structural resonance and excessive vibration, the natural frequencies of the structure must be shifted away from the frequency range of any dynamic loads. Care must also be taken to ensure that the modal frequencies of a structure do not coalesce, which can lead to dramatic structural failure. So far in industry, no aircraft lifting surfaces are designed from the ground up with frequency optimisation as the primary goal. This paper will explore computational methods for achieving this task.This paper will present a topology optimisation algorithm employing the Solid Isotropic Microstructure with Penalisation (SIMP) method for the design of an optimal aircraft wing structure for rejection of frequency excitation.

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