Acoustic Interference Research Articles

Noninvasive acoustic measurements in high explosives using neural networks

Acoustic measurements serve as a noninvasive means of measuring the temperature or mechanical state of high explosive material without disturbing the material. These measurements work by measuring the time-of-flight of an acoustic burst generated by a transmitter on one side of the material and measured by multiple receivers distributed around the material. In many applications, it is a straightforward process to identify the acoustic burst arrival and use that information to derive information about the material state. For HE materials in metallic containers, however, this process is complicated by interference between the bulk waves propagating through the HE material and guided waves propagating around the circumference of the container walls. We demonstrate the use of neural networks to overcome this limitation. In addition to measurements in HE materials, the neural network technique can provide a means of performing acoustic evaluation in a wide range of materials and in conditions with multi-path acoustic propagation and interference. As a result, the work provides a technique to interpret complex acoustic data and extract useful information about the material state.

Long-term variations in calls produced by a potential blue whale species from the central Indian Ocean

The Comprehensive Nuclear-Test-Ban Treaty Organization hydrophones at Diego Garcia record many marine mammal sounds from the central Indian Ocean. A peculiar call between 20 and 40 Hz from a potential blue whale species, referred to as the Diego Garcia Downsweep (DGD), is regularly recorded in the dataset. The call consists of a set of tones that resemble a comb, followed by a downsweep. Long term spectral averages suggest that the call frequencies are drifting. Tracking the change in frequencies by mere visual observations from the spectrograms is however challenging because of interference from anthropogenic noises and other biophony. This talk presents signal processing methods to track the call-frequencies, across years 2002 to 2019. Energy detectors are initially used to identify, and then exclude acoustic interference from shipping and outliers from electronics. Following that, to isolate the DGDs, and cancel other biophony, the presentation constructs subspace detectors. Finally, the talk uses the spectrograms of the detections to track the change in frequencies for each day. The observations show that while the frequencies of the comb steadily increase, the downsweep decrease. There are new frequencies that appear, and some disappear. These changes are unlike behavior observed from other whales in the region.

The frugivorous bat Carollia perspicillata dynamically changes echolocation parameters in response to acoustic playback.

Animals extract behaviorally relevant signals from 'noisy' environments. Echolocation behavior provides a rich system testbed for investigating signal extraction. When echolocating in acoustically enriched environments, bats show many adaptations that are believed to facilitate signal extraction. Most studies to date focused on describing adaptations in insectivorous bats while frugivorous bats have rarely been tested. Here, we characterize how the frugivorous bat Carollia perspicillata adapts its echolocation behavior in response to acoustic playback. Since bats not only adapt their echolocation calls in response to acoustic interference but also with respect to target distances, we swung bats on a pendulum to control for distance-dependent call changes. Forward swings evoked consistent echolocation behavior similar to approach flights. By comparing the echolocation behavior recorded in the presence and absence of acoustic playback, we could precisely define the influence of the acoustic context on the bats' vocal behavior. Our results show that C. perspicillata decrease the terminal peak frequencies of their calls when echolocating in the presence of acoustic playback. When considering the results at an individual level, it became clear that each bat dynamically adjusts different echolocation parameters across and even within experimental days. Utilizing such dynamics, bats create unique echolocation streams that could facilitate signal extraction in noisy environments.

Monophonic and Polyphonic Wheezing Classification Based on Constrained Low-Rank Non-Negative Matrix Factorization.

The appearance of wheezing sounds is widely considered by physicians as a key indicator to detect early pulmonary disorders or even the severity associated with respiratory diseases, as occurs in the case of asthma and chronic obstructive pulmonary disease. From a physician’s point of view, monophonic and polyphonic wheezing classification is still a challenging topic in biomedical signal processing since both types of wheezes are sinusoidal in nature. Unlike most of the classification algorithms in which interference caused by normal respiratory sounds is not addressed in depth, our first contribution proposes a novel Constrained Low-Rank Non-negative Matrix Factorization (CL-RNMF) approach, never applied to classification of wheezing as far as the authors’ knowledge, which incorporates several constraints (sparseness and smoothness) and a low-rank configuration to extract the wheezing spectral content, minimizing the acoustic interference from normal respiratory sounds. The second contribution automatically analyzes the harmonic structure of the energy distribution associated with the estimated wheezing spectrogram to classify the type of wheezing. Experimental results report that: (i) the proposed method outperforms the most recent and relevant state-of-the-art wheezing classification method by approximately 8% in accuracy; (ii) unlike state-of-the-art methods based on classifiers, the proposed method uses an unsupervised approach that does not require any training.

Broadband Sound Intensity Interference Frequency Periodicity and Pulse Source Localization

In order to analyze the frequency periodicity characteristics of acoustic field interference and realize acoustic source ranging (ASR), the normal mode model is used to analyze the interference characteristics of the broadband acoustic field under the condition of horizontally layered medium; the broadband received signal field when the broadband pulse signal passes through the acoustic field is also simulated. The variation of interference patterns with frequency is analyzed, and their spatial interference characteristics and mechanisms are analyzed. Based on the interference theory, the relation between the acoustic source range and the frequency periodicity of the broadband acoustic intensity interference is derived. Simulation and experimental results show that this relation can accurately estimate the far-field acoustic source range, and the estimation accuracy and real-time performance are greatly improved compared with previous methods. Besides, simulation shows that the method combined with multiple-receiver ranging obtains high-precision direction of arrival (DOA) estimation as well as ASR. The relation between acoustic source position and broadband acoustic field interference frequency periodicity can be used to improve far-field ASR and DOA estimation, which is of great value for oceanography, marine engineering, and marine military. In addition, this relation can also be extended to that between the modal interference frequency periodicity and other related parameters in other physical fields for parameter inversion.

Shot Interference Detection and Mitigation for Underwater Acoustic Communication Systems

Underwater acoustic communications (UACs) are demanded in a wide range of marine applications. However, one of the main challenges for UACs is unexpected interferences from nearby acoustic activities, especially dynamic and short-period interferences (called shot interference), which are hard to detect, estimate, and mitigate over time- and frequency-selective acoustic channels. In this article, we propose a novel filter that mitigates the interference effects for both single-carrier and multi-carrier systems without any prior knowledge of the interference. An Adaptive Sliding Window Interference Detection (ASWID) algorithm is developed to detect the location and the number of interfered symbols. Meanwhile, a least trimmed squares (LTS) equalizer is presented for the shot interference estimation and mitigation based on robust regression. The proposed algorithms are evaluated through numerical simulations and real channel measurements. Our results show that the proposed designs can detect and mitigate shot interferences effectively for single-carrier and multi-carrier UAC systems.

A triple-frequency transducer for endoscopic imaging: Simulation design and experimental verification

In endoscopic ultrasound imaging, it is still challenging to acquire images with high resolution and deep imaging depth at the same time, this contradiction limits the performance of the endoscopic ultrasonic imaging system. Multi-frequency imaging and corresponding image fusion technique have the potential to reduce this contradiction. In this work, a triangle-structure triple-frequency transducer that can work at three different frequencies is presented, its outer diameter is less than 1.5mm. Static and transient models are built to assist its design. Simulation results and sound field measurement results suggest that the three different frequency elements have excellent directivity, and the acoustic field interference between elements is small. Pulse-echo results show that the center frequencies of the elements are 13.17MHz, 20.3MHz, and 30.85MHz, respectively. The ultrasound imaging results of phantom prove that the triple-frequency fusing image is better than single-frequency imaging, and the fused image can maintain the imaging depth and image resolution at the same time. The results certify the feasibility of triple-Frequency transducer in endoscopic imaging and show great potential in the diagnosis of gastrointestinal diseases.

Deep-diving beaked whales dive together but forage apart.

Echolocating animals that forage in social groups can potentially benefit from eavesdropping on other group members, cooperative foraging or social defence, but may also face problems of acoustic interference and intra-group competition for prey. Here, we investigate these potential trade-offs of sociality for extreme deep-diving Blainville's and Cuvier's beaked whales. These species perform highly synchronous group dives as a presumed predator-avoidance behaviour, but the benefits and costs of this on foraging have not been investigated. We show that group members could hear their companions for a median of at least 91% of the vocal foraging phase of their dives. This enables whales to coordinate their mean travel direction despite differing individual headings as they pursue prey on a minute-by-minute basis. While beaked whales coordinate their echolocation-based foraging periods tightly, individual click and buzz rates are both independent of the number of whales in the group. Thus, their foraging performance is not affected by intra-group competition or interference from group members, and they do not seem to capitalize directly on eavesdropping on the echoes produced by the echolocation clicks of their companions. We conclude that the close diving and vocal synchronization of beaked whale groups that quantitatively reduces predation risk has little impact on foraging performance.

A Novel Optical Localization Method for Partial Discharge Source Using ANFIS Virtual Sensors and Simulation Fingerprint in GIL

Partial discharge (PD) detection and localization is one of the most effective methods in gas-insulated transmission lines (GIL) insulation fault diagnosis, which is important to the early troubleshooting and safe operation. Compared with the widely used ultrahigh frequency (UHF) and acoustic PD localization methods, the PD localization method based on optical signals has good resistance to electromagnetic and acoustic interference. However, the current optical localization method comes with several shortcomings: narrow detection range, requiring field experiments to accumulate data, and installing a large number of sensors, which renders low feasibility. Therefore, this article proposes a PD localization method utilizing virtual sensors (VSs) and optical simulation fingerprint. Based on the idea of the digital twin, this method constructs a fingerprint database through optical PD simulation in an equal-sized GIL simulation model, which solves the difficulty of fingerprint collection in actual equipment. Meanwhile, this article predicts the detection value of the VS through the adaptive neuro-fuzzy inference system (ANFIS) to greatly reduce the installation of the actual sensor (AS). Finally, through the support vector machines (SVMs) algorithm, the detection fingerprint that includes the virtual and actual detection values matches with the fingerprint database. The location corresponding to the optimal matching result is recorded as the localization result. As experiments have shown, the average localization error of the proposed method is 19.69 mm, which is 54.8% lower than the one without VSs under the same conditions. The results reveal that this method compensates for the loss of localization accuracy caused by the reduction of ASs, which embodies value in practice.

СИСТЕМНЫЙ ПОДХОД К ПОСТРОЕНИЮ ПРОГРАММНО-АППАРАТНОГО КОМПЛЕКСА ДЛЯ ПОДГОТОВКИ СПЕЦИАЛИСТОВ ПО ИНФОРМАЦИОННОЙ БЕЗОПАСНОСТИ

In order to train specialists in information security (IS), a software and hardware complex “Means of protecting information from leakage through technical channels” has been developed; it provides an opportunity to study the process of information leakage through technical channels and methods of its protection, as well as apply various modules and additional software (software) that clearly demonstrate the features of various methods of information security. The composition of this complex is shown: laboratory stands simulating acoustic, vibroacoustic, acoustoelectric channels and a channel of side electromagnetic radiation and interference. At each of the stands there are information security means (ISMs) that prevent the leakage of confidential information through the corresponding technical channel. To adjust the ISMs for acoustic and vibroacoustic channels, the ISIDORA software has been developed; it allows adjusting the level of the generated acoustic interference to meet the requirements of the security of the room and at the same time to have a comfortable conversation in this room.

A comparative experimental study on advance geological prediction between TETSP and TSP303

We introduce a new tunnel long distance prediction seismic reflection imaging system called TETSP. We use TETSP and the latest generation TSP303 to advance geological comparison detection in Zhangcun tunnel in Thousand Island Lake-Hangzhou water transfer project. Firstly, we introduce the layout of TETSP observation system and data processing flow. Secondly, we expound the differences between TETSP and TSP303 in aspect of geophone coupling and acoustic interference suppression. Lastly, we analyze the characteristics of reflection anomalies in the karst cave zone of the rock mass. The actual tunnel excavation results verify the reliability of the TSP303 and TETSP prediction. Several conclusions are drawn as follow. Firstly, two kinds of seismic reflection technology both can detect whose wave impedance interface exist significant difference in front of tunnel face, but the TSP303 is more accurate. Secondly, the poor integrity of the rock mass is corresponding to the low velocity of P-wave and S-wave.

A Filtering Algorithm of MEMS Gyroscope to Resist Acoustic Interference.

To reduce the impact of acoustic interference in a microelectromechanical system (MEMS) gyroscope and to improve the reliability of output data, a filtering algorithm based on orthogonal demodulation is proposed. According to the working principle and failure mechanism of a MEMS gyroscope, the sound and angular velocity frequencies are not identical, which lead to a different frequency signal output of the original single-channel demodulation scheme. Therefore, a Q channel demodulation filtering process was added to the origin single-channel demodulation scheme. For the Q channel demodulated signal, a Hilbert transform was used to compensate for the 90 degree phase shift. The IQ dual-channel difference can remove the acoustic interference signal. The simulation results indicate that the scheme can effectively suppress the acoustic interference signal and it can eliminate more than 95% of the impact of sound waves. We assembled the acoustic interference experimental platform, collected the driving and sensing data, and verified the denoising performance with our algorithm, which eliminated more than 70% of the noise signal. The simulation and experimental results demonstrate that the scheme can eliminate acoustic interference signal without destroying angular velocity signal.

The Behavior of Microdroplets By the Acoustic Wave Interference

The microdroplet in the air have been recently issued in the view of environmental pollution and infectious virus. The microdroplet with fine dust have been challenged to solve with conventional techniques such as filtering, electrostatic, etc. We investigated the novel technology for decreasing the fine particles in air induced by sound wave with the frequency ranging from 20Hz to 20kHz and the sound pressure level (SPL) from 0 to 100dB.The test systems in our study were set up with constraint box, sound wave actuator, ultra-fine particle distributor, particle counter, decibel meter, etc. the variation of density of ultra-fine particles from distributor was characterized with operating time of sound wave, and compared with the density as no operating.When the low frequency and the SPL under 50Hz and 100dB were applied in the constraint box containing ultra-fine particles, the rate of decrease of ultra-fine particles in density was nearly 5 times higher than that without operating. And it can be applied to increase the efficiency of the conventional particle collection technology such as the commercial filter.It is concluded that the behavior of microdroplets was effectively analyzed by the acoustic wave interference, and also is expected to be applied to the various fields

Acoustic analogy of Rabi rotations in coupled microcavities based on porous silicon

A theoretical and experimental study of acoustic wave coupling in strongly coupled microcavities is presented. Here, we propose an acoustic analogy of Rabi rotations in a system based on porous silicon . We realize a structure consisting of two coupled acoustics microcavities fabricated by electrochemical etching from doped p-type (100) silicon wafers . We measure the acoustic transmission spectra in the frequency domain, and by using the Fourier transform, we obtain the transmission in the time domain. The acoustic transmission spectra of the fabricated sample show the two characteristic acoustic cavity modes, and the analysis in the time domain shows the Rabi-like oscillations originally observed in quantum systems. The experimental results are in good agreement with the transfer matrix and time-resolved acoustic interference theoretical methods used in the study. • We show theoretical and experimental demonstrations of acoustic Rabi oscillations in porous silicon structures. • We propose a method by which the coherent evolution of acoustic excitations can be studied in detail. • Our theoretical results and experimental measurements are in good agreement.

In honor of Peter Narin's retirement: Frogs and morse code operators

Acoustic communication between animals runs the gamut of simple to complex in its dynamic time and frequency structure. Narrow bandwidth codes are often used in noisy environments wherein simple filters can be used to recover the signal under poor signal to noise ratios. Tree frogs in the genus Eleutherodactylus use essentially single and double tones to attract mates in very noisy environments with many males calling mostly silent females. Over the last 40 years, Peter Narins has been studying these simple frog codes. He has shown that these frogs have evolved behaviors to avoid acoustic interference with their neighbors, both in time (by call suppression) and by changing their dominant frequencies across species. Radio amateurs using Morse code mimic frog behavior when trying to communicate with highly desired, weak-signal DX (distant) stations, where many strong signals are calling simultaneously. In this scenario, termed a “DX Pileup,” the calling operators use strategies similar to those of frogs to successfully contact the DX station. Peter (K2IXQ) has been an avid radio amateur for most of his life, using Morse code to chase DX around the world. Clearly, there is an overlap between his scientific research and his personal hobby.

Vibro-acoustic analysis of parallel barriers integrated with flexible panels

In urban communities, parallel barriers are commonly erected for controlling environmental noise such as traffic and construction noise. However, owing to the multiple reflections between the parallel barriers, their performance may be worse than that of a single barrier. To improve the performance of parallel barriers, a small piece of flush-mounted panel backed by a slender cavity in an otherwise rigid wall of barriers is proposed. With the excitation of the incident wave from a sound source inside the parallel barriers, the flexible panel vibrates, and sound is radiated out to undergo acoustic interference with the sound field bounded by the parallel barriers. Consequently, the sound energy in this space and diffraction at the barrier top edge are reduced over a broad band in the low-frequency regime. A theoretical model for tackling the vibro-acoustic coupling between the sound field of the open cavity and the vibrating panel is established to investigate the noise reduction mechanism in the shadow zone. With optimal structural properties of the panel, an additional averaged insertion loss of approximately 5 dB can be achieved at 80–1000 Hz. The theorical results, which are experimentally validated, pave the way for the potential applications of the flexible panel devices (FPDs) for improving the noise reduction of parallel barriers.

Optical coherent control of stimulated Brillouin scattering via acoustic wave interference.

We propose and demonstrate a novel method for controlling stimulated Brillouin scattering with light in a phase-sensitive manner. Our results indicate that Brillouin gain can be enhanced or suppressed in a polarization-maintaining fiber via acoustic wave interference by controlling the relative phase of orthogonally polarized light, which induces acoustic waves. This method paves the way for the all-optical control of Brillouin interaction.

Theoretical and experimental studies on broadband photoacoustic response of surface plasmon sensing

The surface plasmon (SP) sensing technique demonstrates high sensitivity and a broad bandwidth of measuring photoacoustic (PA) pressure transients. In this work, we further present a systematic investigation on PA response characteristics of the recently developed SP-based ultrasonic detector, where the ensemble of surface plasmon polaritons (SPPs) at the metal-dielectric interface is approximated as an equivalent acoustic detector. Relying on the intrinsically ultrafast temporal response (∼140 fs) and highly localized evanescent field (optical penetration depth of ∼185 nm) of the SPPs, the SP sensing can respond ultrasounds with the gigahertz frequency band theoretically, which, however, is far higher than the bandwidth in practical PA detection. We reveal that, due to acoustic interference, the finite lateral probing dimension in the SP sensor imposes an ultimate constraint on the accessible ultrasonic cutoff frequency, representing good agreement with the experimental results by acquiring PA impulses from an optically absorbing graphene film using our SP sensor. The theoretical framework enables analyzing the SP response characteristics of ultrasonic/PA pressure transients, which, therefore, offers guidelines for configuring the SP sensor with adequate sensitivity and bandwidths to access various biomedical PA applications, including volumetric imaging and spectroscopic analysis.

Defect detection of FRP-bonded civil structures under vehicle-induced airborne noise

Fiber-reinforced polymer (FRP)-bonded civil structures have been increasingly used in various construction fields, such as building, bridge, and tunnel. To maintain their designed mechanical performance, the integrity of interfacial bonding should be detected on a regular basis. From many recent laboratory studies, acoustic-laser technique is promising to be applied for identifying the presence of delamination or debonding in FRP-bonded civil structures. However, the defect detection performance of this technique towards real infrastructure encounters a challenging problem related to airborne vehicle noise as the number of cars circulating in urban area increases rapidly. In this study, we deal with the effect of vehicle noise on acoustic-laser technique when applying it in defect detection of FRP-bonded structures. Vehicle sound is found to not only raise the noise floor in measured frequency spectrum but also induce noise-related peaks (below 2000 Hz). Noise from a single passing vehicle causes greater reduction in signal-to-noise (SNR) ratio than that from a platoon of vehicle stream. Additionally, detecting large defect is more vulnerable to acoustic interference of vehicle noise than the small one. A quantitative function between the SNR and the noise level is set up to estimate the performance for defect detection in a construction area near the traffic flow. To handle the vehicle noise issue, a de-noising scheme is proposed and demonstrated for practical defect detection in the field.

A new joint noise reduction and echo suppression system based on FBSS and automatic voice activity detector

In hands-free communication framework, the main drawback affecting the system is the presence of the acoustic noise and echo interferences. To address these problems at the same time, we propose a new joint noise reduction and echo suppression system based on forward blind source separation (FBSS) structure and automatic voice activity detection (AVAD). To deal with the acoustic echo issue, we propose to use an echo suppressor (ES) based on the single channel normalized least mean square (SCNLMS) algorithm. In order to obtain an accurate estimate of the echo signal, the punctual noise is pre-processed by a noise reduction (NR) process, where, for the NR process, we propose to use the two channel normalized least mean square (TCNLMS) algorithm based on the FBSS structure. The FBSS structure uses often manual voice activity detection (MVAD) mechanism to separate speech from noise, but this is not practice in real situations. To overcome the use of the MVAD, we propose a system that uses a new automatic voice activity detection (automatic VAD) mechanism based on signal-to-noise-ratio (SNR) estimation. The obtained results in terms of objective criteria have shown the efficiency of the proposed system in dealing with both interferences at the same time.