Distribution Of Acoustic Energy Research Articles

The solution of sound propagation modeling problems for environment impact assessment by the mode parabolic equations methoda).

The method of sound propagation modeling based on the mode parabolic equations (MPEs) theory is applied to the verification scenarios for environmental impact assessment. The results for selected scenarios from the 2022 Cambridge Joint Industry Programme Acoustic Modelling Workshop and the configuration of the computational programs AMPLE and MPE for these scenarios is discussed. Furthermore, it is revealed how the results for these scenarios change in the case of the bottom slope across and along the propagation path. It is observed that for the cross-slope propagation scenario, the distribution of acoustic energy over decidecade frequency bands does not depend on the slope angle and is practically the same as that for range-independent environment. At the same time, the dependence of energy distribution is noticeable for up- and downslope propagation scenarios, where greater slope angles result in higher propagation loss. It is also shown that MPEs are capable of adequately handling typical sound propagation problems related to the environmental impact assessment for frequencies up to 1000 Hz. A possibility of using frequency-dependent mesh size and number of modes must be implemented in codes based on this approach.

On application of sound power radiation of rolling tyre measured using CPX-based methodology

The present paper provides a comprehensive account of sound power radiation measurement from a rolling tyre, utilising a methodology that employs an advanced PolyU Mark III Close-Proximity (CPX) trailer enclosure which is aimed to provide CPX measurement per relevant ISO stsandard with suppressed background noise within the interior. The interior walls and ceiling of the enclosure are equipped with diffuser panels, creating a reverberant environment suitable for sound power measurement using the comparison method. The optimal design of the enclosure, which minimizes acoustic resonance and ensures a uniform distribution of acoustic energy, is determined through extensive numerical simulations. During tyre/road sound power measurements, the spatially averaged sound pressure level (SPL) distributions within the enclosure are obtained with a reference sound source (RSS) of known sound power. The relationships between the RSS SWLs and the corresponding SPLs are established at all vehicle speeds. These relationships can then be utilised to deduce the total SWL, as well as its 1/3-octave spectrum, from the captured averaged SPL radiated by a tyre rolling at any vehicle speed. The effectiveness of the CPX-based sound power measurement are illustrated. Additionally, the potential of utilising the measured SWLs for predicting pass-by noise radiation to roadside is discussed.

Time-dependent dynamical energy analysis via convolution quadrature

Dynamical Energy Analysis was introduced in 2009 as a novel method for predicting high-frequency acoustic and vibrational energy distributions in complex engineering structures. In this paper we introduce the first time-dependent Dynamical Energy Analysis method. Time-domain models are important in numerous applications including sound simulation in room acoustics, predicting shock-responses in structural mechanics and modelling electromagnetic scattering from conductors. The first step is to reformulate Dynamical Energy Analysis in the time-domain by means of a convolution integral operator. We are then able to employ the Convolution Quadrature method to provide a link between the previous frequency-domain implementations of Dynamical Energy Analysis and fully time-dependent solutions by means of the Z-transform. By combining a modified multistep Convolution Quadrature approach for the time discretisation, together with Galerkin and Petrov-Galerkin methods for the space and momentum discretisations, respectively, we are able to accurately track the propagation of high-frequency transient signals through phase-space. The implementation here is detailed for finite two-dimensional spatial domains and we demonstrate the versatility of our approach by performing a range of numerical experiments for regular, non-convex and irregular geometries as well as different types of wave source.

Evaluation Method for Underwater Ultrasonic Energy Radiation Performance Based on the Spatial Distribution Characteristics of Acoustic Power.

In recent years, underwater wireless ultrasonic energy transmission technology (UWUET) has attracted much attention because it utilizes the propagation characteristics of ultrasound in water. Effectively evaluating the performance of underwater ultrasonic wireless energy transmission is a key issue in engineering design. The current approach to performance evaluation is usually based on the system energy transfer efficiency as the main criterion, but this criterion mainly considers the overall energy conversion efficiency between the transmitting end and the receiving end, without an in-depth analysis of the characteristics of the distribution of the underwater acoustic field and the energy loss that occurs during the propagation of acoustic waves. In addition, existing methods focusing on acoustic field analysis tend to concentrate on a single parameter, ignoring the dynamic distribution of acoustic energy in complex aquatic environments, as well as the effects of changes in the underwater environment on acoustic propagation, such as spatial variability in temperature and salinity. These limitations reduce the usefulness and accuracy of models in complex marine environments, which in turn reduces the efficiency of acoustic energy management and optimization. To solve these problems, this study proposes a method to evaluate the performance of underwater ultrasonic energy radiation based on the spatial distribution characteristics of acoustic power. By establishing an acoustic power distribution model in a complex impedance-density aqueous medium and combining numerical simulation and experimental validation, this paper explores the spatial variation of acoustic power and its impact on the energy transfer efficiency in depth. Using high-resolution spatial distribution data and actual environmental parameters, the method significantly improves the accuracy of the assessment and the adaptability of the model in complex underwater environments. The results show that, compared with the traditional method, this method performs better in terms of the accuracy of the acoustic energy radiation calculation results, and is able to reflect the energy distribution and spatial heterogeneity of the acoustic source more comprehensively, which provides an important theoretical basis and practical guidance for the optimal design and performance enhancement of the underwater ultrasonic wireless energy transmission system.

Using soundscape to monitor population size, demographics, and antipredator behavior in a dense aggregation of colonial seabirds

Migratory seabirds are vulnerable to decline due to climate change and anthropogenic disturbances. Common terns (Sterna hirundo) are highly vocal colonial seabirds that serve as bioindicators of their foraging grounds throughout their migratory range. Historically, monitoring colonial seabirds is invasive and time-consuming, and traditional acoustic approaches are complicated by high amounts of call overlap. Monitoring the behavioral ramifications of disturbance, as well as overall colony size and health, is crucial to implementing effective management decisions. However, methods are needed to do so efficiently and with minimal disturbance. In this study, we demonstrate that population size, demographics, and behavior can be assessed acoustically through changes in acoustic energy across varying temporal scales. To do this, we compared acoustic energy to in-person observations of nest density, chick-hatching, and investigator disturbance. We found that trends in acoustic energy align with observations of nest density, and the distribution of acoustic energy across frequency bands is indicative of colony demographics. Furthermore, we found a significant relationship between acoustic energy and investigator disturbance within 20 meters of an acoustic recorder. Overall, our findings suggest that colony-wide trends in population size, demographics, and behavior can be monitored via acoustic energy without the time-consuming analysis of individual calls.

Acoustic Emission Waveform Characterization of Crack Origin In Self-Healing of Mortar Due to Internal Carbonation

In this study, self-healing of mortar was achieved by “built-in” carbonation of soluble Na2CO3 and Ca(OH)2. The effect of carbonate and calcium ions, available either internally or externally by conditioning the specimens with Ca(OH)2 and Na2CO3 solution, on the formation of calcite in cracks was investigated. The acoustic events were monitored and compared in the loading process before and after healing. Furthermore, a calibration test was carried out to distinguish the characteristic acoustic emission events of the fracture of the matrix and of healing products. It was found that the distribution of acoustic energy with FMA (frequency at maximum amplitude) and the hits with duration show a consistent trend with that of calibration. The change of tensile to shear cracking ratio in reloading illustrates a self-healing effect of cracks. Meanwhile, X-ray diffraction analysis indicates more calcite formed in the crack of self-healing specimens. The pretreated ceramsite-containing specimens exhibit the predominate self-healing effect due to the internally available CO32– and sufficient Ca2+ as compared to the others.

Design of a computational method to optimise acoustic output of the human vocal tract

The influence of the geometric configuration of the human vocal tract (HVT) on the character of acoustic energy distribution during phonation of the vowel [a:] has been analysed. The computationally efficient mathematic models of the HVT have been assembled based on super elements and an isoparametric element with higher degree of polynomial shape function. The assembled models enable the easy and quick geometrical reconfiguration of the HVT and they can be used for the time-consuming optimization process with aim to find the suitable geometric configuration of the HVT to generated the so-called singer’s formant.

Sound Power Measurement of Tyre/Road Noise Using the Close-Proximity (CPX) Trailer Enclosure

The present paper reports a new methodology for measuring the sound power level (SWL) of tyre/road noise, using a modified Close-Proximity (CPX) trailer enclosure. Specially designed diffuser panels are implemented to cover the absorption materials on the interior walls and ceiling of the CPX enclosure to create a reverberant chamber. Through numerical simulations, the optimal reverberant chamber design, which holds the least acoustic resonance and most uniform acoustic energy distribution, is determined to guide fabrication. The SWL of a reference sound source (RSS) is determined first. The sound pressure level (SPL) distributions inside the reverberant chamber with the RSS switched on are then obtained under static conditions and road tests. The relationships between the SWL of the RSS and the SPL it produces inside reverberant chamber with various RSS inputs signals show great consistency with theory. Using the linear regression of SWL with respect to spatially averaged SPL reverberant chamber obtained in static condition, the total SWL and its spectrum at a specific vehicle speed can be deduced from the captured SPL information inside the chamber during road tests with the RSS switched off.

Underwater soundfield visualisation using directionally constrained acoustic parameters.

This paper presents an underwater soundfield visualisation method for passive-sonar applications employing circular hydrophone arrays. The method operates by segregating the space by means of beamforming into angular sectors scanning the whole horizontal plane and then computing acoustic parameters within each sector. The information from these directionally constrained parameters is fused in order to produce spatial spectra which depict the distribution of acoustic energy over bearing. The evaluation is performed on simulated data of circular hydrophone arrays mounted on rigid cylindrical baffles. Comparisons against baseline methods of similar computational complexity suggest that, for moderate to high signal-to-noise ratio levels, the proposed method offers improved performance in terms of background noise suppression, angular resolution, and direction-of-arrival estimation accuracy. Additionally, it is demonstrated that, with the appropriate choice of sector pattern, the proposed method can, at least in some cases, achieve superior performance to the baseline methods in the presence of interferers even at low signal-to-interference ratio levels. Last, the sector-based parameter diffuseness, which is directly related to the direct-to-diffuse ratio, may be used both as a weight function to further attenuate the background noise level and as a confidence measure of the estimation accuracy.

Mechanical and Acoustic Emission Characteristics of Grouted Reinforcement in Fissure-Containing Rock-like Specimens

In order to study the reinforcing effect of the different grouting materials applied in fissure rock engineering, ultra-fine cement slurry, cement–silicate slurry, and MARITHAN® were used to carry out grouting tests on specimens of fissure-containing rocks. With the help of a uniaxial compression acoustic emission test system, the mechanical characteristics of the grouted specimens were obtained, and the damage process of the specimens was revealed by using the acoustic emission signals. The tested results showed the following: the residual strength of the grouted specimens using the three grouting materials increased by 16.931%, 13.075%, and 39.998%, respectively; the ultra-fine cement grouting and cement–silicate grouting specimens showed damage patterns of shear-slip damage along the original rupture surface; the specimens of MARITHAN® grouting cracked from a position near the end of the specimen with no damage to the grouted body portion; the cumulative acoustic emission energy curves of the grouted specimens showed obvious stage characteristics; and the acoustic emission energy distribution characteristics of the grouted specimens differed depending on the grouting materials.

Needs of musicians during performance, without electronic amplification, in Concert Halls and Opera Houses

Drawing on experience of having listened to music in 60 concert halls and opera houses around the World, conducted experimental stage and orchestra pit modifications for live performance with audiences, analyzed the onset characteristics of musical instruments and their attack sequences; manipulated the distribution of acoustic energy using stage furniture with performer responses; and taught acoustics for 40 years, the author offers insights into the design of stages and orchestra pits for the performance of music without electronic amplification, in the context of his experience as a musician, architect, and engineer. In the orchestra pit of the Sydney Opera House: A second desk first violinist said he could not hear his instrument before the furniture was installed; and said after the furniture had been installed, “I am like thunder!” The tympani player asked, “What have you done? My instruments are alive!” In the Macquarie Auditorium, a violinist playing her Stradivarius violin said, “I used to dread playing in that auditorium now I am soaring.” The Australian Chamber orchestra refused to make a recording in the Gore Hill ABC TV Studio, without the stage furniture. What was done in several auditoria and responses from musicians is described in the paper.

Energy-distributable waterborne acoustic launcher for directional sensing

Highly directional launch and intensity adjustment of underwater acoustic signals are crucial in many areas such as abyssal navigation, underwater signal communication, and detection for marine biology. Inspired by the phenomenon that aquatic animals like dolphins detect and track prey with high resolution, we propose an energy-distributable directional sensing strategy which can achieve parallel needle-like transmitting sound beams with adjustable energy based on out-coupling valley-polarized edge states. The acoustic spin angular momentum and energy flow distribution at different interfaces inside the phononic crystal are provided and they show tight coupling. Furthermore, a sound beam with a width of 20° and an acoustic intensity enhancement factor ≈ 6.6 are observed in the far field. As an application, we show that this device can be used as an acoustic energy distributor. This communication pattern with excellent functionalities and performance provides a desirable idea for high-energy-level directional collimated underwater sensing and underwater acoustic energy distribution.

Study on sound insulation performance of sonic black hole with micro-perforated plates

According to the traditional law of mass, the insulation of low-frequency sound usually requires thick, high-density materials. However, lightweight metamaterials containing acoustic structures can also achieve high acoustic transmission losses. In this study, we present a sonic black hole (SBH) device coupled with micro-perforated plates (MPPs) and intraluminal column structure to achieve high sound insulation performance with light weight. The finite element model (FEM) is developed to analyze the acoustic energy distribution and dissipation inside the SBH device to evaluate its sound transmission loss (STL), and the accuracy of the analytical model is verified by impedance tube testing. The analysis results show that the SBH device has excellent sound insulation performance in the broadband and low frequency mainly due to the energy dissipation caused by the MPPs and column structure, and wavelength compression, energy focusing caused by the SBH effect. Finally, the sound insulation capacity of SBH can be further improved by improving the structure, such as increasing the complexity of acoustic medium flow and adding the number of layers of MPPs. The numerical model and the calculation results of this paper provide a new way of thinking for the design and optimization of SBH sound insulation structures.

Analysis of Acoustic Emission Energy Distribution and Avalanche Dynamics of Sandstone with Different Particle Sizes.

The mechanical properties of sandstone have an important impact on the stability of the coal mine roof and floor, sandstone gas mining, and underground engineering safety. In order to study the critical characteristics on the failure process of sandstone with different particle sizes under uniaxial compression conditions, avalanche dynamics theory and a critical model are used to analyze the distribution of acoustic emission (AE) parameters, and the maximum likelihood estimation is used to accurately estimate the critical parameters. The results showed that the AE phenomenon of sandstone can be divided into four stages: initial compaction period, quiet period, crack stable growth period and outbreak period. During the process of compression failure, the larger the particle size is, the more seriously the sandstone is damaged. The AE energy probability density distribution follows single power-law distribution, and the AE energy critical exponent is 1.20 and follows the characteristics of scale-free regarding the power-law distribution on the particle sizes. When the stress runs up to 90% of peak stress, the bifurcation ratio increases sharply and shows the characteristics of the critical state. The waiting time and the avalanche size distribution follow double power-law distribution, and the inflection points are 0.03 and 37. Before and after the inflection point, the waiting time critical exponent and the avalanche size critical exponent are 1.90, 0.40 and 2.40, 1.60. This shows that the dynamic evolution process of sandstone under uniaxial compression condition can be characterized well by the fiber bundle model.

Transcranial cavitation mapping of blood–brain barrier opening regions in Alzheimer’s disease patients using a neuronavigation-guided focused ultrasound system

We present real-time cavitation monitoring and mapping in a clinical trial for blood-brain barrier (BBB) opening in Alzheimer’s disease (AD) patients using a neuronavigation-guided focused ultrasound (FUS) system. Six AD patients (N = 6, age = 68.5 ± 9.5) were sonicated at the right prefrontal lobe with a single-element FUS transducer (PNP = 0.2 MPa, fc = 0.25 MHz, pulse length = 10 ms, PRF = 2 Hz, duration = 2 min) with the microbubble administration (Definity). We performed passive cavitation detection (PCD) using a single-element hydrophone (N = 4), and passive acoustic mapping (PAM) with a 64-element phased array transducer (N = 2). Five patients showed successful BBB opening (volume = 654 ± 394 mm3) on day0, and closure on day3, confirmed by contrast-enhanced T1-weighted MRI, while one patient served as a negative BBB opening case due to the insufficient microbubble administration. Ultra-harmonic cavitation dose (CD) correlated with the opening volume (R2 = 0.66, N = 4), but harmonic and broadband CDs showed a relatively poor correlation (R2 = 0.06 and 0.33). Cavitation maps (N = 2) showed a spatial distribution of acoustic energy that roughly coincided with the respective BBB opening location. We thus demonstrated the successful BBB opening and cavitation monitoring with the neuronavigation-guided system that allowed for a cost-effective procedure compared to the MR-guided approaches. The PCD and PAM showed promising results for potentially predicting the BBB opening volume and location found in MRI.

Laser Welding Penetration Monitoring Based on Time-Frequency Characterization of Acoustic Emission and CNN-LSTM Hybrid Network

In-process penetration monitoring of the pulsed laser welding process remains a great challenge for achieving uniform and reproducible products due to the highly complex nature of the keyhole dynamics within the intense laser-metal interactions. The main purpose of this study is to investigate the feasibility of acoustic emission (AE) measurement for penetration monitoring based on acoustic wave characteristics and deep learning. Firstly, a series of laser welding experiments on aluminum alloys were conducted using high-speed photography and AE techniques. This allowed us to in-situ visualize the complete keyhole dynamics and elucidate the generation mechanism of acoustic waves originating from pressure fluctuations at the keyhole wall. Then, an adaptive time-frequency technique namely VMD (Variational Mode Decomposition) was proposed to characterize the acoustic energy distribution among the nine subsignals with low-frequency and high-frequency components under different welding penetrations. Lastly, a novel hybrid model combing CNN (Convolutional Neural Network) and LSTM (Long Short Term Memory) was designed to deeply mine the spatial and temporal acoustic features from the extracted frequency components. Extensive experiments demonstrate that our proposed approach yields a remarkable classification performance with a test accuracy of 99.8% and a standard deviation of 0.21, which obtains a high recognition rate. This work is a new paradigm in the digitization and intelligence of the laser welding process and contributes to an alternative way of developing an efficient end-to-end penetration monitoring system.

Broadband sound absorption of a hybrid absorber with shunt loudspeaker and perforated plates

With the effective couplings between the perforated plates and the shunt loudspeaker, a hybrid absorber of shunt loudspeaker and perforated plates (HSLPP) with multiple resonances is proposed for sound absorption at the mid and low frequencies. The absorption characteristics of HSLPP are investigated analytically and numerically, and verified by experimental measurements using impedance tube. Furthermore, the series–parallel coupling effect is intuitively demonstrated by means of the acoustic energy distribution, and the loss state of each resonance is evaluated by a complex frequency plane method. Besides, the effect of the structure parameters on the sound absorption of HSLPP is analyzed, and the optimal sound absorption of HSLPP is compared with that of classical MPP. The measurement results showed that HSLPP samples with a limited thickness of 100 mm have average sound absorption coefficients higher than 0.9 at 200–1100 Hz over 2 octaves. This indicates that the proposed HSLPP structure is a quasi-perfect and sub-wavelength absorber for broadband sound absorption.

Напівемпіричне оцінювання акустичних навантажень на головну частину ракети при нестандартній конфігурації стартових споруд

The paper deals with assessing the acoustic loads on the surface of a launching rocket obtained using the semiempirical technique NASA SP-8072 adapted for a launch pad located above the water area. The features of the launch facilities include the reduced length of the gas duct and the presence of a wedge-shaped gas-dynamic deflector divided into two symmetrical oppositely directed slopes. The calculations are made with the allowance for the limited length of the rocket jet's laminar core during take-off due to interaction with the gas-dynamic deflector. A corrected dependence is used for the overall acoustic energy distribution along the supersonic jet for the first time in domestic practice. The contributions of the sound sources associated with different jet sections and acoustic reflection from the water surface are assessed, depending on the current height of the rocket lift. A significant dependence of the resulting acoustic field around the rocket head on the length of the horizontal section of the gas duct is noted.

The phonetic interaction of stress and intonation: a study of Standard Lithuanian

It is commonly accepted, that word stress in Standard Lithuanian has a complex phonetic nature. However, empirical data do not support such a view. The functional importance of acoustic parameters can only be proven relying on their “relations of relations” between stressed and unstressed syllables. To put it simply, we cannot state for sure that in all cases stressed syllables are superior in acoustical means. We can rely on intersyllabic relation of some sort only. If this is true, word stress is no more recognizable from a sintagmatic point of view. In addition, such interpretation presupposes a very complex mechanism of stress perception that is difficult to verify by experimental means. This article highlights the phonetic interaction of prosodic elements in the hope that more invariant features of acoustic stress structure can be captured from this perspective. The analyzed data show that prosodic elements selectively regulate the amount of acoustic energy, its degree of variation and dynamics. The first two are the prerogative of the phrasal intonation and the third is determined by the stress. The latter prosodic element, to put it more simply, is a factor that determines the control of acoustic energy distribution at the intersyllabic level.

Non-intrusive mode based analyses to predict uncertainty in sound propagation in the ocean

Ocean dynamics can result in significant sound speed variability that are not well captured by deterministic numerical models and can impact differently high to low frequency acoustic propagation and bottom interactions by constraining horizontal and vertical paths. Uncertainty in the sound speed can, therefore, cause inaccuracies in acoustic based tactical decision tools and severely impact the accuracy of algorithms using sound propagation to estimate ocean volume states (e.g., ocean tomography or data assimilation). In this work, we propose to use a non-intrusive Reduced Order Modelling solution that consists of building a dictionary of static modes from historical ocean simulations with different settings and resolutions and climatology to derive an expedite uncertainty model along a central deterministic forecast. The system will then, through Orthogonal Matching Pursuit along the dictionary, use the available ocean model-data mismatches and/or acoustic innovations (e.g., arrival numbers and times, acoustic energy distribution, etc.) to define an ensemble of possible sound speed volume distributions and associated acoustic propagation outcomes. We will show results using a simplified simulation experiment that extracts “observations” from a nature reference field to document the procedure and benchmark results to reconstruct 3D sound speed fields from ocean-acoustic measurements.