Acoustic Characterization Research Articles

Inverse problem-solving method applied to the acoustic characterisation of a thin film via the Debye series method (DSM)

ABSTRACT The study of the ultrasonic acoustic response of materials is of increasing interest for the characterisation of high-frequency applications. In this work, some elastic properties (acoustic velocity and acoustic attenuation) and some physical properties (thickness and density), together with the phase shift of the transducer, are estimated via one method. Scanning acoustic microscopy was performed via an innovative and different method using a high-frequency (50 MHz) planar wave transducer. In addition, the Debye series model (DSM) was used to model the acoustic response of the bilayer structure of the glass substrate and the resin‒epoxy sample. The inverse problem of estimating the acoustic parameters that results in a DSM reflected echo that matches the experimental signal is solved by proposing an innovative step-by-step curve fitting algorithm. The algorithm for solving the inverse problem is then optimised via relative mean square error (RMSE) curves, resulting in a robust method for assessing the uniqueness of the multiparameter solution.

Acoustic emission characterization of failure modes in banana/ramie/epoxy composites under flexural loading

Acoustic emission characterization of failure modes in banana/ramie/epoxy composites under flexural loading

Multi-scale mechanical and acoustic characterization of low noise pavements.

Using data on in situ performance of low noise pavements, three well performing mixtures were selected: SDA 4, SDA 6, and SDA 8. These mixtures and the corresponding mastic (filler + bitumen + additive) were tested for their mechanical and acoustic performance in non-aged and aged states using a multi-scale approach (mm to km). Thereafter, an optimization protocol was applied to these mastics (mm-scale) and promising combinations were implemented at the mixture scale (cm-scale). As a result, the best performing mixture parameters were implemented in the m-scale slabs where the mechanical and acoustic performance were determined. The proposed work could uniquely combine knowledge from in situ long term and laboratory performance of low noise pavements. Using a traffic simulator and measurements before and after trafficking, the acoustic modeling showed that the modified mixtures' noise levels were maintained after loading. This indicates that the modification assured acoustical integrity of the mixture after loading.

The calls of Vietnamese bats: a major step toward the acoustic characterization of Asian bats

Southeast Asia includes several global biodiversity hotspots and bats account for nearly one-third of mammal species currently known in the region. While acoustic methods have become widespread in bat research, basic information is often lacking on the echolocation calls produced by Asian bat species. Since such information can aid a wide variety of research and conservation initiatives, descriptions of the calls emitted by Asian bats are fundamental. The aim of our study was to provide a standardized analysis and description of the Vietnamese bat echolocation calls. We analyzed call recordings of 87 species arranged in eight families. This constitutes 74% of the echolocating bats presently known in Vietnam and includes the first call descriptions for five taxa. Our use of an open-source software and the deposition of recordings in the ChiroVox repository will facilitate comparative studies in Asia and the information we provide represents one of the most comprehensive bioacoustic databases for Asian bats to date.

Comparison of measurement of integrated relaxation pressure by esophageal manometry with analysis of swallowing sounds with artificial intelligence in patients with achalasia.

Esophageal motility disorders are mainly evaluated with high-resolution manometry (HRM) which is a time-consuming and uncomfortable procedure with potential adverse events. Acoustic characterization of the swallowing has the potential to be an alternative noninvasive procedure. We compared the findings on HRM and swallowing sounds in 43 patients who were referred for evaluation of dysphagia. The sound analysis was done with empirical mode decomposition method and with artificial intelligence (AI) and the estimated integrated relaxation pressure (IRP) from a two-layer neural network method was compared to measured IRP on HRM. The model then was tested in five patients. IRP was estimated with high accuracy using the model developed with two-layer neural network method. The analysis of acoustic properties of swallowing has the potential to be used for evaluation of esophageal motility disorders, this needs to be further evaluated in larger studies.

Recent Advances and Applications of Passive Acoustic Monitoring in Assessing Shrimp Feeding Behaviour Under Laboratory and Farm Conditions

ABSTRACTThe use of passive acoustic monitoring (PAM) has recently been integrated with other noninvasive ethological methodologies to enhance the understanding of shrimp feeding behaviour, as their mandibles emit click sounds during food intake. This review aims to compile recent advances and various applications of PAM in assessing shrimp feeding behaviour under controlled laboratory and farm conditions. It includes a description of key concepts, terms and general methodologies in the field of bioacoustics to facilitate understanding of acoustic characterisation, specific methodologies and the main uses of PAM in shrimp research. Among the primary contributions of PAM in laboratory studies are acoustic characterisation of clicks and mandibular structures associated with their emission for different species; variations in acoustic click parameters related to animal size, feed texture and pellet size; and effects on feeding behaviour caused by shrimp size, stocking density and specific characteristics of artificial diets (texture, formulations, additives and pellet sizes). Finally, future perspectives and recommendations for laboratory studies using PAM are provided. The review highlights the contribution of PAM, which, allied with other ethological methodologies, emerges as a novel tool for researching shrimp behaviour and optimising feed management in aquaculture.

Comparative analysis of two liner acoustic impedance characterization techniques

This study presents the comparison of two methodologies of small size liner acoustic impedance characterization. The first one is based on a normal incidence broadband acoustic excitation up to 160 dB inside a 30-mm diameter circular tube, and uses the two microphones method, with microphones flush-mounted inside the waveguide. This bench, called NTMM and developed at Airbus, allows to directly compute the acoustic impedance at the surface of the sample. The second one lies on a measurement inside the B2A wind tunnel at ONERA, where the sample is mounted as one of the vein walls, leading to a grazing aero-acoustic excitation, up to Mach 0.3 and 155 dB with a broadband excitation. The impedance is then educed by an inverse method. During the MAMBO research project, dedicated samples have been designed and tested with the two benches as well as on the CANNELLE multimodal test rig developed by Airbus. The full paper will analyze the results and offer a cross comparison of the methodologies, highlighting the advantages and limitations of each approach.

Acoustic performances of earthen walls, review of modeling approaches and tools

Earth construction benefits of a renewed interest particularly for environmental reasons. However, due to its mainly artisanal construction process, acoustic characterization data of earthen walls are quite rare which can limit their use for projects involving acoustic requirements. Moreover, the great diversity in materials as well as in related construction techniques could result in a large spread in terms of acoustical performances. In this context, acoustic characterizations and modelings are necessary to provide a better understanding on earth materials behaviors. In this study, the results from different modeling approaches are compared to few earth walls sound transmission loss data publicly available. The modeling tools including simplified formulas or more elaborated softwares present different levels of complexities and assumptions sometimes highlighting the specificities of this material. Depending on the construction techniques used (earth blocks, light earth, earth panels etc ...), different assumptions can be appropriate. Extrapolations of performances on several walls for both sound transmission loss and sound absorption provide information regarding tendencies and potentially achievable performances for future earth construction projects. Nevertheless, the comparison between the modeling approaches allows gaining insight on the limits of some approaches and the necessary critical analysis before a possible generalization to other earth walls.

Acoustical characterization and modelling of the effects of eco-friendly flame retardant treatments on hemp fiber stacks

Vegetal wools are a bio-based insulator which building applications are limited due to their flammability. To overcome this problem while respecting their bio-based nature, it seems relevant to identify and apply an environmentally friendly fireproof treatment. However, the impact of this treatment on the acoustic performance of the vegetal wools is not examined in the literature. The objective of this work is to evaluate the efficacy of two phosphorus-based fireproof treatment methods i.e., impregnation and pulverization, and their impact on the acoustic properties of hemp fiber stacks. To assess the efficacy of the fireproof treatment, the amount of phosphorus grafted and the thermal degradation of the hemp fibers were evaluated through inductive coupled plasma (ICP) and thermogravimetric analysis (TGA), respectively. On the acoustic side, the impedance tube test results showed that the treatment can negatively impact the acoustic performance of hemp fiber samples, by the reduction of the sound absorption coefficient. To better understand the effects of treatments on the porous structure characteristics of the samples, parameters such as porosity, resistivity, tortuosity, etc. are determined and the acoustic absorption of the stacks is simulated using the JCAL modelling method.

Optical interferometry based acoustic field characterization using physics informed neural networks

The acousto-optic effect offers a non-contact way of measuring and visualizing acoustic fields in transparent fluids. Acoustic density fluctuations induce changes in the media's refractive index that can be measured using interferometry. While sensing methods based on acousto-optics have gathered increasing attention, many of such methods are only sensitive to projections of the acoustic field along the optical path, limiting the fields that can be characterized to one or two dimensions, or requiring complex experimental setups. Recently, reconstruction methods that abide by the physics of acoustic wave propagation showed unparalleled performance compared with classical reconstruction methods, reducing the sampling requirements and enabling to characterize three-dimensional acoustic fields. Nonetheless, such reconstruction methods rely on discrete approximations which might be poor at describing spatially complex fields. In this work we use physics-informed neural networks (PINNs) to estimate the acoustic pressure over space from interferometer measurements. The network is flexible enough to represent complex acoustic fields, while its output is constrained to fulfill the wave equation. Once trained on the data available for a given experiment, the PINN can estimate the acoustic pressure at arbitrary positions. The approach is tested in an experimental study, showing an improved performance compared with state-of-the-art reconstruction methods.

Acoustic characterization of a bi-directional turbine

A thermoacoustic engine converts thermal energy into acoustic energy, which can then be converted into electricity using an alternator. The conversion of acoustic-to-electric energy in thermoacoustic electricity generators usually relies on electromagnetic transducers. A bi-directional turbine coupled to a DC motor offers a plausible alternative due to its simplified mechanical design, cost-effectiveness, and relatively good performance. Efficient coupling of a bi-directional turbine with a thermoacoustic engine requires a comprehensive understanding of its operating behavior. This study aims to extend existing research by carrying out experimental characterization of a bi-directional turbine. This will involve measuring its transfer matrix and impedance under various acoustic conditions. The experimental results are then analyzed and compared with the predictions of an electro-acoustic model.

Design of a new low-noise pavement

This paper presents the results obtained from the tests carried out on the different asphalt mixes that have been developed as part of the PERSEUS project. This project aims to develop a low-noise pavement in which, in addition to traditional parameters such as texture or absorption, which have been defined based on aggregate size and void content, the aim has been to improve the acoustic response by introducing rubber as a substitute for part of the aggregate in the recipes. Within the framework of the project, porous mixtures and also stone mastic are being developed to determine the solution with the best acoustic characteristics and durability. The paper presents the results of acoustic characterization tests carried out (absorption, airflow resistance) in the phase of design of mixtures, as well as those obtained from the mechanical impedance test, which together with the results of the mechanical tests will conclude which is the ideal mixture to be tested on a stretch of road with real traffic.

Acoustic characterization of the Municipal Museum Abade Pedrosa

The 2016 interventions concerning the rehabilitation of the Municipal Museum Abade Pedrosa in Santo Tirso, Portugal were analyzed to verify in what way acoustics interferes in the museum enjoyment. In situ measurements were done in every exhibition room: Reverberation Time, RASTI and the Equivalent Sound Level (LAeq). RT[500, 1k, 2k Hz] values were between 2.5 and 3.9 s. The RASTI mean values varied between 0.44 and 0.55 s. LAeq values of background noise reached a top value of 43 dB(A) in the 1000 Hz frequency band and a global value of 57 dB(A) in every room. A multicriteria analysis was carried out to globally characterize the museum in a simple and perceptive way, with an algorithm that ranks all the different rooms, in which they were generally classified as "bad". A comparison of these values was done with similar studies in other museums: Soares dos Reis (Porto), Serralves (Porto) and other international museums, being possible to verify that the Municipal Museum Abade Pedrosa has worse acoustic values compared to those other museums. It was also suggested possible improvements that could contribute for the acoustic correction of the space, with a predictable cost of about 27000 €.

Estimation of the surface impedance based on the discrete complex image source method and array processing

This paper introduces a method for estimating the sound absorption coefficient of a large panel of absorbing material from measurements using a microphone array. The method relies upon describing the pressure field as the set of monopoles obtained when the reflection coefficient is represented as the Laplace Transform of an image source distribution. This formulation results in a well-behaved integral equation, which is discretized using Gaussian quadrature to yield an inverse problem. It is possible to determine the regularized solution to the inverse problem and reconstruct the surface impedance of the sample by conducting measurements of the sound pressure at multiple points of observation. This sound field representation is adequate for sound sources in the close range of the material and the array. The paper presents simulated and experimental investigations to delineate the efficacy of the proposed measurement technique against the well-known image source method, thereby highlighting its significant potential to advance acoustic characterization methodologies.

The measurement of tire-road noise: how does standardization contribute to the development of low noise pavements in Europe

Low-noise road pavements are among the most effective solutions for reducing road traffic noise emission at the source. There was a significant international effort over the past years for developing and standardizing methods for measuring tire-road noise emission, essentially Statistical Pass-By (SPB) and Close ProXimity (CPX) methods. The dedicated Working Group of the European Committee for Standardization (CEN/TC227/WG5) recently investigated how these standards are used in practice and how they contribute to the implementation of low-noise pavements. For this, a survey was launched and 14 European countries responded on their practices. The survey showed a large diversity of use, although all refer to the measurement methods SPB, CPX. Based on these methods, some countries have developed national regulations or reference guidelines to specify and assess the acoustic performance of road surfaces. These procedures are, however, significantly different and lead to varying definitions of low-noise pavements, which prevents sharing knowledge, experience and data. This context justifies the ongoing development within CEN/TC227/WG5 of a standard procedure for the acoustic characterization of road pavements based on existing measurement methods. The paper will present and analyze the results of the survey, then will present the ongoing work in CEN.

Acoustic characterization of porous windscreens for sound pressure and particle velocity sensors

Acoustic measurements of ground vehicles, wind turbines or aircrafts are often performed outdoors in presence of wind. Air movement around an acoustic sensor may significantly disturb the measured signals due to flow-induced vibrations and turbulence. This is specially relevant for pressure-gradient and particle-velocity based acoustic transducers which are more sensitive to these perturbations. To attenuate this effect and improve measurement quality, the sensors are typically covered with windscreens made of porous materials. However, designing an appropriate windscreen poses a challenging task, demanding a deep understanding of sound transmission characteristics. This study works towards quantifying acoustic properties of rigid-frame porous materials through in-situ measurements and fitting a parametric fluid-equivalent model to find optimal model parameters. The parameters are subsequently investigated by comparing windscreen insertion loss through finite-element numerical simulations and measurements on a sound intensity PU probe.

Acoustic and spectroscopic characterization of glycol ethers in vitamin B7 over the range of temperatures (288.15, 293.15, 298.15, 303.15) K

Density (ρ) and ultrasonic speed (u) of butoxyethanol and phenoxyethanol in aqueous solution of biotin concentrations (0.0012, 0.0017, 0.0022) mol·kg−1 at varying temperature range (288.15, 293.15, 298.15 and 303.15) K at 0.1 MPa were measured using Anton Paar DSA 5000 M. The volumetric and acoustical properties such as apparent molar properties (V∅), partial molar volume (V∅0),partial molar volume of transfer (ΔV∅0),apparent molar isentropic compression (K∅),partial molar isentropic compression (K∅0),partial molar isentropic compression of transfer are computed using the experimental data of density (ρ) and ultrasonic speed (u). This investigation is useful to understand the solvation behavior of biotin. Additionally, partial molar expansibilities (E∅0) along with their first order derivatives (∂E∅0/∂T)pare determined using the obtained experimental data. These results are effective in understanding the nature of interaction occurring inside the solution. Further, pair and triplet coefficients are evaluated which determines the structure making and breaking ability of glycol ethers in aqueous solution of biotin. Also, spectroscopic study of solutions is mentioned in current research which reveals the nature and strength of bond formation and various interactions in the mixture. The present study suggests the molecular interaction between the solute and solvent present in aqueous solution of Biotin (Vitamin B7) as solvent, butoxyethanol (BE) and phenoxyethanol (PE) as solute.

An experimental study on three-port measurements for acoustic characterisation of the perforate reactance

The usage of perforated plates in passive noise-control systems in e.g. aircraft liners and mufflers involves the standard operating conditions of grazing flow and high-amplitude acoustic incidence. This study focuses on the usage of the three-port experiment technique for the experimental passive acoustic characterisation of a perforated plate. Expanding on the previous paper about the resistance of the perforate, the influence of operating conditions on the imaginary part of the transfer impedance, i.e., the reactance is discussed here. The relationship between the end correction in the linear range, without the presence of grazing flow, and the frequency of acoustic excitation is demonstrated. The reduction in the value of the mass end correction under the individual effects of grazing flow, and high-amplitude excitation is presented. Additionally, depending on the excitation wavelength, the partial recovery of the reduced value of the end correction under simultaneous exposure is also shown. Using the experimental results, models for the end correction, and by extension the reactance are proposed. These models take into account the geometrical parameters of the perforate, and the dimensionless Mach, Shear and Strouhal numbers.

Mechanical and acoustic characterization of carbon dioxide gas replacement of methane gas hydrate

CO2 replacement presents a promising approach for the extraction of natural gas hydrate, offering advantages in cleanliness and safety. In this study, CO2 replacement CH4 hydrate experiments were carried out by using the triaxial, hydrate specimens with varying replacement ratios were prepared through different methods, and triaxial tests were performed to evaluate the mechanical properties of sediments after replacement. The key findings are as follows: the shear damage behaviors of CH4, CO2, and their mixed hydrate specimens are similar. Acoustic data indicates that initial CO2 injection during replacement causes dissociation of CH4 hydrate, potentially reducing the failure strength of the reservoir. However, post-replacement hydrate specimens exhibited higher failure strength than their original counterparts. This study provides valuable insights into the mechanical stability of CH4 hydrate reservoirs during CO2 replacement process.

Analysis of Acoustic Absorption Coefficients and Characterization of Epoxy Adhesive Compositions Based on the Reaction Product of Bisphenol A with Epichlorohydrin Modified with Fillers.

Material development in acoustic engineering plays a significant role in various applications, such as industrial noise control. It is important and relevant to consider alternative materials capable of reducing noise levels in different frequency ranges. One commonly used material in engineering structures is epoxy adhesive compositions. Favoring the use of adhesive compositions are their main characteristics, including weight reduction in structures, corrosion resistance, relatively low manufacturing costs, and high mechanical strength. This paper aims to discuss the relationship between the mechanical properties of modified epoxy adhesives, their structure, and sound absorption efficiency. The subjects of this study were specimens of an epoxy composition in the cured state. Acoustic absorption coefficients were evaluated using a dual-microphone impedance tube, and tensile, compressive, and bending strength properties were determined using a testing machine. The impact strength of the compositions was also investigated. An analysis of the structure of the adhesives in the cured state was carried out using a scanning electron microscope. The test specimens were made from Epidian 5 epoxy resin cured with a polyamide PAC curing agent. Nanobent ZR2 aluminosilicate in an amount of 1%, CaCO3 calcium carbonate in an amount of 5%, and CWZ-22 activated carbon in an amount of 20% were used as modifiers. The conducted studies revealed that the highest tensile strength was obtained for the adhesive composition with the addition of ZR2 filler. The highest compressive strength was exhibited by the adhesive composition with the addition of CWZ-22 filler. The highest flexural strength was demonstrated by the unmodified composition. For all the tested adhesive compositions, low sound absorption values were achieved, with a maximum of approximately 0.18. From the perspective of the reduction index R, it was observed that these samples performed better in reduction than in absorption. The best values were achieved in the compositions modified with CaCO3.