Journal Description
Acoustics
Acoustics
is an international, peer-reviewed, open access journal on acoustics science and engineering, published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within ESCI (Web of Science), Scopus, and other databases.
- Journal Rank: CiteScore - Q2 (Acoustics and Ultrasonics)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 19.4 days after submission; acceptance to publication is undertaken in 3.8 days (median values for papers published in this journal in the first half of 2024).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Impact Factor:
1.3 (2023);
5-Year Impact Factor:
1.9 (2023)
Latest Articles
Non-Monotonic Variation of Acoustic Spectrum with the Mass or Thickness of a Layered Structure
Acoustics 2024, 6(4), 805-817; https://doi.org/10.3390/acoustics6040045 - 24 Sep 2024
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We are examining the behavior of resonance frequencies and their response to variations of material parameters such as thicknesses, masses, and bulk velocities for certain Rayleigh–Lamb acoustic modes in a multilayered structure. The treatment is based on recent explicit analytic solutions that have
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We are examining the behavior of resonance frequencies and their response to variations of material parameters such as thicknesses, masses, and bulk velocities for certain Rayleigh–Lamb acoustic modes in a multilayered structure. The treatment is based on recent explicit analytic solutions that have allowed us to explore the entire parametric space using dimensionless ratios. This exploration has revealed a complex parametric dependence of the phase velocities and their mass loading response. Specifically, for the fundamental flexural modes in a bilayer, we have shown that both quantities change in a strongly non-monotonic way with thickness, density, or bulk velocity ratios. Even in the regime of thin coating, commonly encountered in acoustic sensing applications, we have found important differences from previously known results, e.g., that response to loading may switch its sign multiple times when the velocity of the deposited material is increased. We have also discovered that the fundamental dilatational modes can be highly effective in stabilizing resonant frequencies against even large variations of the thickness or mass of the exposed layer. This property is demonstrated in an explicit form by the derived expression for the mass coefficient of frequency for an arbitrary number of layers.
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Open AccessArticle
A Decoupled Modal Reduction Method for the Steady-State Vibration Analysis of Vibro-Acoustic Systems with Non-Classical Damping
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Ruxin Gao and Shanshan Fan
Acoustics 2024, 6(3), 792-804; https://doi.org/10.3390/acoustics6030044 - 23 Sep 2024
Abstract
This paper presents a decoupled modal reduction method for the steady-state vibration analysis of vibro-acoustic systems characterized by non-classical damping. The proposed approach initially reduces the order of the coupled governing equations of the vibro-acoustic system through the utilization of non-coupled modes, subsequently
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This paper presents a decoupled modal reduction method for the steady-state vibration analysis of vibro-acoustic systems characterized by non-classical damping. The proposed approach initially reduces the order of the coupled governing equations of the vibro-acoustic system through the utilization of non-coupled modes, subsequently employing the complex mode superposition technique to address non-classical damping effects. By leveraging non-coupled modes, this method circumvents the need to solve for coupled modes as required in traditional modal reduction techniques, thereby diminishing both computational complexity and cost. Furthermore, the complex mode superposition method facilitates the decoupling of coupled governing equations with non-classical damping, enhancing computational efficiency. Numerical examples validate both the accuracy and effectiveness of this methodology. Given that modal decomposition is independent of frequency, an analysis of computational efficiency across various stages further substantiates that this method offers significant advantages in terms of efficiency for computational challenges encountered over a broad frequency range.
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(This article belongs to the Special Issue Vibration and Noise (2nd Edition))
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A Power Law Reconstruction of Ultrasound Backscatter Images
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Kevin J. Parker
Acoustics 2024, 6(3), 782-791; https://doi.org/10.3390/acoustics6030043 - 31 Aug 2024
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Ultrasound B-scan images are traditionally formed from the envelope of the received radiofrequency echoes, but the image texture is dominated by granular speckle patterns. Longstanding efforts at speckle reduction and deconvolution have been developed to lessen the detrimental aspects of speckle. However, we
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Ultrasound B-scan images are traditionally formed from the envelope of the received radiofrequency echoes, but the image texture is dominated by granular speckle patterns. Longstanding efforts at speckle reduction and deconvolution have been developed to lessen the detrimental aspects of speckle. However, we now propose an alternative approach to estimation (and image rendering) of the underlying fine grain scattering density of tissues based on power law constraints. The key steps are a whitening of the spectrum of the received signal while conforming to the original envelope shape and statistics, followed by a power law filtering in accordance with the known scattering behavior of tissues. This multiple step approach results in a high-spatial-resolution map of scattering density that is constrained by the most important properties of scattering from tissues. Examples from in vivo liver scans are shown to illustrate the change in image properties from this framework.
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Open AccessTechnical Note
Text-Independent Phone-to-Audio Alignment Leveraging SSL (TIPAA-SSL) Pre-Trained Model Latent Representation and Knowledge Transfer
by
Noé Tits, Prernna Bhatnagar and Thierry Dutoit
Acoustics 2024, 6(3), 772-781; https://doi.org/10.3390/acoustics6030042 - 29 Aug 2024
Abstract
In this paper, we present a novel approach for text-independent phone-to-audio alignment based on phoneme recognition, representation learning and knowledge transfer. Our method leverages a self-supervised model (Wav2Vec2) fine-tuned for phoneme recognition using a Connectionist Temporal Classification (CTC) loss, a dimension reduction model
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In this paper, we present a novel approach for text-independent phone-to-audio alignment based on phoneme recognition, representation learning and knowledge transfer. Our method leverages a self-supervised model (Wav2Vec2) fine-tuned for phoneme recognition using a Connectionist Temporal Classification (CTC) loss, a dimension reduction model and a frame-level phoneme classifier trained using forced-alignment labels (using Montreal Forced Aligner) to produce multi-lingual phonetic representations, thus requiring minimal additional training. We evaluate our model using synthetic native data from the TIMIT dataset and the SCRIBE dataset for American and British English, respectively. Our proposed model outperforms the state-of-the-art (charsiu) in statistical metrics and has applications in language learning and speech processing systems. We leave experiments on other languages for future work but the design of the system makes it easily adaptable to other languages.
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(This article belongs to the Special Issue Developments in Acoustic Phonetic Research)
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The Historical Building and Room Acoustics of the Stockholm Public Library (1925–28, 1931–32)
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Patrick H. Fleming
Acoustics 2024, 6(3), 754-771; https://doi.org/10.3390/acoustics6030041 - 19 Aug 2024
Abstract
The Stockholm Public Library was realized in two distinct phases of construction in the 1920s and early 1930s, and remains a well-known work in twentieth-century architecture, with a heritage status today. While previous studies have focused on the library’s architectural design, particularly its
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The Stockholm Public Library was realized in two distinct phases of construction in the 1920s and early 1930s, and remains a well-known work in twentieth-century architecture, with a heritage status today. While previous studies have focused on the library’s architectural design, particularly its lighting, acoustics were also an important aspect of the building’s design and construction. This study marks the first detailed investigation of the library’s architectural acoustics, with a suite of standard measurements performed to assess and characterize the library’s historical room and building acoustics. Reverberation time measurements in the library’s reading rooms yielded results of about 1.5–2 s for frequencies associated with speech. A significantly longer reverberation time of 5–6 s was measured in the library’s central rotunda, confirming a prominent acoustic issue in the library, where appropriate heritage discussions are needed in the future as the library undergoes a major renovation in the coming years. A comparison of the measured airborne and impact sound insulation of the 1920s and 1930s reading room ceilings also yielded interesting results. While the materials in library’s two construction periods are notably different, the airborne sound insulation performance of the 1920s and 1930s floors or ceilings was comparable and in line with contemporary standards. Impact sound insulation results from the 1920s and 1930s floors, however, differed significantly, with the latter displaying a relatively poor performance. Flanking transmission effects related to historical construction details and deviations from archival plans were investigated and discussed. This work emphasizes the practical and academic importance of conducting on-site measurements, and the close mutual development of modern architecture, construction, and architectural acoustics.
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(This article belongs to the Collection Historical Acoustics)
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Feasibility Analysis for Active Noise Cancellation Using the Electrical Power Steering Motor
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Dominik Schubert, Simon Hecker, Stefan Sentpali and Martin Buss
Acoustics 2024, 6(3), 730-753; https://doi.org/10.3390/acoustics6030040 - 31 Jul 2024
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This paper describes the use of an electric drive as an acoustic actuator for active noise cancellation (ANC). In the presented application, the idea is to improve the noise, vibration, harshness (NVH) characteristics of passenger cars without using additional active or passive damper
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This paper describes the use of an electric drive as an acoustic actuator for active noise cancellation (ANC). In the presented application, the idea is to improve the noise, vibration, harshness (NVH) characteristics of passenger cars without using additional active or passive damper systems. Many of the already existing electric drives in cars are equipped with the required hardware components to generate noise and vibration, which can be used as compensation signals in an ANC application. To demonstrate the applicability of the idea, the electrical power steering (EPS) motor is stimulated with a control signal, generated by an adaptive feedforward controller, to reduce harmonic disturbances at the driver’s ears. As it turns out, the EPS system generates higher harmonics of the harmonic compensation signal due to nonlinearities in the acoustic transfer path using a harmonic excitation signal. The higher harmonics impair an improvement in the subjective hearing experience, although the airborne noise level of the harmonic disturbance signal can be clearly reduced at the driver’s ears. Therefore, two methods are presented to reduce the amplitude of the higher harmonics. The first method is to limit the filter weights of the algorithm to reduce the amplitude of the harmonic compensation signal. The filter amplitude limitation also leads to a lower amplitude of the higher harmonics, generated by the permanent magnet synchronous machine (PMSM). The second method uses a parallel structure of adaptive filters to actively reduce the amplitude of the higher harmonics. Finally, the effectiveness of the proposed ANC system is demonstrated in two real driving situations, where in one case a synthetic noise/vibration induced by a shaker on the front axle carrier is considered to be the disturbance, and in the other case, the disturbance is a harmonic vibration generated by the combustion engine. In both cases, the subjective hearing experience of the driver could be clearly improved using the EPS motor as ANC actuator.
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(This article belongs to the Special Issue Active Control of Sound and Vibration)
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A Frequency-Independent Phase Shifter
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Máté Csanád, Amira K. F. Val Baker and Paul Oomen
Acoustics 2024, 6(3), 713-729; https://doi.org/10.3390/acoustics6030039 - 31 Jul 2024
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In this paper, we utilise optimization methods to determine a frequency-independent phase shift such that two phase-shifted versions of a signal can be summed and the resulting amplitude spectrum is unchanged. A phase difference between two signals is thus defined, which remains constant
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In this paper, we utilise optimization methods to determine a frequency-independent phase shift such that two phase-shifted versions of a signal can be summed and the resulting amplitude spectrum is unchanged. A phase difference between two signals is thus defined, which remains constant for all frequencies within a given range. For the intended purpose of this study, we set the frequency range to the audible human hearing range of 16 Hz–20 kHz. We found that a new 3-stage filter method provides a variable phase shifter (i.e., ϕ = 0–360°) without the need for additional amplifiers. In addition, we present a new method that reduces the number of filters necessary, improving both the accuracy and efficiency of current techniques.
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Acoustic Analysis of a Hybrid Propulsion System for Drone Applications
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Mădălin Dombrovschi, Marius Deaconu, Laurentiu Cristea, Tiberius Florian Frigioescu, Grigore Cican, Gabriel-Petre Badea and Andrei-George Totu
Acoustics 2024, 6(3), 698-712; https://doi.org/10.3390/acoustics6030038 - 25 Jul 2024
Abstract
This paper aims to conduct an acoustic analysis through noise measurements of a hybrid propulsion system intended for implementation on a drone, from which the main noise sources can be identified for further research on noise reduction techniques. Additionally, the noise was characterized
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This paper aims to conduct an acoustic analysis through noise measurements of a hybrid propulsion system intended for implementation on a drone, from which the main noise sources can be identified for further research on noise reduction techniques. Additionally, the noise was characterized by performing spectral analysis and identifying the tonal components that contribute to the overall noise. The propelling force system consists of a micro-turboshaft coupled with a gearbox connected to an electric generator. The propulsion system consists of a micro-turboshaft coupled with a gearbox connected to an electric generator. The electric current produced by the generator powers an electric ducted fan (EDF). The engineturbo-engine was tested in free-field conditions for noise generation at different speeds, and for this, an array of microphones was installed, positioned polarly around the system and near the intake and exhaust. Consequently, based on the test results, the acoustic directivity was plotted, revealing that the highest noise levels are at the front and rear of the engine. The noise level at a distance of 1.5 m from the turboengine exceeds 90 dBA at all tested speeds. Spectral analyses of both the far-field acoustic signals (measured with a polar microphone array) and the near-field signals (microphones positioned near the intake and exhaust) revealed that the primary contributors to the overall noise are the micromotor’s compressor, specifically the gas dynamic phenomena in the fan (BPF and 2× BPF). Thus, it was determined that at the intake level, the main noise contribution comes from the high-frequency components of the compressor, while at the exhaust level, the noise mainly originates from the combustion chamber, characterized by low-frequency components (up to 2 kHz). The findings from this study have practical applications in the design and development of quieter drone propulsion systems. By identifying and targeting the primary noise sources, engineers can implement effective noise reduction strategies, leading to drones that are less disruptive in urban environments and other noise-sensitive areas. This can enhance the acceptance and deployment of drone technology in various sectors, including logistics, surveillance, and environmental monitoring.
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(This article belongs to the Special Issue Machinery Noise: Emission, Modelling and Control)
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Application of Machine Learning Techniques for Predicting Students’ Acoustic Evaluation in a University Library
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Dadi Zhang, Kwok-Wai Mui, Massimiliano Masullo and Ling-Tim Wong
Acoustics 2024, 6(3), 681-697; https://doi.org/10.3390/acoustics6030037 - 25 Jul 2024
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Understanding students’ acoustic evaluation in learning environments is crucial for identifying acoustic issues, improving acoustic conditions, and enhancing academic performance. However, predictive models are not specifically tailored to predict students’ acoustic evaluations, particularly in educational settings. To bridge this gap, the present study
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Understanding students’ acoustic evaluation in learning environments is crucial for identifying acoustic issues, improving acoustic conditions, and enhancing academic performance. However, predictive models are not specifically tailored to predict students’ acoustic evaluations, particularly in educational settings. To bridge this gap, the present study conducted a field investigation in a university library, including a measurement and questionnaire survey. Using the collected personal information, room-related parameters, and sound pressure levels as input, six machine learning models (Support Vector Machine–Radial Basis Function (SVM (RBF)), Support Vector Machine–Sigmoid (SVM (Sigmoid)), Gradient Boosting Machine (GBM), Logistic Regression (LR), Random Forest (RF), and Naïve Bayes (NB)) were trained to predict students’ acoustic acceptance/satisfaction. The performance of these models was evaluated using five metrics, allowing for a comparative analysis. The results revealed that the models better predicted acoustic acceptance than acoustic satisfaction. Notably, the RF and GBM models exhibited the highest performance, with accuracies of 0.87 and 0.84, respectively, in predicting acoustic acceptance. Conversely, the SVM models performed poorly and were not recommended for acoustic quality prediction. The findings of this study demonstrated the feasibility of employing machine learning models to predict occupants’ acoustic evaluations, thereby providing valuable insights for future acoustic assessments.
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(This article belongs to the Special Issue Acoustical Comfort in Educational Buildings)
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A Study on Adaptive Implicit–Explicit and Explicit–Explicit Time Integration Procedures for Wave Propagation Analyses
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Delfim Soares, Jr., Isabelle de Souza Sales, Lucas Ruffo Pinto and Webe João Mansur
Acoustics 2024, 6(3), 651-680; https://doi.org/10.3390/acoustics6030036 - 23 Jul 2024
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This study delves into the effectiveness of two time integration techniques, namely the adaptive implicit–explicit (imp–exp) and explicit–explicit (exp–exp) methods, which stand as efficient formulations for tackling intricate systems characterized by multiple time scales. The imp–exp technique combines implicit and explicit procedures by
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This study delves into the effectiveness of two time integration techniques, namely the adaptive implicit–explicit (imp–exp) and explicit–explicit (exp–exp) methods, which stand as efficient formulations for tackling intricate systems characterized by multiple time scales. The imp–exp technique combines implicit and explicit procedures by employing implicit formulations for faster components and explicit calculations for slower ones, achieving high accuracy and computational efficiency. Conversely, the exp–exp method, a variation of explicit methods with sub-cycling, excels in handling locally stiff systems by employing smaller sub-steps to resolve rapid changes while maintaining stability. For both these approaches, numerical damping may be activated by adaptive time integration parameters, allowing numerical dissipation to be locally applied, if necessary, as a function of the considered discrete model and its computed responses, enabling a highly effective numerical dissipative algorithm. Furthermore, both these techniques stand as very simple and straightforward formulations as they rely solely on single-step displacement–velocity relations, describing truly self-starting procedures, and they stand as entirely automated methodologies, requiring no effort nor expertise from the user. This work provides comparative studies of the adaptive imp–exp and exp–exp approaches to assess their accuracy and efficiency across a wide range of scenarios, with emphasis on geophysical applications characterized by multiscale problems, aiming to establish under which circumstances one approach should be preferred over the other.
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Open AccessArticle
Silent Neonatal Incubators, Prototype Nica+
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Ricardo Hernández-Molina, Virginia Puyana-Romero, Juan Luis Beira-Jiménez, Arturo Morgado-Estévez, Rafael Bienvenido-Bárcena and Francisco Fernández-Zacarías
Acoustics 2024, 6(3), 638-650; https://doi.org/10.3390/acoustics6030035 - 15 Jul 2024
Cited by 1
Abstract
Objectives: The purpose of this study was to evaluate and compare the noise levels in current incubator models and a prototype designed to improve acoustic comfort in neonatal incubators. Methods: Tests were carried out on three different models of incubators and a prototype
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Objectives: The purpose of this study was to evaluate and compare the noise levels in current incubator models and a prototype designed to improve acoustic comfort in neonatal incubators. Methods: Tests were carried out on three different models of incubators and a prototype called Neonatal Incubator Acoustic Comfort Class (NICA). The tests measured both internal and external sound pressure levels under laboratory conditions. The noise index has been taken as the A-weighted equivalent continuous sound pressure level (LAeq,T) for a time interval of 1 min. Results: The results obtained show variations between the different models of incubators, although, overall, they are high values (around 56/60 dBA). The results prove that premature newborns under normal conditions of using these incubators are exposed to noise levels above international recommendations. The new incubator design minimizes noise generation and generates noise levels lower than international recommendations. Conclusions: The results obtained from the prototype (NICA+) show the effectiveness of the proposed design in improving acoustic comfort in neonatal incubators. The data show that the noise levels generated by the prototype under normal operating conditions are significantly lower than international recommendations.
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(This article belongs to the Special Issue Vibration and Noise (2nd Edition))
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Measurement and Simulation of the Propagation of Impulsive Acoustic Emission Sources in Pipes
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Chika Judith Abolle-Okoyeagu, Samuel Fatukasi and Bob Reuben
Acoustics 2024, 6(3), 620-637; https://doi.org/10.3390/acoustics6030034 - 30 Jun 2024
Abstract
Acoustic Emission (AE) testing is a non-destructive evaluation technique that has gained significant attention in pipeline monitoring. Pencil-lead breaks (PLBs) are commonly used in reproducing and characterising sensors used in AE applications and have emerged as a valuable tool for calibration processes. This
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Acoustic Emission (AE) testing is a non-destructive evaluation technique that has gained significant attention in pipeline monitoring. Pencil-lead breaks (PLBs) are commonly used in reproducing and characterising sensors used in AE applications and have emerged as a valuable tool for calibration processes. This technique involves breaking a pencil lead by pressing it on the surface of the test structure and applying a bending moment at a given angle on a surface. The applied force produces a local deformation on the test surface, which is released when the lead breaks. The fracture in these PLBs is assumed to be a step unload; however, this is not the case. In this work, a series of PLB source experiments complemented with parallel numerical simulations were carried out to investigate the actual unload rate by correlating the relationship between AE speed, frequency, and power from PLBs. This was achieved by varying the simulation unload rates recorded over a duration of 2 s on a steel pipe and comparing to the experiment. Analysis of the investigated results from the experimental and numerical models suggests that although the AE line structure of a PLB can be reproduced by simulation for short times only (1 µs), the actual unload rate for PLBs is in the region of 10–8 s. It is concluded that FEA has the potential to help in the recovery of the temporal structure from real AE structures. The establishment of this model will provide a theoretical basis for future studies on the monitoring of non-impulsive AE sources such as impact on pipelines using finite element analysis.
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(This article belongs to the Special Issue Duct Acoustics)
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On the Applicability of Kramers–Kronig Dispersion Relations to Guided and Surface Waves
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Victor V. Krylov
Acoustics 2024, 6(3), 610-619; https://doi.org/10.3390/acoustics6030033 - 29 Jun 2024
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In unbounded media, the acoustic attenuation as function of frequency is related to the frequency-dependent sound velocity (dispersion) via Kramers–Kronig dispersion relations. These relations are fundamentally important for better understanding of the nature of attenuation and dispersion and as a tool in physical
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In unbounded media, the acoustic attenuation as function of frequency is related to the frequency-dependent sound velocity (dispersion) via Kramers–Kronig dispersion relations. These relations are fundamentally important for better understanding of the nature of attenuation and dispersion and as a tool in physical acoustics measurements, where they can be used for control purposes. However, physical acoustic measurements are frequently carried out not in unbounded media but in acoustic waveguides, e.g., inside liquid-filled pipes. Surface acoustic waves are also often used for physical acoustics measurements. In the present work, the applicability of Kramers–Kronig relations to guided and surface waves is investigated using the approach based on the theory of functions of complex variables. It is demonstrated that Kramers–Kronig relations have limited applicability to guided and surface waves. In particular, they are not applicable to waves propagating in waveguides characterised by the possibility of wave energy leakage from the waveguides into the surrounding medium. For waveguides without leakages, e.g., those formed by rigid walls, Kramers–Kronig relations remain valid for both ideal and viscous liquids. Examples of numerical calculations of wave dispersion and attenuation using Kramers–Kronig relations, where applicable, are presented for unbounded media and for waveguides formed by two rigid walls.
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Open AccessArticle
Ultrasonic Study of Longitudinal Critically Refracted and Bulk Waves of the Heat-Affected Zone of a Low-Carbon Steel Welded Joint under Fatigue
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Alexander Gonchar, Alexander Solovyov and Vyacheslav Klyushnikov
Acoustics 2024, 6(3), 593-609; https://doi.org/10.3390/acoustics6030032 - 29 Jun 2024
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Currently, ultrasonic methods for assessing the fatigue lifetime of various structural materials are being actively developed. Many steel constructions are made by welding. The weld heat-affected zone is the weak point of the construction, as it is most susceptible to destruction. Therefore, it
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Currently, ultrasonic methods for assessing the fatigue lifetime of various structural materials are being actively developed. Many steel constructions are made by welding. The weld heat-affected zone is the weak point of the construction, as it is most susceptible to destruction. Therefore, it is actually important to search for acoustic parameters that uniquely characterize the structural damage accumulation in the heat-affected zone of a welded joint in order to predict failure. In this work, the specimens were made from the base metal and the welded joint’s heat-affected zone. The specimens were subjected to uniaxial tension–compression under a symmetrical cycle in the region of low-cycle fatigue with control of the strain amplitude. The propagation bulk velocities of longitudinal, shear waves and subsurface longitudinal critically refracted (LCR) waves during cyclic loading were studied. The acoustic birefringence of shear waves was calculated, and a similar parameter was proposed for longitudinal and LCR waves. The dependence of the elastic modulus ratio on the cycle ratio was obtained. It was shown that the acoustic parameters change most intensively in the heat-affected zone. According to the data of the C33/C55 ratio changes measured through the ultrasonic method, a formula for calculating the remaining fatigue life in the heat-affected zone was proposed.
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Open AccessArticle
A New CPX Drum Test to Obtain Sound Pressure Levels of Tyre Noise for Type Approval
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David Clar-Garcia, Hector Campello-Vicente, Nuria Campillo-Davo, Miguel Sanchez-Lozano and Emilio Velasco-Sanchez
Acoustics 2024, 6(3), 579-592; https://doi.org/10.3390/acoustics6030031 - 28 Jun 2024
Abstract
The primary cause of noise from vehicular traffic while travelling at speeds over 30 km/h is tyre/road interaction. To reduce this noise source, tyre/road sound emissions research has been carried out using different approaches. Most of this research has been centred around track
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The primary cause of noise from vehicular traffic while travelling at speeds over 30 km/h is tyre/road interaction. To reduce this noise source, tyre/road sound emissions research has been carried out using different approaches. Most of this research has been centred around track tests, leading to the development of various track and road-based methods for evaluating tyre/road noise emissions. The CPX (Close-Proximity), along with the CPB (Controlled Pass-By), the CB (Coast-By) and the SPB (Statistical Pass-By), methods are the most common ones. Nevertheless, since Reg. (EC) 1222/2009 came into force, only the CB method, defined in Reg. (EC) 117/2007, can be used to obtain tyre/road noise emission type approval values in Europe. However, current track test methods have important limitations, such as the variability of the results depending on the test track or the test vehicle, the repeatability, the influence of environmental variables or, the main aspect, the limitation of the registered magnitude in these tests, which is the sound pressure level. The Alternative Drum test method (A-DR) was developed in 2015 in order to avoid these disadvantages. However, it involves a complex and time-consuming microphone array for each test. With the purpose of improving the A-DR test method, a new methodology based on drum tests, the ISO 11819-2 and the ISO 3744 standards, was developed. This paper describes the new Alternative CPX Drum test method (A-CPX-DR) and validates it by testing several tyres according to the CB, the A-DR and the A-CPX-DR test methods and comparing their results. This research has demonstrated that all three methods have equivalent sound spectra and obtain close equivalent sound pressure levels for type approval of tyres in the EU, while drum tests have shown greater accuracy. For both reasons, the new A-CPX-DR methodology could be used for tyre/road noise emission type approval in a more precise and cheaper way.
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(This article belongs to the Special Issue Vibration and Noise (2nd Edition))
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Acoustic Analyses of L1 and L2 Vowel Interactions in Mandarin–Cantonese Late Bilinguals
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Yike Yang
Acoustics 2024, 6(2), 568-578; https://doi.org/10.3390/acoustics6020030 - 17 Jun 2024
Abstract
While the focus of bilingual research is frequently on simultaneous or early bilingualism, the interactions between late bilinguals’ first language (L1) and second language (L2) have rarely been studied previously. To fill this research gap, the aim of the current study was to
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While the focus of bilingual research is frequently on simultaneous or early bilingualism, the interactions between late bilinguals’ first language (L1) and second language (L2) have rarely been studied previously. To fill this research gap, the aim of the current study was to investigate the production of vowels in the L1 Mandarin and L2 Cantonese of Mandarin–Cantonese late bilinguals in Hong Kong. A production experiment was conducted with 22 Mandarin–Cantonese bilinguals, as well as with 20 native Mandarin speakers and 21 native Cantonese speakers. Acoustic analyses, including formants of and Euclidean distances between the vowels, were performed. Both vowel category assimilation and dissimilation were noted in the Mandarin–Cantonese bilinguals’ L1 and L2 vowel systems, suggesting interactions between the bilinguals’ L1 and L2 vowel categories. In general, the findings are in line with the hypotheses of the Speech Learning Model and its revised version, which state that L1–L2 phonetic interactions are inevitable, as there is a common phonetic space for storing the L1 and L2 phonetic categories, and that learners always have the ability to adapt their phonetic space. Future studies should refine the data elicitation method, increase the sample size and include more language pairs to better understand L1 and L2 phonetic interactions.
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(This article belongs to the Special Issue Developments in Acoustic Phonetic Research)
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The Effect of an Emotionalizing Sound Design on the Driver’s Choice of Headway in a Driving Simulator
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Manuel Petersen, Barbara Deml and Albert Albers
Acoustics 2024, 6(2), 541-567; https://doi.org/10.3390/acoustics6020029 - 10 Jun 2024
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This study investigates the impact of emotionalizing sound design on driving behaviour, focusing on the effect of an acoustic stimulus that varies from positive to negative/threatening based on the vehicle’s time headway (THW). Our primary goal was to explore how this sound influences
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This study investigates the impact of emotionalizing sound design on driving behaviour, focusing on the effect of an acoustic stimulus that varies from positive to negative/threatening based on the vehicle’s time headway (THW). Our primary goal was to explore how this sound influences driving durations within specific THW ranges and the mean THW itself. The experiment utilized a control group and a within-participant setting across simulated driving scenarios. The statistical analysis showed mixed results. While participants in the control group setup did not demonstrate significant reductions in the durations of driving in lower THW ranges, a modest but significant increase in mean THW was observed when the emotionalizing sound was active. However, within-participant comparisons showed both a significant decrease in the duration of driving at lower THWs and an increase in mean THW when the negative stimulus was active, suggesting the stimulus’ effectiveness in promoting safer driving habits. These findings highlight the potential of emotionalizing sound design to influence driver behaviour towards maintaining safer distances, although the impact appears to diminish at higher THW ranges. Future research should further investigate the characteristics of sounds that effectively modify driving behaviour, aiming for broader applications in traffic safety.
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Open AccessArticle
Prediction of Time Domain Vibro-Acoustic Response of Conical Shells Using Jacobi–Ritz Boundary Element Method
by
Cong Gao, Jiajun Zheng, Fuzhen Pang, Jiawei Xu, Haichao Li and Jibing Yan
Acoustics 2024, 6(2), 523-540; https://doi.org/10.3390/acoustics6020028 - 31 May 2024
Abstract
Considering the lack of studies on the transient vibro-acoustic properties of conical shell structures, a Jacobi–Ritz boundary element method for forced vibro-acoustic behaviors of structure is proposed based on the Newmark-β integral method and the Kirchhoff time domain boundary integral equation. Based on
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Considering the lack of studies on the transient vibro-acoustic properties of conical shell structures, a Jacobi–Ritz boundary element method for forced vibro-acoustic behaviors of structure is proposed based on the Newmark-β integral method and the Kirchhoff time domain boundary integral equation. Based on the idea of the differential element method and the first-order shear deformation theory (FSDT), the vibro-acoustic model of conical shells is established. The axial and circumferential displacement tolerance functions are expressed using Jacobi polynomials and the Fourier series. The time domain response of the forced vibration of conical shells is calculated based on the Rayleigh–Ritz method and Newmark-β integral method. On this basis, the time domain response of radiated noise is solved based on the Kirchhoff integral equation, and the acoustic radiation characteristics of conical shells from forced vibration are analyzed. Compared with the coupled FEM/BEM method, the numerical results demonstrate the high accuracy and great reliability of this method. Furthermore, the semi-vertex angle, load characteristics, and boundary conditions related to the vibro-acoustic response of conical shells are examined.
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(This article belongs to the Special Issue Duct Acoustics)
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Open AccessArticle
Acoustic Properties of Surfaces Covered by Multipole Resonators
by
Nikolay Kanev
Acoustics 2024, 6(2), 509-522; https://doi.org/10.3390/acoustics6020027 - 25 May 2024
Abstract
Different types of resonators are used to create acoustic metamaterials and metasurfaces. Recent studies focused on the use of multiple resonators of the dipole, quadrupole, octupole, and even hexadecapole types. This paper considers the theory of an acoustic metasurface, which is a flat
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Different types of resonators are used to create acoustic metamaterials and metasurfaces. Recent studies focused on the use of multiple resonators of the dipole, quadrupole, octupole, and even hexadecapole types. This paper considers the theory of an acoustic metasurface, which is a flat surface with a periodic arrangement of multipole resonators. The sound field reflected by the metasurface is determined. If the distance between the resonators is less than half the wavelength of the incident plane wave, the far field can be described by a reflection coefficient that depends on the angle of incidence. This allows us to characterize the acoustic properties of the metasurface by a homogenized boundary condition, which is a high-order tangential impedance boundary condition. The tangential impedance depending on the multipole order of the resonators is introduced. In addition, we analyze the sound absorption properties of these metasurfaces, which are a critical factor in determining their performance. The paper presents a theoretical model for the subwavelength case that accounts for the multipole orders of resonators and their impact on sound absorption. The maximum absorption coefficient for a diffuse sound field, as well as the optimal value for the homogenized impedance, are calculated for arbitrary multipole orders. The examples of the multipole resonators, which can be made from a set of Helmholtz resonators or membrane resonators, are discussed as well.
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(This article belongs to the Special Issue Resonators in Acoustics (2nd Edition))
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Open AccessArticle
Atmospheric Sound Propagation over Rough Sea: Numerical Evaluation of Equivalent Acoustic Impedance of Varying Sea States
by
Andrea Vecchiotti, Teresa J. Ryan, Joseph F. Vignola and Diego Turo
Acoustics 2024, 6(2), 489-508; https://doi.org/10.3390/acoustics6020026 - 23 May 2024
Abstract
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This work presents a numerical study on atmospheric sound propagation over rough water surfaces with the aim of improving predictions of sound propagation over long distances. A method for generating pseudorandom sea profiles consistent with sea wave spectra is presented. The proposed method
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This work presents a numerical study on atmospheric sound propagation over rough water surfaces with the aim of improving predictions of sound propagation over long distances. A method for generating pseudorandom sea profiles consistent with sea wave spectra is presented. The proposed method is suited for capturing the logarithmic nature of the energy distribution of the waves. Sea profiles representing fully developed seas for sea states 2, 3, 4, and 5 are generated from the Elfouhaily et al. (ECKV) sea wave spectra. Excess attenuation caused by refraction and surface roughness is predicted with a parabolic equation (PE) solver. A novel method for estimating equivalent effective impedance based on PE predictions at different sea states is presented. Parametric expressions using acoustic frequency and significant wave height are developed for effective surface impedances. In this work, sea surface roughness is on a scale comparable with the acoustic wavelength. Under this condition, the acoustic scattering is primarily incoherent. This work shows the limitations of using an equivalent surface impedance in such incoherent scattering cases.
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