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Acoustics, Volume 6, Issue 1 (March 2024) – 15 articles

Cover Story (view full-size image): Acoustic emission monitoring (AEM) of large civil infrastructures is a relatively new field of application for acoustic emission analysis. Even though AEM is a promising approach for structural health monitoring, it poses new challenges for data analysis. That is because permanent sensor deployment and the large size of structures demand very sparse sensor networks to make AEM economically interesting. In conjunction with the typically noisy environment, Sparse sensor networks make it difficult to detect acoustic emissions based on the signal's amplitude or energy alone. Hence, a template matching algorithm is proposed to detect acoustic emission signals, even when the signal-to-noise ratio is low. View this paper
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26 pages, 16173 KiB  
Article
Performance Evaluation of Balcony Designs for Mitigating Ground Level Noise
by Long Bin Tan and Linus Yinn Leng Ang
Acoustics 2024, 6(1), 272-297; https://doi.org/10.3390/acoustics6010015 - 11 Mar 2024
Viewed by 877
Abstract
This study aims to tackle the challenge of high noise levels on balconies while preserving natural ventilation. Eight innovative balcony designs, incorporating elements like diffuser edges, undulating ceilings, Helmholtz resonators, grooves, or sound traps, were evaluated via finite element (FE) modeling. The insertion [...] Read more.
This study aims to tackle the challenge of high noise levels on balconies while preserving natural ventilation. Eight innovative balcony designs, incorporating elements like diffuser edges, undulating ceilings, Helmholtz resonators, grooves, or sound traps, were evaluated via finite element (FE) modeling. The insertion loss results showed that for many balcony designs, noise reduction in the balcony could deteriorate beyond an elevation of 8 m. However, the front jagged and full wavy ceiling designs were shown to be more robust in noise attenuation across balconies on different floors. The jagged ledge and grooved parapet designs yielded an overall 1.5 dBA lower SPL at the exterior regions, compared to other designs, which implies that the designs are less acoustically detrimental to nearby residential blocks as they tend to diffract and absorb incident noise. The jagged ledge design is more effective for lower floors while the jagged ceiling design is more effective for higher floors. A combination of the protruded jagged ledge for the lower floor and jagged balcony ceiling for the higher floor would result in the lowest noise ingress over three stories of residential units: this would be capable of achieving more than 3 dB noise reduction and would offer viable options for improving balcony noise mitigation, by providing valuable insights to architects and designers seeking practical solutions for outdoor noise reduction. Our study highlights that whereas the spectrum characteristics of acoustic absorption materials may be less tunable, and where reduced head space is traded for thicker material for greater ab-sorption and added affixation and maintenance cost, the jagged ledge and ceiling curvatures can actually be shape-tuned, say for every 3 to 4 floors up the high-rise to more effective reduce noise ingress and possibly improve the architecture façade outlook. Full article
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15 pages, 1311 KiB  
Article
Acoustic Characteristics of Greek Vowels Produced by Adult Heritage Speakers of Albanian
by Georgios P. Georgiou and Aretousa Giannakou
Acoustics 2024, 6(1), 257-271; https://doi.org/10.3390/acoustics6010014 - 10 Mar 2024
Viewed by 1027
Abstract
Investigating heritage language (HL)-contact effects on the dominant language has received limited attention despite its importance in understanding the dynamic interplay between linguistic systems in situations of bilingualism. This study compares the acoustic characteristics of Greek vowels produced by heritage speakers (HSs) of [...] Read more.
Investigating heritage language (HL)-contact effects on the dominant language has received limited attention despite its importance in understanding the dynamic interplay between linguistic systems in situations of bilingualism. This study compares the acoustic characteristics of Greek vowels produced by heritage speakers (HSs) of Albanian and monolingual Greek speakers, aiming to identify potential differences and explain them. The participants were adult second-generation HSs of Albanian with Greek as their dominant language, born and raised in Greece. A control group of age-matched monolingual Greek speakers was included for comparison purposes. All participants engaged in a controlled speech production task, with the data segmented to extract acoustic values pertaining to the first three formants and the duration of Greek vowels. Bayesian regression models were employed for the subsequent statistical analysis. The results demonstrated differences in the first three formants of certain vowels and the duration of all vowels. These differences can be attributed to the crosslinguistic effect of HL on the dominant language, as well as the interplay between the dynamic and internalized language system of the speakers and the complex effect of the sociophonetic context. These outcomes contribute to the hypothesis positing the emergence of deflected phonetic categories among a distinctive group of bilinguals, namely HSs. Furthermore, this study underscores the significance of a comprehensive exploration of the sociophonetic context of HSs for a nuanced understanding of their phonetic patterns. Full article
(This article belongs to the Special Issue Developments in Acoustic Phonetic Research)
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17 pages, 5223 KiB  
Article
Influence of the Gain–Bandwidth of the Front-End Amplifier on the Performance of a QEPAS Sensor
by Luigi Lombardi, Gianvito Matarrese and Cristoforo Marzocca
Acoustics 2024, 6(1), 240-256; https://doi.org/10.3390/acoustics6010013 - 06 Mar 2024
Viewed by 768
Abstract
The quartz tuning fork used as an acoustic sensor in quartz-enhanced photo-acoustic spectroscopy gas detection systems is usually read out by means of a transimpedance preamplifier based on a low-noise operational amplifier closed in a feedback loop. The gain–bandwidth product of the operational [...] Read more.
The quartz tuning fork used as an acoustic sensor in quartz-enhanced photo-acoustic spectroscopy gas detection systems is usually read out by means of a transimpedance preamplifier based on a low-noise operational amplifier closed in a feedback loop. The gain–bandwidth product of the operational amplifier used in the circuit is a key parameter which must be properly chosen to guarantee that the circuit works as expected. Here, we demonstrate that if the value of this parameter is not sufficiently large, the response of the preamplifier exhibits a peak at a frequency which does not coincide with the series resonant frequency of the quartz tuning fork. If this peak frequency is selected for modulating the laser bias current and is also used as the reference frequency of the lock-in amplifier, a penalty results in terms of signal-to-noise ratio at the output of the QEPAS sensor. This worsens the performance of the gas sensing system in terms of ultimate detection limits. We show that this happens when the front-end preamplifier of the quartz tuning fork is based on some amplifier models that are typically used for such application, both when the integration time of the lock-in amplifier filter is long, to boost noise rejection, and when it is short, in order to comply with a relevant measurement rate. Full article
(This article belongs to the Special Issue Resonators in Acoustics (2nd Edition))
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21 pages, 20618 KiB  
Article
Design of Optimal Sound Absorbers Using Acoustic Diffusers for Multipurpose Auditoriums
by Domingo Pardo-Quiles, Ignacio Rodríguez-Rodríguez and José-Víctor Rodríguez
Acoustics 2024, 6(1), 219-239; https://doi.org/10.3390/acoustics6010012 - 06 Mar 2024
Viewed by 887
Abstract
The main goal of this research was to design and study the best structure, location, and shape of acoustic diffusers to be fitted on the ceilings of multipurpose auditoriums. Their absorbing properties can enhance the acoustics when installed on high ceilings, and behind [...] Read more.
The main goal of this research was to design and study the best structure, location, and shape of acoustic diffusers to be fitted on the ceilings of multipurpose auditoriums. Their absorbing properties can enhance the acoustics when installed on high ceilings, and behind suspended reflecting panels, by mitigating or nullifying specular reflections that could overcome the panels and, thus, avoiding time delay gaps exceeding 30–40 ms compared with the direct sound. For this purpose, a typical medium-sized room, with inclined floors, a stage, and 20 rows of seats, was considered. The allocation and height of the considered diffusers were based on the Schroeder quadratic residue sequence, and they were modeled as rectangles, wedges, cylinders, and Y-shaped elements. A standardized speech source spectrum was analyzed for up to five different receiver locations. In this way, the attenuation parameter as a function of frequency was evaluated and compared between the candidate diffusers in order to identify the best absorber. The simulations were undertaken with a software tool previously validated by the authors called PARDOS, which incorporates an innovative formulation based on the uniform theory of diffraction (UTD) to analyze multiple diffractions and reflections of acoustic waves. The results show that the new Y-shaped diffusers proposed, tuned for the hearing frequency band from 250 Hz up to 10,000 Hz, attained the best acoustic performance in terms of absorption. Full article
(This article belongs to the Special Issue Building Materials and Acoustics)
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15 pages, 1583 KiB  
Article
Matched Filter for Acoustic Emission Monitoring in Noisy Environments: Application to Wire Break Detection
by Alexander Lange, Ronghua Xu, Max Kaeding, Steffen Marx and Joern Ostermann
Acoustics 2024, 6(1), 204-218; https://doi.org/10.3390/acoustics6010011 - 20 Feb 2024
Viewed by 1164
Abstract
Regular inspections of important civil infrastructures are mandatory to ensure structural safety and reliability. Until today, these inspections are primarily conducted manually, which has several deficiencies. In context of prestressed concrete structures, steel tendons can be susceptible to stress corrosion cracking, which may [...] Read more.
Regular inspections of important civil infrastructures are mandatory to ensure structural safety and reliability. Until today, these inspections are primarily conducted manually, which has several deficiencies. In context of prestressed concrete structures, steel tendons can be susceptible to stress corrosion cracking, which may result in breakage of individual wires that is visually not observable. Recent research therefore suggests Acoustic Emission Monitoring for wire break detection in prestressed concrete structures. However, in noisy environments, such as wind turbines, conventional acoustic emission detection based on user-defined amplitude thresholds may not be suitable. Thus, we propose the use of matched filters for acoustic emission detection in noisy environments and apply the proposed method to the task of wire break detection in post-tensioned wind turbine towers. Based on manually conducted wire breaks and rebound hammer tests on a large-scale test frame, we employ a brute-force search for the most suitable query signal of a wire break event and a rebound hammer impact, respectively. Then, we evaluate the signal detection performance on more than 500 other wire break signals and approximately one week of continuous acoustic emission recordings in an operating wind turbine. For a signal-to-noise ratio of 0 dB, the matched filter approach shows an improvement in AUC by up to 0.78 for both, the wire break and the rebound hammer query signal, compared to state-of-the-art amplitude-based detection. Even for the unscaled wire break measurements originally recorded at the 12 m large laboratory test frame, the improvement in AUC still lies between 0.01 and 0.25 depending on the wind turbine noise recordings considered for evaluation. Matched filters may therefore be a promising alternative to amplitude-based detection algorithms and deserve particular consideration with regard to Acoustic Emission Monitoring, especially in noisy environments or when sparse senor networks are required. Full article
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27 pages, 25984 KiB  
Article
Machine Noise—Experimental Study of the Local Environmental Correction for the Emission Sound Pressure Level
by Fabian Heisterkamp
Acoustics 2024, 6(1), 177-203; https://doi.org/10.3390/acoustics6010010 - 08 Feb 2024
Viewed by 1221
Abstract
Determining reliable noise emission values for machinery is key to successfully implement the Sell and Buy Quiet concept. ISO 11202 is a basic noise emission standard to determine the emission sound pressure level of machines outside of special acoustic test rooms (in situ [...] Read more.
Determining reliable noise emission values for machinery is key to successfully implement the Sell and Buy Quiet concept. ISO 11202 is a basic noise emission standard to determine the emission sound pressure level of machines outside of special acoustic test rooms (in situ measurements) and enables machinery manufacturers to determine the noise emission data of their products within their own premises. However, a recent amendment to this standard was made on the basis of an unsatisfactory amount of experimental data. Therefore, this paper systematically examines the validity and accuracy of the amended part of the method. It answers the question, whether the amendment represents an improvement of the existing method. Measurements on a model machine with two configurations allow for an extensive investigation of the effects of the amendment. To that end, the emission sound pressure levels at eight positions near the machine are determined in three different acoustic environments. One finds that the amendment leads to an overestimation of the local environmental correction for the LpA, which, in turn, could lead to an underestimation of the determined emission sound pressure level. Full article
(This article belongs to the Special Issue Machinery Noise: Emission, Modelling and Control)
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20 pages, 4836 KiB  
Article
An Investigation into the Physical Mechanisms of Leak Noise Propagation in Buried Plastic Water Pipes: A Wave Dynamic Stiffness Approach
by Oscar Scussel, Michael J. Brennan, Jennifer M. Muggleton, Fabrício C. L. de Almeida, Phillip F. Joseph and Yan Gao
Acoustics 2024, 6(1), 157-176; https://doi.org/10.3390/acoustics6010009 - 01 Feb 2024
Viewed by 1470
Abstract
In buried plastic water pipes, the predominantly fluid-borne wave is of particular interest, as it plays a key role in the propagation of leak noise. Consequently, it has been studied by several researchers to determine the speed of wave propagation and its attenuation [...] Read more.
In buried plastic water pipes, the predominantly fluid-borne wave is of particular interest, as it plays a key role in the propagation of leak noise. Consequently, it has been studied by several researchers to determine the speed of wave propagation and its attenuation with distance. These features are encapsulated in the wavenumber. By examining the factors that govern the behaviour of this wavenumber, this paper presents an in-depth examination of the physical mechanisms of leak noise propagation. To achieve this, an alternative physics-based model for the wavenumber is developed, using the concept of the wave dynamic stiffnesses of the individual components within the pipe system, i.e., the water in the pipe, the pipe wall, and the surrounding medium. This facilitates a clear interpretation of the wave behaviour in terms of the physical properties of the system, especially the interface between the pipe and the surrounding medium, which can have a profound influence on the leakage of acoustic energy from the pipe wall into the external medium. Three systems with different types of surrounding medium are studied, and the factors that govern leak noise propagation in each case are identified. Experimental results on two distinct test sites from different parts of the world are provided to validate the approach using leak noise as an excitation mechanism. Full article
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23 pages, 5866 KiB  
Article
Comparing the Performance of Robust Controllers for Vibration Suppression in Long Rotor Systems
by Majid Aleyaasin
Acoustics 2024, 6(1), 134-156; https://doi.org/10.3390/acoustics6010008 - 01 Feb 2024
Viewed by 1163
Abstract
In this paper, the vibration control of the multivariable model of rotor bearing systems is considered for investigation. Some simply structured controllers that can suppress vibrational disturbances are tested for their robustness via the H optimality criteria. Initially, intelligent optimisation techniques are [...] Read more.
In this paper, the vibration control of the multivariable model of rotor bearing systems is considered for investigation. Some simply structured controllers that can suppress vibrational disturbances are tested for their robustness via the H optimality criteria. Initially, intelligent optimisation techniques are used to minimize the H mixed-sensitivity norm of the Linear Fractional Transformation (LFT) of the simple two-term PI controllers acting on the rotor system models. This results in some controllers that can suppress the vibration but with a slow oscillatory response. After this, an appropriate interpretation of the Bode plot singular values of the combined sensitivity and control effort matrix is used to explain the performance shortcomings of this controller. Moreover, the existing simply structured controllers in the literature exhibiting a faster performance are examined by using singular value plots. It is shown that when the maximum singular value of the control effort matrix drops below the 0 db line, the performance will be boosted. Finally, the H controllers are designed by using the robust control toolbox in MATLAB. This resulted in rapid disturbance rejection, with the vibration amplitude diminishing to zero after 0.3 s due to double-step disturbances. However, these controllers in the frequency domain have an order of eight and may not be realizable to be implemented in practice. It is concluded that examining the Bode plot of the maximum singular value of the control effort matrix is a useful tool for evaluating performance in the frequency domain. However, designing robust controllers by toolboxes in the time domain can lead to superb performance with higher-order controllers. Full article
(This article belongs to the Special Issue Active Control of Sound and Vibration)
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20 pages, 12510 KiB  
Article
Wooden Rehearsal Rooms from the Construction Process to the Musical Performance
by Maria Cairoli
Acoustics 2024, 6(1), 114-133; https://doi.org/10.3390/acoustics6010007 - 27 Jan 2024
Viewed by 1426
Abstract
Rehearsal rooms play an important role in musicians’ activities to obtain the best results during a performance in front of an audience. Numerous rehearsal rooms are located in complex buildings, such as opera houses and cultural centers, where new research outcomes have led [...] Read more.
Rehearsal rooms play an important role in musicians’ activities to obtain the best results during a performance in front of an audience. Numerous rehearsal rooms are located in complex buildings, such as opera houses and cultural centers, where new research outcomes have led to increasingly complex projects and construction phases. Furthermore, technical complexity has also increased due to the large quantity of used materials and the innovation level of the process. In this context, a new methodology becomes mandatory to control the indoor air quality and the acoustic quality in rehearsal rooms. This paper aims to offer a procedure for rehearsal rooms for large ensembles during the construction and life cycle phases to optimize the indoor environmental quality according to different types of ensembles and repertoires. In particular, rehearsal rooms with wood panel cladding are considered. The proposed methodology is controlled by a digital twin (DT) based on building information modeling (BIM), integrated with acoustic measurements, sensors and actuators aimed at implementing the database in real time. A case study is presented, in which the cladding system is described, the new methodology is applied, and the results are compared with the criteria suggested in the standard ISO 23591. Full article
(This article belongs to the Special Issue Building Materials and Acoustics)
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17 pages, 3780 KiB  
Article
Recording, Processing, and Reproduction of Vibrations Produced by Impact Noise Sources in Buildings
by Franz Dolezal, Andreas Reichenauer, Armin Wilfling, Maximilian Neusser and Rok Prislan
Acoustics 2024, 6(1), 97-113; https://doi.org/10.3390/acoustics6010006 - 17 Jan 2024
Viewed by 1815
Abstract
Several studies on the perception of impact sounds question the correlation of standardized approaches with perceived annoyance, while more recent studies have come to inconsistent conclusions. All these studies neglected the aspect of whole-body vibrations, which are known to be relevant for the [...] Read more.
Several studies on the perception of impact sounds question the correlation of standardized approaches with perceived annoyance, while more recent studies have come to inconsistent conclusions. All these studies neglected the aspect of whole-body vibrations, which are known to be relevant for the perception of low-frequency sound and can be perceived especially in lightweight constructions. Basically, the contribution of vibrations to impact sound annoyance is still unknown and could be the reason for the contradictory results. To investigate this aspect, we measured vibrations on different types of floors under laboratory conditions and in situ. For this purpose, a vibration-sensing device was developed to record vibrations more cost-effectively and independently of commercial recording instruments. The vibrations of predefined impact sequences were recorded together with the sound field using a higher-order ambisonics microphone. In addition, a vibration exposure device was developed to expose the test objects to the exact vibrations that occur in the built environment. The vibration exposure device is integrated into the ambisonics reproduction system, which consists of a large number of loudspeakers in a spherical configuration. The article presents the development and performance achieved using the vibration-sensing unit and the vibration exposure device. The study is relevant for conducting future impact sound listening tests under laboratory conditions, which can be extended to include the reproduction of vibrations. Full article
(This article belongs to the Special Issue Building Materials and Acoustics)
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14 pages, 6610 KiB  
Article
Computational and Theoretical Investigation of Acoustical and Vibrational Properties of Rigid Thin Material
by Haydar Aygun
Acoustics 2024, 6(1), 83-96; https://doi.org/10.3390/acoustics6010005 - 16 Jan 2024
Viewed by 1393
Abstract
A computational and theoretical investigation of acoustical and vibrational properties of rigid thin fiberglass material was carried out for different boundary conditions. Fiberglass materials could be applied in industries varying from the aircraft and automotive sectors to the built environment and construction sectors. [...] Read more.
A computational and theoretical investigation of acoustical and vibrational properties of rigid thin fiberglass material was carried out for different boundary conditions. Fiberglass materials could be applied in industries varying from the aircraft and automotive sectors to the built environment and construction sectors. Plate vibration and acoustic radiation were applied to predict the deflection of the thin fiberglass material and sound radiation efficiency at different locations on its surface, while a study-controlled equation of motion known as the Kirchhoff thin plate theory was applied for a COMSOL simulation of the thin material to determine the deflection of the plate and to obtain stress distribution, velocity contour, displacement, and acoustic pressure at the first resonance of the material. The results of this paper show that thin fiberglass material could be applied to sandwich building elements to form panels for reducing airborne noise and to lessen the sound transmission of structural borne noise, to cover noise barriers to make them more sustainable and weather resistant, to dampen the vibration of machines, and to reduce the structural vibration of buildings. Full article
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18 pages, 5608 KiB  
Article
Experimental Prediction Method of Free-Field Sound Emissions Using the Boundary Element Method and Laser Scanning Vibrometry
by Andreas Wurzinger, Florian Kraxberger, Paul Maurerlehner, Bernhard Mayr-Mittermüller, Peter Rucz, Harald Sima, Manfred Kaltenbacher and Stefan Schoder
Acoustics 2024, 6(1), 65-82; https://doi.org/10.3390/acoustics6010004 - 03 Jan 2024
Viewed by 1701
Abstract
Acoustic emissions play a major role in the usability of many product categories. Therefore, mitigating the emitted sound directly at the source is paramount to improve usability and customer satisfaction. To reliably predict acoustic emissions, numerical methods such as the boundary element method [...] Read more.
Acoustic emissions play a major role in the usability of many product categories. Therefore, mitigating the emitted sound directly at the source is paramount to improve usability and customer satisfaction. To reliably predict acoustic emissions, numerical methods such as the boundary element method (BEM) are employed, which allow for predicting, e.g., the acoustic emission into the free field. BEM algorithms need appropriate boundary conditions to couple the sound field with the structural motion of the vibrating body. In this contribution, firstly, an interpolation scheme is presented, which allows for appropriate interpolation of arbitrary velocity data to the computational grid of the BEM. Secondly, the free-field Helmholtz problem is solved with the open-source BEM software framework NiHu. The forward coupling between the device of interest and BEM is based on the surface normal velocities (i.e., a Neumann boundary condition). The BEM simulation results are validated using a previously established aeroacoustic benchmark problem. Furthermore, an application to a medical device (knee prosthesis frame) is presented. Furthermore, the radiated sound power is evaluated and contextualized with other low-cost approximations. Regarding the validation example, very good agreements are achieved between the measurements and BEM results, with a mean effective pressure level error of 0.63 dB averaged across three microphone positions. Applying the workflow to a knee prosthesis frame, the simulation is capable of predicting the acoustic radiation to four microphone positions with a mean effective pressure level error of 1.52 dB. Full article
(This article belongs to the Special Issue Vibration and Noise (2nd Edition))
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30 pages, 450 KiB  
Essay
Music Listening as Kangaroo Mother Care: From Skin-to-Skin Contact to Being Touched by the Music
by Mark Reybrouck
Acoustics 2024, 6(1), 35-64; https://doi.org/10.3390/acoustics6010003 - 01 Jan 2024
Viewed by 2066
Abstract
The metaphor of being touched by music is widespread and almost universal. The tactile experience, moreover, has received growing interest in recent years. There is, however, a need to go beyond a mere metaphorical use of the term, by positioning the tactile experience [...] Read more.
The metaphor of being touched by music is widespread and almost universal. The tactile experience, moreover, has received growing interest in recent years. There is, however, a need to go beyond a mere metaphorical use of the term, by positioning the tactile experience within the broader frame of embodied cognition and the experiential turn in cognitive science. This article explores the possible contribution of a science of touch by defining music as a vibrational phenomenon that affects the body and the senses. It takes as a starting point the clinical findings on the psychological and physiological value of tender touch with a special focus on the method of kangaroo mother care, which is a method for holding the baby against the chest of the mother, skin-to-skin. It is seen as one of the most basic affiliative bondings with stimuli that elicit reward. Via an extensive review of the research literature, it is questioned as to what extent this rationale can be translated to the realm of music. There are, in fact, many analogies, but a comprehensive theoretical framework is still lacking. This article aims at providing at least some preparatory groundwork to fuel more theorizing about listening and its relation to the sense of touch. Full article
17 pages, 14043 KiB  
Article
Investigations into the Approaches of Computational Fluid Dynamics for Flow-Excited Resonator Helmholtz Modeling within Verification on a Laboratory Benchmark
by Daniil Sergeev, Irina V’yushkina, Vladimir Eremeev, Andrei Stulenkov and Kirill Pyalov
Acoustics 2024, 6(1), 18-34; https://doi.org/10.3390/acoustics6010002 - 22 Dec 2023
Cited by 1 | Viewed by 1523
Abstract
This paper presents the results of a study of self-sustained processes excited in a Helmholtz resonator after a flow over its orifice. A comparative analysis of various approaches to the numerical modeling of this problem was carried out, taking into account both the [...] Read more.
This paper presents the results of a study of self-sustained processes excited in a Helmholtz resonator after a flow over its orifice. A comparative analysis of various approaches to the numerical modeling of this problem was carried out, taking into account both the requirements for achieving the required accuracy and taking into account the resource greediness of calculations, the results of which were verified by comparison with data obtained during a special experiment. The configuration with a spherical resonator with a natural frequency of 260 Hz and an orifice diameter (about 5 cm) in an air flow with a speed of 6 to 14 m/s was considered. A comparison of the calculation results with data obtained in experiments carried out in the wind tunnel demonstrated that the accuracy of calculations of the characteristics of the self-sustained mode using the simplest URANS class model tends to the accuracy of calculations within the large eddy simulation approach formulated in the WMLES model. At the same time, when using WMLES, it is possible to better reproduce the background level of pulsations. From the point of view of resource greediness, expressed in the number of core hours spent obtaining a solution, both models of the turbulence turned out to be almost equivalent when using the same grid models. Full article
(This article belongs to the Special Issue Resonators in Acoustics (2nd Edition))
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17 pages, 6539 KiB  
Article
Identification of Key Factors Influencing Sound Insulation Performance of High-Speed Train Composite Floor Based on Machine Learning
by Ruiqian Wang, Dan Yao, Jie Zhang, Xinbiao Xiao and Ziyan Xu
Acoustics 2024, 6(1), 1-17; https://doi.org/10.3390/acoustics6010001 - 20 Dec 2023
Viewed by 1603
Abstract
The body of a high-speed train is a composite structure composed of different materials and structures. This makes the design of a noise-reduction scheme for a car body very complex. Therefore, it is important to clarify the key factors influencing sound insulation in [...] Read more.
The body of a high-speed train is a composite structure composed of different materials and structures. This makes the design of a noise-reduction scheme for a car body very complex. Therefore, it is important to clarify the key factors influencing sound insulation in the composite structure of a car body. This study uses machine learning to evaluate the key factors influencing the sound insulation performance of the composite floor of a high-speed train. First, a comprehensive feature database is constructed using sound insulation test results from a large number of samples obtained from laboratory acoustic measurements. Subsequently, a machine learning model for predicting the sound insulation of a composite floor is developed based on the random forest method. The model is used to analyze the sound insulation contributions of different materials and structures to the composite floor. Finally, the key factors influencing the sound insulation performance of composite floors are identified. The results indicate that, when all material characteristics are considered, the sound insulation and surface density of the aluminum profiles and the sound insulation of the interior panels are the three most important factors affecting the sound insulation of the composite floor. Their contributions are 8.5%, 7.3%, and 6.9%, respectively. If only the influence of the core material is considered, the sound insulation contribution of layer 1 exceeds 15% in most frequency bands, particularly at 250 and 500 Hz. The damping slurry contributed to 20% of the total sound insulation above 1000 Hz. The results of this study can provide a reference for the acoustic design of composite structures. Full article
(This article belongs to the Special Issue Acoustic Materials)
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