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Acoustics, Volume 4, Issue 1 (March 2022) – 17 articles

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21 pages, 10520 KiB  
Article
Acoustical Treatments on Ventilation Ducts through Walls: Experimental Results and Novel Models
by Erik Nilsson, Sylvain Ménard, Delphine Bard Hagberg and Nikolaos-Georgios Vardaxis
Acoustics 2022, 4(1), 276-296; https://doi.org/10.3390/acoustics4010017 - 18 Mar 2022
Cited by 1 | Viewed by 4223
Abstract
Sound reduction is complex to estimate for acoustical treatments on ventilation ducts through walls. Various acoustical treatments are available for ventilation ducts, including internal lining (absorption along the inner perimeter), external lagging (external sound insulation), silencer, and suspended ceilings. Previous studies have examined [...] Read more.
Sound reduction is complex to estimate for acoustical treatments on ventilation ducts through walls. Various acoustical treatments are available for ventilation ducts, including internal lining (absorption along the inner perimeter), external lagging (external sound insulation), silencer, and suspended ceilings. Previous studies have examined how silencers and the internal lining affect the sound transmission of ventilation ducts. However, there are few theories to predict the effect of external lagging in combination with ventilation ducts and how the total sound reduction is affected. This article aims to investigate different acoustical treatments and develop theoretical models when external lagging with stone wool is used to reduce flanking sound transmission via the surface area of ventilation ducts. Theoretical models are developed for external lagging and compared with measurement data. Measurements and theory are generally in good agreement over the third-octave band range of 100–5000 Hz. The developed models clarify that the distance closest to the wall has the main impact on sound reduction for a combined system with a wall and a ventilation duct. Suspended ceilings and silencers are found to be enough as acoustical treatments for certain combinations of ventilation ducts and walls. However, external lagging seems to be the only effective solution in offices and schools when a large ventilation duct passes through a wall with high sound reduction. Full article
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8 pages, 1428 KiB  
Article
Molecular Dynamics Simulations of Shockwave Affected STMV Virus to Measure the Frequencies of the Oscillatory Response
by Jeffrey Burkhartsmeyer and Kam Sing Wong
Acoustics 2022, 4(1), 268-275; https://doi.org/10.3390/acoustics4010016 - 18 Mar 2022
Viewed by 2764
Abstract
Acoustic shockwaves are of interest as a possible means of the selective inactivation of viruses. It has been proposed that such inactivation may be enhanced by driving the virus particles at frequencies matching the characteristic frequency corresponding to acoustic modes of the viral [...] Read more.
Acoustic shockwaves are of interest as a possible means of the selective inactivation of viruses. It has been proposed that such inactivation may be enhanced by driving the virus particles at frequencies matching the characteristic frequency corresponding to acoustic modes of the viral structures, setting up a resonant response. Characteristic frequencies of viruses have been previously studied through opto-mechanical techniques. In contrast to optical excitation, shockwaves may be able to probe acoustic modes without the limitation of optical selection rules. This work explores molecular dynamics simulations of shockwaves interacting with a single STMV virus structure, in full atomistic detail, in order to measure the frequency of the response of the overall structure. Shockwaves of varying energy were set up in a water box containing the STMV structure by assigning water molecules at the edge of the box with an elevated velocity inward—in the direction of the virus. It was found that the structure compressed and stretched in a periodic oscillation of frequency 65 ± 6.5 GHz. This measured frequency did not show strong dependency on the energy of the shockwave perturbing the structure, suggesting the frequency is a characteristic of the structure. The measured frequency is also consistent with values predicted from elastic theory. Additionally, it was found that subjecting the virus to repeated shockwaves led to further deformation of the structure and the magnitude of the overall deformation could be altered by varying the time delay between repeated shockwave pulses. Full article
(This article belongs to the Special Issue Acoustics in Biomedical Engineering)
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20 pages, 7199 KiB  
Article
The Effects of a Morphed Trailing-Edge Flap on the Aeroacoustic and Aerodynamic Performance of a 30P30N Aerofoil
by Joseph Watkins and Abdessalem Bouferrouk
Acoustics 2022, 4(1), 248-267; https://doi.org/10.3390/acoustics4010015 - 3 Mar 2022
Cited by 5 | Viewed by 3988
Abstract
This paper presents initial results on the aeroacoustic and aerodynamic effects of morphing the trailing-edge flap of the 30P30N aerofoil, over five flap deflections (5–25°), at an 8° angle of attack and a Reynolds number of Re=9.2×105 [...] Read more.
This paper presents initial results on the aeroacoustic and aerodynamic effects of morphing the trailing-edge flap of the 30P30N aerofoil, over five flap deflections (5–25°), at an 8° angle of attack and a Reynolds number of Re=9.2×105. The Ffowcs-Williams–Hawkings acoustic analogy estimates the far-field noise, whilst the flow field is solved using URANS with the four-equation Transition SST model. Aerodynamic and aeroacoustic simulation data for the 30P30N’s full configuration compare well with experimental results. A Courant number (C) ≤ 1 should be used for resolving tonal noise, whilst a C of up to 4 is sufficient for broadband noise. Sound pressure level results show an average 11% reduction in broadband noise across all flap deflections and frequencies for the morphed configuration compared with the conventional, single-slotted flap. The morphed flap eliminates the multiple tonal peaks observed in the conventional design. Beyond 15° flap deflection, the morphing flap achieves higher stall angles, but with increased drag, leading to a maximum reduction of 17% in Cl/Cd ratio compared with the conventional flap. The methodology reported here for the 30P30N is a quick tool for initial estimates of the far-field noise and aerodynamic performance of a morphing flap at the design stage. Full article
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21 pages, 10323 KiB  
Article
Sound Reflections in Indian Stepwells: Modelling Acoustically Retroreflective Architecture
by Densil Cabrera, Shuai Lu, Jonothan Holmes and Manuj Yadav
Acoustics 2022, 4(1), 227-247; https://doi.org/10.3390/acoustics4010014 - 2 Mar 2022
Cited by 5 | Viewed by 5420
Abstract
Retroreflection is rarely used as a surface treatment in architectural acoustics but is found incidentally with building surfaces that have many simultaneously visible concave right-angle trihedral corners. Such surfaces concentrate reflected sound onto the sound source, mostly at high frequencies. This study investigated [...] Read more.
Retroreflection is rarely used as a surface treatment in architectural acoustics but is found incidentally with building surfaces that have many simultaneously visible concave right-angle trihedral corners. Such surfaces concentrate reflected sound onto the sound source, mostly at high frequencies. This study investigated the potential for some Indian stepwells (stepped ponds, known as a kund or baori/baoli in Hindi) to provide exceptionally acoustically retroreflective semi-enclosed environments because of the unusually large number of corners formed by the steps. Two cases—Panna Meena ka Kund and Lahan Vav—were investigated using finite-difference time-domain (FDTD) acoustic simulation. The results are consistent with retroreflection, showing reflected energy concentrating on the source position mostly in the high-frequency bands (4 kHz and 2 kHz octave bands). However, the larger stepped pond has substantially less retroreflection, even though it has many more corners, because of the greater diffraction loss over the longer distances. Retroreflection is still evident (but reduced) with non-right-angle trihedral corners (80°–100°). The overall results are sufficiently strong to indicate that acoustic retroreflection should be audible to an attuned visitor in benign environmental conditions, at least at moderately sized stepped ponds that are in good geometric condition. Full article
(This article belongs to the Special Issue Acoustics, Soundscapes and Sounds as Intangible Heritage)
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24 pages, 3261 KiB  
Article
Prediction of Sound Insulation Using Artificial Neural Networks—Part I: Lightweight Wooden Floor Structures
by Mohamad Bader Eddin, Sylvain Ménard, Delphine Bard Hagberg, Jean-Luc Kouyoumji and Nikolaos-Georgios Vardaxis
Acoustics 2022, 4(1), 203-226; https://doi.org/10.3390/acoustics4010013 - 2 Mar 2022
Cited by 11 | Viewed by 4598
Abstract
The artificial neural networks approach is applied to estimate the acoustic performance for airborne and impact sound insulation curves of different lightweight wooden floors. The prediction model is developed based on 252 standardized laboratory measurement curves in one-third octave bands (50–5000 Hz). Physical [...] Read more.
The artificial neural networks approach is applied to estimate the acoustic performance for airborne and impact sound insulation curves of different lightweight wooden floors. The prediction model is developed based on 252 standardized laboratory measurement curves in one-third octave bands (50–5000 Hz). Physical and geometric characteristics of each floor structure (materials, thickness, density, dimensions, mass and more) are utilized as network parameters. The predictive capability is satisfactory, and the model can estimate airborne sound better than impact sound cases especially in the middle-frequency range (250–1000 Hz), while higher frequency bands often show high errors. The forecast of the weighted airborne sound reduction index Rw was calculated with a maximum error of 2 dB. However, the error increased up to 5 dB in the worse case prediction of the weighted normalized impact sound pressure level Ln,w. The model showed high variations near the fundamental and critical frequency areas which affect the accuracy. A feature attribution analysis explored the essential parameters on estimation of sound insulation. The thickness of the insulation materials, the density of cross-laminated timber slab and the concrete floating floors and the total density of floor structures seem to affect predictions the most. A comparison between wet and dry floor solution systems indicated the importance of the upper part of floors to estimate airborne and impact sound in low frequencies. Full article
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20 pages, 5128 KiB  
Review
A Review of Finite Element Studies in String Musical Instruments
by Evaggelos Kaselouris, Makis Bakarezos, Michael Tatarakis, Nektarios A. Papadogiannis and Vasilis Dimitriou
Acoustics 2022, 4(1), 183-202; https://doi.org/10.3390/acoustics4010012 - 23 Feb 2022
Cited by 15 | Viewed by 6732
Abstract
String instruments are complex mechanical vibrating systems, in terms of both structure and fluid–structure interaction. Here, a review study of the modeling and simulation of stringed musical instruments via the finite element method (FEM) is presented. The paper is focused on the methods [...] Read more.
String instruments are complex mechanical vibrating systems, in terms of both structure and fluid–structure interaction. Here, a review study of the modeling and simulation of stringed musical instruments via the finite element method (FEM) is presented. The paper is focused on the methods capable of simulating (I) the soundboard behavior in bowed, plucked and hammered string musical instruments; (II) the assembled musical instrument box behavior in bowed and plucked instruments; (III) the fluid–structure interaction of assembled musical instruments; and (IV) the interaction of a musical instrument’s resonance box with the surrounding air. Due to the complexity and the high computational demands, a numerical model including all the parts and the full geometry of the instrument resonance box, the fluid–structure interaction and the interaction with the surrounding air has not yet been simulated. Full article
(This article belongs to the Collection Featured Position and Review Papers in Acoustics Science)
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15 pages, 3416 KiB  
Article
Contribution of Even/Odd Sound Wave Modes in Human Cochlear Model on Excitation of Traveling Waves and Determination of Cochlear Input Impedance
by Wenjia Hong and Yasushi Horii
Acoustics 2022, 4(1), 168-182; https://doi.org/10.3390/acoustics4010011 - 21 Feb 2022
Cited by 2 | Viewed by 3166
Abstract
Based on the Navier–Stokes equation for compressible media, this work studies the acoustic properties of a human cochlear model, in which the scala vestibuli and scala tympani are filled with compressible perilymph. Since the sound waves propagate as a compression wave in perilymph, [...] Read more.
Based on the Navier–Stokes equation for compressible media, this work studies the acoustic properties of a human cochlear model, in which the scala vestibuli and scala tympani are filled with compressible perilymph. Since the sound waves propagate as a compression wave in perilymph, this model can precisely handle the wave–based phenomena. Time domain analysis showed that a sound wave (fast wave) first propagates in the scala vestibuli and scala tympani, and then, a traveling wave (slow wave) is generated by the sound wave with some delay. Detailed studies based on even and odd mode analysis indicate that an odd mode sound wave, that is, the difference in the sound pressures between the scala vestibuli and scala tympani, excites the Békésy’s traveling wave, while an even mode sound determines the input impedance of the cochlea. Full article
(This article belongs to the Special Issue Binaural Audition)
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29 pages, 56953 KiB  
Article
Simulation of Ultrasonic Backscattering in Polycrystalline Microstructures
by Dascha Dobrovolskij and Katja Schladitz
Acoustics 2022, 4(1), 139-167; https://doi.org/10.3390/acoustics4010010 - 18 Feb 2022
Cited by 1 | Viewed by 3499
Abstract
Ultrasonic testing of polycrystalline media relies heavily on simulation of the expected signals in order to detect and correctly interpret deviations due to defects. Many effects disturb ultrasonic waves propagating in polycrystalline media. One of them is scattering due to the granular microstructure [...] Read more.
Ultrasonic testing of polycrystalline media relies heavily on simulation of the expected signals in order to detect and correctly interpret deviations due to defects. Many effects disturb ultrasonic waves propagating in polycrystalline media. One of them is scattering due to the granular microstructure of the polycrystal. The thus arising so-called microstructural noise changes with grain size distribution and testing frequency. Here, a method for simulating this noise is introduced. We geometrically model the granular microstructure to determine its influence on the backscattered ultrasonic signal. To this end, we utilize Laguerre tessellations generated by random sphere packings dividing space into convex polytopes—the cells. The cells represent grains in a real polycrystal. Cells are characterized by their volume and act as single scatterers. We compute scattering coefficients cellwise by the Born approximation. We then combine the Generalized Point Source Superposition technique with the backscattered contributions resulting from the cell structure to compute the backscattered ultrasonic signal. Applying this new methodology, we compute the backscattered signals in a pulse-echo experiment for a coarse grain cubic crystallized Inconel-617 and a fine grain hexagonal crystallized titanium. Fitting random Laguerre tessellations to the observed grain structure allows for simulating within multiple realizations of the proposed model and thus to study the variation of the backscattered signal due to microstructural variation. Full article
(This article belongs to the Special Issue Elastic Wave Scattering in Heterogeneous Media)
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16 pages, 8940 KiB  
Article
Acoustic Attenuation of COVID-19 Face Masks: Correlation to Fibrous Material Porosity, Mask Breathability and Bacterial Filtration Efficiency
by Milena Martarelli, Luigi Montalto, Paolo Chiariotti, Serena Simoni, Paolo Castellini, Gianmarco Battista and Nicola Paone
Acoustics 2022, 4(1), 123-138; https://doi.org/10.3390/acoustics4010009 - 16 Feb 2022
Cited by 1 | Viewed by 3182
Abstract
This paper presents an experimental study on acoustic attenuation of different types of face masks in use by the general population during the COVID-19 pandemic. In particular, measurements are performed on ten samples of masks, of which four are medical masks, three are [...] Read more.
This paper presents an experimental study on acoustic attenuation of different types of face masks in use by the general population during the COVID-19 pandemic. In particular, measurements are performed on ten samples of masks, of which four are medical masks, three are respirators, and three are community masks. Breathability and Bacterial Filtration Efficiency (BFE) tests, in compliance to the standard characterization process of medical masks, are also carried out. The porosity on each layer composing the masks is measured by processing their scanning electron microscopy (SEM) images. The analysis of the results aims to establish if acoustic attenuation is correlated to any of these parameters. It emerges that porosity and breathability are strongly correlated to acoustic attenuation, while bacterial filtration efficiency is not. Full article
(This article belongs to the Special Issue Acoustical Materials)
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12 pages, 26151 KiB  
Article
Design of Digital Constrained Linear Least-Squares Multiple-Resonator-Based Harmonic Filtering
by Miodrag D. Kušljević and Vladimir V. Vujičić
Acoustics 2022, 4(1), 111-122; https://doi.org/10.3390/acoustics4010008 - 1 Feb 2022
Cited by 2 | Viewed by 2639
Abstract
Although voiced speech signals are physical signals which are approximately harmonic and electric power signals are true harmonic, the algorithms used for harmonic analysis in electric power systems can be successfully used in speech processing, including in speech enhancement, noise reduction, speaker recognition, [...] Read more.
Although voiced speech signals are physical signals which are approximately harmonic and electric power signals are true harmonic, the algorithms used for harmonic analysis in electric power systems can be successfully used in speech processing, including in speech enhancement, noise reduction, speaker recognition, and hearing aids. The discrete Fourier transform (DFT), which has been widely used as a phasor estimator due to its simplicity, has led to the development of new DFT-based algorithms because of its poor performance under dynamic conditions. The multiple-resonator (MR) filter structure proposed in previous papers has proven to be a suitable approach to dynamic harmonic analysis. In this article, optimized postprocessing compensation filters are applied to obtain frequency responses of the transfer functions convenient for fast measurements in dynamic conditions. An optimization design method based on the constrained linear least-squares (CLLS) is applied. This way, both the flatness in the passband and the equiripple attenuation in the stopband are satisfied simultaneously, and the latency is reduced. Full article
(This article belongs to the Special Issue Resonators in Acoustics)
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22 pages, 10262 KiB  
Article
Analysis of Sensitivity of Distance between Embedded Ultrasonic Sensors and Signal Processing on Damage Detectability in Concrete Structures
by Joyraj Chakraborty, Xin Wang and Marek Stolinski
Acoustics 2022, 4(1), 89-110; https://doi.org/10.3390/acoustics4010007 - 1 Feb 2022
Cited by 2 | Viewed by 3379
Abstract
Damage detection of reinforced concrete (RC) structures is becoming a more attractive domain due to the safety issues arising in the last few decades. The damage in concrete can be caused by excessive exploitation of the structure or environmental effects. The cracks in [...] Read more.
Damage detection of reinforced concrete (RC) structures is becoming a more attractive domain due to the safety issues arising in the last few decades. The damage in concrete can be caused by excessive exploitation of the structure or environmental effects. The cracks in concrete can be detected by different nondestructive testing methods. However, the available methods used for this purpose have numerous limitations. The technologies available in the market nowadays have difficulties detecting slowly progressive, locally limited damage. In addition, some of these methods cannot be applied, especially in hard-to-reach areas in the superstructures. In order to avoid these deficiencies, an embedded ultrasonic methodology can be used to detect cracks in RC structures. In this study, the methodology of crack detection supported with the advanced signal processing algorithm was proposed and verified on RC structures of various types, and cracks occurring between embedded sensors can be detected. Moreover, different pairs of ultrasonic sensors located in the considered structures are used for the analysis of the sensitivity of distance between them. It is shown that the ultrasonic sensors placed in the range of 1.5–2 m can detect cracks, even when the other methods failed to detect changes in the structure. The obtained results confirmed that diffuse ultrasonic sensor methodology is able to monitor real structures more effectively than traditional techniques. Full article
(This article belongs to the Special Issue Recent Developments in Ultrasound Applications)
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2 pages, 173 KiB  
Editorial
Acknowledgment to Reviewers of Acoustics in 2021
by Acoustics Editorial Office
Acoustics 2022, 4(1), 87-88; https://doi.org/10.3390/acoustics4010006 - 26 Jan 2022
Viewed by 2525
Abstract
Rigorous peer-reviews are the basis of high-quality academic publishing [...] Full article
13 pages, 7016 KiB  
Article
Sideband Peak Count in a Vibro-Acoustic Modulation Method for Crack Detection
by Abdullah Alnutayfat, Sophia Hassiotis, Dong Liu and Alexander Sutin
Acoustics 2022, 4(1), 74-86; https://doi.org/10.3390/acoustics4010005 - 24 Jan 2022
Cited by 7 | Viewed by 3866
Abstract
This paper presents a new method of signal processing for vibro-acoustic modulation (VAM) methods in order to detect damage accumulation in steel samples. Damage in the tested samples was produced by cycle loading, which, with a small amplitude, was used as a pump [...] Read more.
This paper presents a new method of signal processing for vibro-acoustic modulation (VAM) methods in order to detect damage accumulation in steel samples. Damage in the tested samples was produced by cycle loading, which, with a small amplitude, was used as a pump wave to modulate an ultrasonic probe wave. Multiple sideband peaks were observed, which were used to characterize the modulation effect. We propose the effectiveness sideband peak number (SPN) method as an indicator of any damage accumulation when the load cycle is applied. Moreover, after comparing the SPN with the previously used modulation index (MI), we concluded that, for some of the samples, the SPN provided better damage indication than the MI. The presented results can be explained by a simple model of bilinear crack nonlinearity. This model demonstrates that the amplitude dependences of the sideband components on the pump and the probe wave amplitudes are very different from the quadratic crack model that is usually used for MI test explanation. Full article
(This article belongs to the Special Issue Elastic Wave Scattering in Heterogeneous Media)
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21 pages, 4578 KiB  
Article
On the Robustness and Efficiency of the Plane-Wave-Enriched FEM with Variable q-Approach on the 2D Room Acoustics Problem
by Shunichi Mukae, Takeshi Okuzono and Kimihiro Sakagami
Acoustics 2022, 4(1), 53-73; https://doi.org/10.3390/acoustics4010004 - 20 Jan 2022
Cited by 3 | Viewed by 3060
Abstract
Partition of unity finite element method with plane wave enrichment (PW-FEM) uses a shape function with a set of plane waves propagating in various directions. For room acoustic simulations in a frequency domain, PW-FEM can be an efficient wave-based prediction method, but its [...] Read more.
Partition of unity finite element method with plane wave enrichment (PW-FEM) uses a shape function with a set of plane waves propagating in various directions. For room acoustic simulations in a frequency domain, PW-FEM can be an efficient wave-based prediction method, but its practical applications and especially its robustness must be studied further. This study elucidates PW-FEM robustness via 2D real-scale office room problems including rib-type acoustic diffusers. We also demonstrate PW-FEM performance using a sparse direct solver and a high-order Gauss–Legendre rule with a recently developed rule for ascertaining the number of integration points against the classical linear and quadratic FEMs. Numerical experiments investigating mesh size and room geometrical complexity effects on the robustness of PW-FEM demonstrated that PW-FEM becomes more robust at wide bands when using a mesh in which the maximum element size maintains a comparable value to the wavelength of the upper-limit frequency. Moreover, PW-FEM becomes unstable with lower spatial resolution mesh, especially for rooms with complex shape. Comparisons of accuracies and computational costs of linear and quadratic FEM revealed that PW-FEM requires twice the computational time of the quadratic FEM with a mesh having spatial resolution of six elements per wavelength, but it is highly accurate at wide bands with lower memory and with markedly fewer degrees of freedom. As an additional benefit of PW-FEM, the impulse response waveform of quadratic FEM in a time domain was found to deteriorate over time, but the PW-FEM waveform can maintain accurate waveforms over a long time. Full article
(This article belongs to the Special Issue Room Acoustics)
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27 pages, 1240 KiB  
Article
On the Incipient Indicial Lift of Thin Wings in Subsonic Flow: Acoustic Wave Theory with Unsteady Three-Dimensional Effects
by Marco Berci
Acoustics 2022, 4(1), 26-52; https://doi.org/10.3390/acoustics4010003 - 18 Jan 2022
Viewed by 2896
Abstract
Enhanced approximate expressions for the incipient indicial lift of thin wings in subsonic potential flow are presented in this study, featuring explicit analytical corrections for the unsteady downwash. Lifting-line and acoustic-wave theories form the basis of the method, within an effective synthesis of [...] Read more.
Enhanced approximate expressions for the incipient indicial lift of thin wings in subsonic potential flow are presented in this study, featuring explicit analytical corrections for the unsteady downwash. Lifting-line and acoustic-wave theories form the basis of the method, within an effective synthesis of the governing physics, which grants a consistent generalised framework and unifies previous works. The unsteady flow perturbation consists of a step-change in angle of attack or a vertical sharp-edged gust. The proposed model is successfully evaluated against numerical results in the literature for the initial airload development of elliptical and rectangular wings with a symmetric aerofoil, considering several aspect ratios and Mach numbers. While nonlinear downwash and compressibility terms demonstrate marginal (especially for the case of a travelling gust), both linear and nonlinear geometrical effects from a significant taper ratio, sweep angle or curved leading-edge are found to be more important than linear downwash corrections (which are crucial for the circulation growth at later times instead, along with linear compressibility corrections). The present formulae may then be used as a rigorous reduced-order model for validating higher-fidelity tools and complex simulations in industrial practice, as well as for estimating parametric sensitivities of unsteady aerodynamic loads within the preliminary design of aircraft wings in the subsonic regime. Full article
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12 pages, 29787 KiB  
Article
Acoustical Environment Studies in the Modern Urban University Campuses
by Hsiao Mun Lee, Heow Pueh Lee and Zhiyang Liu
Acoustics 2022, 4(1), 14-25; https://doi.org/10.3390/acoustics4010002 - 7 Jan 2022
Cited by 3 | Viewed by 3012
Abstract
The quality of the acoustic environments at Xi’an Jiatong-Liverpool University (XJTLU) and Soochow University (Dushuhu Campus, SUDC) in Suzhou City were investigated in the present work through real-time noise level measurements and questionnaire surveys. Before commencing the measurements and surveys, these two campuses’ [...] Read more.
The quality of the acoustic environments at Xi’an Jiatong-Liverpool University (XJTLU) and Soochow University (Dushuhu Campus, SUDC) in Suzhou City were investigated in the present work through real-time noise level measurements and questionnaire surveys. Before commencing the measurements and surveys, these two campuses’ sound sources were summarized and classified into four categories through on-site observation: human-made, machinery, living creatures, and natural physical sounds. For the zones near the main traffic road, with a high volume of crowds and surrounded by a park, sound from road vehicles, humans talking, and birds/insects were selected by the interviewees as the major sound sources, respectively. Only zone 3 (near to a park) at XJTLU could be classified as A zone (noise level < 55 dBA) with an excellent quality acoustical environment. All other zones had either good or average quality acoustical environments, except zone 1 (near to main traffic road) at XJTLU, with a fair-quality acoustical environment. Full article
(This article belongs to the Special Issue Room Acoustics)
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13 pages, 12209 KiB  
Article
Comparison of Cabin Noise of Airport Express Rail Systems
by Heow Pueh Lee, Sanjay Kumar, Saurabh Garg and Kian Meng Lim
Acoustics 2022, 4(1), 1-13; https://doi.org/10.3390/acoustics4010001 - 29 Dec 2021
Cited by 1 | Viewed by 3209
Abstract
In this paper, the cabin noise of four airport express rail systems, namely the Taiwan Taoyuan International Airport MRT, the Hong Kong Airport Express, RER B service from Paris Gare du Nord to Paris Charles de Gaulle Airport, and the Shanghai Maglev, have [...] Read more.
In this paper, the cabin noise of four airport express rail systems, namely the Taiwan Taoyuan International Airport MRT, the Hong Kong Airport Express, RER B service from Paris Gare du Nord to Paris Charles de Gaulle Airport, and the Shanghai Maglev, have been measured. These four airport express rail systems have different specifications and maximum speeds, ranging from 100 to 300 km/h. The results show a significant low-frequency noise content below 100 Hz, which would not be captured if the measurements were conducted in dB(A). The difference between Leq in terms of dB(C) and dB(A) ranges from 11.3 to 17.0 dB. The maximum speed of the Taoyuan Airport MRT was found to be the lowest at 100 km/h and with the lowest Leq in terms of 66.4 dB(A) and 81.4 dB(C). The Shanghai Maglev has a maximum speed of 300 km/h but a relatively low Leq of 69.7 dB(A), although its top speed is almost three times the maximum of the other airport rail systems. It also has the lowest Lmax of 73.1 dB(A) among the four rail systems. Moreover, the Paris RER B railway system, with its top speed of 120 km/h, was measured to have the highest Leq and Lmax values of 72.8 dB(A) and 83.8 dB(A), respectively. Full article
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