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20 pages, 7270 KB

Open AccessArticle

Theoretical Estimation of Wheat Straw Sound Absorption Coefficient Using Computed Tomography Images

by Shuichi Sakamoto, Kohta Hoshiyama, Yoshiaki Kojima, Kenta Saito and Zulhafiz Syazmi Bin Roslan

Appl. Sci. 2025, 15(16), 8803; https://doi.org/10.3390/app15168803 - 9 Aug 2025

Viewed by 377

Abstract

Wheat straw, which is a by-product of wheat production and has a tubular structure, is typically used for animal feed and compost. This study estimated the sound absorption coefficient of wheat straw based on cross-sectional computed tomography (CT) images. After image processing, the [...] Read more.

Wheat straw, which is a by-product of wheat production and has a tubular structure, is typically used for animal feed and compost. This study estimated the sound absorption coefficient of wheat straw based on cross-sectional computed tomography (CT) images. After image processing, the surface area of the wheat straw skeletal outline and the volume of the void area were determined. The propagation constant and characteristic impedance of the void area were obtained by approximating the clearance between two parallel planes representing the void area walls. Each CT image was represented as a transfer matrix to calculate the sound pressure and particle velocity, and the transfer matrix method was used to derive the normal incidence sound absorption coefficients. The measured tortuosity was considered when calculating the normal incidence sound absorption coefficient. The CT images were corrected to reflect the lack of sound absorption by the porous part of the thick-walled portion by considering it as a solid structure. The theoretical sound absorption coefficients calculated from the corrected images were in good agreement with the measured sound absorption coefficients. Full article

(This article belongs to the Special Issue Advances in Architectural Acoustics and Vibration)

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27 pages, 11156 KB

Open AccessArticle

Echo Analysis in Iberian Bullfighting Arenas Through Objective Parameters and Acoustic Simulation

by Sara Girón, Manuel Martín-Castizo and Miguel Galindo

Appl. Sci. 2025, 15(14), 7825; https://doi.org/10.3390/app15147825 - 12 Jul 2025

Viewed by 478

Abstract

The existence of echoes in an acoustic event can ruin the capture of a spoken message and the perception of a piece of music. Likewise, in the performers’ area, clear hearing is essential for the coordination and execution of the ensemble. Bullrings are [...] Read more.

The existence of echoes in an acoustic event can ruin the capture of a spoken message and the perception of a piece of music. Likewise, in the performers’ area, clear hearing is essential for the coordination and execution of the ensemble. Bullrings are buildings with a circular plan in which echo-encouraging focalisations can occur. Since bullrings lack a roof, the density of reflections is lower than that in a closed area, and therefore strong isolated reflections perceived by the audience as an echo can be created. In this work, calculations of the echo parameter (Echo Criterion EK) and inspection of impulse responses and energy decay curves are obtained in an on-site measurement campaign in the audience zones and in arena areas where the EK parameter exceeds the thresholds. To this end, four bullrings very emblematic of the Iberian Peninsula together with a very prominent Roman amphitheatre in a relatively good state of conservation in the Roman province of Hispania comprise the study cases. Experimental results of the EK parameter and from acoustic simulation in two of the bullrings present good concordance and show that there is no echo for music in any of the venues in the spectator zones and that the most critical area is when source and receiver are both in the arena, where even double and triple echoes appear. Full article

(This article belongs to the Special Issue Advances in Architectural Acoustics and Vibration)

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36 pages, 29858 KB

Open AccessArticle

Mode Shape Extraction with Denoising Techniques Using Residual Responses of Contact Points of Moving Vehicles on a Beam Bridge

by Guandong Qiao, Xiaoyue Du, Qi Wang and Liu Jiang

Appl. Sci. 2025, 15(13), 7059; https://doi.org/10.3390/app15137059 - 23 Jun 2025

Viewed by 306

Abstract

This work introduces a novel approach to extract beam bridge mode shapes using the residual response between consecutive contact points of vehicles passing through a bridge. A comprehensive investigation is conducted on several critical parameters, including window size, vehicle velocity, road roughness, and [...] Read more.

This work introduces a novel approach to extract beam bridge mode shapes using the residual response between consecutive contact points of vehicles passing through a bridge. A comprehensive investigation is conducted on several critical parameters, including window size, vehicle velocity, road roughness, and beam damping property, as well as the influence of traffic flow. To enhance the mode shape extraction performance using the approximate expression of the contact points’ displacements under noisy disturbance, two new signal denoising methods, CEEMDAN-NSPCA and CEEMDAN-IWT, are proposed based on complete ensemble empirical mode decomposition (CEEMDAN). CEEMDAN-NSPCA integrates CEEMDAN with principal component analysis and a coefficient-based filtering strategy. While CEEMDAN-IWT utilizes an improved wavelet thresholding technique with adaptive threshold selection. The numerical simulations demonstrate that both methods could effectively attenuate high-frequency noise with small amplitudes and retain low-frequency components. Among them, CEEMDAN-IWT exhibits superior denoising performance and greater stability, making it particularly suitable for robust modal identification in noisy environments. Full article

(This article belongs to the Special Issue Advances in Architectural Acoustics and Vibration)

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26 pages, 8754 KB

Open AccessArticle

Weight Effects on Vertical Transverse Vibration of a Beam with a Nonlinear Energy Sink

by Xiang Fu, Sha Wei, Hu Ding and Li-Qun Chen

Appl. Sci. 2025, 15(3), 1380; https://doi.org/10.3390/app15031380 - 29 Jan 2025

Cited by 2 | Viewed by 831

Abstract

Reductions in the vibration of a continuum system via a nonlinear energy sink have been widely investigated. It is usually assumed that weight effects can be ignored if the vibration is measured from the static equilibrium configuration. The present investigation reveals the dynamic [...] Read more.

Reductions in the vibration of a continuum system via a nonlinear energy sink have been widely investigated. It is usually assumed that weight effects can be ignored if the vibration is measured from the static equilibrium configuration. The present investigation reveals the dynamic effects of weight on the vertical transverse vibrations of a Euler–Bernoulli beam coupled with a nonlinear energy sink. The governing equations considering and neglecting weights were derived. The equations were discretized with some numerical support. The discretized equations were analytically solved via the harmonic balance method. The harmonic balance solutions were compared with the numerical solution via the Runge–Kutta method. Finite element simulations were performed via ANSYS software (version number: 2.2.1). Free and forced vibrations, predicted by equations considering or neglecting the weights, were compared with the finite element solutions. For the forced vibrations, the amplitude–frequency responses determined by the harmonic balance method agree well with those calculated by the Runge–Kutta method. The free and forced vibration responses predicted by the equations considering the weights are closer to those computed by the finite element method than the responses predicted by the equation neglecting the weights. The assumption that weights can be balanced by static deflections leads to errors in the analysis of the vertical transverse vibrations of a Euler–Bernoulli beam with a nonlinear energy sink. Full article

(This article belongs to the Special Issue Advances in Architectural Acoustics and Vibration)

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30 pages, 50440 KB

Open AccessArticle

Development of the Viscous Plane Damper Applicable in Limited Space within Structures Subjected to Dynamic Loads

by Mohd Ridzuan Bin Mohd Ali and Farzad Hejazi

Appl. Sci. 2024, 14(19), 9029; https://doi.org/10.3390/app14199029 - 6 Oct 2024

Cited by 1 | Viewed by 2001

Abstract

Shipping impact and wave loads impose dynamic loads on jetties and platforms in the sea, which cause the vibration of structures. Recently, many advanced viscous damper devices have been developed for implementation in structures to diminish structural vibration due to earthquakes or wind. [...] Read more.

Shipping impact and wave loads impose dynamic loads on jetties and platforms in the sea, which cause the vibration of structures. Recently, many advanced viscous damper devices have been developed for implementation in structures to diminish structural vibration due to earthquakes or wind. However, the longitudinal configuration of conventional viscous damper devices requires adequate space to locate the damper device within the frame structure, which limits the application of viscous dampers for use in jetties or platforms to dissipate the vibrations imposed by ship impact or wave force. For this reason, in this study, an attempt has been made to develop a new viscous plane damper device applicable in limited space positions where the longitudinal damper device is not able to fit. For this purpose, the initial design for the viscous plane damper device is proposed, and the prototype of the device is manufactured. Then, the performance of the fabricated viscous plane damper is examined through experimental tests by applying cyclic loads using a dynamic actuator. In order to investigate the effect of the diameter and configuration of the piston’s orifices, five different diameters for the orifices of 1, 2, 5, 8, and 10 mm are included, and three different distribution configurations of the orifices in the piston plate as Configurations A, B, and C are manufactured and tested experimentally. The lab testing is conducted by applying cyclic loads with different frequencies to evaluate the performance of the developed plane damper device under various load velocities. Accordingly, the dynamic performance of the damper device, including the damping force, effective damping and stiffness and the energy dissipation capacity obtained from the hysteresis response (force–displacement result), is investigated. The results of the experimental tests prove the functionality of the developed device to generate the desired damping force and vibration energy dissipation during applied cyclic loads. Therefore, the new plane damper device can be implemented in any structure to dissipate the effect of imposed vibration. Full article

(This article belongs to the Special Issue Advances in Architectural Acoustics and Vibration)

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13 pages, 2719 KB

Open AccessArticle

Tunable Perforated Panel Sound Absorbers for Variable Acoustics Room Design

by Jesús Carbajo, Pedro Poveda-Martínez, Luís Godinho, Andreia Pereira, Anna Gaspar, Paulo Amado-Mendes, Diogo Mateus and Jaime Ramis

Appl. Sci. 2024, 14(5), 2094; https://doi.org/10.3390/app14052094 - 2 Mar 2024

Cited by 4 | Viewed by 2405

Abstract

Variable acoustics systems are promising engineering developments for multi-purpose rooms and workspaces in many buildings. However, due to space requirements associated with most of the tuning devices used for that purpose, these solutions are hardly adopted in practice. In this work, two innovative [...] Read more.

Variable acoustics systems are promising engineering developments for multi-purpose rooms and workspaces in many buildings. However, due to space requirements associated with most of the tuning devices used for that purpose, these solutions are hardly adopted in practice. In this work, two innovative tunable sound absorbers that cope with this drawback are proposed, one consisting of rotating perforated panels and the other being a panel with an iris-type aperture. Compared with conventional perforated panel sound absorbers, the designed solutions yield a variable open area ratio system, whose configuration allows tuning the absorption bandwidth without misusing space. To assess their sound absorption coefficient, impedance tube experiments were carried out following the standardized method described in ISO 10534-2 over specimens fabricated for this purpose using laser cutting and additive manufacturing technology. The results not only show their good sound absorption performance but also highlight their tuning capabilities. Complementarily, a model based on the ray tracing method was developed to evaluate the performance of these solutions in a case study room, for different occupancy levels, with the results supporting the previous assertions and revealing the improved intelligibility features when used in such scenarios. The proposed solutions, together with the prediction model, provide a feasible approach for the design and development of tunable sound absorbers in variable room acoustics. Full article

(This article belongs to the Special Issue Advances in Architectural Acoustics and Vibration)

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18 pages, 4132 KB

Open AccessArticle

Comparison of Different Omnidirectional Sound Sources with the Validation of Coupled Speakers as a Measurement Source for Room Acoustics

by Bartlomiej Chojnacki, Maria Brzóska and Joanna A. Fijałkowska

Appl. Sci. 2023, 13(24), 13058; https://doi.org/10.3390/app132413058 - 7 Dec 2023

Cited by 1 | Viewed by 2378

Abstract

Omnidirectional sources used in room acoustics usually take the form of multi-speaker sources. Few alternatives for the most commonly used dodecahedral sound source have been derived recently. The project aimed to measure room acoustic parameters using three different sound sources: a dodecahedron, a [...] Read more.

Omnidirectional sources used in room acoustics usually take the form of multi-speaker sources. Few alternatives for the most commonly used dodecahedral sound source have been derived recently. The project aimed to measure room acoustic parameters using three different sound sources: a dodecahedron, a cube, and a new source of two coupled loudspeakers. The measurements were made by rotating the sources every 15 degrees. The differences in the EDT, T30, D50, and C80 parameters in the function of the rotation angle of the sources were analyzed. Statistical analysis was carried out to examine the sensitivity of the measured parameters’ JND (just a noticeable difference) on the source’s rotation angle. This presentation will show the results and analysis of measurements showing the influence of the used source on obtained parameters and the validation of coupled speakers’ use. A comprehensive discussion of the results obtained with different sources (coupled, dodecahedral, cubic) will be provided. The results confirmed using the coupled speakers as an alternative for omnidirectional sound source in the range of 250–2000 Hz. Full article

(This article belongs to the Special Issue Advances in Architectural Acoustics and Vibration)

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20 pages, 6742 KB

Open AccessTechnical Note

Thermal and Acoustic Design of a Shelter for High-Voltage Electrical Equipment

by Somayan Basu and Edoardo Piana

Appl. Sci. 2025, 15(2), 957; https://doi.org/10.3390/app15020957 - 19 Jan 2025

Viewed by 863

Abstract

The growing demand for electric energy requires smarter and quicker distribution systems. In urban contexts, a smarter distribution of electric power to various classes of consumers, according to their demands, is possible through compact sorters. Since this type of device must be protected [...] Read more.

The growing demand for electric energy requires smarter and quicker distribution systems. In urban contexts, a smarter distribution of electric power to various classes of consumers, according to their demands, is possible through compact sorters. Since this type of device must be protected from unwanted access by people, wildlife and inclement weather, protection must be placed around the main components. When deployed in urban areas, housing can be built using solid panels. However, there is a risk of overheating the vital and costly parts of the system with the possibility to cause malfunction and, in extreme cases, damage. Moreover, leaving the system open exposes nearby residents to the impulsive noise produced during the operation of the switchgears being part of the system. Hence, there is a need to reach a suitable trade-off between optimal heat transfer and noise propagation. This article attempts to explain the thermal design backed by experimental validation and the noise-spreading modelling necessary to assess the respect of environmental legislation. Full article

(This article belongs to the Special Issue Advances in Architectural Acoustics and Vibration)

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