Vol. 60 No. 5 (2026): In Progress

Open Access

Article

Article ID: 4406

The Effect of music genre on work productivity in repetitive tasks: An experimental study for sound and vibration applications

by Heri Setiawan, Pawenary, Micheline Rinamurti, Sani Susanto

Sound & Vibration, Vol.60, No.5, 2026;

The physical work environment significantly influences worker performance, with workplace acoustics playing an important role in cognitive functioning and productivity. This study investigated the effect of music genre as an engineered acoustic intervention on productivity during repetitive industrial tasks. Unlike previous studies emphasizing psychological outcomes, this research integrates occupational acoustics, industrial ergonomics, and productivity engineering to evaluate music as a controllable workplace sound variable. A repeated-measures experimental design was conducted under four auditory conditions: no music, jazz, pop, and instrumental music. Productivity was assessed using output and work cycle time during repetitive manual tasks. Data were analyzed using one-way repeated-measures analysis of variance (RM-ANOVA) followed by Bonferroni-adjusted pairwise comparisons. Mauchly's test confirmed that the sphericity assumption was satisfied (W = 0.964, p = 0.119). Music genre had a significant effect on productivity (F(3,897) = 412.68, p < 0.001, partial η² = 0.58). Pop music produced the greatest productivity improvement (33.82%), followed by jazz (13.03%) and instrumental music (10.45%). Bonferroni comparisons showed that pop music significantly outperformed all other auditory conditions, whereas instrumental music did not differ significantly from the control condition. These findings demonstrate that appropriately designed auditory environments can enhance productivity during repetitive work. The study contributes to occupational acoustics by positioning music as an engineered environmental variable that supports human-centered industrial design and operational performance.

Open Access

Article

Article ID: 2029

Influence of parameter changes on honeycomb structure debonding detection based on band gap method

by Ye Yuan, Bin Liu, Chengyou Lei, Zhiguo Zhang

Sound & Vibration, Vol.60, No.5, 2026;

Honeycomb structures have been widely used in many industrial fields due to their excellent properties. However, it is always challenging to rapidly and accurately detect defects such as debonding in the structure, especially in the in-service situation. In response to this, we have proposed an acoustic testing method without coupling agents based on the acoustic band gap feature in the structure. However, the influence of test parameters such as signal excitation and reception on the band gap feature has not been comprehensively and thoroughly investigated, and the parameters have not been optimized. In this paper, the transmission frequency response (TFR) curves were measured, and the band gap features were investigated at different parameters. The results demonstrated that the band gap feature changes a little with the pressure between the probes and the specimen, the amplitude of the exciting signal, the sweep duration, and the detection direction. While it changes significantly with the exciting-receiving distance. Experimental results demonstrated that to form a stable band gap feature, the wave should propagate through at least three honeycomb unit widths before being received. Further analysis indicates that the defect resolution of the proposed method is about two honeycomb unit widths. This work can be used to select the proper detection parameters and further improve the reliability and efficiency of this technique.

Open Access

Article

Article ID: 4413

A practical approach for improving the robustness of MVDR beamformers

by Nguyen Thi Huyen Chau, Quan Trong The, Pham Van Ha

Sound & Vibration, Vol.60, No.5, 2026;

Microphone array (MA) owns the convenience of alleviating the background noise field, interference, and third-party speakers while preserving the original speech component with a high directivity index perspective. MA beamforming utilizes prior spatial information about the direction of arrival of useful signals, the characteristics of the surrounding noise field, the designed geometry of MA, and the obtained parameters after processing received array signals to achieve the advantages of speech enhancement and noise reduction. Minimum Variance Distortionless Response (MVDR) beamformer has the capability of attenuating the surrounding noise field, interference, or third-party talker while saving the original speech component of the desired talker at a specified location. However, under realistic recording scenarios, due to the complex and annoying situation, the movement of the talker during conversation, the error of internal settings for capturing the noisy mixture, the error of sampling frequency, the different time of starting recording of two microphones, the overall effectiveness of the MVDR beamformer is often degraded because of speech distortion and musical noise. In this article, the author proposed an efficient method for enhancing the robustness of the MVDR beamformer under complex and annoying situations. The numerical simulations have shown that the speech distortion was reduced to 5 dB, the musical and residual noise were suppressed to 15.2 dB, and the speech quality was increased from 12.1 to 12.9 dB.

Open Access

Article

Article ID: 4458

Meta-lens for acoustic concentration and enhanced sensing via transformation acoustics

by Botao Yang, Li Cai, KunSheng Xing, Shixin Yu, Huajie Hong

Sound & Vibration, Vol.60, No.5, 2026;

Detecting weak acoustic signals requires broadband energy concentration, but the acoustic power coupled into a device can be strongly curtailed by impedance mismatch at the inlet. Here, we develop a transformation-acoustics-based acoustic meta-lens in which a rectangular virtual domain is mapped to a trapezoidal physical domain, directing incident energy toward a narrow output aperture. In contrast to an air-filled trapezoidal horn with the same outer envelope, the meta-lens reshapes the wavefront through a spatially varying anisotropic mass-density tensor and an equivalent bulk modulus. A cubic-polynomial transition layer is introduced at the inlet to bridge the parameter jump between air and the anisotropic equivalent medium. Finite-element simulations from 200 to 3,000 Hz show positive sound transmission gain for the original design, with a mean value of 3.582 dB. With the transition layer, the mean gain increases to 5.470 dB, the minimum gain rises from 2.695 dB to 3.672 dB, and the mean inlet reflection coefficient decreases from 0.5644 to 0.3239, corresponding to a reduction of 42.6%. A genetic algorithm optimization of the lens length, inlet width, outlet width, and transition-layer thickness further increases the maximum gain from approximately 6.54 dB to 7.36 dB and the minimum gain from approximately 3.67 dB to 4.14 dB. These results indicate that inlet impedance grading and geometric optimization can work together to provide more robust broadband acoustic concentration for weak-signal sensing.

Open Access

Article

Article ID: 4407

Acoustic characterization and modeling of padel courts in urban residential environments

by Aracelly Núñez-Naranjo, Jose Gabriel Vasquez, Paulina Ayala, Marcelo V. Garcia

Sound & Vibration, Vol.60, No.5, 2026;

Padel courts are now common in many residential and mixed-use projects, but the published measurement base for their outdoor noise impact is still small. Recent work has flagged siting conflicts and padel-related acoustic concerns, yet few studies place padel and tennis side by side under the same site conditions. This paper addresses that gap through field measurements and acoustic modeling at one mixed-use development in Abu Dhabi, United Arab Emirates. A padel court and a tennis court were each recorded for a single 15-minute period, and the resulting levels fed an outdoor propagation model. At 10 m, the padel court reached LAeq = 64.2 dB(A) and LAmax = 71.3 dB(A), against LAeq = 58.4 dB(A) and LAmax = 63.6 dB(A) for tennis. Padel showed stronger octave-band content at mid- and high frequencies, consistent with ball-wall impacts and reflections off its rigid glass and metal enclosure. These levels were then carried into a CadnaA model built on ISO 9613-2 to trace propagation toward the nearest residential facades. With 4 m barriers around the padel courts, predicted facade levels at the most shielded positions fell by 4 to 5 dB(A). A single site and one recording per sport bound these conclusions: they describe a case study rather than a general emission standard for padel. What the data do provide is a matched padel-versus-tennis comparison and a worked example of how a small field set can steer acoustic planning early in residential design.

Open Access

Article

Article ID: 4224

Weak fault feature extraction and system fault analysis under strong noise

by Tiejun Cui, Zijian Cui, Shasha Li

Sound & Vibration, Vol.60, No.5, 2026;

To tackle the intractable problems including weak fault feature extraction and evolution uncertainty quantification for complex systems in strong noise environments, a novel method for weak fault diagnosis and evolution analysis is proposed. This method integrates the fuzzy structured element (FSE), cloud model (CM), and Space Fault Network (SFN). The method centers on adaptive wavelet denoising, fault feature cloudification, and SFN probability propagation. The fault signal under strong noise is reconstructed by optimizing the wavelet threshold with the FSE. The uncertainty encapsulation of the peak factor of fault features is realized based on the CM to establish the feature CM. The fault event topology is constructed relying on the SFN. The quantitative transfer of uncertainty in the fault evolution is achieved combined with cloud algebra. Verified by the inner ring pitting fault of axle box bearings, the results demonstrate that the proposed method can extract the fault characteristic frequency of 250.5 Hz. The derived fault probability CM (0.680, 0.059, 0.023) accurately quantifies the system risk level. This result is consistent with the actual fault evolution law in engineering practice. This method provides technical support for early fault warning and maintenance of complex industrial system. Furthermore, comparative experiments confirm its superiority over traditional methods in noise suppression and feature retention. Parameter analysis is also discussed to improve engineering generalization.

(This article belongs to the Special Issue Vibration and System Fault Analysis)

Open Access

Article

Article ID: 4180

Audio signal approximation and fuzzy logic-based acoustic noise-risk assessment using Fourier–Dirichlet analysis and hyperbolic series representations

by Yogeesh Nijalingappa, Asokan Vasudevan, Soon Eu Hui, Zetty Pakir Mastan, Choo Wou Onn, Mohammed Almakki

Sound & Vibration, Vol.60, No.5, 2026;

This paper presents an acoustics-oriented study that combines classical Fourier–Dirichlet signal approximation with a fuzzy logic-based noise-risk interpretation layer. The harmonic-analysis part revisits Fourier series for periodic and quasi-periodic audio waveforms under classical Dirichlet conditions and restates these conditions in a form that is practically checkable on sampled audio segments; no new convergence theorem is claimed. A complementary hyperbolic-series representation is used as an illustrative analytical tool for discussing compact representations of selected waveform classes. The applied contribution of the paper is a Mamdani fuzzy inference system that converts uncertain acoustic measurements into an interpretable Noise-Risk Index using A-weighted equivalent sound level, daily exposure duration, and source–receiver distance. The fuzzy model uses triangular/trapezoidal memberships, an interpretable rule base, min–max inference, and centroid defuzzification. To show the practical usefulness in sound and vibration practice, one waveform-reconstruction example and a twelve-scenario acoustic-risk dataset with regard to traffic, workshop, generator room, and public address contexts are reported in the study. The resulting fuzzy system generates a range of risk scores from 22 to 92, lying within the safe, caution, high, and critical level categories and depicts smooth transitions as we approach decision boundaries where a crisp threshold can often be challenging to decode. This work thus establishes Fourier analysis as the underlying level for acoustic signals and fuzzy inference as a decision-support level in the context of uncertainty-based exposure assessment. The current coupling is linear instead of feature-driven: the Fourier-based signal description forms the basis for exposure descriptors, and the fuzzy system processes these descriptors given uncertainty.

Open Access

Article

Article ID: 4463

Thermoacoustic loss-of-chaos in large diesel engines: Case study on long-timescale events

by Alice Elizabeth González, Pablo Gianoli-Kovar, Héctor Campello-Vicente

Sound & Vibration, Vol.60, No.5, 2026;

This work aims to analyze the occurrence of anomalous acoustic emissions that appeared after the modification of the combustion chambers of eight reconverted four-stroke diesel engines (10 MW each, urban installation). Large variability of the sound pressure levels emitted by the same engine under nominally identical operating conditions was recorded. The phenomenon was interpreted at first as thermoacoustic instability developing inside the combustion chambers, supported by the simultaneous observation of large fluctuations in the fuel inlet pressure. Four precursor episodes were documented through an operational signature qualitatively consistent with the loss-of-chaos pattern reported in the literature. However, most of these events anticipated a decrease in the sound pressure levels in the considered third-octave band, the opposite of what is expected to happen in thermoacoustic instability events. The 0–1 test for loss-of-chaos was applied, ratifying the occurrence of a long precursor condition that should anticipate the installation of a thermoacoustic instability. The shortest timescale of the precursor states was 500 s, in contrast with the millisecond- to second-range timescales typically reported in laboratory-scale studies. Although the sample is limited, the observations suggest that long precursors may occur in megawatt-scale installations, anticipating different types of sudden changes in the operational conditions (not only thermoacoustic instability). If confirmed, it would open a practical window for feedforward active noise control to avoid abrupt changes in the engine operating conditions. A hybrid silencing strategy is proposed as a design recommendation. Limitations and the current operational status of the installation are also discussed.

Open Access

Article

Article ID: 4497

Broadband vibration suppression of a nonlinear beam using a fractional-order inerter-assisted tuned mass damper

by Yogeesh  Nijalingappa, Suleiman Ibrahim  Mohammad, Tarun Madan  Kanade, Asokan  Vasudevan, P. William, Mohammad Faleh  Ahmmad Hunitie

Sound & Vibration, Vol.60, No.5, 2026;

This study presents an analytical method for reducing broadband vibration in a simply supported nonlinear beam fitted with an inerter-assisted tuned mass damper. The first bending mode is obtained by Galerkin projection, geometric nonlinearity is represented by a cubic stiffness term, and beam damping is described by a fractional-order derivative. A single-harmonic balance formulation converts the coupled equations into an amplitude-dependent cubic equation that is solved directly over the forcing-frequency range. The absorber is optimized with respect to inertance ratio, tuning ratio, damping ratio, and fractional order. The objective is to minimize the largest beam amplitude between 7 and 14 Hz. For the beam considered, increasing the inertance ratio from 0 to 0.20 raises the peak-response reduction from about 4.5% to about 52%, while the physical absorber mass ratio remains 0.04. The optimal tuning ratio decreases as inertance increases, whereas the required absorber damping generally increases. A ±5% stiffness study shows that the optimized designs remain effective under moderate uncertainty. The results also clarify how fractional damping modifies the balance between effective stiffness and dissipation, enabling the proposed maps to support robust initial absorber selection before detailed high-fidelity validation. The resulting design maps and regression equations provide useful preliminary settings for later finite-element or experimental verification.

Open Access

Article

Article ID: 4326

Study on the vibration transmission speed and damping characteristics of piano soundboard

by Jinyi Chen, Guanzheng Wan, Lan He, Jing Zhou, Haotian Cui, Zhenbo Liu

Sound & Vibration, Vol.60, No.5, 2026;

The piano soundboard converts string vibrations into radiated sound, affecting tonal quality. However, the propagation and energy dissipation of vibration waves along different grain directions remain insufficiently studied. To study vibration wave propagation and dissipation in piano soundboards of different composite processes, four quarter-size soundboards (moisture content 7%–9%) were selected: one tone-wood soundboard (T) and three laminated boards (L90 with vertical core, L55 with inclined core, L180 with horizontal core). Free boundary conditions were simulated via elastic rope suspension; time-domain responses were recorded at 16 kHz sampling (2,048 points). The angle α between the line connecting the two accelerometers and the core layer direction (for T, grain direction defined as 0°) was varied from 0° (parallel) to 90° (perpendicular) in 15° steps. Wave velocity and damping ratios were extracted using gradient and envelope fitting methods. The results showed: T exhibited the highest wave velocity from 0° to 90°, decreasing with angle (R² = 0.985), and a maximum anisotropy ratio of 4.59; L90 was angle-insensitive with weak correlation (R² = 0.735); L55 showed a trend similar to T (R² = 0.990); the wave velocity of L180 generally decreased but rebounded at 30°. Broadband damping ratios were 0.002–0.007, with T averaging 0.0040 (maximum 0.0058), L90 the lowest (average 0.0035, maximum 0.0049), L55 the highest (average 0.0051, maximum 0.0065), and L180 averaging 0.0038 (maximum 0.0062). Narrowband analysis showed that the damping ratios of all soundboards decreased exponentially with increasing frequency. The results guide piano soundboard vibration, material selection, and processing.

Open Access

Article

Article ID: 4449

LBM-IBM simulation of aeolian vibration of a stranded overhead conductor with resolved cross-sectional geometry

by Xiaoyu Luo, Yunfeng Zou, Ming Nie, Ganyu Wang, Yongchun Liang, Zejia Yang

Sound & Vibration, Vol.60, No.5, 2026;

The outer surface of overhead transmission conductors is formed by wound aluminium strands, exhibiting a corrugated geometric profile. However, aerodynamic analyses typically simplify this geometry to a smooth cylinder. How this simplification influences the fluid-structure coupled vortex-induced vibration response remains unclear. This paper addresses this research gap through comparative numerical simulations between a geometrically refined stranded conductor and an equivalent smooth cylinder with identical outer diameter. A two-dimensional lattice Boltzmann–immersed boundary method (LBM-IBM) computational framework was developed on a fixed Cartesian grid and coupled with a Newmark-β transverse oscillator. Reduced-velocity sweeps and supplementary high-resolution flow-field cases were conducted under fully matched structural and fluid parameters. Results show that the smooth cylinder exhibits a narrow classical lock-in region with rapid amplitude decay beyond the peak. In contrast, the stranded conductor sustains large-amplitude vibrations over a considerably wider velocity range, accompanied by a substantial increase in time-averaged drag. Vorticity and phase analyses indicate that strand grooves function as local flow separation promoters, altering the lift-velocity phase relationship and maintaining positive aerodynamic energy input beyond the desynchronization boundary of the smooth cylinder. The findings confirm that strand-scale surface features significantly broaden the lock-in range, a conclusion that merits incorporation into high-fidelity aerodynamic models to improve conductor response prediction accuracy.

Open Access

Article

Article ID: 4498

Closed-form topological and spectral invariants for periodic ladder-based vibration networks

by Suleiman Ibrahim Mohammad, Yogeesh Nijalingappa, Asokan Vasudevan, P. William, Jonathan Lee, Tarun Madan Kanade , Mohammad Faleh Ahmmad Hunitie

Sound & Vibration, Vol.60, No.5, 2026;

This paper investigates two closely related network families, the open ladder graph and the cylindrical ladder graph, as exact test beds for degree-based, eccentricity-based, distance-based, and spectral descriptors. The two graphs can be seen as graph-theoretic two-rail models with and without periodic closure, allowing an exact comparison boundary effects versus cyclic-closure-effect. We obtain closed expressions for the Sombor index, reduced Sombor index, Sombor coindex, reduced Sombor coindex, first and second Zagreb indices, forgotten index, Randić index geometric-arithmetic index atom-bond connectivity index total eccentricity average eccentricity eccentric connectivity index Wiener Index radius diameter and total π-electron energy. For the energy part, we derive exact spectral sums and trigonometric closed forms using the Cartesian-product spectra of the underlying path and cycle graphs. Numerical tables and plots show that periodic closure increases all degree-regularity descriptors while sharply decreasing distance descriptors. In contrast, the total π-electron energy changes only by a small oscillatory amount, and both families share the same asymptotic energy density. The adjacency-based energy indeed can be interpreted explicitly as graph energy, instead of mechanical vibrational energy. An additional mass-spring formulation rooted on the graph Laplacian provides the analog equations of motion, natural-frequency spectra, dispersion samples and frequency-response operator for those analogous ladder topologies.

Open Access

Article

Article ID: 4490

Condition-based maintenance threshold determination for gearbox fault progression using vibration envelope features and accelerated life testing

by Asokan Vasudevan, Suleiman Mohammad, Mohammad Ahmmad Hunitie, Gui Jie, Jonathan Lee, Mbiatke Andrew

Sound & Vibration, Vol.60, No.5, 2026;

Gearbox failures represent a critical problem faced by industrial machines, considering the impacts of such failures on machine reliability, efficiency, and maintenance cost. Despite the well-established use of vibration-based condition monitoring techniques for diagnosing the presence of faults, few attempts have been made in transforming information about fault progression into thresholds that could be used in making condition-based maintenance (CBM) decisions. In this work, a CBM system for analysing gearbox fault progression based on vibration envelope features is presented, alongside accelerated life testing. An experimental approach has been adopted, whereby accelerated life testing was performed to induce gearbox degradation progressively. Then, vibration data were analysed through the envelope technique, out of which six vibration envelope features, namely RMS Envelope, Kurtosis, Crest Factor, Peak Amplitude, Envelope Energy, and Sideband Energy Ratio, were derived and analysed based on their sensitivity through correlation, monotonicity, trendability, and separability tests. Thereafter, a composite health index based on the most sensitive features was formulated, and a multilevel maintenance threshold system consisting of Alert, Warning, and Critical levels was created. The findings show that Envelope Energy, Sideband Energy Ratio, and Kurtosis have the highest sensitivity to degradation and can accurately represent the evolution of gearbox faults. The composite health index shows a strong correlation with the extent of degradation (R² = 0.962) and successfully discriminates between different health states of the gearbox. The developed framework for determining maintenance thresholds achieves an accuracy of 94.9%, which allows accurate identification of maintenance intervention phases.

Open Access

Article

Article ID: 4152

Simulation and algorithmic implementation of ultrasonic phased-array imaging for curved lead-seal surfaces

by Jian Cheng, Liguang Hu, Fengyin Zhang, Quan Zhang, Lianbing Wang

Sound & Vibration, Vol.60, No.5, 2026;

In ultrasonic phased-array sector scanning of lead-seal defects in high-voltage cable terminations, incomplete contact between the probe and the curved lead-seal surface may cause acoustic-beam spreading, focal shift, weak defect echoes, image distortion, and near-surface artefacts. To address these problems, this study proposes a curvature-adaptive ultrasonic phased-array imaging method for curved lead-seal surfaces. First, an acoustic-field simulation model of the curved lead-seal structure was established to analyze beam propagation through the couplant layer and the lead seal. Then, a delay law based on Fermat’s principle and Snell’s law was derived to account for the curved interface and the two-layer propagation path. The calculated delays were applied during post-processing delay-and-sum beam synthesis, followed by Hilbert-envelope extraction and angular coordinate correction. Numerical results show that the curved interface causes beam spreading and focal-position shift compared with a flat interface, which explains the localization deviation in conventional phased-array imaging. Laboratory experiments were further conducted on lead-seal specimens with internal defects, interlayer defects, and combined internal–interlayer defects. For the internal defect with an actual depth of 15.0 mm, the positioning error was reduced from 13.33% to 6.67%. For the interlayer defect with an actual depth of 25.0 mm, the positioning error was reduced from 10.00% to 4.00%. The results demonstrate that the proposed method improves defect localization accuracy, morphology restoration, and imaging consistency compared with conventional phased-array imaging. This study provides a simulation-supported and experimentally validated method for curved lead-seal ultrasonic imaging, although further validation is still required for naturally formed irregular cracks, variable coupling conditions, and field cable-terminal applications.