Open Access

Article

Article ID: 3786

A low-frequency sound absorption structure easily manufactured by machine for transformers noise

by Ke Xu, Kanyu Wang, Qinhao Lin, Guoqing Di

Sound & Vibration, Vol.60, No.1, 2026;

Many tonal noises existing in environment have high annoyance degree. It is necessary to develop acoustic materials for targeted absorption of tonal noise in order to reduce its impact. As the primary noise source in substations, transformers emit low-frequency noise with distinct tonal characteristics. According to basic constraints of materials in substations, such as fire resistance, weather resistance, and easy manufacturability by machine, a sound absorption metamaterial (SAM) is developed for absorption of noise from 110 kV transformers in this study. SAM is an aluminum alloy flat plate formed by topological arranging several basic sound absorption units on a plane. Each basic unit consists of two Helmholtz resonators stacked vertically, both of which have an inserted duct. Acoustic performance of SAM is studied by theoretical analysis, numerical simulation, and experimental measurement. Analysis results showed that ratios of its surface acoustic impedance to air acoustic impedance at two resonant frequencies of 100 Hz and 200 Hz were close to 1. Measurement results indicated that sound absorption coefficients respectively reached 0.93 and 0.90 in the normal incident sound field, reached 0.83 and 0.88 in the diffuse sound field. Moreover, the fire resistance grade of SAM reached A1 level, which indicated it was completely non-combustible. Laying SAM on reflective surfaces of structures such as transformer firewalls can reduce the impact of low-frequency noise.

Open Access

Article

Article ID: 3765

Simulation modeling of fiber optic sensor subsystem for force and temperature measurement embedded in composite materials

by Murat Kunelbayev, Aliya Kalizhanova, Ainur Kozbakova, Feruza Malikova, Timur Kartbayev

Sound & Vibration, Vol.60, No.1, 2026;

Despite the extensive body of research on fiber Bragg grating (FBG) sensors, embedding FBGs into composite materials still leaves an important challenge unresolved: improving model accuracy while preserving sensitivity under coupled thermo-mechanical loading. In this work, an integrated mathematical model of an FBG-based fiber-optic sensing subsystem is developed and implemented in MATLAB/Simulink, enabling simultaneous estimation of mechanical action (pressure/strain) and temperature from the Bragg-wavelength shift while explicitly accounting for optical, mechanical, and thermal parameters of the composite host. The model combines Bragg-wavelength shift computation with strain-optic and thermo-optic contributions, a composite stress–strain transfer that maps external pressure to axial fiber strain, transient heat transfer to the grating region, and synthesis of the reflected spectrum and optical power profile for interrogation. A calibration-based decoupling stage is included to separate thermal and mechanical components, and the Simulink workflow supports parameter sweeps and uncertainty analysis. Model outputs agree with reference/experimental data, with a discrepancy not exceeding 4% across the considered operating range. Simulations indicate a pressure sensitivity of 5–15 pm/kPa, a refractive-index sensitivity of up to 500 nm/RIU, and a tunable spectral range of 1530–1570 nm, while remaining stable under simultaneous pressure and temperature variations. The proposed model serves as a practical digital prototype for embedded FBG sensing and supports design optimization, compensation-strategy development, and structural health monitoring scenario evaluation.

Open Access

Article

Article ID: 3603

Fre-MaskCycleGAN-VC: A method of speech articulation and original timbre retention in non parallel corpus of stroke dysarthria

by Ning Jia, Chunjun Zheng

Sound & Vibration, Vol.60, No.1, 2026;

 Aiming at the problem of blurred pronunciation caused by dysarthria in stroke patients, we propose a non parallel corpus speech articulation method based on Fre-MaskCycleGAN-VC. The method consists of three core stages: 1) Aiming at the coexistence of fuzzy speech segments and clear retention segments in dysarthria speech of stroke patients, dynamic speech segmentation preprocessing based on equivalent sound level (Leq) is used to accurately locate the fuzzy segments that need to be enhanced; 2) Feature extraction combining dynamic mask and retro production statistical features; 3) The resolution connected generator and resolution wise discriminators architecture that integrate the frequency processing model. Multiple groups of experiments were carried out on the stroke dysarthria speech data set. The experimental results show that the Fre-MaskCycleGAN-VC method has significantly improved the naturalness of speech (Mean Opinion Score (MOS) increased by 14.2%), intelligibility (WA increased by 2.6%) and timbre fidelity (MFCC correlation coefficient 0.92, F0 error rate 4.2%). Phased evolution experiments show that the model can generate four gradual repair versions from heavily blurred speech to near healthy speech, and the repair effect of grade 2–3 is better than that of the original healthy speech. Through multi-stage feature processing and adversarial training mechanism, we provide a clear speech generation scheme that retains the original timbre for patients with dysarthria

Open Access

Article

Article ID: 3785

Sidelobe suppression in loudspeaker line array via sparse optimization

by Yuxin Liu, Hui Ren, Zhen Li, Qian Zhou

Sound & Vibration, Vol.60, No.1, 2026;

Loudspeaker line arrays, widely deployed in venues such as theaters, stadiums, cinemas, and conference halls, are used to achieve uniform sound field coverage and directional control. Due to the spatial sampling effect of the loudspeaker-line-array discrete structure on an ideal continuous line source, periodic sidelobes inevitably appear in the sound radiation directivity pattern, whose pressure level increases with frequency. To mitigate this problem, a sidelobe suppression approach based on sparse array optimization is proposed. To reduce peak side lobe sound pressure levels, particle swarm optimization (PSO) and constrained genetic algorithms (GA) are employed to achieve random sparse optimization of array element positions and sparse optimization of structural symmetry in loudspeaker line array, respectively. Furthermore, due to the increased side lobe sound pressure level after beam steering, a beam steering algorithm combining sparse constraints with an improved Cosh criterion was proposed to achieve effective side lobe suppression following beam steering. This algorithm maintains the sidelobe suppression effect while achieving digital beam steering, allowing the main beam to be directed to a specific direction without requiring mechanical movement. The simulation results indicate that, by sparsifying loudspeaker units, the proposed method effectively suppresses the sidelobe sound pressure levels, with acceptable performance degradation in main-beam gain. In addition, flexible digital beam steering is archived with the sparsely optimized loudspeaker arrays in a low sidelobe level.

Open Access

Article

Article ID: 3816

Application of 3D-DIC in seismic response analysis of graphite core structures

by Tianbao LAN, Zimin Zhan, Siqi Zhu

Sound & Vibration, Vol.60, No.1, 2026;

This study introduces and validates the application of the three-dimensional digital image correlation (3D-DIC) technique for the seismic assessment of graphite core structures in horizontal Micro-High-Temperature Gas-cooled Reactors (MHTGRs). Addressing a critical gap in conventional instrumentation, the non-contact 3D-DIC method was employed to capture the full-field vibrational response of individual graphite blocks within a loosely stacked core assembly under simulated seismic excitation. A full-scale reactor core model, comprising 31 discrete graphite blocks, was subjected to multi-axis seismic loading on a six-degree-of-freedom shaking table. The displacement-time histories and frequency-domain responses of each block were simultaneously measured using 3D-DIC and compared directly with data from traditional accelerometers. The 3D-DIC technique effectively eliminated the mass-loading and cable interference artifacts inherent in wired sensor arrays and captured the full field information of the graphite core structures. Comparative analysis in both time and frequency domains demonstrated amplitude correlations within ±10% between the two measurement methods. The results confirm that 3D-DIC provides a robust, high-fidelity, and non-invasive alternative for capturing complex, full-field structural dynamics in modular reactor cores. This work establishes a novel methodological framework for the seismic safety evaluation of advanced reactor designs and offers significant insights for enhancing structural health monitoring protocols in nuclear energy applications, thereby contributing to improved seismic resilience and operational safety of future high-temperature gas-cooled reactors.

Open Access

Article

Article ID: 3828

Comparative acoustic analysis of treated and untreated small recording rooms using vocal and room-response measurements

by Korab Shaqiri, Armend Xhoni, Xhevdet Gashi, Lulkaçela Jashari

Sound & Vibration, Vol.60, No.1, 2026;

This study investigates the influence of small-room acoustics on sung vocal quality by comparing two adjacent recording environments of nearly identical dimensions: a professionally treated room (Room A) and an untreated room (Room B). Exponential sine-sweep measurements were conducted using calibrated studio equipment, and room impulse responses were analysed using reverberation metrics (EDT, Topt, RT60), clarity indices (C50, C80), definition (D50), modal behaviour, decay characteristics, and total harmonic distortion (THD). Room A incorporates broadband absorption at primary reflection points, corner bass trapping, rear-wall diffusion, and a double-layer wall structure for low-frequency damping. In addition to room-response measurements, three sustained sung vocal phrases were recorded in both rooms at microphone distances of 10, 30, and 60 cm and analysed using spectrograms and formant trajectories. The results reveal acoustic differences between the two environments. The untreated room exhibits prolonged mid-band decay times (Topt ≈ 1.3–1.9 s), elevated EDT values, reduced clarity (C80 between −5 and +8 dB), low definition (D50 ≈ 30–40%), strong low-frequency modal buildup, and increased harmonic masking. In contrast, the treated room shows studio-appropriate decay times (Topt ≈ 0.20–0.30 s), high clarity (C80 ≈ 15–25 dB), excellent definition (D50 ≈ 90–100%), and smooth decay behaviour. Time–frequency analysis of the vocal recordings confirms that acoustic treatment stabilises temporal and spectral response, yielding cleaner harmonic structure, sharper transient articulation, improved intelligibility, and greater formant precision across all microphone distances. These findings demonstrate the critical role of acoustic treatment in achieving reliable, high-fidelity vocal recordings in small-room environments.

Open Access

Article

Article ID: 3752

Damping ratio measurements of multi-degree-of-freedom systems

by MD MAHBUB ALAM, Feiran Chen, Hongjun Zhu, Chunning Ji, Mostafa Zeinoddini, Vahid Tamimi, Tinghai Cheng

Sound & Vibration, Vol.60, No.1, 2026;

Accurate estimation of modal damping ratios is essential for predicting and controlling the dynamic response of multi-degree-of-freedom (MDOF) structures, particularly in bridge and structural vibration studies. Despite the availability of various methods for estimating damping ratios in MDOF systems, most approaches rely on modal decoupling, which often involves considerable complexity and effort. This work introduces two approaches that eliminate the need for modal decoupling: a filter-based method and an improved Half-Quadratic Gain Method (HQGM). The filter-based approach extracts decay characteristics directly from displacement signals using frequency-domain filtering and logarithmic envelope analysis, achieving damping ratio estimates within 3% error for both free and forced vibrations and for systems with low or high damping. The HQGM, originally formulated for single-degree-of-freedom systems, is extended here to MDOF systems and further enhanced by a correction formula that suppresses coupling-induced secondary peaks in frequency response functions. Comparative analysis demonstrates that while the original HQGM performs well in weakly coupled systems, the improved HQGM yields superior accuracy under strong coupling conditions. Both methods provide a robust framework for identifying damping characteristics across a wide range of dynamic systems. The proposed techniques offer practical advantages for structural engineering applications, where damping properties are difficult to measure directly.

Open Access

Article

Article ID: 3845

Acoustic modeling and analysis for a multipurpose auditorium

by Constantin Bîrțan, Dragoș-Laurențiu Popa, Dan Selișteanu, Cătălin Constantinescu, Monica Roman

Sound & Vibration, Vol.60, No.1, 2026;

The architectural acoustics of the theatrical space and the acoustics of the performance are key factors in achieving optimal acoustics in theater halls. This paper addresses innovative techniques for acoustic study dedicated to theater halls. More precisely, the study of the studio hall of the Colibri Craiova Children and Youth Theater is envisaged. This hall must align with recent trends, that of becoming and transforming, in a very short time, from a theater performance hall to an audition hall for classical music, then into a hall that hosts photographic art exhibitions. To define the model of the acoustic system in a virtual space, the existing auditorium was initially scanned in three dimensions using specific hardware and the Geomagic tool. Then the resulting model was loaded into SolidWorks for further modeling. Using Computer Aided Design techniques and the finite element method, various elements such as loudspeakers and chairs are embedded in the acoustic system model to obtain a realistic representation. Then, based on the obtained model of the acoustic system, several analyses and simulations were performed in the Ansys Workbench program. The key simulation results derived in this work are as follows: combined simulation tools and techniques allowed the auditorium's realistic modelling; acoustic pressures, sound pressure levels (SPL), and frequency band SPL measurements and detailed analyses were achieved, for various configurations and frequencies; the developed models and the performed analysis are useful for the optimization of the acoustic performance. These reported results, with areas of the hall subjected to extreme variations in sound pressure, i.e., with reflection and absorption problems, obtained through simulation, allow the practical implementation of acoustic optimization in other similar halls.

Open Access

Article

Article ID: 3669

Effect of stacking sequence and material properties on the damage detection of laminated composite plates using wavelet transform

by Morteza Saadatmorad, Ramazan-Ali Jafari-Talookolaei, Hamidreza Ghandvar, Orifjon Mikhliev

Sound & Vibration, Vol.60, No.1, 2026;

Damage detection of laminated composite structures is crucial because damage may significantly compromise their structural integrity and lead to catastrophic failures. Traditional non-destructive testing (NDT) methods often prove inadequate for detecting subtle damage, such as delamination or matrix cracking, which can initiate and propagate within the composite material. Therefore, advanced damage detection techniques are essential to ensure the safety and reliability of these structures in various engineering applications. The wavelet transform is a popular non-destructive testing method for processing structural signals in laminated composites. According to the literature review, the effect of changes in laminated composite parameters on damage detection by wavelet transform is an open question. This research aims to investigate the effect of changing the parameters of laminated composite plates on the accuracy of damage detection by two-dimensional discrete wavelet transform (2D-DWT). In this paper, damaged rectangular laminated composite plates (RLCPs) are modeled to introduce damage detection by 2D-DWT and evaluate the effect of changes in RLCPs parameters. The considered parameters are the number of layers, composite material, strengths, size, and thickness of laminate composite layups. Various scenarios are tested, and findings show that among these parameters, the most influential parameter on damage detection of RLCPs by the two-dimensional discrete wavelet transform is the changes in material properties of RLCPs.