Sound Field Research Articles

Numerical investigation on the propulsive performance and acoustic characteristics of two flapping foils in tandem

A numerical investigation is conducted on the propulsive performance and acoustic characteristics of two flapping foils in tandem at Re = 200 in uniform flow using the lattice Boltzmann method combined with the immersed boundary method. The effects of phase difference and horizontal spacing on hydrodynamics and acoustics are studied. The results indicate that the propulsive performance and acoustic characteristics of the in-phase foils and anti-phase foils are completely different. As the horizontal spacing increases, the change trend of their propulsive performance is completely opposite. The propulsive performance of the in-phase foils shows a trend of first weakening and then enhancing, while the anti-phase foils show a trend of first enhancing and then weakening. For sound field, the in-phase foils exhibit a dipole-like pattern similar to that of a single foil, while it exhibits a quadrupole-like pattern for anti-phase foils. Compared to the in-phase foils and single foil, the maximum effective sound pressure value of the anti-phase foils is smaller. Meanwhile, the relationship between propulsive performance and acoustic characteristics is analyzed, and it is found that the correlation coefficients follow the same variation pattern. The presented work can offer valuable insights for designing and controlling new bio-inspired autonomous underwater vehicles aimed at suppressing flow noise.

From Body Narratives to Cultural Identity: A Study of Ritualised Representations in Modern Sound Media

For modern people who have been under the hegemony of visual picture for a long time, the sensory balance in the Internet era is the key to releasing body appeals and getting rid of individual heterogeneity. The unique sense of imagination, immersion and companionship created by modern sound media to the audience can directly arouse emotional resonance, so as to achieve the group identity of sound field culture. Based on the perspective of ritual view of media, this paper analyzes the ritualized representation mode of modern sound media from two dimensions: the morphological evolution of body narrative of sound media and the deep aggregation of auditory culture, and thus corresponds to the dual aspects of ritualized representation: the embodied presentation and landscape modeling of sound media. By clarifying the subject’s holistic and differentiated identity cognitive thinking in media practice and the social auditory cultural aggregation phenomenon, the ritualized signs of modern sound media are deeply investigated in order to provide a theoretical perspective for the cultural research of modern sound media.

Analysis of the effect of cavitation on internal fluid excitation characteristics of centrifugal pumps

To explore the influence of cavitation on the internal fluid excitation characteristics of pumps, numerical simulations and performance testing evaluations were performed on the IS65-50-125 centrifugal pump. The prototype pump's exterior characteristic and cavitation performance curves, as well as its bubble volume distribution, were successfully replicated using numerical computations. The effect of cavitation on the internal pressure pulsation characteristics of the centrifugal pump under various operating situations was comprehensively investigated, indicating a relationship between the degree of cavitation and the root mean square values of pressure pulsation. Special emphasis was placed on the changes in features at intermediate and high frequencies, as well as the processes of rising bubble volume and vortex shedding at the impeller trailing edge on pressure pulsation. To validate the simulation results, a centrifugal pump vibration and noise testing platform was built, and studies on vibration intensity and internal sound field noise were conducted. The experimental results revealed that the vibration intensity and internal sound field sound pressure level of the centrifugal pump rose as cavitation conditions deteriorated, confirming the modeling results. This study's significant innovation is the precise identification of the pump's performance changes under different operating conditions by monitoring pressure pulsation changes at various frequencies, as well as an in-depth discussion of the impact mechanism of cavitation phenomena on the internal fluid excitation behavior of centrifugal pumps. The study demonstrates differences in pressure pulsation characteristics on the suction and pressure sides under various cavitation situations, as well as the process of vortex creation and shedding generated by bubbles in the impeller input channel during severe cavitation. This gives new theoretical basis for pump vibration and noise reduction, as well as significant improvements in centrifugal pump performance and stability.

Analytical solution for acoustic radiation force and torque on a spheroid near a rigid or free planar boundary.

An analytical solution is developed for the acoustic radiation force and torque caused by an arbitrary sound field that is incident on a compressible spheroid of any size near a planar boundary that is either rigid or pressure release. The analysis is an extension of a recent solution for a compressible sphere near a planar boundary [Simon and Hamilton, J. Acoust. Soc. Am. 153, 627-642 (2023)]. Approximations that account for a boundary formed by a two-fluid interface may be incorporated as in the previous analysis for a sphere. The present solution is based on expansions of the total acoustic pressure field in spheroidal wave functions and the use of addition theorems. Verification of the solution is accomplished by comparison with a finite element model. Examples are presented for incident fields that are either plane or spherical waves. Effects resulting from the presence of the boundary are studied by comparing the full theory with a simplified model in which multiple scattering is neglected. Numerical implementation of the proposed solution is also discussed.

Vibration and noise mechanism of a 110 kV transformer under DC bias based on finite element method

Global energy and environmental issues are becoming increasingly problematic, and the vibration and noise problem of 110 kV transformers, which are the most widely distributed, have attracted widespread attention from both inside and outside the industry. DC bias is one of the main contributing factors to vibration noise during the normal operation of transformers. To clarify the vibration and noise mechanism of a 110 kV transformer under a DC bias, a multi-field coupling model of a 110 kV transformer was established using the finite element method. The electromagnetic, vibration, and noise characteristics during the DC bias process were compared and quantified through field circuit coupling in parallel with the power frequency of AC, harmonic, and DC power sources. It was found that a DC bias can cause significant distortions in the magnetic flux density, force, and displacement distributions of the core and winding. The contributions of the DC bias effect to the core and winding are different at Kdc = 0.85. At this point, the core approached saturation, and the increase in the core force and displacement slowed. However, the saturation of the core increased the leakage flux, and the stress and displacement of the winding increased faster. The sound field distribution characteristics of the 110 kV transformer under a DC bias are related to the force characteristics. When the DC bias coefficient was 1.25, the noise sound pressure level reached 73.6 dB.

Designing a sparse sensor array for sound field reconstruction using compressive-equivalent source method.

The compressive-equivalent source method (C-ESM) can reconstruct the sound field radiated by sparsely distributed sound sources with a reduced number of sensors. To ensure the performance of the C-ESM, the transfer matrix between the sensors and equivalent point sources should exhibit sufficient incoherence. Given that the configuration of the sensor array affects this incoherence condition, concern regarding the sensor array design would arise. To address such concern, this paper proposes a sensor array design approach. The primary objective of this approach is to minimize the mean coherence of the transfer matrix within the developed iterative framework, providing the incoherence condition required by the C-ESM. Subsequently, the designed sensor array is utilized by the C-ESM for the reconstructions. The effectiveness and practicality of the proposed approach are validated through numerical simulations and experiments.

Bonebridge implants versus atresiaplasty in children with unilateral congenital aural atresia: A comparison study of audiological outcomes

ObjectivesTo evaluate and compare audiological outcomes of atresiaplasty and Bonebridge (BB) implantation in patients with unilateral congenital aural atresia (UCAA), to guide clinical decision-making. MethodsTwenty-seven subjects diagnosed with UCAA were included in the study. Thirteen were implanted with the BB, while 14 undergone atresiaplasty. All patients underwent pre-and post-surgery examinations, including pure-tone audiometry, sound field threshold (SFT), speech reception threshold (SRT), word recognition score (WRS), and horizontal sound source localization tests. Results(1) Postoperatively, the average SFT decreased by 11.79 ± 5.93 dB HL in the atresiaplasty group and by 24.46 ± 9.36 dB HL in the BB group, with a significantly greater decrease in the BB group compared to the atresiaplasty group (P < 0.05). (2) Both groups demonstrated a significant improvement in average disyllabic WRS postoperatively under normal ear-masking conditions, with the BB group showing a significantly higher improvement than the atresiaplasty group. (3) When the speech signal was presented from the CAA side with noise from the normal hearing side, both surgical groups exhibited a significant decrease in postoperative signal-to-noise ratio compared to preoperative levels, with improvements of 2.14 ± 2.95 dB SNR in the atresiaplasty group and 4.92 ± 5.83 dB SNR in the BB group (P < 0.05). (4) The average minimum audible angle preoperative in the atresiaplasty group was 29.71 ± 18.42°, which decreased to 18.1 ± 10.07° at 6 months postoperatively, showing a statistically significant improvement (P < 0.05). ConclusionWe concluded that both atresiaplasty and Bonebridge implantation can significantly improve speech perception under both quiet and noisy conditions in children with UCAA. BoneBridge implantation appears to provide better audiological outcomes than atresiaplasty. Atresiaplasty can significantly improve the accuracy of sound localization. No significant improvement in sound localization accuracy was observed in the short period after Bonebridge implantation. Further research should be conducted with a larger sample size and longer follow-up time.

Sensitivity enhancement of thermal acoustic particle velocity sensor based on metal film optimization

Thermal acoustic particle velocity sensors find widespread application in sound field measurements and sound source localization, owing to their capacity to capture vectorial information. This paper focuses on enhancing the sensitivity of detecting weaker signals by elevating the temperature coefficient of resistance (TCR) in the platinum thin film on the sensor's sensing wires. The study delves into the impact of annealing on the TCR of Pt thin films applied to small-sized elongated wires for thermal acoustic particle velocity sensors. The augmented effects of annealing Pt thin films with three adhesion layer metals—Chromium (Cr) and Titanium (Ti), previously commonplace in this sensor, and the newly introduced Tantalum (Ta) are scrutinized. Additionally, the influence of the deposition of Au electrodes, employed for wire bonding, both before and after annealing, on the annealing effect is also explored. In conclusion, a Pt thin film annealing process tailored for thermal acoustic particle velocity sensors is proposed, along with the recommendation of the optimal adhesion layer metal. This approach results in a substantial 20 % improvement in the TCR of the Pt thin film on the sensing wires, coupled with a corresponding 2.2 dB increase in sensor sensitivity.

Enhancing Ultrasound Power Transfer: Efficiency, Acoustics, and Future Directions.

Implantable medical devices (IMDs), like pacemakers regulating heart rhythm or deep brain stimulators treating neurological disorders, revolutionize healthcare. However, limited battery life necessitates frequent surgeries for replacements. Ultrasound power transfer (UPT) emerges as a promising solution for sustainable IMD operation. Current research prioritizes implantable materials, with less emphasis on sound field analysis and maximizing energy transfer during wireless power delivery. This review addresses this gap. A comprehensive analysis of UPT technology, examining cutting-edge system designs, particularly in power supply and efficiency is provided. The review critically examines existing efficiency models, summarizing the key parameters influencing energy transmission in UPT systems. For the first time, an energy flow diagram of a general UPT system is proposed to offer insights into the overall functioning. Additionally, the review explores the development stages of UPT technology, showcasing representative designs and applications. The remaining challenges, future directions, and exciting opportunities associated with UPT are discussed. By highlighting the importance of sustainable IMDs with advanced functions like biosensing and closed-loop drug delivery, as well as UPT's potential, this review aims to inspire further research and advancements in this promising field.

Sparsity-driven loudspeaker gain optimization for sound field reconstruction with spherical microphone array

The paper presents a sparsity-driven method utilizing loudspeakers to reconstruct spatial sound fields using measurements obtained from a spherical microphone array (SMA). Employing spherical harmonics decomposition (SHD), the SMA recordings are characterized in the spherical harmonics domain. The gains for the loudspeakers are determined through an optimization problem, equating spherical harmonics pressure coefficients from primary and secondary sources. Furthermore, the sparsity within the loudspeaker feeds is redefined as a constrained sparse optimization problem, integrating linearity and orthogonality constraints. This method effectively reduces the required loudspeakers while maintaining sound field quality. The Bregman iteration method is applied to solve the constrained optimization problem. Rigorous evaluation based on reconstructed sound fields and objective measures highlights significant enhancements compared to least square and compressed sensing methods.

Half-Space Sound Field Reconstruction Based on the Combination of the Helmholtz Equation Least-Squares Method and Equivalent Source Method.

In practical conditions, near-field acoustic holography (NAH) requires the measurement environment to be a free sound field. If vibrating objects are located above the reflective ground, the sound field becomes non-free in the presence of a reflecting surface, and conventional NAH may not identify the sound source. In this work, two types of half-space NAH techniques based on the Helmholtz equation least-squares (HELS) method are developed to reconstruct the sound field above a reflecting plane. The techniques are devised by introducing the concept of equivalent source in HELS-method-based NAH. Two equivalent sources are tested. In one technique, spherical waves are used as the equivalent source, and the sound reflected from the reflecting surface is regarded as a linear superposition of orthogonal spherical wave functions of different orders located below the reflecting surface. In the other technique, some monopoles are considered equivalent sources, and the reflected sound is considered a series of sounds generated by simple sources distributed under the reflecting surface. The sound field is reconstructed by matching the pressure measured on the holographic surface with the orthogonal spherical wave source in the vibrating object and replacing the reflected sound with an equivalent source. Therefore, neither technique is related to the surface impedance of the reflected plane. Compared with the HELS method, both methods show higher reconstruction accuracy for a half-space sound field and are expected to broaden the application range of HELS-method-based NAH techniques.

Two-dimensional acoustic analysis using Taylor expansion-based boundary element method

The use of boundary elements in two-dimensional acoustic analysis is presented in this study, along with a detailed explanation of how to derive the final discrete equations from the fundamental fluctuation equations. In order to overcome the fictitious eigenfrequency problem that might arise during the examination of the external sound field, this work employs the Burton-Miller approach. Additionally, this work uses the Taylor expansion to extract the frequency-dependent component from the BEM function, which speeds up the computation and removes the frequency dependency of the system coefficient matrix. The effect of the radiated acoustic field generated by underwater structures’ on thin-walled structures such as submarines and ships is inspected in this work. Numerical examples verify the accuracy of the proposed method and the efficiency improvement.

Advanced acoustic simulation of aircraft test environments: integration of the direct field acoustic testing methodology

In aeroacoustic engineering, replicating real-world environments in a controlled setting presents significant opportunities for reduced flight testing but also comes with challenges when precisely simulating the flight environment. This paper introduces an innovative acoustic simulation model that leverages the Boundary Element Method (BEM) and a Direct Field Acoustic Testing (DFAT) simulation module. The primary objective is to virtually reproduce test sound fields that closely mimic the full fluctuating pressure environments aircraft encounter during flight using only loudspeaker arrays. This approach involves virtually reproducing a sophisticated test setup, typically comprising hundreds of drivers actively managed to generate a specific sound field. This setup is designed to virtually replicate various complex pressure environments, such as those produced by a Turbulent Boundary Layer, the complex pressure fields generated by aircraft propellers or jet engines. The use of active noise generation simulation helps determine the feasibility of a given pressure field and the capability of a test facility to simulate it accurately. The virtually reproduced sound fields simulated by this model show remarkable potential in approximating real-world pressure loadings. This capability is particularly useful in establishing pre-test predictions for fuselage testing such as sidewall build-ups: including insulation, and damping treatments, TVAs and TMDs.

Selecting Measurement Locations for Inverse Pellicular Modes Analysis

Inverse pellicular mode analysis is an approach to reconstruct an acoustic source from measurements in the sound field. After a source is reconstructed, the simulation can be used to predict the sound pressure level at some distance from the source. The method is especially useful for considering acoustic treatments such as partial enclosures and barriers. Pellicular modes are generated by assuming a thin acoustic layer around the source boundary and determining the acoustic modes. These acoustic modes are then used as structural modes and serve as basis functions for the inverse calculation. However, the quality of the reconstruction depends greatly on the selection of measurement locations. In this research, inverse pellicular mode analysis is used to reconstruct the normal boundary velocity on a small generator set. Different measurement set locations are considered and sound pressure levels in the field are calculated and compared to direct measurement to assess the quality of the reconstructed source. The reconstructed source is then utilized to predict the insertion loss of a partial enclosure.

Test method for evaluating the NIOSH Noise Mapper application in a hemi-anechoic chamber

The Noise Mapper Application developed by the National Institute for Occupational Safety and Health (NIOSH) can be used to identify areas in the workplace where workers may be exposed to hazardous noise. The app was created to empower workers to measure sound levels in their workplace, make informed decisions about noise exposure, and prevent occupational hearing loss. To evaluate the maps generated by the app, a single sound source or multiple sources were used to generate steady state sound fields within the NIOSH hemi-anechoic chamber (HAC). A sound level meter (Larson Davis, Model 831C) was used to measure A-weighed equivalent continuous sound levels on a grid with a spacing of 1.5 m (5 ft). The NIOSH Noise Mapper app was then used to generate sound level contour plots with a grid spacing of 3.0 m (10 ft). The accuracy of the map was evaluated by comparing the predicted sound levels with the measured sound levels. The results show the app can estimate the sound levels to within ±1.2 dB(A) of the measured values. The test method used to evaluate the NIOSH Noise Mapper app and the results of the comparison will be discussed in this paper.

Localization and Sound Power Estimation of Sound Sources in Industrial Plants using the Sound Field Scanning Method

Reducing sound emissions from industrial plants requires an initial step of localizing key contributing sources. Acoustic cameras are pivotal for quickly identifying these sources, yet challenges persist in low-frequency source localization and presenting results for effective impact assessment. This contribution introduces the Sound Field Scanning technology, utilizing a rotating linear microphone array covering a measurement surface with diameter of 2.5 meters for low-frequency source localization from 125Hz. The underlying sound imaging method compensates for Doppler distortions in the moving microphone signals and evaluates coherence spectra with a non-moving reference microphone to compute an acoustic image. For analysis, a method quantifying sound power contributions from specific regions in the optical image is presented. Comparing sound power metrics of the full optical field of view with metrics of regions of interest enables users to quickly rank source contributions and assess the impact of reducing these contributions on total sound power. In complex scenarios, preliminary investigations can be streamlined with a few measurements from diverse angles, expediting the problem-solving process with confidence. The method is exemplified through the analysis of sound emissions from a production plant.

Sound field reconstruction using improved ℓ1-norm and the Cauchy penalty method

Sound field reconstruction using improved ℓ1-norm and the Cauchy penalty method

High-sensitivity trace gas detection based on differential Helmholtz photoacoustic cell with dense spot pattern

A high-sensitivity photoacoustic spectroscopy (PAS) sensor based on differential Helmholtz photoacoustic cell (DHPAC) with dense spot pattern is reported in this paper for the first time. A multi-pass cell based on two concave mirrors was designed to achieve a dense spot pattern, which realized 212 times excitation of incident laser. A finite element analysis was utilized to simulate the sound field distribution and frequency response of the designed DHPAC. An erbium-doped fiber amplifier (EDFA) was employed to amplify the output optical power of the laser to achieve strong excitation. In order to assess the designed sensor's performance, an acetylene (C2H2) detection system was established using a near infrared diode laser with a central wavelength 1530.3 nm. According to experimental results, the differential characteristics of DHPAC was verified. Compared to the sensor without dense spot pattern, the photoacoustic signal with dense spot pattern had a 44.73 times improvement. The minimum detection limit (MDL) of the designed C2H2-PAS sensor can be improved to 5 ppb when the average time of the sensor system is 200 s.

A novel model order reduction technique for solving horizontal refraction equations in the modeling of three-dimensional underwater acoustic propagation

Modeling three-dimensional (3D) underwater acoustic propagation is vital for underwater detection, localization, and navigation. This article introduces a novel model order reduction (MOR) technique to solve horizontal refraction equations (HREs) in the modeling of 3D underwater acoustic propagation. This approach relies on an adiabatic approximation of the 3D sound field, representing the field as a combination of local vertical modes with their modal coefficients governed by a system of two-dimensional (2D) HREs. Inspired by normal mode theory, the coefficients in the expansion over vertical modes are determined by projecting them onto a lower-dimensional, orthogonal space defined by their transverse eigenfunctions. By artificially truncating the horizontal domain in the transverse directions using two perfectly matched layers (PMLs), the eigenproblem associated with the transverse eigenfunctions of the modal coefficients is closed and thus can be solved through a modal projection method. The modal projection method enables fast computation of modal coefficients in a longitudinally invariant environment within seconds, offering a naturally wide-angle solution covering ±90°. The MOR method is extended to encompass fully 3D cases by introducing an admittance matrix, a memory-saving strategy that prevents numerical overflow when the longitudinal range is large. Moreover, the fact that the outer boundaries of the PMLs are range-independent allows the proposed MOR technique to perform well on a coarse grid when employing the Magnus scheme, significantly saving the numerical cost for the fully 3D simulation. Numerical simulations are provided for both longitudinally invariant and fully 3D scenarios, demonstrating the high accuracy and efficiency of the proposed MOR technique in solving HREs.

Hybrid physics machine learning for ultrasonic field guided 3D generation and reconstruction of rail defects

Ultrasonic technology is widely used in the field of rail defects detection. 3D reconstruction of rail defects can intuitively restore the 3D size and spatial position of the defects inside the rail. Currently, ultrasound-based 3D reconstruction requires a multi-probe or mechanical scanning platform in a laboratory setting, which is not suitable for the railway environment. In addition, 3D reconstruction requires a large amount of data, making it difficult to collect sufficient ultrasonic 3D defect data for long-distance rail inspections. This paper proposes an ultrasonic field-guided 3D reconstruction method combined with machine learning hybrid physics for rail defects. It combines both sound field GAN model to reconstruct the defect 3D model from the 2D B-scan data. The proposed method can generate a defect cross-sectional image using a deep learning algorithm guided by the acoustic field in the B-scan space, and extract the 3D size information of the defect from the 2D B-scan information by establish a defect echo model. By stablishing a spatial mapping relationship between the B-scan and the rail coordinate system, the position of the defect in the rail coordinate system is obtained. The defect data of standard damage rails are tested. Experiment results indicate that the defects in different parts of the rail can be reconstructed by the proposed method. The average size error rate is 9.56%–21.14 %, and the average height error is 3.458mm–6.353 mm.