Acoustic Level Research Articles

The role of structural and insulating material in the structure-borne noise propagation of superyachts

The insulation and noise and vibration damping characteristics of complex systems used by humans, such as automobiles, airplanes and ships are becoming increasingly important from the early design stages to ensure an adequate level of comfort. Especially in the naval fields, the design of insulation plans is crucial to prevent the propagation of noise and vibrations on board of megayachts. Since it is quite complex to identify and correctly model the sources due to their deterministic and random nature, during the early design stage, the focus is on insulation rather than reducing the acoustic levels of the sources themselves. In this article, a method for analyzing sea trials on a superyacht will be proposed with the aim of analyzing how much the insulation materials can limit the levels of vibrational energy on board during the path between sources and receivers. A new a descriptor based on harmonic transmission energy through the structure is proposed for path insertion loss experimental identification. In particular, by using spectral analyses and synchronous averaging of sound levels in various areas of the superyacht, it will be possible to study the vibroacoustic insulation of structural materials and their damping coefficient.

Office soundscape assessment: A model of acoustic environment perception in open-plan officesa).

The soundscape approach has been utilised in recent research for residential environments, but applications to indoor working environments remain limited. This study investigated the suitability of affective quality evaluations of open-plan office acoustics. Perceptual assessments were completed by occupants of eight open-plan office floorplates, using affective dimensions outlined in PD ISO/TS 12913-3:2019 and indoor soundscape studies. Participant demographic, contextual, work-related quality, and psychological well-being data were collected. Workstation noise levels were measured following BS ISO 22955:2021. Principal component analysis identified Pleasantness, Eventfulness, and Emptiness as the main perceptual dimensions, cumulatively explaining 56% of the total variance. Results indicate the suitability of the PD ISO/TS 12913-3:2019 two-dimensional model for open-plan offices. The perceived presence of human sounds negatively correlated with ISO Pleasantness yet positively correlated with ISO Eventfulness. Participant gender and aural diversity mediated ISO Pleasantness. Psychological well-being and work-related quality correlated positively with soundscape pleasantness. No correlations were found between level-based acoustical indicators-equivalent continuous sound level (LAeq), level exceeded 10% (LA10) and 90% (LA90) of the time, level variability (LA10-LA90) and Liveliness-and perceptual scores. A conceptual representation of open-plan office soundscape perception is presented, offering a framework for evaluating and designing workspaces to enhance well-being.

Combined ANFIS and numerical methods to reveal the mass transfer mechanism of ultrasound-enhanced extraction of proteins from millet

Millet protein, as a promising plant-based protein substitute source, is an excellent basis for essential amino acids compared to commonly consumed staple grains. Compared with the traditional extraction process, ultrasound has been used to enhance the extraction efficiency of various plant-based proteins. To reveal the mechanism of ultrasound-enhanced extraction of proteins, adaptive neuro-fuzzy inference system (ANFIS) algorithm and numerical simulation based on Fick’s law were applied to illustrate the mass transfer behavior of millet proteins under different ultrasonic conditions including solid–liquid ratios (S/L ratios), pH and acoustic energy density levels (AED). The results showed that AED dominated the changes in effective diffusion coefficient (De), showing a positive correlation relationship (p < 0.05). Specifically, when the AED was 47.07 W/cm2, the De value increased by 95 % compared to that of 23.47 W/cm2. Meanwhile, the ANFIS model successfully predicted protein yields across all investigated parameters, achieving a coefficient of determination (R2) greater than 0.97. This model also elucidated the interactions among four critical factors, among which pH and S/L ratios were the main factors affecting protein yield. Concerning the ultrasonic cavitation bubble dynamics, the bubble collapse efficiency enhanced with an increase in AED, and therefore high AED ultrasound can significantly enhance the cavitation effect. Additionally, the results of the yields and physical properties of millet protein also indicated that in contrast with the traditional extraction methods, the ultrasound impactfully improved extraction yield (by 165 %), and combined with pH condition, it decreased the protein particle size (from 813.55 nm to 299.30 nm) without altering the molecular weight distribution. This study offers a novel perspective on the mechanism underlying ultrasound-enhanced protein extraction, drawing upon principles of ultrasonics and extraction processes. The insights gained can serve as a foundation for the food industry to upscale the extraction process, potentially enhancing efficiency and yield.

How speech in acoustically different offices influences a working person? – Experiments in two countries

Working during task-irrelevant speech influences workers. Adequate room acoustic design can reduce the negative effects in open-plan offices, but harmonized target values do not exist. Our purpose was to examine the effects of room acoustic design levels on a working person during the exposure to task-irrelevant speech. The Finnish room acoustic regulation was chosen as a reference, as it is one of the strictest worldwide. Three room acoustic conditions were examined: regulation violated (Reg-) (Speech Transmission Index, STI=0.71), regulation fulfilled (Reg0) (STI=0.37), and regulation surpassed (Reg+) (STI=0.16). To examine the generalizability of the results, asimilar experiment was performed in two countries (two languages and laboratories): Finland and Germany (FinGer study, N=98). Experience was measured with questionnaires, performance with visual and auditory serial recall tasks, and physiological stress with heart rate variability. Results did not depend on the country, suggesting that our findings could be similar also in other countries. Speech annoyance and perceived concentration difficulty differed in each condition. With other experience measures, only Reg+ improved experience compared to the two other conditions. Visual serial recall performance was more accurate and faster in Reg+ than in Reg-. Accuracy was also improved in Reg0 compared to Reg-. The physiological stress levels did not depend on the condition. Our study shows that Reg0 was better than Reg- with respect to experience and performance but experience was further improved from Reg0 to Reg+. Therefore, it is beneficial to design room acoustics better than the Finnish regulation to maximize work performance and experience.

Optimizing a small room for critical listening with Treble

This work presents a detailed validation of new software Treble launched in 2023 that hybridizes the discontinuous Galerkin method and pressure-based geometrical acoustics methods. We investigated a small studio for voice productions both through physical measurements and treble's room acoustic simulations. By employing a dense measurement grid with a spacing of 25 cm at the ear level, a comprehensive validation of the room acoustic simulation was conducted in terms of room impulse responses, transfer functions, ISO 3382 acoustic parameters and sound pressure level distribution. Treble's simulation successfully predict the room modes, ISO 3382 acoustic parameters as well as the sound level distribution. The study demonstrates the impact of speaker positions, particularly regarding their interaction with boundary surfaces and how this can be planned with the simulation.

Acoustic and vibrations measurments in an autonomous shuttle bus

In response to the ADEME's call for Autonomous Road Vehicle Experimentation projects, a consortium was created to propose the SAM project about Safety and Acceptability of Autonomous Driving and Mobility. It was composed of industrial and research teams, associated with local partners. SAM is a national project involving large-scale trials of autonomous driving and mobility on open roads. The assessments covered several topics, including environmental impacts, focusing on air pollution, noise and the life cycle of components. Cerema proposed a methodology to characterize acoustic and vibration levels for autonomous driving in the specific site near Paris. The tests consisted in instrumenting the interiors of an automated shuttle and a conventional car to determine the user's feelings. The vehicles were driven in a quiet area and in a high traffic area. The results displayed by Cerema are based on statistical studies on 20 vehicle passages for each experiment. The indicators were characterized for the entire route and by homogeneous sections. In fluid navigation situation, the measurements showed that the acoustic and vibration impacts are minimal. However, the tests have highlighted the effects of the lack of anticipation of an automated shuttle during specific events requiring rapid braking.

Aerodynamic and acoustic evaluation of a cylinder covered by stretched grooved fabric near critical Reynolds numbers

This study investigates aerodynamic drag and acoustic noise generated from a circular cylinder by wrapping longitudinally grooved fabrics. The fabrics are stretched to different levels to explore their potential for flow and acoustic control near critical Reynolds numbers. To analyze the fabrics' surface characteristics, 3D scanning and several microscopic techniques were employed. The parallel-mounted load cells and an array of microphones were used to measure the drag and noise at Reynolds numbers, based on cylinder diameter, ranging from \num{3.3e4} to \num{1.1e5} in an anechoic wind tunnel. Additionally, hotwire anemometry was used to examine the wake structures in the vicinity of the cylinder. The surface scanning results revealed that stretching the fabric transversely to twice its original size reduced the groove depth by approximately $54\%$ and increased the width by around $25\%$, resulting in an overall reduction of the arithmetic surface roughness $S_a$ by $18.6\%$. Based on the wind tunnel data, it was observed that a grooved fabric with higher stretch, and thus lower surface roughness exhibited a minimum drag coefficient at a higher Reynolds number, along with reduced acoustic tonal noise levels.

Aircraft automatic detection on Station7hz interface using signal processing and artificial intelligence - ACOUDET - First method

The global project is to design a automatic noise event detection and classification system in real time using signal processing and artificial intelligence (AI). The first phase focuses on transport noise (aircrafts, trains, road vehicles, etc.). Secondly, the plan is to extend detection to construction site noise and any natural or life sources. This paper presents the first method developed to detect audible aircrafts pass-by. It focused on the development of a prototype detection algorithm, its results in situ conditions, and insights on future developments to create a robust aircraft and train noise detection system. The data collection method, aircraft audio signal particularities and a first detection method are described. The robustness of the detections is evaluated and limitation induced by real time detection are discussed. Thanks to the proprietary monitoring system Station-7hz. it has been possible to detect aircrafts in different types of sound environments in a straightforward manner, showing better results at night due to a quieter environment. Future developments based on a hybrid algorithm include AI models for audibility assessment and unwanted event filtering during aircraft pass-by. Aircraft's presence is detected via radar data and the detection of maximum acoustic levels correlated with aircraft parameters.

Iterative eigenvalue method coupled with RSM for structural acoustic analysis and optimization of the CLD-damped orthotropic steel deck

In the present work, an iterative eigenvalue method (IEM) is proposed and combined with the boundary element method (BEM) to perform the structural acoustical analysis of the orthotropic steel deck (OSD) damped with constrained layer damping (CLD), through which the frequency-dependent properties of the viscoelastic core can be accurately considered. Then, a series of hammer tests are carried out in a semi-anechoic chamber to verify the acoustic prediction method. It shows that the simulated structural noises basically agree with the test results, and the overall deviations at the field points M2 and M8 are merely 2.4 and 2.3 dB, respectively. Subsequently, taking the thicknesses of the damping layer and the constraining layer, as well as the material properties of the constraining layer as design variables, a central composite experiment is designed and combined with response surface methodology (RSM) to fit the relationship between analysis objectives and design variables. With the objective of minimizing the acoustic radiation power, a program for finding the optimal values of design variables is developed based on the interior penalty function method. Through iterative computations, the optimal points are numerically determined as t 1 = 2.3 mm and t 2 = 0.3 mm for the thicknesses of the damping layer and the constraining layer, respectively. Steel alloy is found to be the optimal material for the constraining layer. After optimizing CLD treatment, the overall acoustical power level can be reduced from 97.7 dB to 93.1 dB and the overall sound pressure levels (SPLs) at the field points M2 and M8 can be reduced from 89.2 dB to 83.5 and 76.9 dB to 70.3 dB, respectively, indicating that the optimization of CLD design parameters can significantly improve acoustic performance of the CLD-damped structures.

Simulasi karakteristik mesin termoakustik pembangkit listrik dengan penambahan model kerugian minor dari dua segmen konis

Acoustic energy output level from regenerator segment of a thermoacoustic engine model is attenuated along it’s loop due to several conditions including minor losses. This article discusses the result of Delta EC simulation of a thermoacoustic engine model acting as simple electric power generator that inserted with two conical segments. The cone segments are capable to lower the energy loss which in turn improve the overall performance of the engine in term of nett heat to acoustic energy conversion efficiency. Combined acoustic energy loss induced by both cones is equivalent to 4.94 watts minor losses. At this condition, regenerator segment amplifies the incoming acoustic energy flow of 57.02 watt up to 93.57 watt, which is equals to 36.55 watts acoustic amplification. It leads to increasing of overall engines heat to acoustic efficiency into 14.05%, which is 1.29% higher than those at the case of without cones. This engine performance improvement addressed to smoother streamline of working fluid flow inside the loop.

Performance Evaluation of Low Thermal Bridging Drywall System with Separating Clips for C-Studs

Drywall systems comprising gypsum boards and steel C-studs are widely used due to their lightweight structure, rapid construction, and ease of installation. These systems must meet the required thermal insulation performance for their specific applications. However, metal C-studs penetrate the insulation layer at intervals, leading to additional heat loss, reduced thermal insulation performance, and lower indoor surface temperatures, which can result in condensation and mold growth. To address these issues, this study proposes a drywall system with low thermal bridging studs made up of two small-sized studs and four or five separating clips made of reinforced plastic. These clips separate the studs to minimize heat transfer through metal elements, maintain structural stability despite the spacing between them, and facilitate easy assembly. The results from mock-up tests showed that the proposed system’s thermal transmittance was 0.370 W/m2K, which is 28.8% lower than the 0.52 W/m2K observed with conventional C-studs. The proposed drywall system also met Korean regulations for acoustic insulation level 3 and the 2 h fire resistance criteria, similar to existing drywall systems with conventional C-studs. Moreover, the maximum and residual displacements were within an acceptable range for a horizontal load of 3000 N applied vertically to the non-load-bearing wall. Building energy analysis indicated that using the proposed drywall adjacent to unconditioned spaces could reduce the annual heating and cooling load by 2.5–3.0%, despite a 1.5–1.9% increase in the annual cooling load. The annual heating load decreased by 4.8–5.9% under infiltration rates of 0.5 to 1.5 air changes per hour for adjacent unconditioned spaces, making this drywall system’s improved insulation quality crucial for achieving heating-dominant zero-energy buildings.

Study of word-in-noise perception scores at saccular acoustic sensitivity level: randomized clinical trial

BackgroundIn humans, saccular acoustic sensitivity has been confirmed. The aim of this study was to determine the scores of the word-in-noise perception test at the saccular acoustic sensitivity level.MethodologyIn this randomized clinical trial study, 101 participants in the age group of 14 to 25 years with normal hearing and middle ear function, detectable vestibular evoked myogenic potentials (VEMP), normal states of mental health, and night sleep were investigated. The scores of word-in-noise perception and word-in-noise discrimination tests were evaluated for each person at two intensity levels, most comfortable level (MCL) and saccular acoustic sensitivity. Mann-Whitney was used for the multiple comparisons.ResultsThere was a significant difference between the scores of the word-in-noise perception test at MCL and saccular acoustic sensitivity (U = 3971.50, Z = − 2.10, p’ = 0.04), and also between the scores of the word-in-noise discrimination test at the MCL compared to saccular acoustic sensitivity (U = 399.89, Z = − 2.49, p’ = 0.04). Word-in-noise discrimination scores in MCL (U = 3484.00, Z = -3.72, p’ = 0.00) and saccular acoustic sensitivity (U = 705.50, Z = − 3.78, p’ = 0.00) were higher than word-in-noise perception.ConclusionsWord-in-noise perception and word-in-noise discrimination scores are higher in saccular acoustic sensitivity level than MCL, suggesting that the vestibular system participates in loud speech perception. Also, in people with normal hearing thresholds, word-in-noise perception scores will be lower than word-in-noise discrimination scores for both loud and common intensity levels.

Numerical and experimental study on the aerodynamic noise characteristics of 600-km/h high-speed maglev trains

Abstract High-speed maglev trains represent a new mode of transportation; however, their 600-km/h traveling speed causes serious aerodynamic noise problems, with very little research on the aerodynamic noise of such trains. To clarify the aerodynamic noise source and radiation characteristics of high-speed maglev trains, both large eddy simulations and wind tunnel experiments with a 1:8 scale three-train model were conducted to obtain the aerodynamic noise source spectrum and spatial distribution characteristics of the maglev train at different speeds; the contribution of the dipole noise source was also analyzed. The results revealed that the train shape has a significant impact on the frequency distribution of the far-field aerodynamic noise below 1 kHz, with the highest sound power concentrated on the train head, especially in the areas around the track joint and streamlined sections. The surface dipole sound source energy increases linearly with speed and is mainly distributed at the bottom of the train head and tail train body. A short-streamlined train exhibited the highest ratio, especially in the trailing edge area, up to 1.42×1011 dB. The far-field sound pressure level of the short-streamlined maglev train is significantly higher, with a maximum difference of about 10 dB(A). The distribution pattern of far-field sound pressure level is influenced by the train type, reflected in the tail train and wake area. Different frequency intervals have different relationships between the acoustic pressure level and frequency; long-streamlined models may enhance broadband features in the sound field distribution of high-speed maglev trains. These findings could be used to guide the aero-acoustic design of maglev trains with a designed speed of 600 km/h.

Insertable, dual-density dielectric barrier for acoustic pressure level reduction in a high-performance human head-only MRI system

We report use of a dual-density dielectric barrier surrounding a detachable high-pass radiofrequency (RF) birdcage coil to achieve an order-of-magnitude reduction of acoustic noise in a high-performance head gradient system. The barrier consisted of a 4.5 mm-thick mass-loaded vinyl and a 6 mm-thick polyurethane foam. It was inserted into the radial gap between the birdcage coil and the RF shield in a prototype head-only gradient system at 3 T. More than 9 dBA reduction of sound pressure level was achieved on the average with representative, high acoustic-noise imaging sequences. Increased acoustic damping was apparent from acoustic impulse response functions. High dielectric constant of the mass-loaded vinyl effectively added distributed capacitance to the birdcage coil, lowering the resonance frequency, but not seriously degrading the RF transmission performance. The barrier occupied the radial space normally used for air cooling of the RF coil and the RF shield. The resulting omission of air cooling was found to be acceptable with efficient gradient thermal management and use of a high-resistivity RF shield for eddy current reduction. The proposed method can improve patient experience while preserving image quality in a high-power head-only gradient system.

Marine compressed air source array acoustic field characterization from at-sea measurements: Long-range propagationa).

In 2007, the Littoral Acoustic Demonstration Center conducted a comprehensive experiment in the northern Gulf of Mexico to measure the three-dimensional acoustic field of a standard marine compressed-air source array used in seismic exploration. This study aims to enhance understanding of long-range acoustic propagation of the array signals, with focus on variations in received sound pressure levels and sound exposure levels (SELs) at various ranges from the source. These variations are influenced by factors, such as receiver depth, array orientation, and propagation conditions. The long-range measurements show that received peak pressure levels and SELs exhibit non-monotonic (oscillatory) behavior with range leading up to 10 dB increase in received levels at longer ranges. At ranges beyond 20 km, acoustic levels at the shallowest hydrophone consistently surpassed those at deeper ones by 3-10 dB, suggesting the impact of surface duct propagation effects. The results demonstrate that range-independent bathymetry leads to approximately 4 dB higher received acoustic levels than range-dependent propagation conditions. The measured long-range propagation acoustic metrics from controlled experiment provide a unique and critical dataset for validating both source and propagation model accuracy in predicting received sound pressure and SEL in the far-field of the source array.

Prosody matters: Preserved prominence marking strategies in people with Parkinson's disease independent of motor status.

While many studies focus on segmental variation in Parkinsonian speech, little is known about prosodic modulations reflecting the ability to adapt to communicative demands in people with Parkinson's disease (PwPD). This type of prosodic modulation is important for social interaction, and it involves modifications in speech melody (intonational level) and articulation of consonants and vowels (segmental level). The present study investigates phonetic cues of prosodic modulations with respect to different focus structures in mild dysarthric PwPD as a function of levodopa. Acoustic and kinematic speech parameters of 25 PwPD were assessed in two motor conditions. Speech production data from PwPD were collected before (medication-OFF) and after levodopa intake (medication-ON) by means of 3-D electromagnetic articulography. On the acoustic level, intensity, pitch, and syllable durations were analyzed. On the kinematic level, movement duration and amplitude were investigated. Spatio-temporal modulations of speech parameters were examined and compared across three different prosodic focus structures (out-of-focus, broad focus, contrastive focus) to display varying speech demands. Overall, levodopa had beneficial effects on motor performance, speech loudness, and pitch modulation. Acoustic syllable durations and kinematic movement durations did not change, revealing no systematic effects of motor status on the temporal domain. In contrast, there were spatial modulations of the oral articulators: tongue tip movements were smaller and lower lip movements were larger in amplitude under levodopa, reflecting a more agile and efficient articulatory movement under levodopa. Thus, respiratory-phonatory functions and consonant production improved, while syllable duration and tongue body kinematics did not change. Interestingly, prominence marking strategies were comparable between the medication conditions under investigation, and in fact, appear to be preserved in mild dysarthric PwPD.

Weighted ultrasound entropy imaging for HIFU ablation monitoring with improved sensitivity and contrast.

Although B-mode imaging has been widely used in ultrasound-guided high-intensity focused ultrasound (HIFU) treatment, challenges remain in improving its quality and sensitivity for monitoring the thermal dose. Recently, quantitative ultrasound (QUS) imaging has been recognized with the potential to better sense the changes in the microstructure of ablated tissues. This study proposed to use a QUS method called weighted ultrasound entropy (WUE) imaging to monitor the HIFU ablation. Based on ex-vivo and in-vivo experiments, WUE images reflecting tissue changes during HIFU treatment under different acoustic power levels (174-308W) were reconstructed with a newly established imaging framework. The performance of the proposed WUE imaging in the monitoring of HIFU treatment was compared with the corresponding B-mode images in terms of their contrast-to-noise ratios (CNRs) between the focal region and the background. It was found that HIFU irradiation with higher power generated larger WUE values in the focal region, and the bright spots grew in size as the acoustic sonication proceeded. Compared with the in-situ B-mode images, the WUE images had higher image quality in indicating lesion formation, with a 39.2%-53.4% improvement in the CNR at different stages. Meanwhile, a correlation (R=0.84) between the damage area estimated in WUE images and that measured from the dissected ex-vivo tissue samples was found. WUE imaging is more sensitive and accurate than B-mode imaging in monitoring HIFU therapy. These findings suggest that WUE imaging could be a promising technique for assisting ultrasound-guided HIFU ablation.

Acoustic Landau levels in a synthetic magnetic field with a symmetric gauge

Acoustic Landau levels in a synthetic magnetic field with a symmetric gauge

An equivalent and simplified approach for acoustic noise prediction in a PM synchronous motor based on the semi‐analytical‐FEM model

AbstractThe vibration and acoustic noise of a permanent‐magnet synchronous motor are analysed and evaluated. Acoustic noise sound levels, their prominent frequencies, and the noisiest motor speed range are predicted. According to many resources, the radial vibration of the stator system due to the magnetic attraction between rotor permanent magnets and stator iron teeth is the main reason for the acoustic noise propagation of the PMSMs. The dominant orders of the spatial circumferential harmonics of the radial magnetic forces (RMFs) have been investigated and compared. The complete and complicated mechanical components, materials, and harmonics of the magnetic forces of the motor and their interaction are simplified and equalised to a vibration model, which consists of the interaction between the stator system and the dominant harmonic orders of the RMFs. Based on this approach, the simplest and most adequate semi‐analytical‐FEM model for noise prediction in PMSMs is proposed. This model, in addition to simplification, clarifies the role of the main mechanical and electromagnetic origins of noise generation. The acoustic noise prediction, using the proposed method has been compared with the experimental results. There is a proper agreement between the analytical, the FEM, and measurement results.

Sound amplitude of discrete bubbles entrained by an impacting water stream.

Experiments were undertaken to develop a relationship between bubble size and acoustic-emission amplitude for a vertical stream of water impacting a water pool. A particular focus is the formation of the discrete bubbles. Although the relationship between bubble diameter and the natural frequency of sound emissions has been established through Minnaert's work, a comprehensive investigation into the amplitude of sound emissions is missing. Air bubbles were generated from the impact of falling-water streams of varying diameters on an underlying water pool and their acoustic emissions were recorded using a nearby hydrophone. Sound amplitude was found to increase monotonically with bubble size. A second-order polynomial relationship between logarithmic acoustic sound pressure level (L) and bubble diameter (Db) was found, L=-0.0401Db2+1.5781Db+110.7225 within the ±3 dB margin of error. The relationship between linear sound pressure level (P) and bubble diameter (Db) is expressed by the equation P=0.0059Db2+0.0505Db+0.3591, within the ±3 dB margin of error. Results demonstrate that larger bubbles (D > 4 mm) exhibit noise emissions similar to bubbles produced by other mechanisms, such as the underwater nozzle, while smaller diameters tend to produce higher noise levels compared to the same mechanism.