bluuebunny/crossref_metadata_2025 huggingface dataset:
Issues and recent research on VHF sound exposure with consideration for young people's hearing perception
Authors: UEDA Mari , HIROE Masaaki , HASEGAWA Hideyuki , NAKAMURA Kentaro
Published: October 2024

We define VHF sound as airborne sound that may be audible to humans above 16 kHz. It has been reported in recent studies that VHF sounds can be annoying when audible. We have therefore carried out various research studies to ensure the safe use of VHF sounds. One of the aim of this
study is to obtain basic data for developing guidelines for VHF sound exposure, if necessary.These include measurements of hearing thresholds in the VHF range, ABR measurements, HRTF measurements and acoustic measurements for simulation and current situation of exposure regarding the effect
of hair. This paper reports on recent trends in VHF sound exposure in Japan and several studies on the perceptions of young people's hearing of VHF sounds.
A study on the sound scattering characteristics in random structure using Voronoi Tessellation
Authors: SUGAHARA Akiko , HAMATANI Koki , HIRAGURI Yasuhiro
Published: October 2024

In room acoustic design, the use of acoustic diffusers is an effective method for achieving a uniform sound field and controlling reverberation. A common approach is to use periodic diffusers that control reflection directions based on the wavelength of sound. In this study, we explore
the utilization of random and nonperiodic structures as acoustic diffusers, taking inspiration from the amorphous structures in nature. The irregularities in random structures are expected to enable the broad diffusion of a wide range of frequencies in various directions. We utilized Voronoi
tessellation in both two and three dimensions to create 2D Voronoi diffusers with irregular aperture shapes and 3D Voronoi diffusers with irregular aperture shapes and slopes. Then, the acoustic diffusion characteristics of the 2D and 3D Voronoi diffusers were compared with a periodic-type
structure through the finite element analysis and experiments. On the basis of these results, the irregularities in the openings and slopes of Voronoi diffusers broaden the scattering frequencies and enhance the scattering coefficients. This suggests that amorphous structures utilizing Voronoi
tessellation can be effective as acoustic diffusers.
Applying noise mapping in studying road traffic noise influence on urban blocks
Authors: LEYAO Zhang , YU Lei , QIU Rui
Published: October 2024

With a thriving 40 years' urbanization, China cities are facing severe noise caused by road traffic that seriously influencing residents' health. To solve such environmental pollution, urban planning and design could play a significant role at the early stage. Therefore, a study on
applying noise mapping simulation to mitigate road traffic noise through making proper plan and design of urban blocks is made. In the study, a rapid urbanization city, Shenzhen, was researched. Through comparing different plan parameters and design layouts, approaches benefitting mitigating
road traffic noise were thoroughly investigated. It is found that bigger block size might bring forth higher noise than smaller one. The study outcomes are useful to help in creating a tranquil urban environment, particularly in urban planning & design stage.
Flux reconstruction approach for long-time calculations of the linearized Euler equation
Authors: DUAN Lishu , JIANG Hanbo
Published: October 2024

The Linearized Euler Equations (LEE) are one of the fundamental governing equations in acoustics research. Due to the relatively small magnitude of acoustic disturbances compared to the physical quantities of the background flow, ensuring highly precise solutions without dissipation
and dispersion over time is essential. The Flux Reconstruction (FR) method, recognized as a high-order numerical method with flexible construction capabilities, has been extensively utilized in recent years for solving partial differential equations numerically. This paper introduces an offsetting
numerical flux for one-dimensional LEE. Subsequently, it develops a flux reconstruction scheme with energy-conserving characteristics, referred to as the ECFR scheme, aimed at achieving high-precision numerical solutions for prolonged computations. The energy-conserving feature of the scheme
is substantiated through theoretical derivation and further corroborated by numerical validation. Moreover, the impact of Mach numbers and the parameter of the offsetting flux on the scheme's performance is discussed. The stability of the scheme is also analyzed, with the limit of the CFL
number being provided. The novel ECFR scheme facilitates obtaining high-precision acoustic numerical solutions, thereby providing strong support for the study of complex engineering problems such as aircraft, submarine, and automobile noise.
Investigation of wind turbine unsteady aerodynamics and trailing-edge noise characteristics under wake steering
Authors: KIM Homin , YUK Taeseok , HAN Wonsuk , LEE Soogab
Published: October 2024

In wake steering strategy, the shaft of an upstream wind turbine is yawed to deflect the wake and decrease the wake-swept area of the downstream wind turbine rotor. This intentional yaw misalignment increases the output power of the downstream wind turbine at the expense of some loss
of upstream wind turbine power, consequently increasing the total wind farm power. However, the asymmetric non-uniform inflow into the downstream wind turbine due to the deflected wake causes unsteady aerodynamic loads and affects the wind turbine noise characteristics. In this study, the
unsteady vortex lattice method coupled with the curled wake model is used to predict the unsteady aerodynamics of a downstream wind turbine in wake steering. Based on the unsteady aerodynamic results, the trailing-edge noise characteristics are predicted by a semi-empirical method. The impact
of wake steering on trailing-edge noise level and amplitude modulation is evaluated. The results show that the asymmetric non-uniform inflow due to wake steering increases the amplitude modulation of the downstream wind turbine.
Numerical investigation of serration angle on trailing edge noise reduction
Authors: AHN Byunghyun , YU Kukhwan , LEE Soogab
Published: October 2024

The influence of serration angle on the three-dimensional flow characteristics and noise attenuation mechanisms of a NACA6512-63 airfoil is explored in this research using large eddy simulation (LES) and spectral proper orthogonal decomposition (SPOD) methods. Analysis of the mean flow
field reveals the formation of counter-rotating vortex pairs, resulting from the outward flow towards the serration edges and the downwash flow in the valleys. This flow modification alters the effective angle of the serration, which in turn impacts its noise reduction performance. Furthermore,
the noise reduction mechanism is investigated by comparing the general solution of Lyu's semi-analytical equation with the SPOD mode results, and the frequency range associated with noise attenuation is analyzed. The findings indicate that the case with λ/h=0.15 demonstrates the most
significant noise reduction effect. This research offers valuable insights into the interplay between serration geometry and the resulting flow characteristics and noise reduction mechanisms.
Challenges and initiatives regarding the extension of operating hours at Osaka International Airport
Authors: DANNO Takuma , INOUE Makiko
Published: October 2024

Osaka International Airport is an urban airport located near the city center, and its operating hours are set at 14 hours, from 7:00 a.m. to 9:00 p.m. The airport extends its hours under unavoidable circumstances and allows takeoffs and landings after 9:00 p.m. However, the airport
has long conflicted with local communities over aircraft noise at night, and now, the airport receives harsh opinions especially regarding noise at night and takeoffs and landings after 9:00 p.m. And the number of flights taking-off and landing outside of the operating hours has been on the
rise, reaching a record high in FY2022, despite all the countermeasures described later. This is caused not only by the congestion of air traffic flow seen for the last several years, but also by severe weather events around the airport, such as frequent typhoons and thunderclouds triggered
by the recent intensifying climate changes. It is becoming even more critical to ensure on-time performance and to gain the understanding of local communities about the circumstances above. The presentation will introduce many initiatives to assess the situation accurately, ensure punctuality
in cooperation with airlines, and engage in regular dialogues with residents in the surrounding area.
A study on the multi layers of automotive interior trim parts to improve the acoustic performance with microfiber applied to the surface layer
Authors: YU NAKYEONG , KIM Keun-Young , PARK Jang-Seok
Published: October 2024

As the world joins environmental regulations, there is an increasing demand for the production of eco-friendly cars. As a result, the driving method of the vehicle was changed from the engine to the electric motor, and the main noise source was changed. In case of existing internal
combustion engines (ICE), the low-frequency sound range, which is the engine's main noise, is the main source of sound. As it is converted into an eco-friendly car, the noise that was hidden by the engine combustion sound and the high-frequency noise of the motor are being highlightened. PP
meltblown generally has a lower denier than other fibers, so it is effective in improving sound absorption performance because the surfaces of the fibers are large compared to the same weight of another fibers. In conclusion, by applying this PP meltblown fibers to the structure of Dash Insulation,
sound absorption performance is improved and resulting in lightweighten effect of Dash Insulation
Experimental analysis of Local Defect Resonance in an aluminum plate
Authors: KOUCHORO Biaou Jean-Baptiste , MEZIANE Anissa , MICHEAU Philippe , RéNIER Mathieu , QUAEGEBEUR Nicolas
Published: October 2024

In the context of non-destructive evaluation and testing of structures, the use of Local Defect Resonance is promising for the detection of delamination-type defects in composites. In this context, an experimental analysis Local Defect Resonance is proposed. It is here carried out on
a model system: a thin aluminum plate with a Flat Bottom Hole (FBH) defect consisting in a self-adhesive aluminum sheet (a shim) adhesively bonded over a circular through hole. First, the local defect resonance frequencies and mode shapes are analyzed assuming linear vibrations of the structure.
Then, a nonlinear approach is used to compare two types of FBH defects, a first flawless one and a second one including a damaged area. For this purpose a high amplitude vibration around the resonance frequencies are used in order to generate high order harmonics. This enhancement is identified
as associated with mainly quadratic nonlinearity.
Effect of discretization on off-axis listeners in binaural synthesis based on the optimal source distribution
Authors: YAIRI Motoki , HOSHINO Tsuguto , TAKEUCHI Takashi , CHRISTIE Colin
Published: October 2024

3D sound reproduction based on binaural synthesis over loudspeakers is one of the most important techniques in immersive spatial audio. The system inversion involved in the binaural synthesis gives rise to several problems such as dynamic range loss, distortion of the reproduction transfer
function, and a lack of robustness to room reflections. The principle of Optimal Source Distribution was proposed to overcome these problems. This utilizes a pair of conceptual monopole transducers whose azimuthal location varies continuously as a function of frequency. Another potential of
the principle is that it can provide listening positions for multiple off-axis listeners, in addition to the on-axis listener whose inverse matrix is given, since the phase interference state is aligned at all frequencies. However, these continuously varying transducers are too conceptual
to realize in practice. It is necessary to provide discretized sound sources with appropriate frequency ranges according to the principle. In this paper, the effect of discretization of the principle on off-axis listeners' performance is numerically investigated to reveal how those off-axis
sweet spots are formed as the discretization becomes finer. An experiment is also carried out using an actual discretized system and the effect of the head-related transfer functions is considered.
Topological valley waveguide state transport based on the nesting difference
Authors: SUN Jie , WANG Xiaopeng
Published: October 2024

Acoustic topological waveguide states are characterized by topologically protected transport. Existing acoustic topological valley-locked waveguide state transport structures can only realize single-scene acoustic field modulation due to the limitation of structural tunability, and
it is difficult to realize width degree of freedom and reconfigurable transport paths of acoustic waves by adjusting the transport structure for complex acoustic field. Therefore, the transport structures become a conceptualized idea in terms of tunability. Our study introduces a nesting method
in the design of the sonic crystal scatterer, which splits the scatterer structure into a removable outer shell and a core, and three topological phase transitions can be realized by only changing the nesting method of the sonic crystal shell, this approach constructs a fully reconfigurable
topological waveguide. The results demonstrate that changing the nesting of the sonic crystals induces effective spatial inversion symmetry breaking, which leads to the valley topological phase transitionSimulations and experiments demonstrate that this transport structure has excellent robust
transport properties with large inflection corners, and it is capable of realizing acoustic focusing, acoustic channeling, and acoustic logic gates. This fully reconfigurable sonic crystal design method can provide implications for the modulation of other classical waves.
Optimal selection of reference microphone for active noise control
Authors: TOYOOKA Shota , KAJIKAWA Yoshinobu
Published: October 2024

This paper proposes two methods for selecting a reference microphone from multiple microphones, focusing on the correlation between the reference signal and the desired signal and the causality constraint of the signal, in order to effectively reduce noise arriving from various locations.
In the first method, a threshold is set for the correlation between the reference signal and the desired signal, and a microphone that satisfies the causality constraint is selected as the reference microphone from microphones with correlation values that exceed this threshold. On the other
hand, the second method selects a microphone with the highest correlation between the reference signal and the desired signal as the reference microphone among the microphones that satisfy the causality constraint. We demonstrate through simulation experiments that the active noise control
system using these proposed methods can provide stable and effective noise reduction for noise arriving from various locations. It is also shown that both methods can reselect an appropriate reference microphone when the noise source moves.
Development of auditory training application for volleyball players
Authors: TANAKA Tetsuo , TAKAHASHI Hayato , MIURA Takahiro , YAMAGUCHI Yuta , UEDA Mari
Published: October 2024

In various ball games, players make appropriate plays by obtaining information from their surroundings. In volleyball, players also obtain auditory information from the sound of balls being hit, people's voices, footsteps, etc. However, details such as how to use it have not been clarified.
The purpose of this research is to develop a method for improving volleyball competitiveness using auditory information. The authors investigated the acoustic characteristics of good and bad sounds that athletes usually express intuitively in words, and also investigated the relationship between
acoustic characteristics and athletes' subjective evaluations of the quality of the meat. We investigated the relationship. As a result, we confirmed that there are differences in the sounds that are perceived as "good" or "bad." Furthermore, we conducted acoustic measurements
and acoustic analysis of serves and spikes for experienced volleyball players, and based on the analysis results, we developed an auditory training system to enable accurate discrimination of sounds during competition. In the future, we will collect logs from experiment participants who trained
using the application and analyze differences in training effects due to differences in years of experience. We will also consider how to create a more efficient training system.
Micro-perforated plates constructions with approaching the theoretical limits of its sound absorption performance
Authors: JIANG Congshuang , LI Xianhui , HU Wencheng , WANG Fang
Published: October 2024

Micro-perforated plates resonant absorbers have a considerable theoretical sound absorption bandwidth upper limit. Three types of MPPs with straight holes, including circular holes on thick plate, circular holes on thin plate, and slotted holes on thin plate, are investigated with approaching
the theoretical limits of its sound absorption performance. It is demonstrated that thin plates are easy to obtain satisfactory sound absorption performance but hard to get high mechanical strength. Slotted holes are beneficial for extending the sound absorption bandwidth of MPP absorbers.
MPPs with straight holes usually require a combination of thin plates, minute holes and high perforation ratios, which is practically difficult to apply on a large scale. Two other types of MPPs with variable cross-sectional holes, fabricated using the subtractive processing method and superposition
processing method, are then proposed to achieve perfect sound absorption performance and good engineering feasibility.
Acoustic performances of earthen walls, review of modeling approaches and tools
Authors: ROMAGNÉ Marc , GLÉ Philippe , GUIGOU CARTER Catherine , GOURDON Emmanuel
Published: October 2024

Earth construction benefits of a renewed interest particularly for environmental reasons. However, due to its mainly artisanal construction process, acoustic characterization data of earthen walls are quite rare which can limit their use for projects involving acoustic requirements.
Moreover, the great diversity in materials as well as in related construction techniques could result in a large spread in terms of acoustical performances. In this context, acoustic characterizations and modelings are necessary to provide a better understanding on earth materials behaviors.
In this study, the results from different modeling approaches are compared to few earth walls sound transmission loss data publicly available. The modeling tools including simplified formulas or more elaborated softwares present different levels of complexities and assumptions sometimes highlighting
the specificities of this material. Depending on the construction techniques used (earth blocks, light earth, earth panels etc ...), different assumptions can be appropriate. Extrapolations of performances on several walls for both sound transmission loss and sound absorption provide information
regarding tendencies and potentially achievable performances for future earth construction projects. Nevertheless, the comparison between the modeling approaches allows gaining insight on the limits of some approaches and the necessary critical analysis before a possible generalization to
other earth walls.
A revised online tool for room acoustic prediction of open-plan offices
Authors: KERäNEN Jukka , ALAKOIVU Reijo , HONGISTO Valtteri
Published: October 2024

Room acoustic conditions in open-plan offices are usually measured using ISO 3382-3 standard. The essential single-number quantities obtained from the measurement are comfort distance and distraction distance. Their values can also be predicted using a regression model of Keränen
& Hongisto (2013). The prediction accuracy of the model has been proven to be high. The input variables for the model are simple to obtain: room dimensions, screen height, ceiling absorption, vertical absorption, speech level, and background noise level. The prediction model was published
online in 2008 but withdrawn in 2013. Since then, we have been repeatedly asked to return the online tool. Since the standard was updated in 2022, we developed a revised online tool that predicts the single-number values of ISO 3382-3 standard. The purpose of this study is to present the online
tool and validate its reliability by comparing online tool results to previously published results. The comparison shows that the online tool results agree with the above-mentioned studies. Therefore, the online tool can be safely used. It is a valuable aid in workplace design, demonstrations,
research, and education.
Semi-empirical model for amplitude fluctuations by atmospheric turbulence in aircraft flyover sound
Authors: LINCKE Dorothea , PIEREN Reto
Published: October 2024

Atmospheric turbulence leads to well-audible fluctuations in the amplitude of sound propagating through the atmospheric boundary layer. However, the best currently available theoretical model is valid only for short propagation distances and low turbulence regimes. A new model for predicting
the standard deviation of amplitude fluctuations was developed based on the existing theoretical model of Ostashev and Wilson and the analysis of empirical data. The dataset includes over 5000 aircraft flyover events in different meteorological conditions from March to August. The model considers
an effective propagation length based on the boundary layer height, frequency-dependent saturation of amplitude fluctuations, turbulence decay time during periods of decreasing solar radiation, and turbulence production by nocturnal low-level-jets. The model adaptations have significantly
reduced the mean squared error from over 10 dB in the pure theoretical model to 0.3 dB in the new model. The findings will help improving the modelling of outdoor sound propagation for elevated sound sources like aircraft and wind turbines. Modelling these fluctuations can considerably improve
the realism of the listening experience in aircraft flyover auralisation. Further, it helps estimating the measurement uncertainty in measured aircraft noise, especially for maximum levels.
Room acoustic survey of open and enclosed learning spaces in Finland
Authors: KERäNEN Jukka , AHONEN Kaisa , HONGISTO Valtteri , RADUN Jenni
Published: October 2024

Use of open learning spaces for education has increased in schools while enclosed learning spaces are still used in most schools in overall. There is some debate that these two learning space types might differ in acoustic perceptions. If they do, room acoustic quality might be one
explaining factor. Therefore, our purpose was to determine, whether these learning space types differ in room acoustic properties. We studied 10 schools with mostly enclosed and another 10 schools with open or flexible learning spaces in Finland. Altogether 73 learning spaces were investigated
among the 20 schools. Measurements concerned reverberation time, Speech Transmission Index, and background noise level. Most of enclosed learning spaces (63%) met the new requirements of Finnish building regulations for enclosed learning spaces. Opposite to that, most of open learning spaces
(91%) did not meet the regulations for open learning spaces. The results can be used in the root cause analysis of a teacher survey conducted in the same 20 schools. Teacher survey will be reported in another study. Parallel analysis of objective and subjective results is necessary to judge
whether the current regulations are justified.
Gender difference on loudness perception and evaluation
Authors: TSURUTA-HAMAMURA Mariko , HASEGAWA Hiroshi
Published: October 2024

Factors affecting gender differences in loudness perception and evaluation were examined from three perspectives: verbal criteria, brain perception (ratio scale evaluation), and cultural background. When the verbal criteria such as "soft" and "loud" was used for
evaluation of perceived loudness, the gender differences were observed for Japanese, Chinese and Malaysian participants. Meanwhile, the gender difference was observed only for Chinese men and women when the ratio scale was used for evaluation of perceived loudness.However, this tendency was
only observed for some stimuli, thus the experiment was conducted again with Chinese participants under more detailed evaluation conditions, and no clear gender difference was observed as in the case of Japanese and Malaysian participants. From these result, it was suggested that the gender
difference in loudness perception might be caused by the process of more higher-order auditory signal processing that uses verbal expression.
Virtual sound source construction based on adaptive crossfade processing with electro-dynamic and parametric loudspeaker arrays
Authors: IWAGAMI Mizuki , HIROSE Ayano , GENG Yuting , NAKAYAMA Masato , NISHIURA Takanobu
Published: October 2024

Among the various high-presence sound field reproduction technologies, we focus on wave field synthesis (WFS) using a loudspeaker array, as it can construct a virtual sound source (VSS) with few restrictions. A VSS using parametric array loudspeakers (PALs) can provide more accurate
direction perception than VSS using electro-dynamic loudspeakers (EDLs) because PALs hold sharp directivity by utilizing ultrasounds. However, the distance perception tends to be degraded. We previously proposed a VSS construction based on WFS with hybrid control of an EDL and a PAL arrays.
This method enhances distance perception by exploiting the difference in radiation characteristics between PALs and EDLs. However, the difference in frequency responses between PAL and EDL is noticeable to the listener when switching between them. In this paper, to enable more smooth transition
of the EDL and PAL arrays, we propose a VSS construction method based on adaptive crossfade processing with EDL and PAL arrays. For an arbitrary VSS construction position, the coefficients of crossfade for each frequency are determined by an adaptive filter based on measured impulse responses
of VSSs with EDL and PAL arrays. We demonstrated the effectiveness of the proposed method through evaluation experiments.
Analysis of nonminimum phase components of noise control filters in active noise control
Authors: MIZUTANI Maoto , IWAI Kenta , NISHIURA Takanobu , SOETA Yoshiharu
Published: October 2024

In the active noise control (ANC), it is known that the optimal filter becomes a noncausal filter due to the effect of the nonminimum phase components of the secondary path. We have investigated how to make the causal optimal filter by replacing the nonminimum phase components with
the frequency components of the primary path. Through the computer simulations, we have confirmed that this filter maintained some noise reduction performance and can be used as a quasi-optimal filter. In this paper, as another approach, we attempt to identify noncausal components using the
pre-trained adaptive noise control filter. The nonminimum phase components of the secondary path exist in the frequency band below the lowest resonance frequency of the secondary loudspeaker. Based on this fact, we design a noise control filter by using band-limited white noise only with the
low frequency components below the lowest resonance frequency in advance. Then, we design another adaptive noise control filter by using the band-limited white noise with high frequency components above the lowest resonance frequency. Finally, we combine these filters in the frequency domain.
Through the computer simulations, we show the difficulty to handle the nonminimum phase components in the ANC system.
Temperature effect on acoustic waves reflection condition in anisotropic crystals
Authors: KOSTYLEVA Ekaterina , MANTSEVICH Sergey
Published: October 2024

The reflection of acoustic waves in anisotropic media has found important applications in acousto-optics (AO). It may be realized both with changing the type of acoustic mode and without it. The latter case is applied for the realization of the quasi-collinear AO diffraction geometry
for which the incident light and ultrasound wave group velocity vectors are collinear. The acoustic wave involved into the AO interaction exists due to the reflection from the AO cell input optical face. Quasi-collinear configuration of AO interaction enables achieving exceptionally high spectral
resolution and diffraction efficiency, therefore, it is applied for the laser pulse shaping. However, the application of AO tunable filters for such purposes requires high acoustic power values, which induce the temperature gradients in the AO crystal. Temperature variations influence the
stiffness constants of the AO crystal, impacting the characteristics of incident and reflected acoustic waves, affecting the acoustic wave reflection condition and consequently, the AO diffraction characteristics. This study presents the theoretical and experimental examination of the temperature
influence on the acoustic beam reflection in anisotropic crystals on the example of tellurium dioxide crystal. This paper is supported by the Russian Science Foundation, grant 23-12-00057.
All-optical infrasound sensor based on a Fabry-Perot interferometer
Authors: REZKI Amazigh , GUIANVARC'H Cécile , SILVESTRI Zaccaria , WALLERAND Jean-Pierre
Published: October 2024

Recent demands for infrasound measurement, whether for detecting violent atmospheric events or evaluating the environmental impact of wind farms, require new acoustic calibration standards in the frequency range below 2Hz. Expanding the frequency bandwidth of microphones remains a limited
strategy since they are designed to filter out continuous components. An alternative method for measuring infrasound is proposed, which relies on a Fabry-Perot interferometer. This technique has been studied extensively for static pressure measurements with success. Therefore, adapting a Fabry-Perot
refractometer to perform acoustic measurements is not only a technical challenge but also an opportunity to bridge the gap between static pressures and acoustic metrology. As acoustic movement involves both small pressure and temperature variations, it is important to account for their coupled
effects in interferometer measurement results. Since the temperature variation field in the measurement system cannot be characterised experimentally, an analytical model has been developed. The chosen theoretical and technical solutions are validated by the good agreement between experimental
results obtained with the refractometer carried out and other calibrated sensors in the frequency range from 40mHz to 1.5Hz. These results also highlight the improvements required to bring the device up to the level of an infrasound reference instrument.
Analysis of the flow induced vibration transition sustained by a hydrofoil
Authors: LEDUC Marine , WATINE Yann
Published: October 2024

Hydrofoils sustain severe flow induced vibrations when a hydrodynamic excitation source couples with a natural frequency, a phenomenon called lock-in responsible for early fatigue and acoustic radiations. The present paper focuses on the fluid-structure interaction during the transition
between a non-resonant and a lock-in regimes. Tests were performed in the hydrodynamic tunnel of the French Naval Academy Research Institute with a truncated NACA 66-306 hydrofoil for chord-based Reynolds numbers ranging between 255000 and 374000 at zero angle of attack. Laser vibrometry,
particle image velocimetry and spectral proper orthogonal decomposition were used to investigate the fluid-structure interaction mechanisms. The analysis has highlighted a transition between a low magnitude vibration regime occurring at Reynolds 255000 and a lock-in regime occurring at Reynolds
374000. A primary excitation source has been associated with Karman vortex shedding. Also, during the lock-in, a specific type of vortices is observed at a characteristic frequency equal to twice the Karman vortex shedding frequency. Also, a flow recirculation region located in close vicinity
of the trailing-edge is reinforced at this particular regime. The understanding of the mechanisms leading to high magnitude vibrations will reduce the acoustic radiations and enhance the efficiency of next generation hydrofoils.
Vibration and noise reduction on a cover for power electronics for electric vehicles with vibroacoustic metamaterials
Authors: RIEß Sebastian , WEBER Armin , HüLSEBROCK Moritz , CóNDOR LóPEZ José , KLEINFELLER Nikolai , USZYNSKI Olaf , ATZRODT Heiko
Published: October 2024

Electric vehicles represent a particular challenge in terms of noise, vibration and harshness, since there is no masking of the combustion engine anymore. For consumer acceptance, long distances need to be covered with electric vehicle, which makes lightweight structures necessary.
Consequently, vibration problems occur during operation, as lightweight structures are more susceptible to vibrations. Common measures for vibration and noise reduction add a considerable amount of mass to the vehicle, counteracting the lightweight efforts. Vibroacoustic metamaterials as a
novel approach promise greater vibration reductions than common measures like Alubutyl or bitumen and are accompanied by a lower weight. This study deals with the design of vibroacoustic metamaterials for the noise and vibration reduction of a cover for power electronics of an electric vehicle.
The design process is demonstrated for two different kinds of vibroacoustic metamaterials made from sheet metal and a plastic film. The structural dynamic behavior of both approaches is experimentally investigated and compared with a cover equipped with Alubutyl. The vibroacoustic metamaterial,
which is made from sheet metal, is furthermore tested in a vehicle under driving condition. A reduction of tonal noise components by 11 dB is achieved within the passenger compartment.
Acoustic pattern of a full scale simplified ship
Authors: PETRIS Giovanni , CIANFERRA Marta , ARMENIO Vincenzo
Published: October 2024

Underwater radiated noise from ship propellers is one of the major contributors to the increase in overall noise levels in marine environments. The development of numerical tools for the computation of noise propagation is of paramount importance for the assessment of the noise impact
on the environment. Hybrid approaches, based on the decoupling of the computation of the fluid flow and the successive evolution of the noise using an acoustic analogy, are typically conducted in open-water conditions, which do not correspond to a realistic environment. The Full Acoustic Analogy,
which couples a propagation model based on the solution of the acoustic wave equation to the hybrid approach, enables the propagation of the noise generated by a marine propeller in a confined heterogeneous domain. The near-field scattering characteristics of a simplified hull positioned in
front of a ship's propeller are analyzed in shallow and deep water, in the presence of the free surface, and compared to the open water case. The analysis determines the directivity of the propeller noise and how this may affect how the noise propagates in the marine environment.
Development of low-cost MEMS microphone array for sound localization in urban environments
Authors: PECIOSKI Damjan , DOMAZETOVSKA MARKOVSKA Simona , GAVRILOSKI Viktor , ANACHKOVA Maja , IGNJATOVSKA ANGJUSHEVA Anastasija
Published: October 2024

Understanding noise pollution and mitigating its impact on the quality of life in urban environment is a major challenge from a societal and health point of view. In order to monitor and ultimately understand these noisy environments a process of long term acoustic measurements and
analysis is required. These urban environments are noisy and obtaining a clear recording of a desired acoustic signal is difficult hence an effective approach is the use of beamforming theory coupled with a microphone array. In this paper a novel approach utilizing compact low-cost microphone
arrays equipped with MEMS sensors for continuous sound localization in urban areas is proposed. This approach focuses on leveraging the affordability and scalability of MEMS sensors to deploy distributed acoustic sensor networks across diverse urban locations. The aim is to capture real-time
acoustic data, enabling comprehensive monitoring of sound sources and their spatial distribution within the urban environment. This sensor unit can be upgraded with a camera, i.e. acoustic camera, which will provide information on the conditions of the environment where the measurements are
performed. This low-cost solution facilitates long-term monitoring, providing valuable insights into the dynamic nature of urban soundscapes.
Determination of a diffusion coefficient function for long rooms using a least square optimization approach
Authors: FICHERA Ilaria , VAN HOORICKX Cédric , HORNIKX Maarten
Published: October 2024

Over the last decades, considerable attention has been devoted to improving the diffusion equation model within the field of room acoustics. It has been found that this model is subject to certain limitations, with one constraint regarding the diffusion coefficient. The diffusion coefficient,
a parameter integrated into the model, is a value that scales the sound intensity to the gradient of the sound energy density. Currently, this value is often treated as a constant, but research has shown that it is spatially dependent. This paper explores a method to optimise the diffusion
coefficient for long rooms such as corridors and tunnels by comparing the results of the diffusion equation model with those computed with the radiosity model and using the least-square optimization method, minimising the difference between the results of both methods. The parameters of a
diffusion coefficient function are optimised, targeting a function that can be applied to a range of elongated spaces.
Ultrasonic signatures of multiphase architectured media: Application to biomechanics
Authors: GATTIN Max , BOCHUD Nicolas , GROSSMAN Quentin , RUFFONI Davide , ROSI Giuseppe , NAILI Salah
Published: October 2024

Assessing the mechanical characteristics of periodic architectured scaffolds employed in bone tissue repair, while preserving their structural integrity, poses a significant challenge from both theoretical and experimental viewpoints. By leveraging concepts arising from the phononic
crystals community, here we investigate the reflection and transmission of elastic waves propagating through water-immersed biphasic architectured samples in the MHz regime, which exhibit a periodic organization at a length scale of a few hundred micrometers. Experimental outcomes are systematically
compared with modeled predictions, spanning a range of scaffold-like samples engineered to mimic the expected variations that take place in a biological environment. A particular attention is given to critical modeling considerations such as the behavior in reflection, the interaction of Bloch
waves with the viscoelastic properties of the constituent phases, as well as the role of modal conversion at the interface between the homogeneous incident medium and the architectured one. Altogether, the reported results suggest that specific ultrasonic signatures associated with elastic
wave propagation in periodic media, encompassing phenomena such as bandgaps and dispersion, offer valuable insights towards the nondestructive monitoring of micro-architectured media like scaffolds.
Prediction and validation of flanking sound transmission in cross-laminated timber junctions with resilient interlayers
Authors: MOONS Stijn , REYNDERS Edwin , LANOYE Reinhilde
Published: October 2024

Propelled by its small carbon footprint, low weight and high stiffness, cross-laminated timber (CLT) has experienced a significant commercial growth in the last decade. However, these latter two features potentially contribute to poor acoustic performance. A critical factor is flanking
sound, in which vibrational energy is transmitted between two elements connected through a common junction, driving the need to include vibration isolation solutions such as resilient interlayers in the junction design. In this work, the vibration reduction index across CLT junctions is predicted
with an analytical wave approach for semi-infinite thin plates. Each CLT panel is modelled as an orthotropic or isotropic equivalent single layer (ESL). Multiple options to determine the ESL properties are compared, including the law of mixtures and the modified gamma method. The interlayer
is considered to be a thick, flexible waveguide, whose out-of-plane motion is governed by shear. The prediction model is validated experimentally with on-site measurements for a vertical T-junction with a polyurethane foam interlayer. The predictions are moderately accurate in the entire frequency
range, with deviations below 10 dB across all 1/3 octave bands. Depending on the layer configuration, the orthotropy of the ESL can significantly influence the predictions.
Validation measurement of vehicle pass-by models for dynamic urban environments
Authors: MöHLMANN Chalotorn , ASPöCK Lukas , FELS Janina
Published: October 2024

Simulation and auralization of urban traffic noise can help city planners and residents to improve existing urban areas or plan new attractive living spaces while enabling discussions about shared auditory experiences, regardless of expertise. Evaluating street noise in the context
of urban areas requires careful consideration of their urban surroundings, such as landscapes, buildings, and other structures. Obtaining measurements to validate simulations may be difficult given the variety and complexity of sounds within an urban setting. Recreating the real urban scenario
on a test track, e.g., including building facades and exact source and receiver positions, helps validate simulations but also poses challenges due to varying road surfaces, weather conditions, and disturbances such as industrial or fly-over sounds. This research represents a method of bringing
a measurement set-up consisting of source (e.g., vehicle), receiver (e.g., pedestrian), and surfaces (e.g., walls) to the more controlled environment of a hemi-anechoic chamber. The method is intended for the validation of previous vehicle pass-by measurements by utilizing sine sweeps with
walls parked at varying distances. These environments aim to deliver more insight into the relevance of diffracted sound for configuration of urban sound simulation models.
Towards better visualizations of urban sound environments: insights from interviews
Authors: TAILLEUR Modan , AUMOND Pierre , TOURRE Vincent , LAGRANGE Mathieu
Published: October 2024

Urban noise maps and noise visualizations traditionally provide macroscopic representations of noise levels across cities. However, those representations fail at accurately gauging the sound perception associated with these sound environments, as perception highly depends on the sound
sources involved. This paper aims at analyzing the need for the representations of sound sources, by identifying the urban stakeholders for whom such representations are assumed to be of importance. Through spoken interviews with various urban stakeholders, we have gained insight into current
practices, the strengths and weaknesses of existing tools and the relevance of incorporating sound sources into existing urban sound environment representations. Three distinct use of sound source representations emerged in this study: 1) noise-related complaints for industrials and specialized
citizens, 2) soundscape quality assessment for citizens, and 3) guidance for urban planners. Findings also reveal diverse perspectives for the use of visualizations, which should use indicators adapted to the target audience, and enable data accessibility.
Towards validating the diffraction-enhanced image source method
Authors: XU Zeyu , ERSINADIM Kaan , HABETS Emanuël A. P. , PRINN Albert G.
Published: October 2024

Accurately simulating room acoustics between directional sources and receivers in reverberant environments can be challenging. Wave-based numerical models can be used at low frequencies, but at higher frequencies, the cost of solving these models is often too prohibitive to permit practical
use. Geometrical models can be used to simulate sound fields in rooms at higher frequencies but with limited accuracy due to the inherent assumptions made when deriving the models. Therefore, there are ongoing efforts within the room acoustics community to improve the accuracy of geometrical
models. Recently, an extension to the image source method called the diffraction-enhanced image source method, which uses spherical harmonic descriptions to include directional sources and receivers, has been proposed. The proposed method can be used to efficiently model sound fields in shoebox-shaped
rooms with directional sources and receivers at high frequencies. In this paper, predictions of the proposed method are compared to data measured in a shoebox-shaped room. It is shown that the proposed method captures many of the pertinent features of the measured transfer functions and impulse
responses.
The innovated national noise monitoring network in The Netherlands
Authors: LOLKEMA Dorien , BOUWMAN Dagmar , WARTENBERG Tijmen , KOK Arnaud , LOON, VAN Rob , DRUKKER Derko , HAAIMA Marty , GLENN Hendriks
Published: October 2024

Over ten years ago, the National Institute for Public Health and the Environment started monitoring noise emissions from major roads and railways in The Netherlands. Today, this monitoring program is still going strong. The measured data is used to validate the yearly reported noise
production levels calculated by the Dutch road and railway authorities, to monitor trends in noise production, and to check the validity of the Dutch noise calculation method. Measurements in the entire network are performed at an altitude of four meters close to fifty meters from the major
road or railway in free field as these are the requirements for the reported calculated levels. The network therefore, has to operate stand-alone, resulting in challenges in terms of power supply, datastorage and communication. Ten years ago, we started with a battery-powered network of simple
and cost-effective dataloggers. Recently, we made innovations by transitioning to a solar-powered network of modern sound level meters with remote data communication. In this presentation I will give a brief history of this monitoring network, how it developed, and show you the possibilities
of the present-day innovated network.
Sound insulation of partially open windows - alternative laboratory measurement methods
Authors: SøNDERGAARD Lars Sommer , SELL Liisa
Published: October 2024

Sound insulation with partially open windows has had growing attention in recent years. In Denmark, this is primarily caused by the Danish Environmental Protection Agency's guideline from 2007 "Noise from roads", which introduces noise limits with open windows (opening area
of 0.35 m2) for situations with a high traffic noise level. The sound insulation of traditional windows in open position have been measured in both the laboratory and external environment, and for certain setups too different results have been observed. To investigate the reasons behind the
discrepancies, the traditionally reverberant source room of laboratory measurements was modified to a semi-anechoic room to remove reflections from unwanted reflections from room surfaces and to imitate the external environment during field measurements. Four different window types were tested
as part of the research projects "Optimized measurement method for sound reduction of partially open windows part 1 and 2" (MetÅV and MetÅV2) in collaboration with four Danish window manufacturers. The primary focus of the project is to explore alternative laboratory
methods to the traditional diffuse field method by studying reference cases from field measurements and taking into consideration different sound source positions and window geometry. This paper describes the results so far.