bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibro-acoustic modeling of aircraft structures using Finite Element- informed Statistical Energy Analysis
Authors: Mejdi Abderrazak , Alimonti Luca , Gardner Bryce
Published: September 2021

This paper addresses the problem of predicting the structure born and airborne sound transmission in aircraft using Statistical Energy Analysis (SEA). Often analytical formulations are used to approximate the SEA parameters. In the present prediction method, a finite element (FE)-informed
SEA approach is employed. To compute the coupling coefficient, the structure is represented with a repetition of unit cell and an FE model of the unit cell is assigned to evaluate the direct field dynamic stiffness matrix of the SEA subsystems at the connections. An efficient strategy is employed
to determine the equivalent material properties of the FE model. Thus, a two-dimensional unit cells of different constructions such as composite, sandwich, visco-elastic laminate and ribbed section sections can be used. To evaluate the equivalent properties of multilayers structures, each
layer is assumed as thick laminate with orthotropic orientation. Moreover, rotational inertia and transversal shearing, membrane and bending deformations are accounted for. First order shear deformation theory is employed. The developed approach handles symmetrical layouts of unlimited number
of transversal compressible or incompressible layers. The accuracy of this modeling approach is confirmed through comparison to alternate validated theoretical approaches. Representative examples of spacecraft structural response and interior noise predictions for typical load cases are shown
and the use of SEA models as a tool for guiding construction of complex structures to meet acoustic performance targets and optimize designs are presented. Conclusions about the application and advantages of this approach is presented.
Analyzing transportation noise during the pandemic.
Authors: Curley Josh , Snow Kody
Published: September 2021

The COVID-19 pandemic has introduced new challenges in the approach to many types of projects in the field of acoustical consulting. An important one being the impact on how transportation noise studies are conducted, in particular on-site noise measurements and subsequent computer
modeling. The pandemic has affected roadway, railway, and aircraft travel, and consequently the noise generated by these transportation noise sources. This raises questions about the methods used to determine existing and future transportation noise impact upon residential sites. After a year
into the pandemic, it appears that postponing an analysis is no longer feasible and that the need for an adaptable method of analysis is required to meet jurisdictional transportation noise analysis requirements. How should these studies be completed during this time in which it is highly
likely that roadway, railway, and aircraft volumes are not what they were pre-pandemic? How or even should on-site noise measurements be taken? Will the local jurisdictions accept the studies completed during the pandemic? When will roadway, railway, and airport volumes be back to pre-pandemic
levels, or will they ever be back to that volume? Will there be a significant impact on noise? This paper will follow the process used to complete transportation noise studies during the pandemic, which involved creatively adapting known methods to address these new questions while working
closely with local jurisdictions, providing the education and guidance needed for them to comfortably review studies so that the transportation noise component of site approval does not slow down residential projects.
Design of Acoustic Cloak Using Generative Modeling and Gradient-Based Optimization
Authors: Zhuo Linwei , Amirkulova Feruza
Published: September 2021

Metamaterials are engineered composites that can achieved electromagnetic and mechanical properties that do not exist in natural materials by rearranging their structures. Due to the complexity of the objective functions, it is difficult to find the globally optimized solutions in metameterial
design. This talk outlines a gradient-based optimization with generative networks that can search for the globally optimized cloaking devices over a wide range of parameters. The GLO-Net[1] model was developed originally for one-dimensional nano-photonic metagratings is generalized in this
work to design two-dimensional broadband acoustic cloaking devices by perturbing positions of each scatterer in planar configuration of cylindrical scatterers. Such optimized cloaking devices can efficiently suppress the total scattering cross section to the minimum at certain parameters over
range of wavenumbers. During training each iteration, a generative model generates a batch of metamaterials and compute the total scattering cross section and its gradients using an in-house built multiple scattering MATLAB solver. To evaluate our approach, we compare our obtained results
with fmincon in MATLAB. Reference: [1] Jiaqi Jiang and Jonathan A. Fan. Simulator-based training of generative neural networks for the inverse design of metasurfaces. Nanophotonics, 9(5):1059-1069, nov 2019.
Comparison of roadwheel and roadway noise generated by a mono-pitch tire tread
Authors: Ruhala Richard , Burroughs Courtney , Ruhala Laura
Published: September 2021

Tire-pavement interaction noise (TPIN, aka tire-road noise or tyre-road noise) is most efficiently measured in acoustically controlled laboratories with large diameter roadwheels (drums) that have surface treatments which replicate some pavement properties, especially when comparing
the acoustic performance of different tires. However, it is not clear how closely the roadwheel replicates the road surface, including differences that include road curvature and mechanical impedance of pavements. On the other hand, measuring on a moving vehicle with a microphone array presents
it own set of challenges. In this study, a Nearfield Acoustical Holography (NAH) method is used to measure tire/pavement interaction noise on roadways and roadwheels with similar smooth pavement and rough pavement properties. Sound intensity fields, overall sound power levels, and sound pressure
levels are reconstructed very close to the tire surface. An experimental passenger car tire with a mono-pitch tread is used in this study. The experimental tire has three circumferential grooves and 64 equally spaced transverse grooves cut into the tread. Differences in sound fields and levels
between roadway and roadwheel test conditions for this tire are shown.
The study of ultrasonic layer-matched to penetrate bone
Authors: Li Lianchun , Diao Yifan , Wu Haijun , Jiang Weikang
Published: September 2021

Acoustic metamaterial layer-matched was designed to enhance ultrasound penetration through bones. The conventional ultrasound layer-matched, known as coupling agent, can only enhance the transmittance of ultrasound to soft biological media, such as cartilage and muscle, but cannot penetrate hard media, i.e. bone. An ultrasound layer-matched based on the impedance matching principle is presented to make ultrasound penetrate bone, which parameters are designed by acoustic metamaterial equivalent parameter technique. The ultrasound layer-matched is fabricated by 3D printing which can correct the aberrations of the bone. Some configurations are investigated by numerical simulation as well as experiments in the anechoic chamber. In particular, a bone matching layer can be designed optimally for the definite thickness of the bone and the definite operating frequency of the ultrasound probe, which enhanced ultrasound to penetrate both of the layer-matched and the bone with no echo. The results of experiments and simulations show that the proposed ultrasound layer-matched metamaterial can enhance the transmission efficiency of ultrasound to penetrate some hard biological media bones.
Acoustic characterization of membranes attached to sound absorbing base materials
Authors: Rodríguez Vercher Juan Carlos , Alba Jesús , Rey Romina del
Published: September 2021

The use of membranes attached to sound absorbing materials, with the aim of modifying its absorption properties, is quite a usual practice in acoustic conditioning applications. The behavior of the final composition formed by the sound absorbing base material and the attached membrane
can serve to characterize the effect of the membrane, if the properties of the base material are known. This can be of great interest for several reasons. Firstly, the difficulty to characterize the materials separately, due to the thinness of the membranes. Secondly, the effect of the binding
method used between the absorbing material and the membrane (glue, seams, etc.) can modify the properties of the membrane. This work presents a model that enables us to determine the acoustic impedance of the membranes from an initial analysis of the base material and a second analysis of
the composition formed by the base material with the membrane. These analyses are carried out in an impedance tube by following the ISO 10534-2 standard and the results obtained allow modeling the attached membrane effect.
Estimation and experimental test of the sound-absorption coefficient of a pin-holder structure (Case of sound waves incidence upon the side surfaces of a group of cylinders)
Authors: Sato Takamasa , Sakamoto Shuichi , Nitta Isami , Unai Shunsuke , Isobe Takunari , Iizuka Kenta , Tasaki Katsuhiko
Published: September 2021

In this study, we conducted theoretical analyses and experiments related to the acoustic characteristics of the situation where sound waves are incident upon the side surfaces of a group of cylinders forming a pin-holder structure. The sound-absorption coefficient, entering its clearance
between cylinders through the geometrical dimension of the clearance or the physical property of gas, was calculated. In the analytical model, the gap part of the pin-holder structure was divided into elements and approximated as a gap surrounded by two parallel planes. The characteristic
impedance and propagation constant of the approximate gap were obtained and treated as one-dimensional transfer matrices; the sound-absorption coefficient was then calculated using the transfer-matrix method. The calculated value was compared to that obtained in an experiment with a sample
prepared using a 3D printer; the sound-absorption coefficient was measured using a 2-microphone impedance-measuring tube. We attempted to make a simple yet accurate estimation of sound-absorption coefficient using these procedures. Our theoretical values displayed a similar tendency to that
obtained by experiment.
OTPA method-based contribution analysis of components on the vibration of fuel cell in fuel cell vehicles
Authors: Nan Zequn , Behrendt Matthias , Lu Mengting , Petersen Manuel , Albers Albert
Published: September 2021

Due to the introduction of auxiliary components in fuel cell vehicle powertrains and absence of internal combustion engine, the vibration sources and transfer paths are very different from conventional vehicles. These vibrations interact on the output performance of the fuel cell system.
Therefore, it is necessary to investigate the vibration characteristics of the fuel cell system under vehicle operating conditions. IPEK conducted vehicle measurements regarding different driving manoeuvres and environments. In order to quantitatively evaluate contributions of each vibration
source on the total vibration of fuel cell, frequency-domain contribution was investigated based on Operational Transfer Path Analysis method with the singular value decomposition as well as principal component. The results of vibration in Z-direction in the vehicle coordinate system show
that the hydrogen pump dominantly contributes to the vibration of fuel cell in a wide range of frequency in the majority of the driving manoeuvres. However, the results vary in various driving manoeuvres, environments and frequencies. The Paper will discuss in detail the vibrational contributions
in X-, Y- and Z-direction.
A Hybrid and Efficient Low-noise assessment Platform for Urban aerial mobility (HELPU)
Authors: Zhong Siyang , Zhou Peng , Fang Yi , Zhang Xin
Published: September 2021

Urban aerial mobility (UAM) is a promising approach to improve the traffic situation in gigantic cities, which, however, may encounter significant noise pollution issues. An integrated research platform, which is being established at HKUST, to include noise generation, long-distance
propagation, and perception at the observers is timely to assess the environmental impact of UAM noise and to develop low-noise designs and flight planning. A high-quality test rig in the anechoic aerodynamic facility at HKUST is employed to measure the propeller aeroacoustics and aerodynamics,
and to enable the innovative noise control device and design studies. The measurements and high-fidelity simulations using an in-house computational aeroacoustics solver can lead to comprehensive databases to facilitate and validate the development of physics-oriented noise prediction models.
Also, high-efficient implementation of the boundary element method is conducted to account for the noise scattering due to the fuselage and then to evaluate the impact of UAM layout on the directivity patterns, which will then be efficiently projected to the far-field observers using the advanced
Gaussian beam tracing with the effects due to moving source, atmospheric attenuation, and refraction, complex boundary absorption and reflection incorporated. Low-noise flight planning is then be made accordingly.
Influence of the Poisson's ratio on the efficiency of viscoelastic damping treatments
Authors: Rouleau Lucie , Ruas Henriques Isadora , Deü Jean-François
Published: September 2021

An efficient way of mitigating noise and vibration is to embed viscoelastic patches into the host structure. Viscoelastic properties are of significant importance in determining the performance of the passive damping treatment. The behaviour of homogeneous isotropic materials is described
by two elastic constants (generally the Young modulus and the Poisson ratio, or the shear and bulk moduli), which are frequency- and temperature-dependent in the case of viscoelastic materials. In practice, the Poisson's ratio is often considered as independent of temperature and frequency.
One goal of this work is to numerically evaluate the validity of this assumption and its limitations (frequency range, thickness of the viscoelastic layer). To this end, a thermo-mechanical characterization of a viscoelastic material is carried out by dynamic measurements of the complex shear
and bulk moduli, allowing the indirect measurement of the frequency- and temperature-dependent Poisson's ratio. Moreover, the measurements of the Poisson's ratio (direct or indirect) can lead to considerable uncertainties. For instance, large discrepancies have been observed when characterizing
the Poisson's ratio of polymer foams. Another goal of this work is to investigate the influence of those uncertainties on the dynamic response of a damped structure.
Audibility of emergency broadcasting sound in a mechanical room in an office building
Authors: Jeong Jeongho
Published: September 2021

Fire alarm and emergency broadcasting sound are important in fire and disaster situations. For the clear presentation of the fire alarm and emergency broadcasting sound to occupants of buildings, some guidelines and requirements were established. In NFPA 72 and BS standard, a specific
alarm sound level for alarm sound of residential facilities was proposed and Speech Transmission Index(STI) was regulated for the emergency broadcasting system. In the fire and disaster situation, one of the important facility is a mechanical and electrical system to maintain water and electricity
supply. To maintain this function in the buildings, clear presentation of emergency broadcasting sound to the workers in the mechanical and electrical room is crucial for the emergency operation of the system. In this study, the noise level in the mechanical rooms and electricity facilities
of more than 40 years old office building were measured. Also, audibility and room acoustic properties such as reverberation time and STIwas simulated using Odeon 12. In order to deliver emergency broadcasting sound more clearly, sound absorption material and a soundproof chamber for noisy
devices are needed. Also, the emergency broadcasting system in noisy facilities should be improved to produce the broadcasting sound louder and clearer.
Soundscape evaluation to identify audio visual aspects in café for student's activities
Authors: Octaviani Rizky , Rizkiyani Diandra , Sudarsono Anugrah Sabdono , Sarwono Sugeng Joko
Published: September 2021

A café is a type of restaurant that typically serves coffee and tea, in addition to light refreshments such as baked goods or snacks. Nowadays, students also consider cafés as a social place to do various activities. The different activities might need a different environment.
However, the existing studies regarding the soundscape in a café do not consider the different activities and only focus on the auditory aspects. In this study, the activities in a café and the important audio-visual aspects are identified. This information is beneficial to design
appropriate cafés environment for different student activities. The data were collected using an online survey. The survey asked several pieces of information such as activity preference and audio-visual preference. The survey shows that the students' activities in a café are
classified into four types: discussion-chatting (27%), group-studying (27%), eating drinking (20%), self-studying (16.5%), and others (9.6%). The survey also shows the five most important audio and visual aspects in a café: general noise (13.61%), dynamics (8.9%), the loudness of music
(8.12%), color contrast (8.12%), and hubbub (7.85%).
Differences in perceived loudness between men and women: A cross-cultural comparison among Japanese, Chinese, and Malaysians
Authors: Tsuruta-Hamamura Mariko , Nakada Kumi , Kikuchi Ryoga , Watanabe Naoki
Published: September 2021

Previously, we investigated gender difference in loudness perception among Japanese and Chinese. Among Chinese, female participants tended to assigned higher loudness scores than did males for the same sound. That difference was also evident when a ratio scale, such as magnitude estimation,
was used to evaluate loudness. However, among Japanese, that difference was not clearly observed when the ratio scale was applied. To examine factors affecting gender differences in loudness perception, we conducted the same rating experiments among Malaysian males and females. We found that
a rating experiment using the verbal interval scale showed that the female Malaysian participants tended to rate the same sounds as louder than did males. In one test, we measured the limit of sound pressure level that would be perceived as soft or as loud: we observed the above gender differences
with the lowest limit of loud sound. However, that gender difference did not emerge in the rating experiments using the ratio scale. The tendency we recorded among Malaysians was the same as Japanese. Thus, differences in judging loudness between males and females may actually reflect differences
in the use of verbal expressions rather than differences in perception.
Test bench development and validation for blocked force measurements in six degree of freedom
Authors: Burkhardt Martin , Hensel Eric , Drossel Welf-Guntram
Published: September 2021

For transfer path analysis (TPA) methods, the description of the source is essential. The possibilities of source characterization are as different as the TPA methods. For the classical methods, the source is considered in the installed state with feedback from the receiver structure,
while for component-based TPA the source is described without feedback from the coupled structure. In addition to TPA, source characterization is also used in the product development process for evaluation or comparisons. Also in these cases, the source must be characterized without feedback
from the test structure, which can generally be realized by measuring free velocities or blocked forces. Because of the need of external load to reach the components operating point, force measurements are often used. However, the realization of a reactionless test setup for the measurement
of forces poses some challenges. The paper presents a setup that can be used to perform a direct force measurement at a point in six degrees of freedom. The necessary boundary conditions to approximate the idealized blocked force assumption are discussed, the calculation of the blocked force
in six degrees of freedom is presented, the structural dynamic response at a reference point is calculated and compared with operational measurements.
Amplitude modulations increase annoyance due to wind turbine noise immission
Authors: Pörschmann Christoph , Großarth Stephan , Arend Johannes M. , Schmitter Sebastian , Schreckenberg Dirk , Wunder Klaus
Published: September 2021

Current literature suggests that annoyance of wind turbine noise is strongly affected by amplitude modulations (AM). A survey was carried out at five German residential study sites near wind turbines with a total of about 500 residents to study the effects of AM in more detail. Annoyance,
disturbances, and the perception of wind turbine noise characteristics, including AM, were assessed. For each participant, address-related exposure to rating levels of wind turbines was estimated. Further, we carried out headphone-based listening experiments with participants from three of
the five study areas and with non-exposed participants from another 'control' location. In the listening experiments, perceived annoyance was rated for varying AM and for different A-weighted sound pressure levels for a total number of 79 subjects. As expected, the results show an increase
in annoyance with sound pressure level. Furthermore, annoyance increased significantly with the extent of amplitude modulations. Interestingly, annoyance showed a strong rise as soon as amplitude modulations became audible in the signal and this rise was hardly affected by the sound pressure
level. In our contribution, we present comparisons of the results of the survey and the listening experiments.
Prediction of wind turbine blade trailing edge noise under various flow conditions for a passive damage detection system
Authors: Inalpolat Murat , Traylor Caleb
Published: September 2021

Noise generated by turbulent boundary layer over the trailing edge of a wind turbine blade under various flow conditions is predicted and analyzed for structural health monitoring purposes. Wind turbine blade monitoring presents a challenge to wind farm operators, and an in-blade structural
health monitoring system would significantly reduce O&M costs. Previous studies into structural health monitoring of blades have demonstrated the feasibility of designing a passive detection system based on monitoring the flow-generated acoustic spectra. A beneficial next step is identifying
the robustness of such a system to wind turbine blades under different flow conditions. To examine this, a range of free stream air velocities from 5 m/s to 20 m/s and a range of rotor speeds from 5 rpm to 20 rpm are used in a reduced-order model of the flow-generated sound in the trailing
edge turbulent boundary layer. The equivalent lumped acoustics sources are predicted based on the turbulent flow simulations, and acoustic spectra are calculated using acoustic ray tracing. Each case is evaluated based on the changes detected when damage is present. These results can be used
to identify wind farms that would most benefit from this monitoring system to increase efficiency in deployment of turbines.
A Sound Insulation Prediction Model for Floor Structures in Wooden Buildings Using Neural Networks Approach
Authors: Bader Eddin Mohamad , Menard Sylvain , Bard Delphine , Kouyoumji Jean-Luc , Vardaxis Nikolas-Georgios
Published: September 2021

Recently, machine learning and its applications have gained a large attraction in different fields. Accurate predictions in building acoustics is vital especially in the design stage. This paper presents a sound insulation prediction model based on Artificial Neural Networks (ANNs)
to estimate acoustic performance for airborne and impact sound insulation of floor structures. At an initial stage, the prediction model was developed and tested for a small amount of data, specifically 67 measurement curves in one third octave bands. The results indicate that the model can
predict the weighted airborne sound insulation for various floors with an error around 1 dB, while the accuracy decreases for the impact sound especially for complex floor configurations due to large error deviations in high frequency bands between the real and estimated values. The model
also shows a very good accuracy in predicting the airborne and impact sound insulation curves in the low frequencies, which are of higher interest usually in building acoustics. Keywords: building acoustics, airborne sound, impact sound, prediction model, neural networks
Directivity of sound propagation from an commercial supersonic engine inlet
Authors: Sugar Mitchell , Slaboch Paul
Published: September 2021

The effects of mean flow variations on sound propagation from an axisymmetric commercial supersonic engine inlet were studied using numerical methods. A finite element model of the inlet was constructed in Ansys Fluent and used to solve for flow fields given by different initial conditions.
Results from this model were fed into the aeroacoustic solver, Actran, and used to calculate far field radiated noise as well as the directivity of that noise. The acoustic source of this noise was a plane wave of a known strength placed at the fan face. In addition to assessing the effects
of mean flow on the radiated noise transfer functions, the duct modes of the model were compared across different flow regimes. Relationships between mean flow parameters and the directivity of duct modes are developed. The results of this study will be used in further studies to gain a deeper
understanding of how the underlying physics which govern the system create favorable or unfavorable directivity patterns.
Measurement of very high frequency (VHF) sound in our daily experiences
Authors: Harusawa Koki , Inamura Yumi , Hiroe Masaaki , Hasegawa Hideyuki , Nakamura Kentaro , Ueda Mari
Published: September 2021

Recently, it is frequently reported that very high frequency (VHF) sounds are emitted from daily necessaries such as home electric appliances. Although we measured VHF sounds from home electric appliances in our previous study, the origins of such VHF sounds have not yet been identified.
In the present study, we tried to identify the VHF sound source in each home electric appliance using a "sound camera", which visualizes the spatial distribution of the sound intensity using a microphone array. The sound camera visualized the location of the sound source at frequencies
from 2 to 52 kHz with a field of view of 63 degrees. The sound camera elucidated that the VHF sounds were emitted from the power source of a LET light, the ventilation duct of an electric fan, and the body of an IH cooker. Their frequency characteristics were dependent on the sound source,
i.e., combinations of pure tones in the LED light and distributing in a wide frequency range in the electric fan.
Auditory training system for improvement of auditory perception ability in blind soccer.
Authors: Ueda Mari
Published: September 2021

Blind soccer is a sport designed for people with visual impairment. All players (except the goalkeepers) are people with visual impairment but not limited to complete vision loss (i.e. without any ability to see; blind in both eyes) . Considering the various degrees of the disability,
all players put on an eye mask for a complete vision blockage so they just rely on their audio sensation for the location of the ball and the goals to drift, shoot, and defend as a game with a high degree of movement. Different from conventional soccer games, the ball makes a sound in which
the callers at the back of the shooting goal provide audio guidance in order to make the game highly dependent on audio information. However, the ability to recognize and locate rely solely on training and personal experience of individual players that essential audio information of the game
has never been analyzed in a scientific manner and theories about distance positioning is especially inadequate. Hence, this study aims to utilize the audio sensation for better game performance. First, we focus on the distance attenuation feature when the ball spins, which is followed by
a description about an audio training system for distance positioning from sounds.
Extensive study of receiver point interpolation methods for drawing estimated road traffic noise maps in Japanese city blocks.
Authors: Yamashiro Yudai , Sugahara Akiko , Hiraguri Yasuhiro , Harada Kazunori , Oshima Takuya , Saito Yoshinori , Atobe Satoshi
Published: September 2021

There are various issues need to be addressed when drawing estimated road traffic noise maps in Japan. One of them is there is a trade-off between computational load and estimation accuracy due to the number of sound receiver points on the building facades where the noise exposure is
evaluated. An interpolation to generate receiver points on facades as post-processing of a computation made on relatively coarse receiver points can be a solution to achieve compromise between computational load and estimation accuracy. In this study, estimated noise maps are drawn in nine
real city blocks in Japan with different land-use areas by placing sound receiving points with intervals of 1m, 5m and 10m. The map of the 1m interval is used as the reference noise levels. The maps of the 5m and 10m intervals are interpolated to the 1m interval using 29 interpolation methods.
The optimal combination of the interval of sound receiving points and the interpolation method are found based on error of the interpolated maps compared to the reference map.
Investigation into effects of side-window rubber sealer on cabin interi-or noise due to external flow disturbances of vehicle
Authors: Lee Sangheon , Lee Songjune , Cheong Cheolung , Kwon Hyerin , Seo Changman
Published: September 2021

Electric vehicles' rapid commercialization increases the relative importance of wind noise, especially for cabin interior noise. In this study, systematic numerical methods are developed to assess the wind noise insulation performance of side-window rubber seals in a design stage. First,
the simplified automotive cabin model (SACM) is constructed to test the rubber seals' sound insulation performance due to external flow disturbance generated by jet flow. The pressure signals due to the jet flow are measured inside and outside the SACM. The difference between the two signals
is used as sound insulation performance criteria, so-called insertion loss (IL). Second, a numerical methodology is developed to predict the IL. The surface pressure field on the side window due to jet flow is predicted by using the high-accurate Lattice Boltzmann Method. The predicted surface
pressure fluctuations are applied as input load causing side-window vibration. The interior sound is then computed by using the calculated window vibration as input. The validity of numerical methods is confirmed by comparing the predicted results with the measured ones. Finally, the present
methods' ability as a design tool is confirmed by comparing the IL of the pad-added rubber seal with that of the regular seal.
Intelligibility of bone-conducted speech detected on the scalp
Authors: Nanri Satoshi , Shinobu Taishi , Otsuka Sho , Nakagawa Seiji
Published: September 2021

Bone-conduction microphones (BCMs) can detect speakers' voices with high signal-to-noise ratio even under extremely noisy environments like a machine factory or an engine room of a watercraft. BCMs are ordinarily attached to the front of the neck (larynx), therefore, it is sometimes
accompanied by discomfort and esthetic problems. In order to solve such problems, we have been developing a novel BCM system built in a helmet, however, characteristics of bone-conducted speech detected on the scalp need to be clarified. In this study, mono-syllable articulations of bone-conducted
speech detected at several locations on the head and neck were measured. Also, the speech transmission index (STI), objective measure of signal transmission quality, was calculated. The results indicated that the forehead and the vertex showed better articulation and STI than the mastoid process
of the temporal bone, the mandibular condyle, and the occiput. In terms of the gender difference, the forehead and the vertex showed higher scores for the male voice, whereas the cheek showed the highest for the female voice. Additionally, the larynx showed lower scores than others. These
results indicated that the attenuation of high-frequency components are smaller at the forehead and the vertex.
The multi-functional rotor aerodynamic and aeroacoustic test platform at HKUST
Authors: Wu Han , Zheng Chuntai , Zhou Peng , Fattah Ryu , Zhang Xin , Zhou Guocheng , Chen Bao
Published: September 2021

This paper describes the multi-functional rotor noise and aerodynamics test platform at the Hong Kong University of Science and Technology (HKUST). To investigate the noise characteristics of propellers with aerodynamic flows, the test rig is installed in the 2.5×2 (m) low-speed
and low-noise wind tunnel in the Aerodynamic and Acoustic Facility (AAF) at HKUST. The wind tunnel can facilitate flow from 0 to 40 m/s. The test rig is assembled in a turntable on the ceiling of the tunnel wall, which enables the testing range of pitch angle can vary from 0° (axial flow)
to 90° (parallel flow), with an accuracy of 0.1°. The noise produced by the rotor is measured by a set of wall-mounted surface microphones. Semi-empirical calibration is conducted to quantify the noise reflection by the tunnel walls. A low-noise struct has been designed and manufactured
to locate a set of far-field microphones equipped with nosecone, to improve the quality of acoustic measurement inside the flow. In addition, a synchronized system is developed to conduct the phase-locking Particle Image Velocimetry (PIV) measurement on the rotor, to study the flow pattern
to better understand the noise generation mechanism.
Experimental assessment of the noise characteristics of propellers for commercial drones
Authors: Wu Han , Zhou Peng , Zhong Siyang , Zhang Xin , Luo Kunyu
Published: September 2021

Multi-copters or drones are engaged in a wide range of industrial applications for their flexibility, safety and low-cost. The noise emission is becoming an issue with the expanding applications, among which the propellers that drive the drones are the major sources of noise. In this
work, the noise characteristics of small-scale propellers is experimentally investigated using the advanced rotor aerodynamics and aeroacoustics test platform in an anechoic chamber at the Hong Kong University of Science and Technology (HKUST). The study will focus on the representative off-the-shelf
propellers. The rotor noise will be measured by a linear array with 20 microphones, and the aerodynamic forces will be acquired by using the high-accuracy load cells. The dependence of both the tonal and broadband noise radiation with the thrust and rotation speed at various conditions will
be tested. The study will enhance our understanding of the noise features of the multi-rotor powered drones, and will provide us with a better understanding of the status of the drone noise impact on the environment.
Re-evaluation acoustic quality in lecture halls using G and C50: University of Sharjah Case Study
Authors: Elmehdi Hussein , Sanjinez Monica
Published: September 2021

In our previous studies, we focused on the common approach of measuring Reverberation Time (RT) for assessing acoustic quality in various types of lecture halls at the University of Sharjah (United Arab Emirates). The absorbing surfaces at the lecture halls at the University of Sharjah
are limited to one surface (hanging ceiling), which has been shown in the literature to affect the accuracy in the description of the acoustic response as a result of the introduced uncertainty in the measured reverberation times. Because of these reasons, it has been highlighted in the literature
that RT is considered not a good predictor of acoustic quality, namely speech intelligibility, in the lecture halls. Therefore, additional acoustic parameters need to be measured of calculated to accurately predict the acoustic response in lecture halls, especially speech intelligibility during
activities that takes place within the lecture hall. The focus of our current research is to extend our precious work on RT to calculate additional acoustic parameters, namely the acoustic strength, G, and the speech clarity, C. Our goal is to investigate the practical use of G and C to describe
acoustic response in the examined lecture halls. In addition to special variations with frequency, we will examine the effects source position, room dimensions at different locations within the lecture hall. The measurements were conducted in the same lecture halls under the same conditions
including the acoustic absorbers and sound diffusers, which have shown to influence measured acoustic parameters. The results were compared to standards for the purpose of providing recommendations for range of acoustic parameters to support adequate speech communication during various teaching
and learning activities in lecture halls.
Empirical estimation of engine-integration noise for high bypass ra-tio turbofan engines
Authors: Lee Incheol , Zhang Yingzhe , Lin Dakai
Published: September 2021

To investigate the impact of installation on jet noise from modern high-bypass-ratio turbofan engines, a model-scale noise experiment with a jet propulsion system and a fuselage model in scale was conducted in the anechoic wind tunnel of ONERA, CEPRA 19. Two area ratios (an area of
the secondary nozzle over an area of the primary nozzle), 5 and 7, and various airframe configurations such as wing positions relative to the tip of the engine nacelle and flap angles, were considered. Based on the analysis of experimental data, an empirical model for the prediction of engine
installation noise was proposed. The model comprises two components: one is the interaction be-tween the jet and the pressure side of the wing, and the other is the interaction between the jet and the flap tip. The interaction between the jet and the pressure side of the wing contributes to
the noise at the low frequencies (≤ 1.5 kHz), and the interaction between the jet and the flap tip con-tributes to the noise at the high frequencies. The proposed model showed a good agreement with the experimental data.
How well does Spain manage occupational noise and vibration risks?
Authors: Sánchez-Guardamino Elorriaga Rafael , García Tomás María José
Published: September 2021

From the analysis of Spanish national statistics on occupational diseases notification during the period 2009 - 2018, a prospective study on the level of compliance with the national implementation of both European Union directives 2003/10/CE and 2002/44/CE respectively, is undertaken.
Research is developed by Occupational Health and Safety National Institute in liaison with Spanish autonomous regional governments. Questionnaires were designed by technical personal from the national Institute in order to collect relevant information. These questionnaires were fulfilled in
situ by specialized and qualified civil servants from several autonomous regions. Up to 566 companies take part of the study from different economical activities, in which outstanding noise and/or vibration risk is present. The study conclude in relation to preventive management of noise that,
both there are serious deficiencies in the characterization of the exposure, and it also entails a very low effectiveness in reducing risk. As far as vibration risk management is concerned, a deficient specific legal regulatory implementation is found. As a result, of such conclusions, an
action plan is being designed to improve working conditions by means of assuring the compliance with legislation.
Annoyance from community and neighborhood noise during the COVID-19 lockdown in Serbia: a pilot study
Authors: Paunovic Katarina , Jakovljević Branko , Mirčić Radmila
Published: September 2021

We present a pilot study on noise perception and annoyance related to community and neighborhood noise sources during the COVID-19 lockdown in Serbia, enforced from March 15 to May 6, 2020. The online anonymous survey was conducted using social network platforms. Respondents from all
over the country, aged 15 to 75 years took part in the study. All participants worked or studied from their homes during the investigated period. Overall, during the lockdown, participants perceived less noise from the major community sources, such as road traffic, air traffic, and construction
works on the streets; at the same time, they perceived more noise from their neighbors, such as noise from electrical appliances and elevators inside the buildings, as well as noise from humans (music, voices, steps) and animals. In addition, respondents more often perceived "new"
community sounds, such as birds, church bells, and emergency vehicles. They found the sirens of emergency vehicles and noise from their neighbors most annoying at that time. Many participants changed their behavior and attitudes toward noise during the lockdown. Every sixth participant complained
about neighborhood noise. This study points to the need for the improvement of the acoustic environment at home in the future.
Power balance analysis of nonperiodic structural components from a model converted from FEM to SEA.
Authors: Hinz Mathias , Cordioli Júlio Apolinário , Alimonti Luca , Gardner Bryce
Published: September 2021

Using Statistical Energy Analysis (SEA) to characterize the power flow within a vibroacoustic system is a challenging task when the subsystems have irregular shape and complex construction. Retrieving analytical solutions for the ordinary SEA parameters is nearly impractical without
restricting simplifications and periodicity is usually not exploitable due to the lack of repetition patterns. A promising option to perform the power balance for such cases is to filter part of the information contained in a Finite Element Method (FEM) model of the system, in order to convert
it into a SEA model. In this paper, the Lorentzian Frequency Average and the Nonparametric Random Matrix Theory are applied to randomize the dynamic stiffness matrix of the FEM components from a system of industrial application. The obtained direct field dynamic stiffness matrices are employed
along the diffuse field reciprocity relationship as a general framework to determine the energetic content of each component. The results obtained with this procedure are evaluated against the ones from classical SEA and Monte Carlo techniques.
Long Term Ambient Sound Level Survey
Authors: de Haan Henk , Senden Virgini
Published: September 2021

A 32 month long nighttime ambient sound level survey was conducted between from April 2017 and December 2019, inclusive. Sound level data was recorded at three locations within approximately 600 m of one another. Weather data was collected at one site. The measurement locations were
at the edge of the city, where the suburbs make way for the countryside. Two noise monitoring stations were located near the back yards of detached houses. The third station was located in a more rural setting. This paper will look at trends in the nighttime ambient sound level (e.g. summertime
vs wintertime), and try to establish the minimal duration of a measurement program for generating reliable results.
The evolution of quiet lawn mowers and their impact on community noise and hearing conservation
Authors: Blomberg Leslie , Trezza Dave
Published: September 2021

Noise measurements of more than 600 lawn mowers were made at 25 feet and at the operator's ear between 2004 and 2021. These data are presented and compared with the measurement of more than 60 mowers in 1973 by the US EPA. With the exception of electric lawn mowers, very little progress
has been made quieting lawn mowers. Electric lawn mowers are significantly quieter than gas mowers. Recently, with improvements in battery technology, the performance of electric mowers has improved significantly. There are currently electric push, self-propelled, and ride-on mowers with comparable
performance to gas powered mowers. Finally, the impacts of lawn mower noise on community noise and hearing conservation are discussed.
Scalable Machine Learning Approach to Classifying Transportation Noise at Two Urban Sites in Greater Boston, Massachusetts
Authors: Wang Tiange , Jiang Ruijie , Lin YuLun (Elain) , Monahan Kyle , Leaffer Douglas , Doroff Stephen , Tracey Brian
Published: September 2021

The goal of this study was to characterize transportation noise by vehicle class in two urban communities, to inform studies of transport noise and ultra-fine particulates. Data were collected from April to September 2016 (150 days) of continuous recording in each urban community using
high-resolution microphones. Training data was created for airplanes, trucks/buses, and train events by manual listening and extraction of audio files. Digital signal processing using STFT and Hanning windowing was performed in MATLAB, creating audio spectrograms with varying frequency: log
vs linear frequency scales, and 4K vs 20K max frequency. For each of the four spectrogram sets, a neural net model using PyTorch was trained via a compute cluster. Initial results for a multi-class model provide an accuracy of 85%. Comparison between a selection of frequency scales and expanding
to longer time periods is ongoing. Validation with airport transport logs and local bus and train schedules will be presented.
Inverse metacluster design using generative modeling for minimal scattering response
Authors: Lai Peter , Amirkulova Feruza
Published: September 2021

Metamaterials are subwavelength-sized artificial structures with the ability to manipulate incident waves in such a way that affects how the energy propagates throughout the medium. In acoustics, particularly placed scattering elements can reduce the total scattering cross section (TSCS)
response. We propose a method to inversely design acoustic metamaterial configurations using deep learning and generative modeling. Using our proprietary multiple scattering solver with MATLAB optimization toolbox, we generate a dataset of optimal configurations with minimized TSCS within
a discrete range of wavenumbers. We use this dataset to train a Conditional Wasserstein Generative Adversarial Network (cWGAN) to generate similar metacluster designs corresponding to specified input TSCS. To improve the coordinate recognition ability of the cWGAN, we include the novel CoordConv
layer in the generator and critic. After training, the cWGAN can produce a variety of optimal configurations given an expected TSCS. Evaluating TSCS of generated configurations shows that the model is capable of proposing scatterer configurations that are comparable or better than the dataset
within the optimized range.
New ECMA 74 operating conditions for personal computers and workstations
Authors: Beltman Willem , Bard Seth , North Travis , Oppenheimer Charles , Peterson Chris , Wiltzius Andrew , Zimmerman Sean
Published: September 2021

ECMA-74 Annex C.15 prescribes procedures for acoustical testing of personal computers and workstations. The dramatic advances in computer technology and use over the past two decades motivated the formation of an IT industry workgroup shortly after InterNoise 2018 to update the annex for these changes. The updated procedures, which will be published in the 18th edition of ECMA-74, are described. The updated procedures comprise new operating conditions: 1) web browsing, 2) office productivity, 3) media content creation, and 4) power user/gaming, in addition to the idle condition, and how computer system power and performance settings, which affect computer noise, are to be set and reported.