bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic characterization of Zea Mays culm fibers (corn) and Musa X Paradisiacal (banana) stem fibers in proportion 50% - 50%.
Authors: Alvarez Ruiz Yesika Patricia , Ruiz Hernández José Alcides
Published: September 2021

The following research arises as a proposal to the implementation of Zea Mays culm fibers and Musa X Paradisiaca stem fibers in proportion 50% - 50% for the development of a new eco-material with acoustic properties, the objective was to measure the absorption coefficient based on the
international standard ISO 10534-1 Determination of the acoustic absorption coefficient and acoustic impedance in impedance tubes. Using the impedance tube to identify the minimums and maximums needed to perform the computational procedure in the MATLAB software tool, and finally obtain the
sound absorption coefficients of the material. The measurement process is supported by the implementation of the impedance tube, having all its consideration and previous measures that support the veracity of the data taken through this process, in addition to the fact that background noise
measurements were made in order to pass these values to ensure reliable results in the measurement, performed with a class 1 sound level meter; The fibers analyzed had a range between 0.8136 and 0.9225 absorption coefficient in the bands of 1000, 2000 and 4000 Hz, testing the effectiveness
in their implementation as an acoustic barrier. Keywords: absorption, eco-material, fibers, barrier, acoustics.
Subjective evaluation of the combining effect between the virtual bass and head related transfer functions
Authors: Chen Yunqi , Shi Chuang , Mu Hao
Published: September 2021

Earphones are commonly equipped with miniature loudspeaker units, which cannot transmit enough power of low-frequency sound. Meanwhile, there is often only one loudspeaker unit employed on each side of the earphone, whereby the multi-channel spatial audio processing cannot be applied.
Therefore, the combined usage of the virtual bass (VB) and head-related transfer functions (HRTFs) is necessary for an immersive listening experience with earphones. However, the combining effect of the VB and HRTFs has not been comprehensively reported. The VB is developed based on the missing
fundamental effect, providing that the presence of harmonics can be perceived as their fundamental frequency, even if the fundamental frequency is not presented. HRTFs describe the transmission process of a sound propagating from the sound source to human ears. Monaural audio processed by
a pair of HRTFs can be perceived by the listener as a sound source located in the direction associated with the HRTFs. This paper carries out subjective listening tests and their results reveal that the harmonics required by the VB should be generated in the same direction as the high-frequency
sound. The bass quality is rarely distorted by the presence of HRTFs, but the localization accuracy is occasionally degraded by the VB.
Noise reduction of plenum window with add-in dual staggered sound scatterer arrays
Authors: LI Xiaolong , Tang Shiu Keung , Tang Shiu-Keung,
Published: September 2021

In present study, a 1:4 scaled down model was used to explore the noise reduction across the plenum window with add-in dual staggered scatterer arrays (sonic-crystal). Reverberation time inside the model space was measured firstly to eliminate the effect of the possible reverberation
variation on the sound transmission loss of the plenum window. Two sonic-crystal arrays, the two-by-two and two-by-three scatterer arrangements, were adopted for measurement. A total of four arrays was thus tested after the staggering. Computational simulation was conducted for the sound field
inside the plenum chamber to study the noise reduction mechanism of the present window system. Results show that the noise reduction of the plenum window was improved by varying degrees due to the placement of the dual staggered sonic-crystal. The Installation of the dual staggered sonic-crystal
increased the sound energy reflections out of the plenum window inlet and decreased the sound energy that passed through the plenum window cavity. At the same time, the resonances inside the window cavity also contributed to the sound transmission loss of the plenum window. The noise reduction
across the plenum window was enhanced. The improvement was between ~2 to ~2.7 dBA.
Montevideo, walkable city: pedestrianization of a large avenue during 2020 pandemic
Authors: Gonzalez Alice Elizabeth , Gianoli Kovar Pablo , Ramírez Lady Carolina , Luzardo Rivero Micaela
Published: September 2021

On March 13, 2020, the first cases of SARS-COVID19 were detected in Uruguay. During the first weeks of the pandemic, mobility was significantly reduced with the slogan "If you can, stay home"; it was not a mandatory but voluntary confinement. After a couple of months, there
was a big drop in the number of people affected by the disease. Thus, the Municipality of Montevideo, betting on a more human and walkable city, defined that the main avenue of the city had a pedestrian section on Saturday afternoons. This resulted in a greater enjoyment of the city by its
inhabitants, as they had more space to walk while maintaining safe distances between people. It was also possible to promote trading, since classically Ave. 18 de Julio is also a commercial stroll. Additionally, the sound pressure levels recorded by the Municipality's stationary sound level
meters located at three points along the avenue, showed the reduction of environmental sound levels in pedestrian areas, improving the acoustic quality of the walk. In this paper, sound pressure levels on Saturday afternoons at different times of the year before, during and after the initial
lockdown due to the COVID-19 pandemic, are compared and discussed.
Detection and identification of illegal-modified private cars through frequency band analysis
Authors: Chow Hok Man Joyce , Cheung Sau Cheong , Cheng Kit Wing , Lee Chee Kwan , Tsang Terence , Ng Hin-long
Published: September 2021

Post-purchase-illegal-modification of road vehicles' exhaust systems by vehicle fanatics for loudness has caused an upsurge in nuisances to local residences when driven and rallied during late night and early mornings. Traditional enforcement measures rely on setting up roadblocks by
the Police at rallying hotspots. These measures involve the judgement of individual police officer and can be subjective. With the aid of noise monitoring equipment, the accuracy and efficiency of on-site exhaust system-modified vehicle detection can be enhanced. Since the sound profile of
a single-vehicle exhaust cannot be captured by simple roadside noise level measurements alone, segregation and analysis of the noise spectrum are employed to identify vehicles with modified exhaust systems. The paper presents the findings of investigating the feasibility and accuracy of off-the-shelf
devices for detecting vehicles fitted with modified exhaust systems, with private cars being the primary target. A pilot test by roadside noise monitoring has been conducted with a sound level meter and an acoustic camera and revealed an on-site accuracy of up to 75%. Data collected during
the tests were further used to explore the applicability of integrating artificial intelligence with traditional noise monitoring devices.
Evaluation of floating floors performances using the reception plate method
Authors: Serpilli Fabio , Lori Valter , Di Loreto Samantha
Published: September 2021

This paper concerns the development and experimental validation of a simplified method to evaluate the performances of materials for floating floors. The method is based on the reception plate theory. The porpouse is to evaluate the impact sound pressure level reduction ΔL by
the differences of the sound power level ΔP measured on the reception plate with and without the acoustic material. The results are compared with the values measured in accordance with ISO 10140 standards.
Which aspects of soundscape can the soundscape attributes measure?
Authors: Nagahata Koji
Published: September 2021

The eight perceptual attributes for soundscape assessment provided in ISO/TS 12913-2: 2018 are widely used in recent soundscape studies. Several studies across the language showed that the basic structure of the soundscape appraisal two-dimension space obtained from the attributes are
robust. However, this robustness of the basic structure only means the robustness of the linguistic structure of the eight perceptual attributes, and never means those attributes cover the whole human perception of the soundscapes. Some studies suggest there are some appraisal scales which
cannot be expressed in the two-dimensional appraisal space. This study discusses which aspects of soundscape can the soundscape attributes measure.
ConvTasNet-based anomalous noise separation for intelligent noise monitoring
Authors: Li Han , Chen Kean , Seeber Bernhard U.
Published: September 2021

Noise pollution has become a growing concern in public health. The availability of low-cost wireless acoustic sensor networks permits continuous monitoring of noise. However, real acoustic scenes are composed of irrelevant sources (anomalous noise) that overlap with monitored noise,
causing biased evaluation and controversy. One classical scene is selected in our study. For road traffic noise assessment, other possible non-traffic noise (e.g., speech, thunder) should be excluded to obtain a reliable evaluation. Because anomalous noise is diverse, occasional, and unpredictable
in real-life scenes, removing it from the mixture is a challenge. We explore a fully convolutional time-domain audio separation network (ConvTasNet) for arbitrary sound separation. ConvTasNet is trained by a large dataset, including environmental sounds, speech, and music over 150 hours. After
training, the scale-invariant signal-to-distortion ratio (SI-SDR) is improved by 11.40 dB on average for an independent test dataset. ConvTasNet is next applied to anomalous noise separation of traffic noise scenes. We mix traffic noise and anomalous noise at random SNR between -10 dB to 0
dB. Separation is especially effective for salient and long-term anomalous noise, which smooth the overall sound pressure level curve over time. Results emphasize the importance of anomalous noise separation for reliable evaluation.
Noise emission of combustion engines and road vehicles - a historical review
Authors: Spessert Bruno , Fischer Martin
Published: September 2021

This paper deals with the historical development of the noise emission of cars, trucks and their petrol and diesel engines; it focus on the European Union and the time period between 1910 and 2020. Combustion engines were and are important noise sources of road vehicles. Until around
1970 engine noise levels were increased strongly by higher speeds, by higher cylinder pressures and especially for truck engines by the introduction of the diesel combustion process. The noise emission was mainly caused by the drive train until the 1960ies for cars and until the 1970ies for
trucks. Since then the development of acoustically more advantageous engines was forced by noise regulations and simultaneously enabled by technical advancements. As a consequence of the acoustical optimization of the engines the tire/road noise became dominant. Despite of the technical advancements
the road noise stress of the population is still much too high. Therefor the necessary short-term reduction of noise stress has to be realized by regulatory measures.
Optimization of an absorbing surface with 2D Helmholtz resonators for reduced sensitivity to the incidence angle
Authors: Garza-Agudelo Diana Maria , Cutanda Henriquez Vicente , Jeong Cheol-Ho , Andersen Peter Risby
Published: September 2021

It has been shown in several recent publications that acoustic materials consisting of a combination of resonators tuned to different frequencies can render high absorption coefficient values over an extended frequency range while maintaining compactness. This makes them attractive
solutions for applications in which low frequency sound control is needed, and/or when there are significant space constraints. Nevertheless, the acoustic performance of these surfaces varies with the angle at which a wave impinges on the surface. The changes in the absorption characteristics
with the incidence angle occur both on the maximum absorption coefficient, and on the effective frequency bandwidth. Numerical optimization is a tool that can help realize designs with a large degree of geometrical freedom, and using this framework we have demonstrated an array of coupled
2D Helmholtz resonators that is less sensitive to changes in the incidence angle.
Effectiveness of neoprene pad vibration isolators at high frequencies
Authors: Lilly Jerry
Published: September 2021

The natural frequency, dynamic stiffness, and insertion loss of commercially available neoprene pad vibration isolators have been measured in a simple, single degree of freedom system over a wide range of pad loadings out to a maximum frequency of 10 kHz. The results reveal that dynamic
stiffness can vary significantly with pad loading as well as the durometer of the material. It will also be shown that insertion loss follows the theoretical single degree of freedom curve only out to a frequency that is about 5 to 10 times the natural frequency, depending upon the pad durometer
rating. Above that frequency wave resonances in the material cause the insertion loss to deteriorate significantly out to a frequency near 1 kHz, above which the insertion loss maintains a relatively constant value, again depending upon the pad durometer rating. In some instances the insertion
loss values can approach 0 dB or even become negative at specific frequencies in the frequency region that is 10 to 20 times the natural frequency of the system.
Isolating an above grade MRI from traffic induced vibration
Authors: Moore James , Kinsey Kaolin
Published: September 2021

MRI installations require that ambient floor vibration levels not exceed limits defined by the manufacturer. In this study, vibration measurements for a second-floor installation exceeded the allowed levels. A road adjacent to the building experienced heavy traffic and was in poor condition
with potholes and asphalt patches. The second-floor exhibited resonances in the same 8-15Hz frequency range as ground-borne vibration due to traffic close to the building. The MRI comes supplied with resilient pads that effectively isolate above 20 Hz. For isolation of the floor resonances
excited by vehicular traffic, an additional stage of isolation pads was designed that lowered the system resonance frequency of the MRI on the floor to 6.5Hz. The added pads, with greater thickness and softer material, raised concerns of the MRI collapsing sideways like a thin, tall column
above its critical buckling load. Lateral snubbers were incorporated where their compressive stiffness constrained the rails laterally and a low shear stiffness did not significantly increase the system resonance frequency. Vibration measured on the MRI after installation showed the novel
system provided effective isolation of traffic induced vibration, satisfying vibration requirements for the MRI. Model predictions of MRI vibration relative to floor vibration agreed well with measurements.
Impact of a tunnel on the TL of a vehicle floor in bare and trimmed conditions and investigation on the most suitable simplified geometry able to better represent such impact
Authors: Di Marco Federico
Published: September 2021

NVH engineers are faced with the challenge of designing trim parts for vehicle interior and exterior, like inner dash insulators, carpets, underbody shields or engine encapsulations, which can be made with very different Bills of Materials (BOMs) including among others foams, felts
or heavier layers. The measurables commonly used to rank various solutions are Transmission Loss (TL) and absorption. Depending on the numerical analysis method, different approaches may be considered for the evaluation of the TL of an automotive component. In particular, in Statistical Energy
Analysis (SEA), automotive components are modeled as an assembly of panels having a simple shape, e.g. flat panels and/or panels with single or double curvature. Furthermore, in SEA the trim is normally modeled by means of the Transfer Matrix Method (TMM), which is essentially a 2-dimensional
methodology. This paper intends to analyze in some depth the level of approximation that these practices bring with themselves, specifically in relation to the modelling of an automotive floor. More in detail, the aim of the paper is first to investigate what impact has the presence of the
tunnel on the TL of a vehicle floor in bare and trimmed conditions and then to evaluate if the presence of the tunnel can be better modeled by using a semi-cylinder or three flat plates welded together in a trapezoidal shape, both shapes considered as a reasonable simplification of the actual
geometry of a typical tunnel. The analysis is carried out at simulation level using FE. To investigate both air bone noise and structure borne noise transmission, two types of excitations are used: a diffuse acoustic pressure field applied to the entire floor surface and an imposed displacement
applied to the edge of the floor surface. Furthermore, 3 different kind of trims are taken into consideration in order to analyze if and how the tunnel modeling strategy may influence the evaluation of the trim effectiveness.
An optimization method for reverberation room design
Authors: Didier Paul , Van hoorickx Cédric , Reynders Edwin
Published: September 2021

The ISO 354:2003 standard relating to sound absorption measurements is currently under revision to improve the reproducibility of the procedure it describes. Round robin tests conducted across various reverberation rooms indeed revealed significant disparities between sound absorption
measurements of the same sample. One of the reasons is that, at low frequencies, the sound field in a single laboratory cannot be considered fully diffuse. However, the average sound field across different laboratories may be considered diffuse if the interaction between the finite sample
and the diffuse field is duly accounted for and the direct field close to the absorber is disregarded. In this work, a method is developed for optimizing reverberation room design such that measured absorption values are as close as possible to ensemble average diffuse values. The reverberation
room is modelled using the finite element method and standardized measurements of an absorptive sample are simulated. The distance between resulting absorption coefficients and diffuse target values is minimized in an optimization procedure having the geometrical characteristics of the model
as input parameters. The results are anticipated to participate to the revised ISO 354 as guidelines for the construction of new reverberation rooms or the improvement of existing ones.
Tunable frequency bandgaps in elastic metamaterials with internal contacts
Authors: Kim Eunho , Kim Guenil , Cho Kyeong Min , Jang Yeongtae
Published: September 2021

We design an elastic metamaterial with internal contacts and study the tunable frequency band structure of the metamaterial. It is well-known that the frequency band of granule structures consisting of particles changes depending on the system's compression because of the nonlinearity
of the contact between particles. We adopt this efficient tunning mechanism, i.e., contact, in the design of continuum type elastic metamaterials. We first design a unit cell structure showing internal contacts under compression and fabricate it using a 3D printer. We numerically and experimentally
identify that the unit cell's stiffness suddenly increases when the internal contact happens. This sudden change of the stiffness induces a change of frequency characteristics of the structure. Here, we demonstrate that internal contacts are useful for designing various frequency bandgaps
and tuning them efficiently.
Application of psychoacoustic analyses according to ECMA-418-2
Authors: Becker Julian , Sottek Roland , Lobato Thiago
Published: September 2021

Assessing and assuring sound quality has become a very important task for product design. Customers expect product sounds without disturbing noises. This is a challenge because spectro-temporal noise patterns (such as tonal sounds or modulated signals that generate a roughness sensation)
must be taken into account, in addition to frequency-weighted values like dB(A) and loudness. If the sound of a technical product exhibits these characteristics, it is most likely perceived as having poor quality. The new standard ECMA-418-2 describes methods for the automatic quantification
of tonal sounds and modulated sounds, which generate a sensation of roughness. The methods are based on a psychoacoustic hearing model and thus emulate human perception very closely. This paper describes the application of these methods. Several examples show how these parameters can be used
for sound engineering and how to interpret the results.
Sound reflection of acoustic porous metasurfaces under uniform mean flow
Authors: Qu Renhao , Guo Jingwen , Fang Yi , Zhong Siyang
Published: September 2021

Acoustic metasurfaces are artificial 2D structures with a sub-wavelength thickness that can realize some exotic properties such as non-trivial refraction, broadband and low frequency absorption. However, most relevant studies are still in a static medium, hindering their realistic applications
in aviation, where background flow exists. To address it, the effects of mean flow on the acoustic performance of metasurfaces, which is designed based on the generalized Snell's law (GSL) to achieve anomalous reflections, are systemically studied. Firstly, an analytical model of GSL taking
the effect of background uniform mean flow into account is built, in which the wavenumbers of both incident and reflected waves are corrected. Then, taking an acoustic porous metasurface for instance, the effectiveness of the derived model is validated by numerical simulations. Results reveal
that the reflected waves are deflected in the presence of background flow. The critical incident angle, at which the incident sound wave is converted to surface wave, decreases with the increasing flow velocity. Since the converted surface wave can only propagate along the metasurface, there
is little sound energy radiated into far field, which is benefit for the noise attenuation in the presence of flow.
An integrated toolchain for the design of aeroacoustic metamaterials: the AERIALIST H2020 project.
Authors: Iemma Umberto
Published: September 2021

The project AERIALIST (AdvancEd aicRaft-noIse-AlLeviation devIceS using meTamaterials), funded within the Breakthrough Innovation topic of the H2020 program, has closed its activity on May 2020. The objective of the project was the disclosure of the potential of metamaterials in developing
disruptive devices for the mitigation of aircraft noise, in order to contribute to the identification of the breakthrough technologies targeted at the achievement of the noise reduction targets foreseen by the ACARE Flightpath 2050. Although targeted to low TRL, AERIALIST has been focused
on the development of an integrated toolchain capable to address the entire design loop, from the early conception to the numerical and experimental proof of concept, up to the final design and manufacturing. The toolchain was founded onto four pillars: i) the extension of the acoustic metamaterial
theory to aeroacoustics; ii) the exploitation of the latest additive manufacturing technologies; iii) the wind-tunnel assessment of the selected concepts; iv) the identification of a development roadmap towards higher TRL. After three years of activity, the project has attained all its objectives.
The present paper is a review of the main outcomes of the project, their application potential and relevance to the ACARE objectives.
Sound absorption of polydisperse heterogeneous porous composites
Authors: Núñez Gabriel , Venegas Rodolfo , Zielinski Tomasz G. , Bécot François-Xavier
Published: September 2021

Sound absorption of polydisperse heterogeneous porous composites is investigated in this paper. The wave equation in polydisperse heterogeneous porous composites is upscaled by using the two-scale method of homogenisation, which allows the material to be modeled as an equivalent fluid
with atypical effective parameters. This upscaled model is numerically validated and demonstrates that the dissipation of sound in polydisperse heterogeneous porous composites is due to visco-thermal dissipation in the composite constituents and multiple pressure diffusion in the polydisperse
heterogeneous inclusions. Analytical and semi-analytical models are developed for the acoustical effective parameters of polydisperse heterogeneous porous composites with canonical geometry (e.g. porous matrix with cylindrical and spherical inclusions) and with complex geometries. Furthermore,
by comparing the sound absorption coefficient of a hard-backed composite layer with that of layers made from the composite constituents alone, it is demonstrated that embedding polydisperse heterogeneous inclusions in a porous matrix can provide a practical way for significantly increasing
low frequency sound absorption. The results of this work are expected to serve as a model for the rational design of novel acoustic materials with enhanced sound absorption properties.
Are online meetings noisier than conventional meetings?
Authors: Boulter Nicholas , White Jim
Published: September 2021

Design of sound insulation in office meeting rooms is typically based on 'normal' speech levels, but anecdotal evidence suggests that raised speech levels may be common where video/teleconferencing (VC/TC) is in use. If this is the case, then partitions in meeting rooms may be under-designed.
In order to gain an understanding of the real-world occupational noise levels that exist in VC/TC enabled meeting rooms, long-term noise monitoring was conducted in multiple offices across the globe and matched to records of VC/TC use. Correlations uncovered include a link between VC/TC use
and increased Lp, and higher speech Lw in larger meeting rooms.
Acoustic regulations for hospital bedrooms - Comparison between selected countries in Europe
Authors: Rasmussen Birgit , Carrascal Garcia Teresa , Secchi Simone
Published: September 2021

Regulatory acoustic requirements for hospitals exist in several countries in Europe, but many countries have either insufficient regulatory limits or only recommendations. The main purpose of limit values is to ensure optimal acoustic conditions for patients under treatment and for
personnel for the various tasks taking place in many different rooms, e.g. bedrooms, examination and treatment rooms, corridors, stairwells, waiting and reception areas, canteens, offices, all with different acoustic needs. In addition, some rooms require special considerations like psychiatric
rooms and noisy MR-scanning rooms. The extent of limit values varies considerably between countries. Some specify a few, others several criteria. The findings from a comparative study carried out in selected countries in various geographical parts of Europe show a diversity of acoustic descriptors
and limit values. The paper includes examples of criteria for reverberation time, airborne and impact sound insulation, noise from traffic and from service equipment. The discrepancies between countries are discussed, aiming at potential learning and implementation of optimized limits for
more room types. In addition to regulations or guidelines, some countries have hospitals included in national acoustic classification schemes with different acoustic quality levels. Indications of such classification criteria will be included in the paper.
Parameter study of Variation noise in outdoor of air conditioner
Authors: KIM Minkyu , Ahn Byoungha , Chin Simwon
Published: September 2021

In the outdoor unit of a room air conditioner, the main factors that made it possible to vary the ability of cooling and heating are the development of BLDC motors, advances in inverter technology, and the development of refrigerant volume control technology. The main reason for this
change in cooling and heating capacity is that it is possible to change the RPS of compressors. As the range of the compressor's RPS expands, so does the range of response to load variations. This is mainly based on the capacity of the high-pressure refrigerant produced by the compressor.
When the compressor rotates at high speed or low speed, the difference in noise occurs depending on the difference in rotational speed. Of course, fans and motors also contribute to noise fluctuations, but the overall governing factor is the greater contribution of refrigerant from compressors
and compressors. The refrigerant flows into the cycle configured in the outdoor unit and varies in speed and flow rate depending on the amount of refrigerant. This results in vibration and noise appearing in the form of radiations, resonances, solid sounds, resonances, and so on. There are
several factors that can cause vibration or noise changes depending on the flow velocity and flow rate. In this paper, we selected reactance of compressor motors, mufflers directly connected to compressor discharge ports and accumulator at compressor inlet where fluid vibrations occur the
most. First of all, reactance of motor responds quickly to load fluctuations and has a large instantaneous torque to instantaneous load fluctuations. The muffler, which is directly connected to the compressor discharge port, is the first Cavity where high-pressure gas meets, and can evaluate
the concentration of kinetic energy that generates noise and improve the collection center to reduce fluctuating noise. The Accumulator is the part with the lowest temperature of refrigerant gas entering the compressor, and the rapid change in the flow path causes the most fluid to generate
vibration and radiation of the structure. For this reason, we select three elements first. In this paper, we specifically describe the background of selecting three elements of an air conditioning outdoor unit for the variability of noise over RPS changes. We demonstrate that these factors
can review the feasibility of the experiment, explain the results of the analysis, and possibility of reduce the variation noise.
Sound power and sound energy measurements using an ellipsoidal measurement surface
Authors: Zechmann Edward
Published: September 2021

To support purchasing low noise products, sound power and sound energy measurements of sufficient quality need to be routinely made by consumers on a global scale. Sound power measurements using ISO 3744, 3745, and 3746 are conducted in a free field using an acoustic far-field approximation
of the intensity integrated over an enveloping measurement surface. Sound power and sound energy measurements generally use a hemispherical, parallelepiped, or cylindrical measurement surface. Those measurement surfaces have limitations and assume that the measurement points lie on the measurement
surface often in preferred positions. An alternative approach is to choose microphone positions that optimally satisfy the assumptions of the measurement. The measurement surface should then be fit to the chosen microphone positions. Regression methodologies are available for fitting ellipsoids.
The number of microphone positions can be as few as three to fit an ellipsoid. An ellipsoidal measurement surfaces can abut zero, one, two, or three orthogonal reflecting planes. Correction equations for the microphone locations and the angle errors for the microphone orientation and wave
propagation direction are shown. This paper will present simulations of sound power, sound energy, and corrections for environmental reflections for ISO 3745 and other measurement surfaces.
Auralization of electric vehicle's interior noise SEA simulation
Authors: Jo Eunsoo , Chae Ki Sang , Park Dong Chul , Song Wookeun , Hwangf Moonju
Published: September 2021

Statistical Energy Analysis (SEA) has become an essential step to minimize the vehicle interior noise level. The outcome of SEA is typically 1/3 octave spectrum, and consequently it is difficult to understand the subjective effect of interior noise. This study investigated two approaches
to achieve the binaural synthesis of SEA results. One is directly from the SEA 1/3 octave result and the measured coherence function. The other makes use of Source Path Contribution (SPC) to estimate the time signals on the exterior panels and subsequently applies the SEA results as a set
of Finite Impulse Response (FIR) functions. Both approaches seem to result in realistic binaural signals as well as the correctly scaled sound pressure levels at the receivers. The one using SPC results can generate the input data for an NVH driving simulator by decomposing the harmonics and
the masking noises. This means that the SEA result can be experienced by driving the simulated vehicle freely.
Numerical Study of Airfoil Tonal Noise Reduction using Segmented Elastic Panel Configuration
Authors: Irsalan Arif Muhammad , Lam Garret C. Y. , Leung Randolph C. K.
Published: September 2021

In this paper, a novel passive method for airfoil tonal noise reduction is proposed using a configuration of two segmented elastic panels mounted on the airfoil. Numerical investigation using perturbation evolution method is carried out at a low Reynolds number based on airfoil chord
of 5x10 and an angle of attack of 5. The passive method of employing a single panel has shown promising tonal noise reduction capabilities where the resonating panel located just ahead of the sharp growth of boundary layer instability within the airfoil separation bubble provided the strongest
reduction of instabilities and noise reduction up to 3 dB has been achieved. The idea is extended in the present study by employing a two-panel configuration based on the localized flow characteristics over the airfoil surface. Five different panel configurations are designed and their effectiveness
in terms of tonal noise reduction is evaluated and compared with baseline configuration. The azimuth and spectral analyses indicate the different extent of noise reduction for each configuration and even noise amplification in one of them. A significant noise reduction up to 8 dB is observed
for the optimum configuration indicating the effectiveness of this novel method for devices operating at low Reynolds number.
Soundscape restoration model based on psycho-physiological response with audio-visual interaction in natural environment
Authors: Jo Hyun In , Jeon Jin Yong
Published: September 2021

In this study, a soundscape restoration model was proposed in terms of audio-visual interaction based on psycho-physiological response by natural soundscape experience. To this end, audio-visual stimuli were collected in 6 sites of 2 types of natural environment (greenery and water)
and 3 sites of urban environment (as control), and a laboratory evaluation environment was implemented using virtual reality technology. Sixty subjects participated in the experiment for two days, and the individual's health status, personality and temperament, and sensitivity were investigated
before the evaluation. In the experiment on the first day, a stress test (mental arithmetic) was performed before the stimulation experience, and questionnaires related to psychological recovery was answered after the stimulation experience. In all the experimental procedures, physiological
responses such as heart rate, electroencephalogram (EEG), and eye-tracking were measured so that before/during/after response from experience could be compared. In the experiment on the second day, they were asked to respond to a questionnaire related to the soundscape and landscape of environment.
Finally, the relationship between the audio-visual environment (soundscape and landscape perception) and the psycho-physiological response was investigated using structural equation model, and based on this, design guidelines for healthy urban city were proposed.
SOPRANOISE - update and analysis of noise barrier database including new current results
Authors: Conter Marco , Fuchs Andreas , Reiter Paul
Published: September 2021

In the frame of the SOPRANOISE project (funded by CEDR in the Transnational Road Research Programme 2018) work package 2 focused first on providing theoretical and practical background information on measurement of the acoustic performance of noise barriers due to a state-of-the-art
regarding correlations and possible trends between diffuse (EN 1793-1, EN 1793-2) and direct sound field methods (EN 1793-5, EN 1793-6). After that, the objective of this research was to extend and update the database of the European noise barrier market developed during the QUIESST project,
including more detailed analyses on single-number ratings as well as third-octave band measurement results. The data collected and the analysis performed show relevant facts and figures about acoustic performances of noise barriers measured under diffuse and direct sound field conditions,
together with a better understanding of the respective significance, similarities and differences of these standardized methods, improving data analysis and correlations between these methods. This paper gives a general overview of the data collected, summarising the main results of the statistical
analyses performed. Overall results and comparisons between results of measurements performed under diffuse and under direct sound field conditions are shown. Finally, conclusions and possible outlook of the research are presented.
Additional noise reduction with diffracting elements on barriers using numerical and standard calculation methods
Authors: van der Eerden Frits , Kurylek Rafal , Blaak Sandra , Salomons Erik , Eisses Arno , Van der Laan Tessel , Vliet Willem Jan van
Published: September 2021

The noise reduction of a (low) barrier can be enhanced by using an additional element with quarter-wavelength resonators with varying depths. A so-called Whiswall or WHIStop deflects sound upwards for specific frequencies. Measurements for a 1.1 meter high Whiswall and for a 1.1m barrier
are compared in a separate paper. The enhanced barrier effect is measured at a short distance behind the barrier, for several situations. In this paper these measurements are compared with the results of a numerical finite element model (FEM) to validate this model. Next, the noise reduction
is calculated at long ranges, up to 600 meters, for different point-to-point scenarios representative for road and rail traffic. A numerical parabolic equation method (PE) is coupled to the FEM model and a representative downwind condition is taken into account. The results at longer distance
are used to design an engineering method for the enhanced barrier effect that can be used in standard noise calculation models, such as the Dutch national calculation model (SRM2) or the ISO 9613-2 standard.
Exploiting data from the NoiseCapture application for environmental noise measurements with a smartphone
Authors: Picaut Judicaël , Bocher Erwan , Aumond Pierre , Petit Gwendall , Fortin Nicolas
Published: September 2021

NoiseCapture is a smartphone application initially developed as part of a participative approach for environmental noise mapping. After more than 3 years, the database produced from all over the world contributions is considerable (more than 77k contributors, nearly 300k tracks representing
about 72 million 1-second measurements, in nearly 200 countries). Beyond the initial objective, other uses of the application have emerged: individually by users for their own needs, by associations of people in charge of the fight against noise pollution, within the framework of educational
activities, by researchers for the realization of their own research, by communities to address the subject of noise pollution. As these new applications emerged, the development team of NoiseCapture was led to extend the possibilities of exploitation of these data. Thus, in this paper, we
present different possibilities for a user to perform his own data analysis, namely: a local export of data from the smartphone, access to raw data and pre-processed data from the NoiseCapture server, access to formatted GIS layers from OGC standard service. All these methods are enabled thanks
to the open source ecosystem, such as Python libraries, R software suite and GIS tools.
Trailing-edge noise reduction of a wing by a surface modification
Authors: Bharadwaj Ananthan Varun , Akkermans R.A.D. , Kozulovic Dragan
Published: September 2021

There is an increased emphasis on reducing airframe noise in the last decades. Airframe noise is sound generated by the interaction of a turbulent flow with the aircraft geometry, and significantly contributes to the overall noise production during the landing phase. One examples of
airframe noise is the noise generated at a wing's trailing edge, i.e., trailing-edge noise. In this contribution, we numerically explore the local application of riblets for the purpose of trailing-edge noise reduction. Two configurations are studied: i) a clean NACA0012 wing section as a
reference, and ii) the same configuration with riblets installed at the wing's aft part. The numerical investigation follows a hybrid computational aeroacoustics approach, where the time-average flow is studied by means of RANS. Noise sources are generated by means of a stochastic approach
called Fast Random Particle Mesh method. The results show a deceleration of the flow behind the riblets. Furthermore, the turbulent kinetic energy indicates increased unsteadiness behind the riblets which is shifted away from the wall due to the presence of the riblets. Lastly, the sound sources
are investigated by means of the 3D Lamb-vector, which indicates a slight reduction in magnitude near the trailing edge.
Study on aircraft noise directivity of behind the start of takeoff roll
Authors: Nakazawa Toshiyasu , Shinohara Naoaki
Published: September 2021

This paper discusses aircraft noise directivity behind the start of takeoff roll. Aircraft noise has the radiation directivity because of aircraft engine mount position and the engine noise directivity. Thus, lateral noise directivity correction is recommended in airport noise calculation
guidelines such as ECAC Doc.29 and ICAO Doc9911. In these guidelines, the directivity of flyover noise and the directivity at the start of takeoff roll on ground are prepared separately. A 90-degree dipole model is used for the directivity of the flyover noise, and another similar directivity
is used for the directivity behind the start of takeoff roll. It is necessary to properly evaluate the directivity behind the takeoff roll because it has a large contribution to noise calculation of the vicinity of the airport. Therefore, we measured aircraft noise behind the start of takeoff
roll with sound level meters placed half-concentrically around Narita Airport in Japan. From these measurement results, various types of aircraft noise directivity behind the takeoff roll are examined and considered the effects of weather conditions such as wind direction. Finally the differences
from existing models are compared.
Integrating environmental noise considerations into public policy: the case of Ireland
Authors: Faulkner Jon Paul , Murphy Enda
Published: September 2021

European Commission Directive (EU) 2020/367 describes how harmful effects from environmental noise exposure are to be calculated for ischemic heart disease (IHD), high annoyance (HA), and high sleep disturbance (HSD) for road, rail, and aircraft noise under the Environmental Noise Directive's
(END) strategic noise mapping process. It represents a major development in understanding the extent of exposure from transport-based environmental noise given it is a legal requirement for all EU member states from the 2022 reporting round. It also has the potential to accelerate the development
of stronger noise-health policies across the EU. While this development is to be welcomed, there are a number of basic noise-health policy applications that first need to be implemented in the Irish case if the noise-health situation is be accurately assessed and if public health is to be
adequately protected. In order to address this requirement the following paper presents concrete policy and practice recommendations as well as an evaluation of the current application of noise management policy in Ireland which is administered to protect the public from the harmful effects
of environmental noise. This paper provides guidance on how noise-health considerations can be integrated into key relevant areas of Irish policy including healthcare, the environment, transportation, and planning.
A compact active structural acoustic control method for minimizing radiated sound power
Authors: Sommerfeldt Scott
Published: September 2021

Active structural acoustic control is an active control method that controls a vibrating structure in a manner that reduces the sound power radiated from the structure. Such methods focus on attenuating some metric that results in attenuated sound power, while not necessarily minimizing
the structural vibration. The work reported here outlines the weighted sum of spatial gradients (WSSG) control metric as a method to attenuate structural radiation. The WSSG method utilizes a compact error sensor that is able to measure the acceleration and the acceleration gradients at the
sensor location. These vibration signals are combined into the WSSG metric in a manner that is closely related to the radiated sound power, such that minimizing the WSSG also results in a minimization of the sound power. The connection between WSSG and acoustic radiation modes will be highlighted.
Computational and experimental results for both flat plates and cylindrical shells will be presented, indicating that the WSSG method can achieve near optimal attenuation of the radiated sound power with a minimum number of sensors.
Application of Blocked Force Methodology in NVH development of Electrical Machines
Authors: Chen Keyu , Hartwig Marcus , Buening Duane , Warner Borg
Published: September 2021

To determine excitation forces of electrical machines from measurements, Transfer Path Analysis is commonly used. Transfer Path Analysis yields input forces indirectly utilizing measured responses and transfer functions. When conducting transfer function measurement, it is recommended
that the source of excitation is mechanically isolated from the receiver structure. However, in practice this is difficult to achieve without affecting the transfer path itself. The concept of the Blocked Force method introduces blocked forces which are independent of the receiver structure,
thus allowing measurement of transfer functions without isolating the source. In this research, a stator / rotor assembly is considered as the source. This assembly is bolted to a test-housing, considered as the receiver. Blocked forces are determined at the mounting locations between stator
and test-canister. The correctness of the calculated blocked forces is verified by comparing the predicted and measured responses at selected target points which were not used for determining the blocked forces.