bluuebunny/crossref_metadata_2025 huggingface dataset:
Suggestive Sound Design - How to use Active Interior Sound Design to improve traffic safety
Authors: Petersen Manuel , Etri Marc , Behrendt Matthias , Albers Albert , Spekker Manuel , Lefringhausen Tim Jonathan
Published: September 2021

Active sound design becomes an important addition to the newest generation of premium class electrical vehicles to enhance the emotionality of the driving experience. Musicological research indicates that emotions are altered by certain harmonic sets of pitches, whereas results in traffic
psychology show that emotions can influence the driving behavior. Despite these findings, there is no research done on how changes to an active vehicle sound could influence the driving behavior. In this paper, we describe an approach for a suggestive sound design. It's based on the hypothesis,
that the chosen safety distance by a driver could be altered by changing the inherent dissonance of an active interior vehicle sound based on the current safety distance. The suggestive sound design is based on an additive synthesizer utilizing the Shepard-Risset glissando. The sound can be
controlled by external signals e.g. CAN signals from real or virtual vehicles. To verify this hypothesis, a driving simulator was built in which the driving experience with a suggestive sound and the resulting driving behavior can be validated through subject studies within an immersive and
reproducible virtual reality environment. The research aims at improving road safety by influencing the driver through changes in the interior vehicle sound.
Aircraft interior acoustics - background noise contamination
Authors: Kappagantu Ramana , Etchessahar Manuel , Matas Edgar , Vansant Koen
Published: September 2021

Aircraft interior noise is an important factor to be considered for cabin comfort. In a cruising condition this noise source is mostly broadband in nature and is coming from the exterior, primarily the turbulent boundary layer (TBL) of the flow around the moving aircraft. Capturing
this noise to a high frequency is critical for designing the sound packaging. Also, this becomes important in the design of public announcement (PA) system for the aircraft cabin, i.e. the correct placement of speakers. One of the metrics used for this acoustic design is speech transmission
index. Deterministic techniques like finite or boundary element techniques for low frequencies and ray tracing method to reach higher frequencies are better suited for getting the narrow band responses. On the other hand, to characterize the background noise due to the TBL loads, statistical
energy analysis (SEA) route is pursued. In this paper the authors combine different techniques to capture the background noise and use them with PA sources and eventually capture the sound perceived at points of interest. The articulation metrics are compared for different operating conditions
of the aircraft. In the presentation attempts will be made to play the auralized sounds.
Optimization of underdetermined hologram points in reconstructing the vibro-acoustic source field based on ESM
Authors: Jiang Laixu , Ih Jeong-Guon
Published: September 2021

The distribution of measurement points is important in reconstructing the vibro-acoustic source field using the near-field acoustical holography (NAH) based on the equivalent source method (ESM). Because too close measurement impose a limit in the implementation of ESM, an optimal arrangement
of the hologram data is needed to enable a longer distance measurement although the points are still within the near field. In this work, the optimal measurement positions are determined by adopting the method that assures the independence among the measuring positions as far as possible.
Singular value decomposition of the transfer matrix is employed in the loop-iteration calculation fashion, in which the candidate measuring point affecting the increase of singularity is eliminated at each iteration step. Comparison is made with the uniformly distributed hologram points, the
monopole version of ESM model, and the patch holography method. The test results reveal that the acoustic field of sound sources can be reconstructed meaningfully from the optimized hologram points of underdetermined condition. Under the predetermined reconstruction accuracy, the test results
varying the hologram distance show that it is possible to realize the underdetermined far-distance measurement than the usual NAH.
Silencer for high-frequency turbocharger compressor noise via an acoustic straightener
Authors: Sriganesh Pranav , Dehner Rick , Selamet Ahmet
Published: September 2021

Decades of successful research and development on automotive silencers for engine breathing systems have brought about significant reductions in emitted engine noise. A majority of this research has pursued airborne noise at relatively low frequencies, which typically involve plane
wave propagation. However, with the increasing demand for downsized turbocharged engines in passenger cars, high-frequency compressor noise has become a challenge in engine induction systems. Elevated frequencies promote multi-dimensional wave propagation rendering at times conventional silencer
treatments ineffective due to the underlying assumption of one-dimensional wave propagation in their design. The present work focuses on developing a high-frequency silencer that targets tonal noise at the blade-pass frequency within the compressor inlet duct for a wide range of rotational
speeds. The approach features a novel "acoustic straightener" that creates exclusive plane wave propagation near the silencing elements. An analytical treatment is combined with a three-dimensional acoustic finite element method to guide the early design process. The effects of mean
flow and nonlinearities on acoustics are then captured by three-dimensional computational fluid dynamics simulations. The configuration developed by the current computational effort will set the stage for further refinement through future experiments.
Numerical investigation into effects of gas concentration and bubble collapse on tip vortex cavitation noise of NACA16-020 wing
Authors: Ku Garam , Cheong Cheolung , Seol Hanshin , Jeong Hongseok
Published: September 2021

In this study, the effects of gas concentration and bubble collapse on tip vortex cavitation noise of NACA16-020 wings are investigated using coupled Eulerian-Lagrangian method based on sequential application of Reynolds averaged Navier-Stokes (RANS) solver, bubble dynamics model and
acoustic analogy. The bubble dynamics model used in the preceding study (Ku et al., 2020) is modified by including the gas pressure terms and the bubble collapse model, which depends on the timing and threshold of bubble collapse, the number, initial radius and location of divided bubbles.
The validity of the modified bubble dynamics model is confirmed through its application to a benchmark problem where single bubble is triggered by laser. Then, the coupled Eulerian-Lagrangian method based on the modified bubble dynamic model is applied for the prediction of tip-vortex cavitation
noise of NACA16-020 wing. The predicted results of the tip vortex pattern and acoustic pressure spectrum are compared with the measured results, which shows closer agreements between two results than those in the previous study.
Shooting noise annoyance in communities around German military training areas
Authors: Schreckenberg Dirk , Großarth Stephan
Published: September 2021

Shooting noise is characterized as impulsive, intermittent sound with high energy and low frequencies. Studies have shown that for given average sound levels shooting noise is regarded as more annoying than transportation noise, particularly road traffic noise. In comparison to transportation
noise, responses to shooting noise are less frequently studied. The latest published German studies on community responses to shooting noise were conducted in the 1980ies and 1990ies. The study presented in this contribution aims to provide new data on shooting noise responses in communities
around military training areas. Annoyance responses were collected using a survey with 1043 residents living around three military training sites in Germany. For the address of each resident, on the basis of shooting training in the year 2019 the average continuous sound levels and the sound
exposure levels for day and night-time with the frequency weightings A, C, and Z was estimated for grid cells of 250 x 250 m. Results on the exposure-response relationship between these noise metrics and the percentage of highly annoyed persons (%HA) are presented. Among others, the results
indicate, that non-acoustic factors, particularly attitudes related to the source have a strong impact on the annoyance.
Why do clogged porous asphalt pavements give better traffic noise reduction than a dense-graded asphalt pavement?
Authors: Sandberg Ulf
Published: September 2021

In Europe, porous asphalt concrete pavements (PAC) are commonly used to reduce traffic noise. Especially the double-layer type (DPAC) provides substantial traffic noise reduction. Unfortunately, PAC pavements compared to dense asphalt pavements have reduced acoustic longevity; the main
reason being clogging of the pores and voids, sometimes also more ravelling. The dense-graded pavements considered here are stone mastic asphalts (SMA, in the US known as stone matrix asphalt) which often have surface macrotexture of the same size as the PAC. The main difference is that the
PAC has accessible pores/voids providing sound absorption, while the SMA has practically no porosity. One would expect that when the pores in the PAC have become clogged while ravelling is not yet substantial, that the noise property of the PAC would approach that of the SMA. But experimental
studies suggest that even when PAC:s are effectively clogged, they retain a certain noise reduction compared to SMA:s. This paper examines this feature of clogged PAC versus SMA and reasons for this unexpected property, for a few Swedish DPAC pavements compared to SMA pavements, with due consideration
of possible difference in maximum aggregate size and macrotexture as represented by mean profile depth (MPD) and grading curves.
Sound, noise, annoyance? Information as a means to strengthen the public acceptance of civil drones
Authors: Eissfeldt Hinnerk , End Albert
Published: September 2021

Civil drones are becoming ever more present in public perception. Ranging from parcel delivery to wildlife protection and from precision farming to law enforcement, many applications are said to have market-changing potential. Against this background, nations and institutions around
the world are trying to keep up with the dynamic technological developments by means of rules and regulations. Since all parties involved expect a strong increase in both the number of drones and the range of their uses, there is a rising interest in the public acceptance of these vehicles.
Widespread acceptance can promote the dissemination of new technologies. Conversely, citizens' concerns about the use of drones in their daily environment may pose barriers to the further proliferation of civil drones, especially in urban areas. The psychoacoustic properties of the vehicles
have repeatedly been discussed as being one such limiting factor. This paper discusses results of a representative national study on the social acceptance of civil drones, taking a closer look at effects of information about drones as potential means to foster public acceptance. The findings
underline the role of well planned information campaigns as well as community engagement in managing the contribution of drones in future urban soundscapes.
The impact of COVID-19 lockdown on the noise pollution: case study in the city of Skopje
Authors: Domazetovska Simona , Anachkova Maja , Gavriloski Viktor , Sokolikj Ankica , Stojkovska Sandra
Published: September 2021

The lockdown that the city of Skopje has suffered during the months of April to June 2020 in order to control the spread of COVID-19 has significantly changed the acoustic environment in the urban parts of the city. The absence of vehicles, people on the streets and closed restaurants
has led to a noise reduction captured by the low-cost wireless sensor network in the City of Skopje. The analysis carried out in this paper show reduction in noise pollution strongly correlated with the population's activity and behavior to the new circumstances. Overall, the sound pressure
levels vary around 65 dB; however, some extreme decrease can be noticed, especially during the quarantine weekends. Also, the noise levels were compared between the same time periods during the year of 2019 and 2020, where it can be perceived reduction in the sound level for 36,5% for the
day-evening-night noise level indicator (L). Significant variations occur for the indicators L, L, and L, especially during the lockdown weekends.
Ferry M/V Kramer noise mitigation
Authors: Bahtiarian Michael
Published: September 2021

The Motor Vessel (M/V) Edward V. Kramer is an aluminum vessel that operates as a small passenger ferry, which is owned and operated by the Department of Homeland Security (DHS) and used to transport DHS personnel and materials to Plum Island, NY. It was placed in service in 2018 and
right from the start the sound levels inside the Main Deck compartment were found to be excessive. The original vessel specification included a noise limit of 75 dBA in the Main Deck Passenger Lounge and measured levels were as high as 87 dBA. A ship survey of sound and vibration was performed.
Noise predictions to determine the controlling sound paths was also performed based on engine sound and vibration source levels. Recommendations for mitigation were presented and carried out by another shipyard. Mitigation included vibration isolation of the main engines and sound attenuation
improvements to the Main Deck Passenger Lounge. After completion of the modifications, another survey was performed in 2021 and results show a reduction by as much as 11 dB in the Main Deck Passenger lounge. Noise estimation methods and details on the noise control treatments are given in
the paper.
Structural Dynamics, Noise and Vibration: Buildings Adjacent to Train Lines
Authors: Reboredo Gasalla Pablo
Published: September 2021

In architecture and civil engineering there is a growing interest in the study of the dynamics of structures. The dynamic effects are due to various actions, but their influence is widened or reduced according to the design of the structure. Structures can be highly susceptible to the
action of dynamic loads produced by the action of wind, earthquake, industrial activities, blasting activities, construction sites, road vehicles, trains, building services and human activities. Noise and vibration can have significant environmental impact on buildings and structures and can
damage track components, crack roadways, unsettle foundations, affect sensitive equipment, impact human comfort and damage structures. Structure-borne noise and vibration can be a major and often overlooked consideration in the planning, design and operation of existing or new developments.
A reliable, considered approach to assessing noise and vibration is needed to achieve outcomes that meet client expectations while maintaining on-going compliance with relevant standards and regulatory and planning requirements. The proposed paper will focus on a general overview of the structure-borne
noise and vibration risks, associated with new developments that are adjacent to existing rail lines during the early design stages, from commercial and residential buildings to sensitive research facilities. It will further explain the general description of the design process, including
problem descriptions, measurements of ground and structural vibration levels at the proposed site, vibration criteria, finite element analysis and provisions of the isolation system required to be considered at the building to achieve the relevant criteria.
Using Inverse Transient Statistical Energy Analysis to determine the transient power input from a heavy impact on floating floors
Authors: Hirakawa Susumu , Hopkins Carl
Published: September 2021

To aid design decision concerning heavy impacts on heavyweight floors, it is necessary to be able to predict Fast-time weighted maximum sound pressure levels (Lp,Fmax) in the receiving room. For excitation directly on the heavyweight floor this can be carried out using Transient Statistical
Energy Analysis (TSEA) in a predictive mode. However, the performance of floating floors is not always possible to accurately predict hence an inverse approach to TSEA, referred to as ITSEA, has been developed to determine the transient power. This paper compares the prediction of the Lp,Fmax
using TSEA with normalized transient power input determined by ITSEA with measurements conducted in two test chambers with and without floor small floor toppings. For one-third octave bands, the maximum difference in Lp,Fmax between measurement and TSEA ranged from 5.3 to 8.3dB and 6 to 7dB
when using W`in,ForcePlate and W`in,ITSEA respectively. For octave bands, the maximum difference in Lp,Fmax between measurement and TSEA ranged from 2.1 to 7.5dB and 2 to 7dB when using W`in,ForcePlate and W`in,ITSEA respectively
Accurate noise modeling for petrochemical plants - impact of compressor Piping
Authors: Ghosh Arindam
Published: September 2021

Compressor piping is a dominant noise source in petrochemical plants with large centrifugal compressors. Acoustic insulation is used on compressor suction, discharge and recycle lines as a measure to mitigate noise radiating from compressor piping. This paper will demonstrate using
case studies the importance of acoustic insulation on compressor piping as the primary and most cost effective noise control method for both community and in-plant noise. Case studies include the predicted and measured noise levels obtained during post startup noise surveys. This paper will
also illustrate that to obtain good agreement with measured noise levels it is imperative to accurately model the piping sources following the actual piping layout and account for distance attenuation. A cost-benefit analysis of using complete compressor houses and/or acoustic blankets will
be presented along with the efficacy of various types of acoustic insulation including elastomeric foam and aerogel based insulation systems. Different acoustic requirements for hot and cold insulation systems will also be presented.
Room acoustics criteria and measurements of lobbies and atria for various building types
Authors: Pyper Ted , Whitney Matt , Porter David
Published: September 2021

The lobby or atrium for a building may serve many purposes -- entryway, welcome area, circulation zone, and architectural point of interest. Increasingly, lobbies and atria serve more and more functions: gathering area, presentation area, music and event space, study area, and dining,
among other uses. Since variable acoustics in lobby spaces are not typically feasible or desirable, the acoustical design of lobby spaces must strike a balance for the variety of events planned for the space. Working with design teams and owners to understand the needs of each space, acoustical
design criteria evolve based on project-specific needs and previous experience. In this presentation, lobbies are considered for various building types, including education facilities, student commons, museums, and performing arts buildings. In addition to studies of existing spaces and modeling
of buildings in design, this presentation expands on the authors' previous efforts by documenting the measured reverberation and background noise in several lobbies and atria after the completion of design and construction.
Performance of a friction ring DVA for vibration control of a flywheel
Authors: He Xiaodong , Huang Xiuchang , Hua Hongxing
Published: September 2021

A flexible ring DVA with friction contact interfaces (essentially a viscoelastic-friction DVA) is proposed to suppress vibration of a flywheel, two other cases are also studied, i.e., viscoelastic DVA and friction DVA. Based on an equivalent 3 degrees of freedom (DOFs) dynamic model,
displacement response of the flywheel-DVA are obtained by using harmonic balance method (HBM). It is shown that all three types of DVA can suppress vibration of the flywheel effectively, bandwidth of the viscoelastic-friction DVA is enlarged due to the existence of friction interface. Performances
of the DVA are evaluated by analyzing the displacement responses and forces (i.e., spring force, damping force and friction force). It is shown that the frequency corresponding to the turning point on the response curve is the critical frequency at which dynamic vibration absorption takes
place, and it is also the frequency at which the friction force begins to take effect. In the process of emergence and disappearance of the dynamic vibration absorption, the friction force plays a role similar to a "switch"
Innovative elastomeric shear leg mount concepts for quasi-zero stiffness isolation
Authors: Fredette Luke , Singh Rajendra
Published: September 2021

Passive vibration isolation may be a cost-effective solution to isolate a supported system containing a source and/or receiver from the supporting structure. The standard linear theory suggests a low-stiffness joint to create a mobility mismatch in the transmission path, but this solution
may lead to large amplitude motions in the supported system. To achieve both motion control and isolation with the same mount and without compromising either objective, an innovative, nonlinear mount concept is proposed. Taking advantage of geometric nonlinearity for large displacements, a
quasi-zero stiffness is generated by exploiting the interaction between the nonlinear mechanisms that govern the motion of a number of inclined shear legs. For example, a three-regime stiffness profile is created, including a medium-stiffness preload regime, a quasi-zero stiffness isolation
regime, and a high-stiffness motion control regime. This concept offers significant benefits compared with a more conventional compromise approach in that low-amplitude vibrations are exceptionally isolated while large amplitude transient motions are controlled. Illustrative computational
examples will be presented to support the underlying linear and nonlinear design principles. Limiting cases will be discussed as well.
Variation in vibro-acoustic noise due to the defects in an automotive drum brake
Authors: Ramesh Ananthapadmanabhan , Sriram Sundar
Published: September 2021

Drum brakes are significant contributors to noise and vibration in automobiles causing discomfort to the passengers. The vibration and hence the resulting noise increase due to various inherent defects in the drum brake, such as asymmetry. This work aims to quantify the variation in
the vibro-acoustic noise due to several common defects in the drum brake using an integrated non-linear vibration analytical model and a numerical acoustic model. The sources of vibro-acoustic noise sources such as contact and reaction forces are predicted using a four-degree-of-freedom non-linear
contact mechanics based analytical model. A finite element based acoustic model of the drum brake is utilized to predict the force to the sound pressure transfer function in the drum brake. Product of the transfer functions and the forces gives the corresponding sound pressure level from which
the overall sound pressure levels are estimated. The variation in the overall sound pressure levels due to different drum brake defects is evaluated by introducing defects to the analytical model. The results show that the overall sound pressure level is a strong function of the defects. It
is envisioned that the current work will help in the development of effective health monitoring systems.
Techniques for adaptive metamodelling of propeller arrays far-field noise
Authors: Iemma Umberto , Poggi Caterina , Rossetti Monica , Bernardini Giovanni
Published: September 2021

The fast development of Urban-Air-Mobility as well as the constant growth of the air transport have made the acoustic pollution abatement a crucial requirement for the aviation industries in order to comply with the increasingly demanding constraints for the community acceptance. The
aeroacoustic characterization of arrays of electrically-powered propellers is one of the most challenging issues. The vast majority of the UAM concepts under development adopt propulsion systems based on multiple propellers, for which reliable and cost-efficient aeroacoustic models are still
lacking. The present paper proposes the development of surrogate models for the description of acoustic emission of multi-propeller configurations. The numerical investigation focuses on surrogate models able to take into account the effects of the propeller blade geometry (e.g., chord and
twist distributions) and global propeller-array geometric parameters (e.g., propellers clearance) on acoustic performances of the whole system. An innovative Artificial Neural Network adaptive metamodelling technique is applied on a numerical database obtained through a boundary integral formulation
for the solution of incompressible potential flows around lifting/thrusting bodies, followed by the application of the Farassat 1A boundary integral formulation for the noise field evaluation.
Rail noise grade separation alternative analysis case study
Authors: Burge Paul , Cowan Jim
Published: September 2021

The San Francisco Bay Area has an existing commuter rail system that brings commuters from southern regional communities into the downtown city center. One of the communities served by commuter rail service is the City of Palo Alto, CA, which includes four active grade crossings, each
requiring train horn sounding for each train event. The City wished to evaluate various options to eliminate the noise generated from horn soundings by creating road/rail grade separations at each existing grade crossing and other possible noise and vibration control elements. The alternatives
included crossing closures, rail bed trenching, viaducts, roadway underpasses, and tunnels. A noise and vibration study was undertaken to provide an analysis of which alternatives would provide better reductions in noise and vibration in the surrounding community. The study included an assessment
of existing noise levels and predicted future noise and vibration levels for construction and operation of each proposed alternative using current established noise and vibration methodology. The results of this study included comparisons of the noise and vibration associated with each of
the of the proposed alternatives that could be used in conjunction with other studies considering cost, traffic, safety, aesthetics and other factors to select an overall preferred alternative.
Numerical analysis of the transmission loss of dissipative mufflers with polygonal cross-section
Authors: Geyer Thomas , Mai Christopher , Henke Anna-Sophia
Published: September 2021

Dissipative mufflers are often used for the reduction of broadband noise transmitted in ducts. Many common calculation procedures for the transmission loss of such mufflers require conventional shapes like rectangular or circular cross-sectional areas. In an effort to analyze the effect
of the cross-sectional area of dissipative mufflers on the resulting noise reduction, the transmission loss of axially uniform mufflers with polygonal cross-sectional areas was investigated using the finite element method. The mufflers are designed to have the same open area, and hence in
a practical application would lead to a similar pressure drop. The results were compared to those obtained with the well known approximative method of Piening. Good agreement between simulation and estimation was found regarding basic trends at low frequencies, while notable differences were
revealed regarding the maximum transmission loss.
Influence of green space design on individual noise perception
Authors: Zapf Verena
Published: September 2021

Especially in urban areas, green spaces are important recreational destinations, yet they are often exposed to high levels of traffic noise. Therefore, it should be investigated to what extent the design of green spaces affects the perception of noise within the green spaces. For this
purpose, four soundwalks with a total of 34 participants were conducted in the Großer Garten in Dresden, Germany. A range of acoustic and perceptual properties were measured and examined. Furthermore, the green space was characterised with regard to its vegetative design and the visibility
of the noise sources, as well as evaluated by the participants with respect to visual impression and appropriateness. The statistical evaluation has shown that the visual impression, the appropriateness and the masking of the noise sources correlate significantly with the perceived loudness
and pleasantness - but not with the eventfulness. With regard to vegetation, it was found that the diversity of vegetation correlates significantly with all three parameters of individual noise perception, whereas the quantity of vegetation does not. Thus, it can be said that appealing design,
masking of the noise sources and diversity of vegetation reduce individual noise perception and therefore increase the recreational value.
A review of techniques and errors involved in sound isolation testing
Authors: Dickman Jameson
Published: September 2021

Construction industry design standards are increasingly calling for new construction to be inspected and tested for compliance with design specifications after the project is built; otherwise known as the commissioning process. As part of this trend, owners, sensitive to the acoustics
of their facilities, are seeking confirmation via measurements that their buildings meet sound isolation and background noise requirements, particularly when pursuing certifications under the US Green Building Council LEED standard, the WELL Building Standard, or other green building or wellness
standards. In general, the error of sound isolation measurements is not officially established. This poses challenges to designers tasked with specifying assemblies and components to meet field verification requirements. This paper will briefly review current research and standards on the
error of measurements such as Noise Isolation Class (NIC) and the Weighted Level Difference (D) and discuss example design standards and guidelines which do or do not account for this error. It will also propose further research topics to better define the error in sound isolation measurements
and best practices when establishing or designing to sound isolation criteria in new or renovated buildings.
Empirical study on the correlation between measurement methods under diffuse and direct sound field conditions for determining sound absorption and airborne sound insulation properties of noise barriers
Authors: Fuchs Andreas , Wehr Reinhard , Conter Marco
Published: September 2021

In the frame of the SOPRANOISE project (funded by CEDR in the Transnational Road Research Programme 2018) the database of the European noise barrier market developed during the QUIESST project was updated with newly acquired data. This database gives the opportunity for an empirical
study on the correlation between the different measurement methods for the acoustic properties of noise barriers (according to the EN 1793 series) to further investigate the interrelationships between these methods by using single-number ratings and third-octave band data. First a correlation
of the measurement methods for sound absorption under diffuse field conditions (EN 1793-1) and sound reflection under direct sound field conditions (EN 1793-5) is presented. Secondly, a correlation of the measurement methods for airborne sound insulation under diffuse field conditions (EN
1793-2) and airborne sound insulation under direct sound field conditions (EN 1793-6) is shown. While for airborne sound insulation a distinct correlation is found due to the wide data range, for sound absorption no robust correlation can be found.
A machine learning-based methodology for computational aeroacoustics predictions of multi-propeller drones
Authors: Legendre Cesar , Ficat-Andrieu Vincent , Poulos Athanasios , Kitano Yuya , Nakashima Yoshitaka , Kobayashi Wataru , Minorikawa Gaku
Published: September 2021

The rapid progress in technological developments of small Unmanned Aircraft Systems (sUAS) or simply "drones" has produced a significant proliferation of this technology. From multinational businesses to drone enthusiasts, such a technology can offer a wide range of possibilities, i.e., commercial services, security, and environmental applications, while placing new demands in the already-congested civil airspace. Noise emission is a key factor that is being addressed with high-fidelity computational fluid dynamics (CFD) and aeroacoustics (CAA) techniques. However, due to uncertainties of flow conditions, wide ranges of propellers' speed variations, and different payload requirements, a complete numerical prediction varying such parameters is unfeasible. In this study, a machine learning-based approach is proposed in combination with high-fidelity CFD and CAA techniques to predict drone noise emission given a wide variation of payloads or propellers' speeds. The transient CFD computations are calculated using a time-marching LES simulation with a WALE sub-grid scale. In contrast, the acoustic propagation is predicted using a finite element method in the frequency domain. Finally, the machine learning strategy is presented in the context of fulfilling two goals: (i) real-time noise prediction of drone systems; and (ii) determination of propeller's rotation speeds leading to a noise prediction matching experimental data.
Using noise control principles when evaluating the acoustic impacts of face coverings during the coronavirus pandemic
Authors: Ruhala Richard , Ruhala Laura
Published: September 2021

Several different combinations of face masks and shields are evaluated for their acoustic performance using a head and torso simulator (HATS). The HATS is used as a controlled and repeatable artificial sound source using white noise in a classroom environment. Sound pressure levels
at octave band frequencies due to the face coverings are evaluated at a location of 2.0 meters from the HATS which is within the direct field to reduce the room acoustical effects. The problem is modeled as a barrier separating a source and receiver using fundamental noise control principles.
Fabric material properties are used such as thickness, density, stiffness, and damping. The results are compared with experimental tests. The face shield with clear plastic barrier produces a resonance in the 1000 Hz octave band. Analytical models of cavity resonances, standing wave resonances,
or plate resonances are calculated and compared with the experimental resonance. The speech interference level is used to determine the frequency content that is most likely to cause hearing difficulties and compared with A-weighted differences between the unmasked condition and masked.
Design of a metamaterial-based muffler for a target frequency range
Authors: An Byunghun , Lee Jinwoo
Published: September 2021

This work proposes an acoustic metamaterial-based muffler that effectively blocks a transmission noise for a target frequency range. Since the acoustic metamaterial-based muffler consists of arrayed unit cells, its noise attenuation performance is strongly affected by the internal layout
of the unit cell. The wave transmission characteristics of an acoustic metamaterial is explained by the effective bulk modulus and dispersion curve of an unit cell. Therefore, the internal layout of the unit cell should be optimally designed so that its band gap should include the target frequency
range of a muffler. To the end, an acoustical size optimization problem is formulated to design a unit cell of the muffler and is solved for a given design requirement. The noise blocking frequency range of the unit cell is characterized by the bandgap in its dispersion curve during the optimization
process. The wave transmission characteristics of the metamaterial muffler is validated experimentally.
Reuse of coffee waste and paper cups for acoustical panel applications in architectural studios
Authors: Sel Ece , Düzova İpek , Şireli Anıl Ege , Yazıcı Beyza , Sü Gül Zühre
Published: September 2021

This study has been initiated with an aim of enhancing the acoustical comfort levels in the architectural studios of Bilkent University in Ankara. Initial assessment of the studios by field tests indicated very long reverberation times, supporting the complaints by the students and
instructors. In order to be applied in studio environment, acoustical panels are developed out of recycled materials. The increasing coffee demand and consumption of our era have motivated the reuse of both paper cups and coffee waste. The end-product is composed of two layers. The outer layer
is out of recycled coffee cups, placed in different arrangements in terms of orientation, size, and spacing. The backing layer is a panel of compressed and kiln-dried coffee grains and tea leaves. The coffee/tea residues are adhered together by using natural binders. In order to determine
the best possible alternative of the waste materials with the highest sound absorption performance, different density variations have been explored. Both impedance tube tests and acoustical field measurements are utilized during the process of research and development. Considering the increasing
demand for green technology, the layered panel system is proposing cost minimized, environmentally friendly, and biodegradable solutions with improved acoustical and aesthetical values.
Novel features for the detection of bearing faults in railway vehicles
Authors: Kreuzer Matthias , Schmidt Alexander , Kellermann Walter
Published: September 2021

In this paper, we address the challenging problem of detecting bearing faults from vibration signals. For this, several time- and frequency domain features have been proposed. However, these proposed features are usually evaluated on data originating from relatively simple scenarios
and a significant performance loss can be observed if more realistic scenarios are considered. To overcome this, we introduce Mel Frequency Cepstral Coefficients (MFCCs) and features extracted from the Amplitude Modulation Spetrogram (AMS) as features for the detection of bearing faults. Both
AMS and MFCCs were originally introduced in the context of audio signal processing but it is demonstrated that a significantly improved classification performance can be obtained using the proposed features. Furthermore, the data imbalance problem that is prevailing in the context of bearing
fault detection, meaning that typically much more data from healthy bearings than from damaged bearings is available. Therefore, we propose to train a One-class SVM with data from healthy bearings only. Bearing faults are then classified by the detection of outliers. Our approach is evaluated
with data measured in a highly challenging scenario comprising a state-of-the-art commuter railway engine which is supplied by an industrial power converter and attached to a gear and load.
Towards predicting noise-power-distance curves for propeller and rotor powered aircraft
Authors: Amargianitakis Daniel , Self Rodney H. , Torija Antonio J. , Proença Anderson R.
Published: September 2021

Propeller and rotor based propulsion systems are the dominating choice of power delivery system in the upcoming Urban Air Mobility market. Fully electric air-taxis (car sized vehicles with Vertical Take-off and Landing, VTOL, capabilities) concepts are using the benefits of the scalable
properties of electric motors to distribute propulsor units all over the airframe. The large variety of concepts and configurations of these vehicles poses a serious issue in predicting noise generated on the ground. The need for a high-level model to aid in acoustic decision making is evident.
Through the demonstrated methodology of computationally deriving Noise - Power - Distance curves for conventional turbo fan aircraft, this paper delivers the capability of dealing with propeller propulsion systems and the associated propeller tonal noise sources to generate the NPDs and therefore
noise exposure maps. The aims can be broken down into two objectives: a) demonstrate the capabilities of the proposed propeller harmonics noise scaling laws to calculate noise variation from a baseline scenario and b) incorporate the scaling components into the larger capability of producing
noise exposure contours, by the means of computationally deriving NPD curves for propeller powered aircraft. Preliminary NPD curves for General Aviation sized propeller power aircraft are generated and discussed.
Loudspeaker configuration in reverberation rooms for sound absorption measurement using room mode determination
Authors: Moos Niels Peter , Jeong Cheol-Ho , Bolberg Mads , Skov Rasmus Stahlfest Holck
Published: September 2021

For Sabine absorption coefficient measurements in reverberation rooms, it is preferable to excite as many room modes as possible. But the number of excited room modes is significantly affected by many factors, among which one dominating factor is the loudspeaker location particularly
at frequencies below the Schroeder frequency. In turn, this could significantly influence the statistical absorption coefficient obtained according to ISO 354. Therefore, this study aims to investigate the impact of loudspeaker configurations on the excitation of room modes. Frequency response
functions are measured using a broad band steady state noise signal using four sound sources at various locations, and the numbers of excited room modes in the one-third octave bands are quantified and compared against those by Green's function simulations. A procedure for determining favorable
loudspeaker positions based on the excited room modes is proposed, which can be a useful input to the working group of the ISO 354 standard.
Bibliographic review of socio economic effects of environmental noise for public policies in Chile
Authors: Campos Alexis , Raimann Arias Felipe , Gonzáles Padilla Pablo
Published: September 2021

The Ministry of Environment of Chile is currently updating the public policies that regulate noise mainly from industrial sources. For this reason, a background record of studies that describe the benefits and socioeconomic effects of noise in the population is needed. Through a bibliographic
review it was possible to identify a variety of benefits and effects in the economy, health and social ambit, as well as new investigation lines that take in consideration the mental health and non favorable socioeconomic conditions (economic inequality, racial and ethnic problems). The different
works analyzed include the recent systematic reviews for the elaboration of the "Environmental noise guidelines for the European Region" of the World Health Organization, a series of works mainly of European origin and two Latin American economic studies. Finally, due to the low
regulation in Latin American countries regarding noise, it is possible that these problems are greater than those reported in developed countries and therefore their study is of interest to create or apply other public policies in the region to a greater extent.
An analytical model for predicting noise radiated by switch reluctance electric motors
Authors: Sarikaya Bahadir , Ozdemir Enes Timur , Inalpolat Murat , Lee Hyun Ku , Kim Moo Suk
Published: September 2021

Switch reluctance motors (SRM) have become a prominent alternative for electric vehicles in recent years due to their simple, high power density architecture and cost-effective manufacturability. Despite its potential, NVH problems have been one of the biggest challenges for SRM's implementation.
Vibration and noise generated by the SRM are mainly caused by phase switching related torque ripple, unbalanced electromagnetic forces from air gap variations and lamination problems. Our proposed model is an analytical noise radiation prediction model which relates geometrical, material and
electrical design inputs to radiated sound power. The electromagnetic part of the model is nonlinear with saturation and provides back-emf and flux linkage by receiving design inputs. The computed magnetic energy, radial and tangential rotor forces are utilized as excitation sources to a continuous
shell dynamic model to obtain the steady-state vibration response. Finally, surface velocities obtained from the shell model are used to calculate sound power. Utilizing a shell structure provides axial, radial and tangential information on the casing by considering the effect of magneto-restrictive
forces of laminations, torque ripples and unbalanced electromagnetic forces. The effect of air gap, lamination error, and stator and rotor geometry on sound radiation are studied through an example case study.
A dynamic shell model for diagnostics of rotating machinery under periodic excitation
Authors: Inalpolat Murat , Ozdemir Enes Timur
Published: September 2021

In this paper, a generalized dynamic model of a shell structure has been developed and utilized for diagnostics purposes. The dynamic model is three-dimensional, includes the effects of rotary inertia and shear deformation, and can handle moving loads in radial, tangential and axial
directions. The model is utilized to determine in-plane radial displacements of the shell structure under concentrated radial loads for different boundary conditions. The periodic loads are constructed using harmonics obtained through the Fourier series expansion method. The modal expansion
technique is implemented for calculation of the steady state forced response of the shell structure. A simplified acoustic radiation model is also implemented in conjunction with the dynamic shell model to predict the noise radiated from a rotating circular cylindrical shell structure under
different kinematic, loading and boundary conditions. Moreover, forced vibration response and acoustic radiation predicted will be employed to reveal patterns in the signals that can potentially be used for diagnostics of rotating machinery applications. The shell model is derived using a
comprehensive approach and thus can be used to model prevalent engineering applications ranging from electric motors to gears and bearings.
Perceptual Difference on HVAC Sound Quality between Electric and Conventional Vehicles
Authors: Yamauchi Katsuya , Dan Minori , Cioffi Federico , Maffei Luigi , Masullo Massimiliano
Published: September 2021

The heating, ventilation and air-conditioning (HVAC) system is one of the most critical sources in in-vehicle noise environment, especially when cars are moving at low speed or at lower engine rotation. With the transition to electric vehicles (EV) from internal combustion engine vehicles
(ICEV), the contribution of powertrain becomes lower on the background noise inside car cabins. The authors have been conducting a collaborative research on HVAC sound quality inside car cabins. In this paper the results of a subjective evaluation of HVAC sound quality were presented, that
attempted to compare the perceptual differences among the two groups, i.e. EVs and ICEVs. The result revealed the difference in the noise perception among the two types of vehicles especially softer air flow rate conditions.