bluuebunny/crossref_metadata_2025 huggingface dataset:
Controlling the amount of acoustic absorption by using clusters of hard cylinders
Authors: Cutanda Henriquez Vicente , Sánchez-Dehesa José
Published: September 2021

The viscothermal absorption of a cluster of hard cylinders periodically arranged in air is directly related with the filling fraction of the underlying lattice. In this work, we present a comprehensive study of the viscous absorption of clusters with circular external shape. The study
has been performed by using a homogenization theory in which the clusters have been represented by a single fluid-like cylinder with effective parameters. The validity of the homogenization approach has been supported with numerical experiments in which the viscosity of the actual cluster
is calculated with an improved version of the boundary element method. The simulations have been performed by embedding the clusters in a multimode impedance tube. For example, for a circular cluster containing 817 hard cylinders distributed in a hexagonal lattice with filling ratio of 0.836,
the absorptive factor calculated with the homogenization approach is 41.5%, which underestimates by about 1% the value obtained with the complete cluster.
The relevance of psychoacoustic percentiles for the description of morphological characteristics in urban areas
Authors: de la Prida Daniel , Sibylle Engel Margret , Fels Janina , Pedrero Antonio
Published: September 2021

Research over the last decade has explored the relevance of psychoacoustic indicators such as Loudness (N), Sharpness (S), Roughness (R) and Fluctuation Strength (FS) for the description of the perceptual construct of soundscapes. Furthermore, the recent ISO 12913-2 standard, published
in 2018, recommends their use for the quantitative assessment of soundscapes. However, usually, investigations on soundscapes are using averages of the psychoacoustic indicators, and little research has evaluated the relevance of percentiles for the perceptual description of physical environments
in terms of geometrical features, prevailing noise sources, temporal and meteorological variables, etc. This study aims to verify whether psychoacoustic percentiles can representatively describe the geometrical features of different urban sonic environments. For this purpose, recordings were
taken in Aachen and Madrid in different days and seasons, at 14 certain locations in each town. In addition, morphological data was collected of the sites. A Principal Component Analysis (PCA), conducted on psychoacoustic percentiles (i.e., P1, P5, P10, P50, P90, P95, P99) of N, S, R and FS
and geometrical features (road, pedestrian sidewalk and propagation path widths, as well as building heights), showed well-defined components, highlighting the fact that some percentiles can describe specific geometrical features of the urban sonic environments.
Prediction of one-third-octave band sound and vibration levels from heavy-hard impacts
Authors: Golden Matthew , LoVerde John , Dong Wayland , Rawlings Samantha , Silva Richard
Published: September 2021

Noise and vibration due to dropping hard heavy weights is a common source of disturbance and complaint in residential, commercial, and mixed-use building types. The authors and others have worked on developing methodologies to accurately, repeatably, and conveniently measure heavy-hard
impact noise and vibration in the field based on a standard weight drop. Separately, systems have been created to measure the force being injected into a building from heavy-hard impact. It has been shown that this force data can be used to successfully predict vibration levels in buildings
if in-situ transfer functions are known. In this paper, the authors will present a novel one-third-octave band prediction method using the laboratory force data and a reference impact sheet to predict field performance without the need to measure transfer function. The method is evaluated
using both noise and vibration measurements.
A study of the effects of structural delamination location on delamina-tion detection using a non-linear chaotic oscillator method
Authors: Li Xuan , Halim Dunant , Liu Xiaoling
Published: September 2021

This work aims to investigate the effects of structural delamination location on the effectiveness of delamination assessment using a vibration-based non-linear chaotic oscillator method. The change in structural vibration characteristics due to delamination at different structural
locations can pose a challenge for accurate delamination detection due to the possible weak changes in the measured vibration signal and the existence of noise that can corrupt the signal. Thus in this work, a chaotic oscillator method was used due to its sensitivity to relatively small changes
in measured vibration signal and robustness to measurement noise. The effects of vibration sensing location on the sensitivity in detecting the location of delamination was also investigated in this work. The Lyapunov Exponent was used in conjunction with the chaotic oscillator as a damage
index, for the purpose of defining an effective measure to locate the delamination damage in a laminated structure. The correlation between the damage index and vibration sensing location for different delamination locations was investigated for a laminated beam structure, with a method for
finding an optimal location for vibration sensors proposed. It was found that a vibration sensor placed in selected structural regions can provide an increased level of sensitivity in detecting certain delamination locations. The results from this work also demonstrated the effectiveness of
the developed method in determining an optimal placement for vibration sensors for delamination detection.
Regularized spherical harmonics-domain spatial active noise cancellation in a reverberant room
Authors: Kaneko Shoken , Roy Nirupam , Gumerov Nail , Duraiswami Ramani
Published: September 2021

Active Noise Cancellation (ANC) at a target area in an open space, as opposed to cancellation in the ears through headphones, can lead to future applications. For instance, a personal acoustic environment in an airplane seat or inside a car, or a quiet zone in a noisy shared workspace
can be possible using such open-space ANC without any uncomfortable on-body audio equipment. Recent advancements reinforce the practicality of such systems. However, regularization of the cancellation signal has been a crucial challenge in open-space ANC as it causes amplification of noise
at locations away from the target area. This work presents a spherical harmonics-domain feed-forward spatial ANC method with a room-wide global cost function to address this issue. This room-wide global cost function is used for optimizing the set of regularization hyperparameters, while at
run time only local information captured by a microphone array surrounding the target listening zone is required. Numerical experiments applying the proposed method in a simulated reverberant room show the effectiveness of the proposed method in creating a specific zone of silence with low
to moderate noise amplification in the rest of the room.
DISC BRAKE SQUEAL ANALYSIS USING NONLINEAR MATHEMATICAL MODEL
Authors: Yavuz Akif , Sen Osman Taha
Published: September 2021

Many academics have examined the disc brake squeal problem with experimental, analytical, and computational techniques, but there is as yet no method to completely understand disc brake squeal. This problem is not fully understood because a nonlinear problem. A mathematical model was
created to understand the relationship between brake disc and pad thought to cause the squeal phenomenon. For this study, two degree of freedom model is adopted where the disc and the pad are modeled. The model represents pad and disc as single degree of freedom systems that are connected
together through a sliding friction interface. This friction interface is defined by the dynamic friction model. Using this model, linear and nonlinear analyzes were performed. The stability of the system under varying parameters was examined with the linear analysis. Nonlinear analysis was
performed to provide more detailed information about the nonlinear behavior of the system. This analysis can provide information on the size of a limit cycle in phase space and hence whether a particular instability is a problem. The results indicate that with the decrease in the ratio of
disc to pad stiffness and disc to pad mass, the system is more unstable and squeal noise may occur.
Welding distortion generated uncertainties in the vibrational behavior of a ladder-like structure
Authors: Sipos David , Treszkai Marcell Ferenc , Feszty Daniel
Published: September 2021

Recent developments in acoustic simulation methods allowed engineers to assess the vibroacoustic behavior of various type of structures within a virtual environment, thus allowing the replacement of prototype-based development with simulations. However, there are some factors, that
cannot be considered in simulations in advance. In the present study, the effect of the distortions generated due to welding on a ladder-like structure equipped with flat plates was investigated. The measured acceleration frequency response functions were compared to finite element simulation
results. The measured responses differed significantly from the simulation, even in the low frequency range, where the global modes were not expected to be altered or vanished. Investigation of the simulated results revealed that the additional modes were related to the vibration of the plates,
which were assumed to be flat, instead of considering the warping caused by the welding process. After measuring the approximate deformation of the plates, an updated simulation model was made, introducing an approximate curvature in them. The results obtained with the updated simulation model
performed much better in the low frequency range as well as in the third octave-averaged frequency bands up 1200 Hz. The sensitivity of the warping was also systematically evaluated.
The effect of aspect ratio on the inerstion loss of lined ducts
Authors: Li Caoyang , Herrin David
Published: September 2021

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Handbook provides tabulated information that can be used to determine the insertion loss of a variety of lined and unlined ducts. However, the tabulated cross-sections are primarily for square ducts.
Not surprisingly, there is a need for information on the insertion loss of ducts having different aspect ratio cross-sections. Hence, the insertion loss for large aspect ratio cross-sections are investigated using a previously validated finite element simulation approach. A coupled structural-acoustic
finite element analysis is performed, and data is compared to measurement results from the literature for a few configurations. An analysis campaign is then performed which better explains the effect of aspect ratio on duct insertion loss.
Frequency dependence of vertical whole-body vibration perception - is your car rattling or humming?
Authors: Schwendicke Anna , Altinsoy M. Ercan
Published: September 2021

Humans perceive whole-body vibration in many daily life situations. Often they are exposed to whole-body vibration in combination with acoustic events. Sound and vibration usually stems from the same source, for example concerts or travelling in vehicles, such as automobile, aircrafts,
or ships. While we can describe acoustic stimuli using psychoacoustic descriptors such as loudness or timbre, the description human perception of whole body vibration frequently has been reduced to comfort or quality in the past. Unlike loudness or timbre, comfort and quality are dependent
on the overall context. Especially in vehicles expectations might differ lot between different vehicle classes. Previous studies have evaluated a large range of suitable descriptors for whole-body vibrations that are independent of context. They suggest that certain descriptors are driven
to a large extend by the frequency content of the vibration. This study systematically investigates the influence of frequency content on the perception of whole-body vibration varying frequency content and intensity of the vibrations. The results verify the frequency dependence of specific
descriptors and identify the respective frequency ranges.
The effect of bamboo clip dimension and position towards the frequency spectrum of a vibrating inhomogeneous bundengan string
Authors: Kusumaningtyas Indraswari , Sedjati Ayrton Fithiadi , Hifzhuddin Asadulloh Julda , Parikesit Gea Oswah Fatah
Published: September 2021

Bundengan is a traditional musical instrument from Indonesia. One of its unique features is the ability to produce sound imitating the gamelan, a percussive metallophone. This is generated by plucking on the bundengan strings, which have small bamboo clips attached to them. In this
work, the effect of the clip dimension and position on the frequency spectrum of the vibrating string is analysed by means of computer simulation and experiment. The string was modelled using Scilab, taking into account the transversal and rotational vibration of the string and bamboo clip,
including air drag force. The height to diameter ratio of the clip can be varied in the model. Furthermore, we set up a bundengan string on a sonometer with no resonator, attached specially made bamboo clips on it, and measured the sound frequency spectrum of the vibrating string. The results
showed that increasing the height to diameter ratio of the clip decreased the overtone frequencies of the string. It was also found that the fundamental frequency of the string decreased, but its overtones increased, when the clip is shifted towards the middle of the string. The frequency
spectrum from the simulation corresponds well to that from the experiment.
Protecting National Park Soundscapes: Summary of the 2012 NAE workshop
Authors: Fleming Gregg G. , Maling George C.
Published: September 2021

After reviewing the 2010 National Academy of Engineering (NAE) report "Technology for a Quieter America", the National Park Service (NPS) asked the NAE to undertake a consensus study on the importance of quiet to both visitors and wildlife in its hundreds of properties. The
aim of the workshop was to provide best practices to assist NPS park managers, contractors, and concessionaires in protecting park soundscapes. The workshop was hosted by the NPS in Fort Collins, Colorado in October 2012 and was attended by twenty-four participants including park personnel
and noise control specialists from government, academia, industry and consulting firms. The NAE report published in cooperation with the NPS and the Volpe National Transportation Systems Center identified seventeen cost-effective actions for reducing noise in our national parks. This paper
describes and summarizes the issues raised at the workshop and those recommendations.
Operable walls: where the rubber meets the mullion
Authors: Cudequest Brandon
Published: September 2021

The architecture that surrounds an operable wall often determines its acoustical success. There are standard guides for detailing operable walls; however, these offer a rigid take on design aesthetics. Abstracting these principles into general goals, the designer can accommodate a variety
of architectural styles. The surrounding construction should act as a safety net by providing labyrinths when seals fail or by blocking problematic flanking paths. The architecture should also ease system operation allowing users to deploy the operable wall with minimal fail rate. This paper
compares several off-the-shelf and custom systems, highlighting the importance of construction details and coordination and their impact on the installed product performance. The architecture can only support these systems to a degree and the designer should select an operable system that
works within the given conditions. By comparing design trends in operable walls from an acoustical consultant standpoint, this paper will spotlight architecturally harmonious systems as well as several system features to be aware of when evaluating options.
Estimation of otoacoustic emission and excitation force of bone conduction actuator by combined lumped parameter model
Authors: Fujise Akiko , Wakatsuki Naoto , Mizutani Koichi
Published: September 2021

In sound presentation system using actuators which excite the surface of the pinna or head, both otoacoustic emission and vibration transmission inside the body contribute to the perception of the sound. The contribution of these pathways is affected by both the location of the excitation
and mechanical characteristic of the actuator, leaving the optimal output level of the actuator to mask environmental sound or to present information yet to be estimated. This study, therefore, proposes a simplified model which combines an acoustic equivalent circuit of ear canal and a mechanical
equivalent circuit of the tissues of the head. The model enables to estimate both otoacoustic emission component directly corresponding with the loudness for air conducted sound and the component of the transmission inside the head which requires the measurement of the loudness level individually
by each excitation location. As the preliminary investigation preceding the establishment of the proposed model towards the human, these two components were calculated using the known parameter values for artificial ear and artificial mastoid. The results indicate that the stiffness of the
excited soft tissue and the type of the actuator strongly affect the cutoff frequencies, resonances, and anti-resonances observed within the audible range.
An overview of room acoustics requirements in North American, nonresidential, building standards
Authors: Madaras Gary
Published: September 2021

In the United States and elsewhere in North America, acoustics requirements for nonresidential buildings in Federal acts, codes, official standards and unofficial guidelines and rating systems tend to be voluntary, grass-roots and bottom-up instead of being mandatory, top-down or governmentally
mandated. This relates to the governmental viewpoint that noise is merely a nuisance, not a health risk as viewed in other parts of the world. Existing requirements associated with noise control - whether they are related to environmental/community noise, transmission of transportation noise
through the building envelope or occupant noise through the interior construction assemblies or minimizing noise from building services - are more prevalent in these standards. Requirements for good room acoustics related to sound absorption, speech intelligibility and distraction-free and
comfortable interiors that promote human health and well-being are appearing in more standards and being updated to have more stringent values. Much improvement is still needed in older standards that do not have regular revision cycles and open, public, review periods. An overview of the
types of room acoustics metrics used, their evolving values, advantages/disadvantages and the research behind them will be provided. Recommendations for future advancements will be offered.
Assessing the Potential for Noise Complaints due to Backyard Chickens
Authors: Moritz Charles
Published: September 2021

During the past decade, there has been tremendous growth in the popularity of backyard chickens in urban and suburban locations throughout the United States. While there are many advantages to raising chickens, their introduction has not gone without controversy. Noise has been a common
concern during discussions of municipal ordnances and a common complaint against flock owners. There is very little data on the sound levels produced by chickens in the technical literature. What data is published is not appropriate for predicting sound levels at owners' property lines. In
addition, the non-technical literature, social media, newspaper stories, etc. abounds with misinformation. To determine the sound power of various chicken breeds, the author has been measuring sound levels from birds in his flock. This data can then be compared to the sound level from other
typical back yard sound sources, existing community annoyance prediction models, and records of noise complaints.
Effects of the reduction of aircraft noise emission due to the travel restriction during the COVID-19 pandemic at residential areas around Tan Son Nhat Airport
Authors: Nguyen Thulan , Nguyen Tran Thi Hong Nhung , Trieu Bach Lien , Morinaga Makoto , Hiraguri Yasuhiro , Yano Takashi , Sasazawa Yosiaki
Published: September 2021

The travel restrictions caused by the epidemic outbreak in early 2020 worldwide have caused many changes in all aspects of life, especially in the acoustic environment. This study examines the impact of this environmental change at Tan Son Nhat International Airport (TSN), the largest
airport in Vietnam, by comparing the situations before and after the airport stopped operating all international flights in March 2020. The after-the-change survey was conducted in 2 phases, June and September 2020, three months and six months after the stop decision. The number of flights
observed in August 2019 was 728; this number is 413 and 299 for the two surveys in 2020. The range of noise levels estimated for 12 sites around TSN decreased from 63-81 dB in 2019 to 32-67 dB in June 2020 and 33-69 dB in September 2020. At the same aircraft noise level, the percentage of
highly annoyed (% HA) and the percentage of insomnia (%ISM) in the 2020 survey are higher than those in the 2019 survey. The comparison results of reaction to noise before and after the TSN's noise change indicated an increase in negative responses to noise might happen in the increased noise
and reduced noise situation.
Influence of vehicle source directivity in Japanese and European outdoor sound prediction models under a semi-finite thick barrier configuration
Authors: Oshima Takuya , Takeda Fumiya , Kurosaka Yumi
Published: September 2021

The Japanese ASJ RTN-Model 2018, European Harmonoise and CNOSSOS-EU outdoor sound prediction models are respectively known to have symmetric, asymmetric and omnidirectional sound emission directivities along front-back direction of the source vehicle. However, the influence of such
difference in directivities to final predicted sound levels has not been investigated much. In this study, the influence is investigated using the ASJ Model and the Harmonoise under a configuration of semi-finite thick barrier along a source road. The configuration is an idealization of Japanese
roadside buildings that have gaps in between, unlike European buildings that continuously extend over a whole urban block. Under the configuration, distribution of A-weighted sound levels around the end face of the barrier are computed with and without source directivity taken into account
by each model. It is found from the results that the source directivity of the ASJ model makes little difference in the noise level distribution. In contrast, the source directivity of Harmonoise is found to make differences of 0.5-0.8 dB at right behind the barrier depending on vehicle running
direction. However, a combined effect of source directivity and reflection at the end face is found to be negligible.
Cancer research lab, a challenging micro-vibration design
Authors: Mahajan Siddharth , Bayat Ahmad , Georgalis Michael
Published: September 2021

A donated land to three universities near a river bank, in an urban setting prompted the universities to commission a state-of-the-art cancer research lab for a prominent scientist. The site ambient vibration was measured around 2000 micro-inches/sec due to nearby highways, light-rail
system, and long-term construction staging area, among others. The research lab requirements were dictated by high-end Scanning Electron Microscopes, Transmission Electron Microscopes, etc. The vibration specification for these tools demanded the environment to perform at or below 50 micro-inches/sec,
a factor of 40 reduction. Typically, we desire the site ambient to lie below the vibration criterion with some margin to allow for contribution from building MEP sources. This unusual site condition presented on the surface, an impossible design challenge. We developed a multi-pronged design
approach that took advantage of the soil condition at the site and designed a specialized foundation for the lab floor, and supplemented it with improvement on the tool-based isolation system by implementing an active isolation system. The final result was that the 40x site vibration was reduced
to below lab vibration criterion curve of 50 micro-inches/sec. To our knowledge, the structural and foundation system of this lab is one-of-a-kind in the world.
Numerical study on the contribution of surface and volume components of flow-induced noise in baffle silencers
Authors: Chmielewski Bartosz , Herrero-Durá Iván , Nieradka Paweł
Published: September 2021

Baffle silencers are a well-known solution for noise mitigation in industrial applications. One of the issues concerning these devices is the flow-inducted noise produced when a non-laminar flow of the medium in the duct occurs. These situations occur, for example, in dedusting installations
or exhaust systems with the high-speed flow (large Reynolds number of the turbulence and small Mach number). This kind of installation has a complex shape that causes a turbulent flow in the medium. Installing a baffle silencer in these conditions causes additional noise. This noise cannot
be predicted by using a standard approach with equations for laminar flow conditions. This paper presents the first step of the research in this field. The first step is to find a relation between CFD simulations' results and self-noise of the baffle silencer. In this work, we use the formulation
proposed by Proudman in 1952 to calculate the sound power generated by the flow. The formulation is based on the turbulent kinetic energy k and dissipation rate ε of the flow, which is calculated by CFD simulations. The resulting sound power level needs to be calibrated. The calibration
method is developed and presented. The aim of this research is to design an experimental setup.
SEA model for structural acoustic coupling by means of periodic finite element models of the structural subsystems
Authors: Alimonti Luca , Mejdi Abderrazak , Parrinello Andrea
Published: September 2021

Statistical Energy Analysis (SEA) often relies on simplified analytical models to compute the parameters required to build the power balance equations of a coupled vibro-acoustic system. However, the vibro-acoustic of modern structural components, such as thick sandwich composites,
ribbed panels, isogrids and metamaterials, is often too complex to be amenable to analytical developments without introducing further approximations. To overcome this limitation, a more general numerical approach is considered. It was shown in previous publications that, under the assumption
that the structure is made of repetitions of a representative unit cell, a detailed Finite Element (FE) model of the unit cell can be used within a general and accurate numerical SEA framework. In this work, such framework is extended to account for structural-acoustic coupling. Resonant as
well as non-resonant acoustic and structural paths are formulated. The effect of any acoustic treatment applied to coupling areas is considered by means of a Generalized Transfer Matrix (TM) approach. Moreover, the formulation employs a definition of pressure loads based on the wavenumber-frequency
spectrum, hence allowing for general sources to be fully represented without simplifications. Validations cases are presented to show the effectiveness and generality of the approach.
The Brazilian performance standard revision. Sumary and next steps
Authors: Holtz Marcos , Akkerman Davi , Monteiro Carolina
Published: September 2021

In 2019, the Brazilian Standard NBR 15575: 2013 start a periodical revision process. This standard presents performance criteria for dwellings, such as acoustic, thermal, lighting, durability, etc. During this first enforcement period, some requirements result in divergent interpretations,
e.g. difficulties to define the noise class, proposed as a subjective criteria. Technical groups were created to analyze the current text and propose modifications to solve these issues. This article presents an overview of the mains issues related to the acoustic requirements found in the
standard. A summary of the proposals is presented, which went through a national ballot.
A closer look at rail methodology in the BTS National Transportation Noise Map
Authors: Rapoza Amanda , Shumway Meghan , Baker Gary , Wilke Peter
Published: September 2021

In 2017, the Bureau of Transportation Statistics released the inaugural national, multi-modal transportation noise map prototype. The noise modeling and mapping effort was envisioned as a way to facilitate the geographic tracking of national trends and provide insight into transportation
noise-related questions as changes occur over time - changes between modes, types of vehicles within modes and the geographic shifts of populations. How do changes in aircraft technology change the transportation noise landscape? Does increased high speed rail availability affect highway-related
noise? How does a population shift away from urban centers affect the soundscape? The inaugural model included aviation and highway sources. The first update, released in November 2020, includes passenger rail-related noise in addition to aviation and highway sources. Operations in this new
mode include commuter rail mainline, high-speed electric, light rail, heavy rail and streetcars, along with commuter rail horns at highway-rail grade crossings. The data for this noise map were modeled based on USDOT methods, with adjustments and simplifications to model on a national scale.
This paper focuses on the modeling methods and geospatial approach used to develop the passenger rail noise data layer.
Experimental and numerical investigations of ventilated acoustic metamaterial based in-parallel arrangement of Helmholtz resonator for façade screen
Authors: Ramos Denilson , Godinho Luís , Amado-Mendes Paulo , Mareze Paulo
Published: September 2021

Understanding urban noise as a serious environmental problem in urban centers, the development and application of noise control strategies have demanded a recent effort by several researches. In this case, the development of acoustic metamaterial artificially designed to manipulate
the wave phenomena has become a recent topic, aiming at optimized responses, and enables the development of subwavelength devices with potential application in passive ventilation and noise mitigation, providing better environmental conditions in buildings. The present paper intends to contribute
to the knowledge in this field by investigating the concept of an acoustic metamaterial with negative bulk modulus based in a parallel arrangement of Helmholtz Resonators. Experimental and numerical investigations are carried out to determine the acoustic potential of the proposed meta structure
in terms of sound absorption and sound transmission loss. The developed concept exhibits significant benefits in the properties of sound transmission loss, and seems a potential application for noise control at specific frequency bands (mainly at low to middle frequency) in building façades.
Development of a Unique Experimental System Investigating Vibroacoustic Characteristic of Geared Transmission Systems
Authors: Gök Umut Murat , Sen Osman Taha
Published: September 2021

Gearboxes are widely using in industry, especially in automotive transmission systems. In actual technology level, different component-based quality control methods are applied for the quality control of powertrains but test systems, designed for assembled products, are based on subjective
evaluations and scalar measurement of total sound pressure. These systems, especially operating in industrial conditions where background noise is effective, cannot meet the technical requirements. In this paper, the development of a unique experimental platform, capable of testing the powertrain
under real operating conditions (torque, rotational speeds), and the experimental results are explained. In the system where transmission error, noise and vibration measurements are carried out, defective samples were determined according to statistical evaluations and errors were classified.
In future studies, using the ability to calculate mechanical efficiency based on measurements, the correlation between deviations in mechanical efficiency and transmission error will be examined.
Sensor placement for sound field reconstruction in enclosures.
Authors: Verburg Samuel A. , Fernandez-Grande Efren
Published: September 2021

Sampling spatio-temporal acoustic fields is a challenging problem since it demands a large number of sensors. Typically, to characterize the pressure field inside an enclosure, the number of measurements required increases linearly with frequency and cubically with volume, becoming
an intractable problem for rooms of moderate size even at low and mid frequencies. Sparse representation techniques, such as Compressed Sensing, rely on the sparsity of natural signals in certain representation domain to drastically reduce the number of measurements needed to sample such signals.
In this study, we optimize the placement of sensors inside an enclosure in order to reduce the measurements required for a given reconstruction accuracy. The proposed methodology selects a sparse set of sensor positions from predefined grid via the QR factorization of the sensing matrix. Numerical
results show an effective reduction in the required number of measurements when their positions are optimized, in contrast to standard random positioning. Unlike the majority of existing approaches, we study the placement problem for wide-band acoustic fields.
Machining and Fabrication Equipment in Workplaces
Authors: Rosentel William
Published: September 2021

Increasingly well-developed workplace acoustic standards have resulted in more consistent outcomes across projects and normalized occupant expectations of acoustic quality, enhancing productivity and satisfaction. Yet these standards are often not developed for or applied to R&D
and manufacturing spaces that include traditional workplace room types and uses; design criteria is limited to OSHA-assessment for noise-at-work violations. Hybrid office buildings incorporating prototyping and maker spaces are common today and often contain high-noise equipment traditionally
found in dedicated machine shops. As these facilities are incorporated alongside traditional offices, noise and vibration levels generated by fabrication equipment should be accurately quantified to avoid compromised workplace acoustics. While sound data is available for most large construction
equipment, available data for smaller fabrication machines typically found in machine shops is often non-standardized and difficult to obtain. Field measurement of existing equipment installations can ground an acoustical analysis with real-world data and be highly valuable in evaluating potential
noise and vibration impacts and applying cost-effective mitigation during design. This case study will present measurements obtained during a noise and vibration assessment of an existing machine shop located within an office building. The discussion will include limitations of the data and
an assessment of potential for disruptions.
Psychoacoustic evaluation of soundscapes by means of repeated measurements
Authors: Fiebig Andre
Published: September 2021

Research on soundscape explore facets of how acoustic environments affect human perception in context. By means of psychoacoustic parameters the sound character of acoustic environments can be described comprehensively as those parameters play an important role with respect to manifold
auditory sensations. Although there seems to be a consensus of the benefit of psychoacoustics for soundscape evaluations and the ISO/TS 12913-2 particularly requests to give consideration to psychoacoustic indicators in soundscape investigations rather little is known about the relationships
between psychoacoustic quantities and significant soundscape dimensions. Numerous investigations aimed to establish links between psychoacoustics and soundscape appraisal, but the gained results were often not suited for generalization. Moreover, it is rather unclear how urban locations vary
in their sound character over longer periods and how the level of variation drives soundscape assessments. In order to establish an understanding of potential psychoacoustic characterization of urban locations for soundscape evaluations, repeated measurements of different locations are analyzed
and the general behavior of psychoacoustic quantities derived. Based on these investigations it is intended to expand knowledge on the usefulness of psychoacoustics from the perspective of the soundscape approach.
Relational analysis in soundscape preservation
Authors: Jordan Pamela
Published: September 2021

Given the musical origins of soundscape studies, soundscape preservation might suggest the need to protect specific features-such as prominent soundmarks or long-standing natural sounds-to maintain a sonic environment's composition. However, the identification of a soundscape primarily
by its discrete elements misses the importance of relational longevity. A relational lens of identification can distinguish a soundscape's effects on visitors rather than simply the presence of specific components, placing human perception candidly at the center of consideration. For instance,
an urban courtyard might no longer echo with hand-drawn carts from the street, yet visitors continue to experience a distanced connection with evolving traffic sounds - here the sonic-spatial relationship persists rather than sonic elements being frozen in time. This paper will discuss longevity
in the relationships connecting use, architectural space, and sonic character. The discussion draws from architectural analysis, soundwalking, and psychoacoustic research in exploring soundscape preservation within the orbit of heritage conservation more broadly. Case studies focus on a variety
of historic contexts, including a military installation, medieval church, and factory landscape, highlighting the limitations of a compositional soundscape reading, the fundamental role of transit through a soundscape for visitors, and the potentials for relational analysis in soundscape preservation
efforts.
Change in the self-reported health status of residents associated with the reduced aircraft noise around Tan Son Nhat Airport after the epidemic outbreak
Authors: Trieu Bach Lien , Nguyen Tran Thi Hong Nhung , Nguyen Thu Lan , Morinaga Makoto , Hiraguri Yasuhiro , Yano Takashi , Sasazawa Yosiaki
Published: September 2021

The change in the self-reported health status of residents associated with the reduced aircraft noise around Tan Son Nhat airport (TSN) after the epidemic outbreak in early 2020 was investigated in three stages. Stage 1 is pre-outbreak when the airport was operating at its highest capacity.
Phases 2 and 3 are three months and six months after the stop of international flight operation implemented in March 2020. Data on the residents' health status was obtained from face-to-face interviews. The questionnaire items were composed of Noise annoyance questions using the 11-point ICBEN
scale, the Total Health Index, Health and lifestyle questionnaire, Depression Scale revised questionnaire, and questionnaires to identify insomnia, hypertension, and hearing loss. Other factors related to living conditions such as education, income, or housing were also collected as health
adjustment factors. The noise levels of phases 2 and 3 were estimated by updating the noise contour map of phase 1 using the TSN airport's operation data in corresponding periods in 2020. This study provided evidence relating to variation of the residents' health status due to the noise situation
change.
Calculation of statistical absorption coefficient using ensemble averaged surface normal impedance of material
Authors: Okamoto Noriko , Otsru Toru , Tomiku Reiji , Masuda Masahiro , Tabaru Arisa
Published: September 2021

To predict and control the indoor sound field, it is important to comprehend sound absorption characteristics of building materials. In the previous studies, the authors have proposed an in-situ sound absorption measurement method of materials using ensemble averaging technique, namely
EA method. The method yields a simple and efficient in-situ measurement of surface normal impedance of materials at random-incidence. In this paper, the authors calculate the statistical absorption coefficient using the surface normal impedance of material by the EA method to obtain random
incidence absorption coefficient. At first, the procedure of calculating the statistical absorption coefficient from the normal impedance by EA method is described. Next, the sound absorption characteristics for five kinds of materials are measured by the EA method and the reverberation room
method. Finally, the statistical absorption coefficients are calculated from results obtained by the EA method and are compared with absorption coefficients by the reverberation room method.
Theoretical and numerical study of nonlinear acoustic absorbers for low frequency noise control
Authors: Yang Min , Li Xianhui , Cai Zenong , Zhao Junjuan , Zhang Peng , Liu Yunan
Published: September 2021

In this paper, the sound absorption characteristics of cubic nonlinear sound-absorbing structures are analyzed by theoretical and numerical methods. The slow flow equations of the system are derived by using complexification averaging method, and the nonlinear equations which describe
the steady- state response are obtained. The resulting equations are verified by comparing the results which respectively obtained from complexification-averaging method and Runge-Kutta method. It is helpful to optimize the structural parameters and further improve the sound absorption performance
to study the variation of the sound absorption performance of cubic nonlinear structure with its structural parameters.
3D printed multifunctional, load-bearing, low-frequency sound absorbers
Authors: Johnston William , Kankanamalage Pulitha Godakawela , Sharma Bhisham
Published: September 2021

Cellular porous materials are an attractive choice for lightweight structural design. However, though their open porous architecture is ideally suited for multifunctional applications, their use is typically limited by the pore sizes achievable by traditional as well as advanced fabrication
processes. Here, we present an alternative route towards overcoming this pore size limitation by leveraging our recent success in printing fibrous structures. This is achieved by superimposing a fibrous network on a load-bearing, open-celled porous architecture. The multifunctional structure
is 3D printed using a novel technique that enables us to simultaneously print a load-bearing scaffold and the necessary fibrous network. The acoustic properties of the printed structures are tested using a normal-incidence impedance tube method. Our results show that such structures can provide
very high absorption at low frequencies while retaining the mechanical performance of the underlying architected structure.
Learning-based estimation of individual absorption profiles from a single room impulse response with known positions of source, sensor and surfaces
Authors: Dilungana Stéphane , Deleforge Antoine , Foy Cédric , Faisan Sylvain
Published: September 2021

In situ estimation of the individual absorption profiles of a room remains a challenging problem in building acoustics. This work is aimed at studying the feasibility of this estimation in a shoebox room of fixed and known geometry, using a room impulse response measured from a source
and sensor at fixed and known positions. This problem is tackled using supervised learning. Three neural network architectures are compared. Simulated training and validation sets featuring various types of perturbations (surface diffusion, geometrical errors and additive white Gaussian noise)
are generated. An extensive empirical simulated study is carried out to determine the influence of these perturbations on the performances of learned models, and to determine which components of the room impulse response are most useful for absorption coefficients prediction. Trained models
are shown to yield errors significantly smaller than those of a naive mean estimator on every simulated datasets, including those featuring realistic perturbation levels. Our study outlines the benefit of using convolutional neural network layers, especially when geometrical errors exist.
It also reveals that early acoustic echoes are the most salient feature of room impulse responses for absorption coefficient prediction under a fixed geometry.
Influence of different materials used for 3D printing in miniature speaker enclosure development
Authors: Chojnacki Bartlomiej , Pawlik Jan , Kamisinski Tadeusz
Published: September 2021

Additive manufacturing techniques are commonly used in industry and mechanical prototyping. The past years brought rapid growth in this technology development, also in the speaker cabinets manufacturing industry. We observe numerous DIY projects on the market based on the 3D printed
cabinet parts; however, this technology also offers novel options that should be investigated and documented. In the current state of the art, the basic properties and construction aspects for speaker acoustic performance is not provided as the 3d printing technique is usually treated as the
tool for other projects' development. This paper will provide a detailed comparison of the most common 3D printing materials used in FDM techno9logy, such as PLA, TPE, PET-G, and others with different mechanical properties. Example enclosure for a loudspeaker of 37 mm diameter will be printed
in different shapes and compared for frequency and sensitivity differences. The results will be discussed, investigating the possible use of different than traditional rigid plastic enclosures and new options using complicated geometry shapes possibly to manufacture with 3D printing techniques.
Diffusion equation modelling for energy flow analysis in reverberation chambers
Authors: Hao Ryan , Xiang Ning
Published: September 2021

Noise is a growing concern in the built environment. Sound absorbers are a viable option for noise treatment. However, the characterization of their absorption coefficient in standardized measurement chambers still show challenges for high accuracy as required in practice. In recent
years, experimental analysis has shown that assumptions of diffuse sound fields made in well-known reverberation chambers are unfulfilled. Specifically, that sound intensities in chamber-based measurement methods are presumed to be isotropic or diffuse. Diffusion equation models have shown
dramatic changes in energy flow in the presence of highly absorptive materials under test. This has been attributed to well-documented inconsistencies reported from reverberation chamber measurements across different laboratories. This work will demonstrate that the diffusion equation model
is proving to be a computationally efficient and viable method for predicting sound energy flows, garnering an increasing amount of interest from the acoustical community.