bluuebunny/crossref_metadata_2025 huggingface dataset:
Intervención oportuna en prematuros extremos: dos casos tratados en Terapia Ocupacional, Toluca, México
Authors: Esquivel-González Xochitl , Martínez-Cosme Arturo
Published: September 2021

El “prematuro extremo” representa un gran reto en la Unidad de Cuidados Intensivos (UCIN), siendo prioridad la vida en dicho periodo. A su egreso de la UCIN, se enfrenta a un nuevo desafío.  Se presentan dos casos de prematuros extremos de 26 semanas de gestación atendidos en el servicio de Terapia Ocupacional. El abordaje de intervención fue Neurodesarrollo y Modelo de Ocupación Humana, los indicadores de evaluación: Evaluación Neurológica para niños menores de cinco años en el primer y segundo nivel de atención, la Evaluación del Desarrollo Infantil (EDI) y Cuestionario Volicional Pediátrico (CVP) y la observación clínica. Promover el desempeño ocupacional en el niño posterior a una estancia prolongada en la UCIN, implica un reto en el abordaje, se debe buscar el proceso de interacción social, intencionalidad a través de la participación en experiencias con significado. En la actualidad, una de las metas para la consolidación de campos de conocimiento, atención y prospectiva es profundizar en la intervención que realiza el respectivo profesional en la UCIN.
COVID Teaching of acoustics and noise control: Lab in a box for experiments at home
Authors: Dance Stephen
Published: September 2021

In June 2020 with the advent of COVID emergency plans were put in place to deliver the Masters course in Environmental and Architectural Acoustics totally on-line. This was necessary as although the acoustics laboratory is large, it was deemed to be unsafe for face-to-face teaching
due to a complete lack of ventilation in the anechoic and reverberation chambers. Hence, it was necessary to create an alternative. It was decided that a "lab in a box" supported by on-line demonstrations and pre-recorded films would create the best alternative experience for the
students. The "lab in a box" allowing the demonstrations to be replicated at home or in the garden. The results showed that the students gained from more independence, increased flexibility in deliver achieving very similar marks. This has opened up the possibility of increasing
student numbers by reusing these alternative teaching strategies.
Ultralight micro-perforated sandwich panel with double-layer hierarchical square honeycomb core for broadband sound absorption
Authors: He Wei
Published: September 2021

The micro-perforated panel (MPP) has only one sound absorption peak, and the sound absorption performance is poor in the wide frequency range. Besides, the stiffness and strength of MPP are insufficient, so it can not bear the external load. In this study, double layers of hierarchical
square honeycomb are placed within the air-back cavity of MPP to produce a sandwich structure. On the one hand, hierarchical honeycombs divide the air-back cavity into several sub-cavities. The perforations on the panel together with the sub-cavities form a series-parallel system of Helmholtz
resonators. The sound absorption curve of the structure has multiple peaks and the half-absorption bandwidth is extensively widened. On the other hand, the hierarchical honeycomb with excellent load-bearing properties can strongly support the MPP to resist external loads. This new structure
possesses both sound absorption and load bearing capabilities, and has practical application value in the noise reduction of high-speed trains and civil aircraft. Through theoretical and simulation analysis, the sound absorption performance of the structure is systematically studied and the
influence of key parameters is quantified, providing guidance for the design of noise reduction materials.
Distortion measurements of sound pressure level generated by a pistonphone
Authors: Bacelar Milhomem Thiago Antônio , Martins Defilippo Soares Zemar , Palmeira Ripper Gustavo , Hanes Peter , Solano Mena Adrian , Ariel Serrano Federico , Guevara Chuquillanqui Giancarlos Miguel , Ayala Breña Juan Pablo
Published: September 2021

A supplementary interlaboratory comparison on pistonphone calibration was performed between 2018 and 2020 under the auspices of the Inter-American Metrology System. Seven national metrology institutes took part in this comparison. One pistonphone was circulated among the participants
for measurement of the generated sound pressure level, frequency, total distortion + noise and total harmonic distortion. This paper presents the results of distortion measurements and analyzes them. From the stability check, notable variances with respect to reported measurement uncertainty
were observed. From reported results, a large difference between the estimated uncertainties by the participants was noted. Convergence between results was found when measurements were performed using one-inch microphone while some divergence between results was found when measurements were
performed using half-inch microphone. In addition, these results (using one-inch and half-inch microphones), even when obtained by the same institute, sometimes were different. Reasons for these findings are discussed and suggestions for future comparisons are presented.
Assessing a parallel baffle splitter, an experimental and numerical study on insertion loss and pressure drop
Authors: Escudero Juan Pablo , Fuentes Héctor
Published: September 2021

HVAC systems are composed of different noise sources and paths. The non-attenuated propagation of noise through the system has detrimental effects on acoustic comfort of people inside the premises. In order to mitigate the propagated noise, classic parallel baffe splitters are used to reduce the transmitted noise through acoustic coatings. Different methods have been developed to predict the insertion loss of those elements, however, if the input data is not well known these models can lead to deviated results. Additionally, the use of splitters in HVAC systems produces pressure drop which can damage the installed mechanical equipment if that is not well predicted. Currently, the models that estimate pressure drop relate dimensional features and design velocity. However, these models can give overestimated results. In this work an experimental rig was implemented to assess a splitter installed inside of a test duct. Measurements were performed to estimate insertion loss and pressure drop coeffcient, following the guidelines exposed on the ISO 7235 standard. The results were compared with analytical methods. Finally, a numerical method analysis of the test rig was performed, showing the correlation between these results and the experimental data.
A case study of noise pollution levels during the restrictions period due to COVID-19.
Authors: Montes-González David , Barrigón-Morillas Juan Miguel , Bejarano-Quintas Ana Cristina , Parejo-Pizarro Manuel , Rey-Gozalo Guillermo , Vílchez Gómez Rosendo , Atanasio-Moraga Pedro
Published: September 2021

The pandemic of coronavirus disease (COVID-19) led to the need for drastic control measures around the world to reduce the impact on the health of the population. The confinement of people in their homes resulted in a significant reduction in human activity at every level (economic,
social, industrial, etc.), which was reflected in a decrease in environmental pollution levels. Studying the evolution of parameters, such as the level of environmental noise caused by vehicle traffic in urban environments, makes it possible to assess the impact of this type of measure. This
paper presents a case study of the acoustic situation in Cáceres (Spain) during the restriction period by means of long-term acoustic measurements at various points of the city.
Uncertainty in the standardized method "Characterization of the acoustic properties of road surfaces" by CEN TC227 WG5
Authors: van Blokland Gijsjan , Goubert Luc
Published: September 2021

TC227 of CEN has developed a method to determine the effect of the road pavement on the sound emission of road vehicles. The proposed methods can be applied to define the acoustic label value of a generic or proprietary pavement type, to check compliance of a pavement with the specifications
for that pavement type and to monitor the development of the acoustic properties over the lifetime of the product. With the procedure one can additionally derive the coefficients for the pavement correc tion in the noise emission formulae for road vehicles in the CNOSSOS-EU calculation model.
The application of the method exhibits a limited accuracy. The paper investigates the sources of uncertainty of the standardized method and combine the contributions into a single overall uncertainty according to the procedures laid down in Guide 98-3 of ISO. The uncertainty is determined
for each of the listed application areas. From the uncertainty analysis the major contributions are identified. Improvement of the method shall focus on only these contributions.
A two-zone sound field reproduction based on the region energy control
Authors: Du Bokai , Zeng Xiangyang , Wang Haitao
Published: September 2021

Multizone sound field reproduction aims to create different acoustical environments in regions without physical isolation. For a real reproduction system, it is always expected to improve system performance and reduce measurement effort. In this paper, a two-zone sound field reproduction
is investigated with a proposed region control method. Conventional multipoint method only controls sound field at limited number of measurement points. However, the proposed method tries to control the sound field energy over the whole region. Considering the system's diverse work environment,
different interpolation methods are applied in the proposed method. Simulations are conducted under free field and reverberation condition in order to deeply compare with conventional method and another harmonic domain method. Simulation results show that the proposed method achieves better
performance than the conventional multipoint method in free field and reverberant environment. On the other hand, the region control method proposed in this paper is free from microphone array geometry requirement, which means the method is more convenient for the practical application.
Realizing a Self-powered Real-time Monitoring System on High-speed Trains
Authors: Lai S.K. , Wang C. , Zhang L.H. , Ni Y.Q.
Published: September 2021

The development of the worldwide high-speed rail network is expanding at a rapid pace, imposing great challenges on the operation safety. Recent advances in wireless communications and information technology can integrate the Internet of Things and cloud computing to form a real-time
monitoring platform of high-speed trains. To realize this system, a sustainable power source is indispensable. In this case, an ideal solution is to deploy a vibration-based energy harvester instead of batteries for the electrical supply of wireless sensors/devices, as vibrations induced by
rail/wheel contact forces and vehicle dynamics are an abundant energy source. To address this challenge, a multi-stable, broadband and tri-hybrid energy harvesting technique was recently proposed, which can work well under low-frequency, low-amplitude, and time-varying ambient sources. In
this work, we will introduce our idea, following the recently proposed energy harvester and the dynamic responses of a train vehicle, to design a self-sustained sensing system on trains. Supported by this self-powered system, accelerometers and microphones deployed on an in-service train (in
axle boxes/bogie frames) can measure vibration and noise data directly. The correlation of the vibration and noise data can then be analyzed simultaneously to identify the dynamic behavior (e.g., wheel defects) of a moving train.
Development of a metric for predicting people's responses to gusting wind noise in automobiles
Authors: Carr Daniel , Davies Patricia
Published: September 2021

Automobile manufacturers are trying to improve the interior noise environment in their cars. A more thorough understanding of how people perceive the noise is an important step towards this goal. The focus of the current research is on modeling the acceptability of time-varying wind
noises containing gusts. A listening test was designed containing sounds that were simulated on the computer, based on pre-defined airflow profiles. The time-varying noises in the test follow one of two simple gusting scenarios. The primary scenario contained two segments of steady wind flanking
a series of consecutive equal-strength gusts. The number, duration, and strength of the gusts were varied between sounds. This was done to examine general trends of acceptability with modulation rate, modulation depth, and duration. The second scenario contained two gusts of equal or unequal
strength, occurring either without a break or separated by a time gap. This was done to examine the relationship between people's reactions to the individual gusts in a pattern and their reactions to the whole pattern. A small number of steady-wind noises were included for reference. Terms
in an acceptability model containing a previously proposed gusting metric were estimated. Possible refinements to the metric and model are discussed.
Development of acoustic mufflers for cabin noise reduction in Orion spacecraft
Authors: Dandaroy Indranil , Chu S. Reynold , Dornak Jeffrey , Allen Christopher S.
Published: September 2021

Controlling cabin acoustic noise levels in the Crew Module (CM) of the Orion spacecraft is critical for adequate speech intelligibility, avoid fatigue, and prevent any possibility of temporary and permanent hearing loss to the crew. The primary source of cabin noise for the on-orbit
phase of the mission is from the Environmental Control and Life Support System (ECLSS) which recycles and conditions breathing air and maintains cabin pressurization through its ducting network and components. Unfortunately, as a side effect, noise from the ECLSS fans propagates through theses
ducts and emanate into the cabin habitable volume via the ECLSS inlet and outlets. To mitigate excessive duct-borne noise, two ECLSS mufflers have been designed to provide significant acoustic transmission loss (TL) so that the cabin noise requirements can be met. Each muffler is meant to
be installed in the ducting of the ECLSS air inlet and outlet sides, respectively. Packaging constraints and tight volume requirements necessitated the mufflers to be of complex geometry and compatible with the bends of the ECLSS duct layout. To design and characterize the acoustic performance
of the inlet and outlet mufflers, computational acoustic models were developed using the Finite Element Method (FEM) with software. Characterization of the acoustic material and perforations in the mufflers were addressed with poro-elastic theory. Once the mufflers were designed on paper and
its TL predicted, prototypes of these mufflers were created using additive manufacturing. The muffler prototypes were subsequently tested for acoustic TL in the laboratory with various configurations of acoustic materials. Comparing the analytical predictions to the test performance yielded
excellent correlation for acoustic TL and demonstrated significant broadband noise attenuation. The ECLSS mufflers are currently scheduled to be installed on the Artemis II CM of the Orion spacecraft and will provide significant cabin comfort to crew during the mission.
An investigation into the impact of unmanned aerial vehicles on soundscape perception in urban and rural environments
Authors: Nicholls Rory , Martinez Antonio Torija
Published: September 2021

It is predicted that urban air mobility, including the use of small to medium sized unmanned aerial vehicle (UAV) delivery systems, will be introduced into cities across the globe within the next 15 years. It is known, however, that noise is one of the main limiting factors for the
wider adoption of these vehicles. Neither the metrics nor the methods used for conventional aircraft seem to be optimal for this novel source of noise. This research will aid in developing suitable psychoacoustic methodologies and metrics, specifically designed to quantify community noise
impact of these vehicles. This paper describes a psychoacoustic experiment used to gather participant responses to UAV sound recordings, both isolated and with typical background noise in a diversity of soundscapes. Results from this psychoacoustic experiment will be used to correlate perceptions
of UAV noise with objective sound quality metrics, and build new regression relationships that could describe the impact of a given UAV on the perception of soundscape environments. Future extension to the research may include evaluating the differences in psychoacoustic responses when introducing
more accurate reproduction methods, such as virtual reality systems, and how these could be incorporated into a standardised human response measurement procedure.
Use of a transient SEA for calculation of structure-borne interior noise in trains from an induction motor controlled by multi-mode PWM
Authors: Tanabe Yosuke , Yoshizawa Takashi , Sugimoto Shinji , Hara Takafumi
Published: September 2021

This paper presents a transient SEA (Statistical Energy Analysis) approach to predict the structure-borne interior noise in trains from an induction motor controlled by multi-mode PWM (Pulse Width Modulation). Most of the induction motors installed in trains are controlled by multi-mode
PWM, which switches between asynchronous and synchronous modes according to the speed to reduce switching losses. This control causes the electromagnetic forces of PWM harmonics to change, resulting in a transient interior noise depending on the vehicle's speed. In this paper, we model the
bogie using FEM to calculate the transmission of the electromagnetic forces to the vehicle body through traction bars and dampers. Next, we model the vehicle body using a transient SEA to calculate transient energy in a 1/3 octave band excited by the transmitted electromagnetic forces. Finally,
we restore the waveform of interior noise by applying the appropriate phase to the transient energy to auralize the analysis result. We obtained reasonable agreement by comparing the analysis results of the interior noise with the actual measurements.
High Lift Device Modifications for Reducing Airport Noise - A Review
Authors: Allaei Daryoush , Reydel Benjamin , Rall James
Published: September 2021

Aircraft noise has been one of the top environmental issues at and near airports across the country because of its negative impact on communities. The growth of the nation's air transportation system is restricted predominantly due to regulations on limiting aircraft noise generated
around airports. Reducing aircraft noise will lead to wider community acceptance of new or larger airports, lower airline operating costs by reducing noise quota fees, and increase air traffic growth through operating more flights. One of the most significant contributors to aircraft noise,
structural vibrations caused by air flow across its frame, are high lift devices. A review of high lift devices, such as flaps, and methods to reduce their noise levels will be presented. Solution reviews will focus on reducing flap trailing-edge scattering and flap side-edge vortices.
Simulation research on low frequency sound absorption of monostable metamaterials
Authors: Xing Tuo , Li Xianhui , Gai Xiaoling , Cai Zenong , Guan Xiwen
Published: September 2021

The monostable acoustic metamaterial is realized by placing a flexible panel with a magnetic proof mass in a symmetric magnetic field. The theoretical model of monostable metamaterials has been proposed. The method of finite element simulation is used to verify the theoretical model.
The magnetic force of the symmetrical magnetic field is simplified as the relationship between force and displacement, acting on the mass. The simulation results show that as the external magnetic force increases, the peak sound absorption shifts to low frequencies. The theoretical and finite
element simulation results are in good agreement.
Underwater acoustic communication using nonlinear frequency modulation waveform with low side-lobe characteristics
Authors: An Jeongha , Ra Hyoungin , Youn Changhyun , Kim Kiman
Published: September 2021

In fluctuating underwater acoustic (UWA) communication, reducing the interference caused by multi-path propagation is important to get better performance. For this reason, Chirp Spread Spectrum (CSS), which has insensitive Doppler effect and having effective bandwidth, using Linear
Frequency Modulation (LFM) waveform was used in UWA communication before. But LFM waveform has high auto-correlation function sidelobes it becomes interference and gets worse performance in reverberation environment. This presentation proposes an UWA communication using Generalized Sinusoidal
Frequency Modulation (GSFM) waveform which is generalized form of sinusoidal FM. GSFM waveform usually attains much higher spectral efficiency and lower peak-to-average power ratio than LFM while maintaining same bandwidth and pulse duration. GSFM waveform has various types and we use two
GSFM pulses that is a Forward type in time-frequency domain and a time reversing type of Forward type in this presentation. Each type represents binary values '0' and '1', respectively. Each of pulses occupy same band of frequency and each of GSFM pulses have nearly orthogonality. Simulation
results in various underwater channel environments with noise will be presented. A Bellhop-based underwater channel model is used for simulation. The proposed method will be analyzed compared to the conventional CSS method with LFM waveform.
Psycho-acoustic evaluation of the automotive acoustic comfort using vibro-acoustic prediction methods
Authors: Miqueau Valentin , Parizet Etienne , Germes Sylvain
Published: September 2021

In the automotive industry, the acoustic comfort is considered as a selling point of utmost importance. To help the OEMs improve the acoustic comfort in cars, as a one-tier supplier of automotive glazing, Saint-Gobain is currently working on the acoustic comfort within the cabin in
order to propose the right set of glazing consistent with the OEMs' specifications. The characterization of the acoustic comfort mostly relies on physical demonstrators required for carrying out the relevant measurements. It is however not available early in the project phase, delaying the
subjective analysis late in the development phase. To have the opportunity to develop effective solutions, the acoustic comfort has to be investigated as early as possible in the design process. Saint-Gobain is thus currently developing relevant acoustic models in order to predict the mid-high
frequency airborne interior noise generated by the wind excitations. The subjective acoustic comfort has then to be assessed using the predicted interior sound pressure levels converted into audio soundtracks for the auralization purposes. In this paper, we briefly present the Statistical
Energy Analysis model developed by Saint-Gobain. The psychoacoustic methodology deployed to evaluate its reliability for the subjective evaluation of the automotive acoustic comfort is detailed.
Predicting vibration transmission across junctions using diffuse field reciprocity
Authors: Stalmans Wannes , Van hoorickx Cédric , Reynders Edwin
Published: September 2021

Predicting the sound insulation of an engineering system is a complex problem since not only the direct path through a separating element but also the flanking transmission paths can largely influence the sound insulation of the system. When conventionally analyzing flanking transmission,
a diffuse field is assumed in the walls and floors, which are modelled as plates. The junction connecting the walls and floors is assumed to be of infinite extent and the transmission of vibration across the junction is calculated by integrating over all possible angles of incidence. Due to
the limitations of the conventional approach, a new approach based on diffuse field reciprocity is proposed. The diffuse field reciprocity relationship relates the vibration transmission to the direct field of a diffuse subsystem to the direct field dynamic stiffness of the subsystem, i.e.,
the dynamic stiffness of the equivalent infinite subsystem as observed at the junction. The direct field dynamic stiffness matrices of thin, isotropic, elastic plates can be analytically derived. For more complex walls or floors a possible approach is to calculate the direct field dynamic
stiffness using finite elements and perfectly matched layers. The perfectly matched layer surrounding the finite element model absorbs the wave propagating outwards from the bounded domain, thus simulating an infinite subsystem.
Community noise from a drone delivery distribution center: challenges and options
Authors: Poling Jacob
Published: September 2021

As drone package delivery services are expanded, community noise will be an issue that every operator will need to consider. Drones represent a unique new community noise source that will operate and be perceived differently than traditional aircraft and ground transportation vehicles.
It is also likely that some early implementations of drone delivery services by major retailers will operate out of existing distribution centers, which may not be ideally located from a noise perspective. This study considers potential drone delivery noise in the community surrounding an
existing distribution center, assuming the facility were to be utilized as the hub of a future drone package delivery service. The predicted noise levels from drone deliveries are compared to typical community noise limits, and potential alternative noise metrics for assessing annoyance from
drone noise in communities are discussed. Options to reduce community noise from drone deliveries by altering flight altitude and speed, utilizing different flight path routing strategies, and taking advantage of the potential masking of drones by existing roadway noise are considered.
Wavenumber domain analysis of full-band energy harvesting and damping dissipation characteristics of plate embedded with heterogeneous ABH array
Authors: Bao Yue , Liang Haoming , Liu Xiandong , Shan Yingchun , He Tian
Published: September 2021

The Acoustic Black Hole (ABH) structure has been developed as a promising approach for passive vibration attenuation and noise control. The basic theory of ABH effect hinges on the geometry thickness gradual decreasing according to the power law. This feature of structure reduces flexural
wave speed, resulting in "trapping" flexural wave into ABH indentation to achieve energy focalizing. In this work, the FE model of a plate embedded with ABH indentation and damp structure is established and excited by a series of harmonic forces respectively. The characteristics
of energy distribution in this plate in full frequency band are investigated by the power flow method and wavenumber domain analysis. By transforming the spatial vibratory energy into wavenumber domain, the ABH effect is analyzed and compared with a uniform panel. Meanwhile, the dissipation
effect of vibration and sound radiation energy has been studied with addition of damping material. Furthermore, the energy harvesting and dissipation performances of a plate embedded with heterogeneous ABH array are investigated in order to demonstrate the influence of ABH structure parameters
and configuration. The research will be beneficial for the vibration energy control in full frequency band.
Community Acceptance of Drone Noise
Authors: Thalheimer Erich
Published: September 2021

Within the next five years, small package delivery drones and larger human passenger drones will become the next mode of transportation to fill our environment with noise. They are already being used in test markets around the world to gauge community acceptance of the concept; none
the least of which being the noise generated by these drones. In fact, along with safety, noise is the prime concern for gaining acceptance and regulatory approval for widespread use of drones. Title 14 CFR Part 36 contains FAA's current certification requirements for drone flyover noise at
the source. But what about receiver noise criteria? This paper will describe some of the prototype drones in use today, the major manufacturers and drone delivery services already well into development, and the current federal regulatory setting for community noise in the United States for
various modes of transportation. The paper concludes with a recommended noise criteria approach, for FAA to consider adopting, that would provide a balance between the drone manufacturers' need to produce noise with the community's need for peace and quiet.
Vibrational energy distribution in plate excited with random white noise
Authors: Victor Tyrode , Totaro Nicolas , Maxit Laurent , Le Bot Alain
Published: September 2021

In Statistical Energy Analysis (SEA) and more generally in all statistical theories of sound and vibration, the establishment of diffuse field in subsystems is one of the most important assumption. Diffuse field is a special state of vibration for which the vibrational energy is homogeneously
and isotropically distributed. For subsystems excited with a random white noise, the vibration tends to become diffuse when the number of modes is large and the damping sufficiently light. However even under these conditions, the so-called coherent backscattering enhancement (CBE) observed
for certain symmetric subsystems may impede diffusivity. In this study, CBE is observed numerically and experimentally for various geometries of subsystem. Also, it is shown that asymmetric boundary conditions leads to reduce or even vanish the CBE. Theoretical and numerical simulations with
the ray tracing method are provided to support the discussion.
Understanding the Effect of Restorativeness in Indoor Soundscapes through a Conceptual Model
Authors: Orhan Cemre , Yilmazer Semiha
Published: September 2021

The soundscape is defined as the acoustic environment perceived or experienced by a person or people. Soundscape research, where human perception is at the center, has generally been conducted on unwanted sound sources to identify sounds' negative health effects. Therefore, wanted sound
sources and their impact on being exposed to soundscapes that may induce positive outputs on health has been neglected. People tend to be in places that reduce stress and increase restoration. However, many indoor places cause stress in our daily lives and decrease the quality of living. This
study aims to generate the conceptual model that would be used to identify what causes stress indoors and what can be done to transfer these spaces into restorative ones from the soundscape perspective. To generate a comprehensive model, by centering the soundscape framework of ISO, its constructs
were combined with Attention Restorative Theory (ART), Stress Recovery Theory (SRT), and Biophilic Design approach into positive and negative relations based on their effects on health.
Solving linear systems from dynamical energy analysis - using and reusing preconditioners
Authors: Richter Martin , Tanner Gregor , Carpentieri Bruno , Chappell David J.
Published: September 2021

Dynamical energy analysis (DEA) is a computational method to address high-frequency vibro-acoustics in terms of ray densities. It has been used to describe wave equations governing structure-borne sound in two-dimensional shell elements as well as three-dimensional electrodynamics.
To describe either of those problems, the wave equation is reformulated as a propagation of boundary densities. These densities are expressed by finite dimensional approximations. All use-cases have in common that they describe the resulting linear problem using a very large matrix which is
block-sparse, often real-valued, but non-symmetric. In order to efficiently use DEA, it is therefore important to also address the performance of solving the corresponding linear system. We will cover three aspects in order to reduce the computational time: The use of preconditioners, properly
chosen initial conditions, and choice of iterative solvers. Especially the aspect of potentially reusing preconditioners for different input parameters is investigated.
Sound source modelling by nonnegative matrix factorization for virtual reality applications
Authors: Dreier Christian , Vorländer Michael
Published: September 2021

Auralization is a suitable method for subjective noise evaluation of virtual prototypes. A basic requirement is the accurate modelling of the sound sources. This includes a dynamic and parametric description at multiple operating conditions. In the case of wave propagation including
flow, such as aircraft or vehicle noise, aeroacoustics or fluid dynamics simulations are practically limited to the acoustic near field due to high computational costs. Especially challenging are simulations of rotating systems, such as fan noise radiation. For better applicability, the proposed
method is based on in-situ recordings of flyovers. The processing chain compensates for source position and movement as well as atmospheric and soil damping effects on recorded data. The compensated source signal is decomposed into partial sources in spectro-temporal domain with nonnegative
matrix factorization (NMF) and can optionally be enhanced by physically-based source information. The format of the source model obtained is ready to use for dynamic sound synthesis in real-time virtual reality applications.
3-D sound field reproduction with reverberation control on surround sound system by combining parametric and electro-dynamic loudspeakers
Authors: Harada Yuna , Iwai Kenta , Nakayama Masato , Nishiura Takanobu
Published: September 2021

Recently, with the development of video technology, 3-D sound field reproduction systems that can provide a high presence have attracted attention. Conventional systems with electro-dynamic loudspeakers have a problem that the sound image lacks sharpness when constructing a narrow sound
image. To solve this problem, we utilize a parametric array loudspeaker which has sharp directivity by the straightness of ultrasounds. Parametric array loudspeakers can produce sharper sound images due to the sharper directivity and lower reverberation compared with electro-dynamic loudspeakers.
However, it is difficult to represent reverberation by parametric array loudspeakers. In this paper, we propose a method for 3-D sound field reproduction to achieve both the sharp images and reverberation presence by combing parametric array loudspeakers and electro-dynamic loudspeakers in
surround sound system. In the proposed method, sharp sound images are rendered by parametric array loudspeakers and the reverberation presence is provided by electro-dynamic loudspeakers, emitting reverberation signals synthesized with a reverberation control filter. The reverberation control
filter is adaptively designed to reproduce the reverberation time and the direct-to-reverberation ratio of the target sound field in other environments. The experimental results show that the proposed method can achieve the reproducing the sharp sound image with some reverberation presence.
Bubble curtain modelling: analytical prediction of piling noise mitigation
Authors: Huisman Marco , Lederwasch Louis , Lützen René Smidt
Published: September 2021

In order to mitigate underwater noise caused by pile driving, bubble curtains are widely used during offshore constructions. These form an impedance barrier to the acoustic pressure wave, and the resulting attenuation on the interface of water to bubbly water is the main driver behind
the insertion loss that can be achieved. A secondary effect is energy absorption by bubble resonance; however, normal bubble sizes are such that the resonance frequency is considerably higher than the peak in the piling noise spectrum, rendering the resonance contribution to the overall insertion
loss relatively small. The broadband insertion loss and sound level reduction spectra of bubble curtains are mainly determined on an empirical basis, comparing actual project data and noise monitoring results across sites. Although several efforts have been made to capture the noise mitigation
by bubble curtains in numerical models, there is no straight-forward integrated modelling method available to quantify the influence of individual design and operational parameters. Using a number of assumptions and simplifications, this paper presents an analytical model for the frequency-dependent
and broadband insertion loss achieved by bubble curtains, that combines both impedance and resonance effects.
Designing a tuned-shunt electrodynamic metamaterial in the presence of uncertainties
Authors: Singleton Lawrence , Cheer Jordan , Daley Stephen
Published: September 2021

Resonant structural vibrations are a common source of disruptive noise, and suppressing these vibrations is often the most direct way to reduce the noise levels. Elastic metamaterials (EMMs) consist of distributed resonant substructures, at a scale which is small compared to the wavelength
of vibration. This allows these materials to be used in applications where space is limited, and more traditional vibration suppression techniques would be impractical. Tuned resonators can be designed through selection of geometry or material properties, but an alternative approach, which
requires significantly less prototyping, is through the use of shunted electrodynamic inertial actuators. In this paper, a novel electrodynamic metamaterial (EDMM) is proposed consisting of an array of mass-produced inertial actuators, each connected to a tuned shunt impedance. It is considered
impractical to measure the dynamic and electrical parameters of a large number of actuators, and so the effect of uncertainties in the actuators is investigated on both the performance and the stability of the EDMM.
Are on board comfort classes noise and vibration levels really suitable?
Authors: Bregant Luigi , D'Agostin Flavia , Lorenzino Martina
Published: September 2021

In shipbuilding industry, comfort is a relevant issue both for crew members and passengers. A comfortable environment enables crew members to perform accurately their tasks and it is an effective factor contributing to the satisfaction of passengers. Noise and vibration, as environmental
parameters, play an important role in subjects' comfort. Naval Classification Societies established series of noise/vibration comfort level criteria, which, however, did not take into account some aspects: 1) noise/vibration recordings are carried out during time periods shorter than the exposure
time of passengers; 2) the subjective mood is not investigated. In the present study, we studied comfort perception by measuring heart rate variability and mood. We exposed participants to four levels of acoustic noise [from 45 to 55 dB(A)] and three levels of vibration (1.5, 1.8, 2 mm/s)
inside a full-scale mock-up of a cruise ship cabin. We found that the increase of noise/vibration intensity determines an increase of heart rate variability and negative mood. However, changes in comfort responses did not occur for the noise/vibration comfort thresholds identified by the Classification
Societies. Our results evidence the importance to include psychophysiological measure of comfort when defining comfort criteria on board.
Quantifying sound transmission of building structures for optimization in early-stage design
Authors: Broyles Jonathan M. , Shepherd Micah R. , Brown Nathan C.
Published: September 2021

Technological advancements in computational building modeling have enable designers to conduct simulations at the component level. With the evolution of parametric modeling, designers can evaluate multiple design options and identify the best performing solutions before expending resources on physical testing and eventual construction. However, to conduct design space exploration or optimization, an objective function is necessary to evaluate performance. While defined objectives exist for design goals such as sustainability, energy usage, structural performance, and daylighting, there does not yet exist an encompassing objective that can accurately quantify the sound transmission of structures in building design. This paper proposes four transmission rating strategies that can describe air-borne and impact performance of floors, walls, or other acoustic barriers. The approaches consider air-borne and structure-borne sound for four floor constructions, revealing strengths and weaknesses across the methods. Implementation of the approaches in an optimization framework is discussed, along with practical methods for optimizing the objectives in early-stage design.
Implementation of Direct Acoustic Simulation using ANSYS Fluent
Authors: Huang Dennis , Yang Zhigang , Leung Randolph Chi Kin
Published: September 2021

Direct Acoustic Simulation (DAS) is a powerful Computational Aero Acoustics method that obtains hydrodynamic and acoustic solutions simultaneously by solving compressible Navier-Stokes equation together with state equation of ideal gas. Thus, DAS has advantages for cases with flow acoustic
coupling and high Mach numbers (). With an increasing demand of massive-scale calculations, a robust numerical solver for DAS is required. ANSYS Fluent is a suitable CFD platform with proven robustness. However, there is no direct implementation of DAS in the current version of ANSYS Fluent.
The present study, therefore, aims to investigate an approach for implementing DAS using ANSYS Fluent. Given the acoustic part of fluctuations is much smaller than the hydrodynamic part in amplitude, a DAS solver requires high accuracy and low dissipation. Based on these needs, proper solution
methods, spatial discrete methods and boundary conditions are firstly determined through simple calculations of two dimensional propagating plane waves. Afterwards aeroacoustics of a two-dimensional cavity flow at 0.6 is calculated to verify the capability for solving separating flow with
the aforementioned set-up. Finally, aeroacoustics of a cylindrical bluff body at a turbulent regime and 0.2 is calculated in three-dimensions to verify the capability for solving turbulent flow using Monotonically Integrated Large Eddy Simulation.
Low excitation spur gears with variable tip diameter
Authors: Götz Joshua , Sepp Sebastian , Otto Michael , Stahl Karsten
Published: September 2021

One important source of noise in drive trains are transmissions. In numerous applications, it is necessary to use helical instead of spur gear stages due to increased noise requirements. Besides a superior excitation behaviour, helical gears also show additional disadvantageous effects
(e.g. axial forces and tilting moments), which have to be taken into account in the design process. Thus, a low noise spur gear stage could simplify design and meet the requirements of modern mechanical drive trains. The authors explore the possibility of combining the low noise properties
of helical gears with the advantageous mechanical properties of spur gears by using spur gears with variable tip diameter along the tooth width. This allows the adjustment of the total length of active lines of action at the beginning and end of contact and acts as a mesh stiffness modification.
For this reason, several spur gear designs are experimentally investigated and compared with regard to their excitation behaviour. The experiments are performed on a back-to-back test rig and include quasi-static transmission error measurements under load as well as dynamic torsional vibration
measurements. The results show a significant improvement of the excitation behaviour for spur gears with variable tip diameter.
Numerical feasibility study for transverse vibration control of rotating shaft with a neural network-based tracking algorithm
Authors: Hong Dongwoo , Lee Hyeongill , Han Youkyung , Kim Byeongil
Published: September 2021

Rotary elements have been applied to a variety of mechanical systems such as pumped-storage hydroelectricity and nuclear power plant. Due to their vibration problems occurred by misalignment, bent, and unbalance, a sharp decline efficiency of system and malfunction can be caused and
furthermore, the rotor may be damaged. In order to control the rotor vibration actively, active vibration control using the magnetic bearing and piezo actuator is being vigorously studied to improve operating conditions of rotary devices. This research accomplished numerical simulations of
active vibration control for an unbalanced rotor system using the active bearing system applying piezo actuators. Overall rotor system is modeled using energy method and an active bearing model with two actuators placed in both x- and y-direction is developed using lumped parameter method.
For implementing active control scheme through the active bearing system, a signal tracking algorithm based on neural network is developed and utilized to the rotor system. The active bearing system shows good performance on transverse vibration reduction for rotating systems.
Underwater acoustic target classification based on u-shaped network
Authors: Lingzhi Xue , Xiangyang Zeng
Published: September 2021

Target recognition is a key task and a difficult technique in underwater acoustic signal processing. One of the most challenging problem is that the label information of the underwater acoustic samples is scarce or missing. To solve the problem, this paper presents a local skip connection
u-shaped architecture network(U-Net)based on the convolutional neural network(CNN).To this end, the network architecture is designed cleverly to generate a contracting path and an expansive path to achieve the extraction of different scale features. More importantly, a local skip connection
mechanism is proposed to optimize classification rates by reusing former feature maps in contracting path. The experimental results of the measured dataset demonstrate the recognition accuracy of the model is better than that of deep belief network(DBN) and generative adversarial network(GAN)
networks.Further research on three kinds of network by visualization method shows that the proposed network can learn more effective feature information with limited samples.
Advanced design of Close-Proximity (CPX) trailer enclosure acoustics on tyre/road noise measurement
Authors: Li Dong Fang , Leung Randolph Chi Kin
Published: September 2021

The PolyU Mark II Twin-wheeled CPX trailer was developed for the measurement of tyre/road noise in Hong Kong urban environment according to a standard methodology (ISO/CD 11819-2) - the Close-Proximity (CPX) method. Numerical simulations of the acoustics of PolyU Mark II CPX enclosure
were conducted and a good agreement between numerical and experimental results was obtained. In order to extend the capacity of the Mark II CPX trailer and enhance the acoustic performance within the enclosure for future tyre/road noise studies, the validated numerical simulations were carried
on to design the next generation of the PolyU CPX system. Through analyzing the acoustic performance within the enclosures of different dimensions and the distributions of sound pressure level (SPL) inside the anechoic chamber, the geometry of the PolyU Mark III CPX enclosure was finally determined.
With newly designed enhanced interior wall absorption, the new PolyU Mark III CPX enclosure design was delivered into numerical simulations for acoustic analysis. Fewer room modes and high uniformity of SPL distributions were observed within the new enclosure design. The PolyU Mark III CPX
enclosure was fabricated based on the corresponding dimensions and the specific absorption layers. Great consistency was achieved between the numerical and measured results of the Mark III CPX enclosure. In addition, the PolyU Mark III CPX enclosure shows an improved acoustic property with
a lower background noise level during road tests than Mark II CPX enclosure. The outcome of this study firmly establishes the feasibility of designing advanced CPX enclosure with numerical simulations with results that can be realized in realistic CPX measurement.