Acoustic weapons? Effects of very high sound levels

We present a study of acoustic oscillations induced by an internal airflow over a shallow and a deep cavity. The Kelvin-Helmholtz instability is interacting with an acoustic mode of the duct, leading to a resonance which produces a very high sound level. The influence of upstream boundary layer thickness and neck thickness is studied. Some results obtained by modifying the upstream lip shape, by crenel addition, are also given. It is also shown that the numerical simulations using a lattice-gas method give relatively good results by comparison with the experiments. Especially the resonance with the duct acoustics was qualitatively reproduced.

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Automotive traffic noise and urban public spaces

Revista Nacional de Gerenciamento de Cidades ◽

10.17271/2318847297220212964 ◽

2021 ◽

Vol 9 (72) ◽

Author(s):

Greicikelly Gaburro Paneto ◽

Cristina Engel de Alvarez ◽

Paulo Henrique Trombetta Zannin

Keyword(s):

Urban Space ◽

Sound Pressure ◽

Traffic Noise ◽

Motor Vehicles ◽

Open Spaces ◽

Sound Levels ◽

Measurement Results ◽

Sound Pressure Levels ◽

High Sound

In contemporary cities, and usually without realizing it, the population has been exposed to high sound pressure levels, which besides causing discomfort, can lead to health problems. Considering that a large part of this noise comes from emission from motor vehicles, this research aims to evaluate the sound behavior in sound environments configured by voids in the urban fabric, in order to identify whether open spaces can act as attenuators of sound levels. To obtain the expected results, the methodology used was structured from a review of the state-of-the-art and computer simulations relating the variables that influence the formation of urban space and sound emission and propagation, taking as a case study an urban portion of the municipality of Vitória/ES. In parallel, questionnaires were applied to evaluate the user's perception of their exposure. The measurement results indicated that the sound pressure levels caused by traffic noise are above the limit tolerated limit by the NBR norm 10151:2000 for the daytime period. In turn, the results obtained from the population indicated that there is little perception of noise by the users of the spaces surveyed.

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Exposure to industrial noise: impacts on cognitive performance

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-2180 ◽

2021 ◽

Vol 263 (4) ◽

pp. 2590-2600

Author(s):

Luiz Henrique Mesa Casa Pereira ◽

Björn Knöfel ◽

Jan Troge ◽

Welf-Guntram Drossel ◽

Marcel Klein ◽

...

Keyword(s):

Cognitive Performance ◽

Noise Analysis ◽

Low Frequency ◽

Cumulative Effect ◽

Noise Sources ◽

Industrial Noise ◽

Sound Levels ◽

Office Environments ◽

High Sound ◽

High Frequency Content

Research on the relation between exposure to noise and cognitive performance inside industrial environments is not as broad as on office environments. For a better understanding of the specific industrial noise problems, participants performed arithmetic tests inside a hemi anechoic room while they were exposed to sounds of five typical industrial noise sources. The subjects also classified how annoying they perceived the noise signals. The effect of noise on the arithmetic test's performance was larger on accuracy than on velocity, which was verified using a Student t-test. Spectral-temporal characteristics - especially high frequency content and strong low frequency modulation - appear to relate better with lower performance on the test than high sound levels. Subjects that evaluated noise as more annoying performed worse in a final arithmetic test (under silence) after being exposed to the noises, indicating a possible cumulative effect of noise on performance. The findings provide a better insight in the cognitive behavior of people who are exposed to industrial noise. Hence, the study will proceed with the specific noise analysis of single industrial workplaces.

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Acoustic Simulation’s Verification of WFI ATHENA Filterwheel Assembly

Archives of Acoustics ◽

10.1515/aoa-2017-0051 ◽

2017 ◽

Vol 42 (3) ◽

pp. 483-489

Author(s):

Adam Pilch ◽

Tadeusz Kamisinski ◽

Mirosław Rataj ◽

Szymon Polak

Keyword(s):

Main Part ◽

Sound Pressure ◽

Pressure Level ◽

Noise Levels ◽

Large Area ◽

Fem Simulations ◽

Absorbing Material ◽

Reduce Risk ◽

High Sound ◽

Very High

Abstract Ariane 5 rocket produces very high sound pressure levels during launch, what can influence structures located in the fairing. To reduce risk of damage, launch in vacuum conditions is preferred for noise sensitive instruments. In Wide Filed Imager (WFI) project, the main part of the filterwheel assembly is an extremely thin (~240 nm) filter of large area (170×170 mm), very sensitive to noise and vibrations. The aim of this study was to verify numerical calculations results in anechoic measurements. The authors also checked the influence of WFI geometry and sound absorbing material position on sound pressure level (SPL) affecting the filter mounted inside the assembly. Finite element method (FEM) simulations were conducted in order to obtain noise levels in filter position during Ariane 5 rocket launch. The results will be used in designing of WFI filterwheel assembly and endurance of the filter during launch verification.

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