Study of the Acoustic Oscillations by Flows Over Cavities: Part 1 — Internal Flows

2002 ◽  
Author(s):  
Xavier Amandole`se ◽  
Pascal He´mon ◽  
Clotilde Regardin
Keyword(s):  
Lattice Gas ◽  
Acoustic Mode ◽  
Sound Level ◽  
Acoustic Oscillations ◽  
Helmholtz Instability ◽  
Internal Flows ◽  
Duct Acoustics ◽  
Neck Thickness ◽  
High Sound ◽  
Very High

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.

An Experimental Study of the Acoustic Oscillations by Flows Over Cavities

2004 ◽  
Vol 126 (2) ◽  
pp. 190-195 ◽  
Author(s):  
Xavier Amandole`se ◽  
Pascal He´mon ◽  
Clotilde Regardin
Keyword(s):  
Experimental Study ◽  
Boundary Layer Thickness ◽  
Acoustic Mode ◽  
Sound Level ◽  
Acoustic Oscillations ◽  
Helmholtz Instability ◽  
Deep Cavity ◽  
Neck Thickness ◽  
High Sound ◽  
Very High

We present an experimental 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 cavity or 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.

Quantifying Vocal Power: Correlation of Whole-Body Anaerobic Power to Vocal Function Measures

2020 ◽  
Vol 63 (8) ◽  
pp. 2597-2608
Author(s):  
Emily N. Snell ◽  
Laura W. Plexico ◽  
Aurora J. Weaver ◽  
Mary J. Sandage
Keyword(s):  
Fundamental Frequency ◽  
Forced Vital Capacity ◽  
Vital Capacity ◽  
Anaerobic Power ◽  
Performance Outcomes ◽  
Sound Level ◽  
Whole Body ◽  
Vocal Function ◽  
Laryngeal Diadochokinesis ◽  
High Sound

Purpose The purpose of this preliminary study was to identify a vocal task that could be used as a clinical indicator of the vocal aptitude or vocal fitness required for vocally demanding occupations in a manner similar to that of the anaerobic power tests commonly used in exercise science. Performance outcomes for vocal tasks that require rapid acceleration and high force production may be useful as an indirect indicator of muscle fiber complement and bioenergetic fitness of the larynx, an organ that is difficult to study directly. Method Sixteen women (age range: 19–24 years, M age = 22 years) were consented for participation and completed the following performance measures: forced vital capacity, three adapted vocal function tasks, and the horizontal sprint test. Results Using a within-participant correlational analyses, results indicated a positive relationship between the rate of the last second of a laryngeal diadochokinesis task that was produced at a high fundamental frequency/high sound level and anaerobic power. Forced vital capacity was not correlated with any of the vocal function tasks. Conclusions These preliminary results indicate that aspects of the laryngeal diadochokinesis task produced at a high fundamental frequency and high sound level may be useful as an ecologically valid measure of vocal power ability. Quantification of vocal power ability may be useful as a vocal fitness assessment or as an outcome measure for voice rehabilitation and habilitation for patients with vocally demanding jobs.

scholarly journals Acoustic Simulation’s Verification of WFI ATHENA Filterwheel Assembly

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.

The Sound Environment of the Foetal Sheep

Behaviour ◽  
1982 ◽  
Vol 81 (2-4) ◽  
pp. 296-315 ◽  
Author(s):  
B.A. Baldwin ◽  
B.C.J. Moore ◽  
Sally E. Armitage ◽  
J. Toner ◽  
Margaret A. Vince
Keyword(s):  
Sound Pressure ◽  
Body Wall ◽  
Low Frequency ◽  
Sound Level ◽  
The Body ◽  
Human Foetus ◽  
Low Frequencies ◽  
Sound Environment ◽  
High Sound ◽  
Foetal Lamb

AbstractThe sound environment of the foetal lamb was recorded using a hydrophone implanted a few weeks before term in a small number of pregnant ewes. It was implanted inside the amniotic sac and sutured loosely to the foetal neck, to move with the foetus. Results differ from those reported earlier for the human foetus: sounds from the maternal cardiovascular system were picked up only rarely, at very low frequencies and at sound pressures around, or below, the human auditory threshold. Other sounds from within the mother occurred intermittently and rose to a high sound pressure only at frequencies above about 300 Hz. Sounds from outside the mother were picked up by the implanted hydrophone when the external sound level rose above 65-70 dB SPL, and the attenuation in sound pressure was rarely more than 30 dB and, especially at low frequencies, usually much less. However, attenuation due to the transmission of sound through the body wall and other tissues tended to change from time to time. It is concluded that the foetal lamb's sound environment consists of (1) intermittent low frequency sounds associated largely with the ewe's feeding and digestive processes and (2) sounds such as vocalisations from the flock, human voices and other sounds from outside the mother.

Hearing, listening and deep neural networks in hearing aids

2021 ◽  
Vol 13 (1) ◽  
pp. 5-8
Author(s):  
Douglas L Beck
Keyword(s):  
Neural Networks ◽  
Hearing Aids ◽  
Digital Technology ◽  
Deep Neural Networks ◽  
Sound Processing ◽  
Speech In Noise ◽  
Acoustic Feedback ◽  
Processing Techniques ◽  
High Sound ◽  
Very High

Hearing aids have undergone vast changes in the last 30 years from basic analog sound processing techniques, to advanced digital technology, to Deep Neural Networks (DNNs) “on-the-chip” providing real-time sound processing. In addition to making sounds audible, advanced hearing aids with DNN on-the-chip are better able to provide clearer understanding of speech in noise, improve recall, maintain interaural loudness and timing differences, and improve the wearer’s ability to selectively attend to the speaker of choice in challenging listening situations. These improvements are delivered without acoustic feedback and with very high sound quality.

Active Stabilization of Surge in an Axicentrifugal Turboshaft Engine

1999 ◽  
Vol 122 (3) ◽  
pp. 485-493 ◽  
Author(s):  
E. B. Nelson ◽  
J. D. Paduano ◽  
A. H. Epstein
Keyword(s):  
Mass Flow ◽  
Acoustic Mode ◽  
Open Loop ◽  
Control Law ◽  
Duct Acoustics ◽  
Operating Range ◽  
Stable Operating ◽  
Active Stabilization ◽  
Surge Control ◽  
Turboshaft Engine

Active stabilization of surge was implemented on an Allied Signal LTS-101 axicentrifugal gas producer, reducing the surging mass flow by 1 percent, for an operating range increase of 11 percent. Control was achieved using high-response sensors in the inlet and diffuser throat, coupled to actuators that injected air near the diffuser throat. System identification and modeling indicate that a classical surge-type eigenmode and an eigenmode associated with engine duct acoustics dominate the engine’s input–output properties. The surge eigenmode’s stability determines the open-loop surge mass flow. A robust linear controller with three inputs and one output stabilized this eigenmode without destabilizing the acoustic mode. The controller facilitated a 1 percent reduction in surging mass flow at 95 percent N1 corrected; this increases the engine’s choke to surge stable operating range by 11 percent. This paper elucidates the measured unsteady presurge behavior of the engine, and outlines a systematic procedure for surge control law development. [S0889-504X(00)01803-1]

Characterization of the Content of the Cavity Behind a High-Speed Supercavitating Body

2006 ◽  
Vol 129 (2) ◽  
pp. 136-145 ◽  
Author(s):  
Xiongjun Wu ◽  
Georges L. Chahine
Keyword(s):  
Sound Speed ◽  
High Speed ◽  
Test Facility ◽  
Direct Visualization ◽  
Acoustic Measurements ◽  
Supercavitating Flow ◽  
Flow Test ◽  
High Sound ◽  
Very High

A high speed/high flow test facility was designed and implemented to study experimentally the supercavitating flow behind a projectile nose in a controlled laboratory setting. The simulated projectile nose was held in position in the flow and the cavity interior was made visible by having the walls of the visualization facility “cut through” the supercavity. Direct visualization of the cavity interior and measurements of the properties of the cavity contents were made. Transducers were positioned in the test section within the supercavitation volume to enable measurement of the sound speed and attenuation as a function of the flow and geometry parameters. These characterized indirectly the content of the cavity. Photography, high speed videos, and acoustic measurements were used to investigate the contents of the cavity. A side sampling cell was also used to sample in real time the contents of the cavity and measure the properties. Calibration tests conducted in parallel in a vapor cell enabled confirmation that, in absence of air injection, the properties of the supercavity medium match those of a mixture of water vapor and water droplets. Such a mixture has a very high sound speed with strong sound attenuation. Injection of air was also found to significantly decrease sound speed and to increase transmission.

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