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.

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.

Study of the Acoustic Oscillations of Flow Over Cavities: Part 2 — Sound Reduction

2002 ◽  
Author(s):  
Pascal He´mon ◽  
Xavier Amandole`se ◽  
Franc¸oise Santi ◽  
Jan Wojciechowski
Keyword(s):  
Resonance Frequency ◽  
Helmholtz Resonator ◽  
Sound Level ◽  
Broadband Noise ◽  
Two Dimensional ◽  
Acoustic Oscillations ◽  
Deep Cavity ◽  
Natural Resonance ◽  
Sound Reduction ◽  
Natural Resonance Frequency

We present experimental results obtained with a deep cavity, like an Helmholtz resonator, excited by an airflow. The resonance under the action of the vortices generated in the shear layer is well described and quantified. The mounting of actuators, based on a few piezo-electric elements, allows to generate a series of two-dimensional vortices forced at a frequency which is different than the natural resonance frequency. The sound level in the cavity is strongly decreased and the broadband noise of the turbulence only remains.

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.

Effect of No-load and Load Condition on Transformer Sound

2018 ◽  
pp. 11-15
Author(s):  
Dr. Hitesh Paghadar
Keyword(s):  
Experimental Study ◽  
Power Transformer ◽  
Load Condition ◽  
Noise Pollution ◽  
Sound Level ◽  
Measurement Scale ◽  
Dominant Factor ◽  
Public Attention ◽  
Level Measurement ◽  
Human Ear

Increasing environment noise pollution is a matter of great concern and of late has been attracting public attention. Sound produces the minute oscillatory changes in air pressure and is audible to the human ear when in the frequency range of 20Hz to 20 kHz. The chief sources of audible sound are the magnetic circuit of transformer which produces sound due to magnetostriction phenomenon, vibration of windings, tank and other structural parts, and the noise produced by cooling equipments. This paper presents the validation for sound level measurement scale, why A-weighted scale is accepted for sound level measurement, experimental study carried out on 10MVA Power Transformer. Also presents the outcomes of comparison between No-Load sound & Load sound level measurement, experimental study carried out on different transformer like - 10MVA, 50MVA, 100MVA Power Transformer, to define the dominant factor of transformer sound generation.

Experimental Study of the Plastic Interaction of Model Surface Asperities during Sliding

1968 ◽  
Vol 10 (2) ◽  
pp. 121-132 ◽  
Author(s):  
C. M. Edwards ◽  
J. Halling
Keyword(s):  
Experimental Study ◽  
Friction And Wear ◽  
Normal Force ◽  
Tangential Force ◽  
Experimental Results ◽  
Interfacial Conditions ◽  
High Adhesion ◽  
Theoretical Predictions ◽  
Very High ◽  
Low Shear

The paper describes an experimental study of the plastic interaction of triangular shaped lead model asperities deformed under conditions of plane strain. The investigation yields values of the normal and tangential force variations throughout the junction interaction and details of the plastic deformation particularly in relation to junction growth. A number of asperity interfacial conditions are considered ranging from complete adhesion to very low shear strengths achieved using p.t.f.e. strip. The experimental results are compared with an earlier theoretical solution to this problem and show reasonable agreement with the theoretical predictions. In particular it is shown that the normal force, which is usually compressive, may become tensile for conditions of high adhesion between the asperities. This leads to very high values of the macroscopic friction coefficient such as occur in hard vacuum situations. The experimental results for the various surface conditions show sufficient agreement with theoretical predictions to justify the use of this type of theoretical approach for the wider study of the friction and wear of mating surfaces.

Experimental Study on Restoration of Deteriorated Timber due to Termites by Resin Filling

2022 ◽  
Author(s):  
Takashi Yajima ◽  
Kei-ichi Imamoto ◽  
Chizuru Kiyohara ◽  
Mikako Yamada
Keyword(s):  
Experimental Study ◽  
Injection Pressure ◽  
Theoretical Formula ◽  
Internal Cavity ◽  
Strength Recovery ◽  
The World ◽  
Stable Manner ◽  
Long Time ◽  
Filling Method ◽  
Very High

There are many valuable wooden buildings in the world, because timber has been used all over the world as a building material for a long time. However, there is an issue that timber deteriorates due to various factors. Therefore, in order to preserve these valuable wooden buildings, it is necessary to appropriately repair or reinforce treatment. One of the treatments is the resin filling method. In this method, filling the resin in order to restore the strength into an internal cavity caused by deterioration. It has become clear that it is possible to recover the strength using this method, however, we are still conducting construction based on the rule of thumb. Therefore, authors examined the resin characteristics in order to inject the resin in stable manner and ensure strength recovery. Authors focused on deteriorated timber due to termites, because Japan has a very high amount of such type of timber. Authors reports the following four aspects of the characteristics of resin filling into timber. 1. The Area velocity is determined by the injection pressure, width of the gap, and viscosity of the resin. 2. The resin spreads concentrically in the gap of wood, but there is no regularity in the random gap like deteriorated timber due to termites. 3. Authors proposed a new coefficient for the application, of a theoretical formula to deteriorated timber due to termites. 4. Authors proposed a flowchart of resin filling method to perform stable construction.

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.

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