Paper Information

Journal:   MODARES MECHANICAL ENGINEERING   JANUARY 2017 , Volume 16 , Number 10 #F0070; Page(s) 155 To 162.
 
Paper: 

ANALYTICAL AND EXPERIMENTAL INVESTIGATION OF REMOTE MICROPHONE SYSTEM RESPONSE FOR PREDICTION OF SURFACE PRESSURE FLUCTUATIONS

 
 
Author(s):  AFSHARI ABBAS, DEHGHAN ALI AKBAR*, KALANTAR VALI, FARMANI MOHAMMAD
 
* DEPARTMENT OF MECHANICAL ENGINEERING, YAZD UNIVERSITY, YAZD, IRAN
 
Abstract: 

Accurate measurement of unsteady pressure fluctuations along a surface requires experimental set up with high spacing resolution and high frequency domain. Therefore, in recent decades extensive studies have been conducted on remote microphone approach. In this method, instead of using flash mounted sensors, they were installed remotely and connected to the model surface through one or several continuously connected tubes. Surface pressure fluctuations travel within the tubing in the form of sound waves and they are measured when passing over the remote pressure sensor, mounted perpendicular to the tubing. In the present study, an analytical solution of sound waves propagation inside the rigid tubes is used for modelling of the remote microphone system and to investigate the effects of its parameters on dynamic response. In order to verify the accuracy of proposed modeling, the dynamic response of a typical remote microphone has been obtained through experimental calibration.
Comparing the analytical and experimental results indicates high accuracy of the analytical modeling.
Results show that changes in tubing diameter lead to occurrence of resonance and creating harmonics in two frequency regions. The amplitude of low-frequency harmonics depends on the length of the damping duct and decreases with increasing of its length. Instead, the amplitude and frequency of highfrequency harmonics depend on the length of the first tube and they decrease with the increase of first tube length. Also, increase of the first and second tube lengths leads to an increase in phase of dynamic response of the remote microphone system.

 
Keyword(s): REMOTE MICROPHONE SYSTEM, ANALYTICAL SOLUTION OF SOUND PROPAGATION, DYNAMIC RESPONSE, UNSTEADY PRESSURE FLUCTUATIONS, EXPERIMENTAL CALIBRATION
 
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