Vibration detection and analysis using laser technology

number: 
864
Undefined
Degree: 
Author: 
Hussam Maki A. K. Muhamed Salih
Supervisor: 
Dr. Mohamed A. Hussain
year: 
2004
Abstract:

An experimental listener device has been designed and implemented using laser technology. He–Ne laser has been used in the form of transmitter and laser listener receiver has been designed and constructed to detect human speech and other types of sound behind vibrating panels. The designed laser listener receiver consists of: a photodetector, low noise signal amplifier for frequency spectrum up to 3kHz of amplification factor of 45 dB, bandpass filter of a range from 500 to 2000 Hz which covers human voice spectrum and audio amplifier. The bandpass filter has been designed to pass also the spectrum near from the boundaries limitation of the above bandwidth spectrum to cover extraordinary low or high natural voice frequencies.Ordinary conversation has been detected from the vibrated panel. Both periodic and non–periodic (speech) vibrations have been detected successfully by the listener device.Two rectangular vibrating panels have been used, an x-ray film and window glass panel. The panels have been located at different distances from the source of sound ranged from 0.5 to 5 m. This range has been used mainly because of laboratory space limitation.Two computer programs have been written using Matlab environment to calculate the natural frequency of panel material and to determine the displacement of the vibrating panel. Theoretical results for silica glass show that the glass window can be considered as a linear system because the natural frequency of the glass is far from the excitation frequency of speech, i.e. the glass will vibrate at frequency equal to the excitation frequency (e.g. human voice frequency).