Detection of vibrating sound fields using speckle shearography

E. A. Abd El-Ghafar; Hatem El-Ghandoor

doi:10.1117/12.363789

28 September 1999 Detection of vibrating sound fields using speckle shearography

E. A. Abd El-Ghafar, Hatem El-Ghandoor

Proceedings Volume 3786, Optomechanical Engineering and Vibration Control; (1999) https://doi.org/10.1117/12.363789
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1999, Denver, CO, United States

Abstract

A loudspeaker at certain frequencies, producing vibrating sound wave causes periodic pressure variations in air. This pressure variation can be displayed in the form of a corresponding variations in the refractive index of air. The induced variation of the refractive index of air lead to a deflection of light rays traveling through the disturbed area of air by the vibrating sound waves. Speckle photography technique has been sued in this work to measure the light deflection along a certain cross-section of the integrated sound fields. The deflection angle of light rays can be measured as a speckle shift in the image plane leads to the formation of interference fringes similar to Young's fringes pattern. In the present work, a fringe pattern displaying the speckle shift due to the refractive index variation has been obtained using the electronic speckle pattern shearing interferometry. This fringe pattern in a measure of the speckle displacement due to light deflection caused by a vibrating sound source making a periodic pressure and refractive index variations of air.

Citation Download Citation

E. A. Abd El-Ghafar and Hatem El-Ghandoor "Detection of vibrating sound fields using speckle shearography", Proc. SPIE 3786, Optomechanical Engineering and Vibration Control, (28 September 1999); https://doi.org/10.1117/12.363789

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