TRANSMISSION NOISE REDUCTION USING HOLOGRAPHIC SOURCE IDENTIFICATION AND CONSTRAINED LAYER DAMPING

As the noise of various vehicle components is reduced, transmission noise will become more apparent. Most transmission noise is generated by vibration of the transmission housing caused in turn by meshing of gear teeth. To effectively reduce airborne noise eminating from the housing, the critical areas of the housing that act as speakers must be identified.

A photographic technique using laser light, called Double-Pulsed Holography, has been adapted for this purpose. A five-step test program has been successfully completed and has resulted in a quieter prototype through use of constrained layer damping materials at critical points on the transmission housing. Thus, it is expected that holography will be a very useful tool in locating housing areas which are the source of airborne noise.