1981-02-01

Application of a Structural-Acoustic Diagnostic Technique to Reduce Boom Noise in a Passenger Vehicle 810398

An acoustic finite element capability and a Fourier analysis capability are employed to identify the structural areas that cause boom noise in a vehicle. The noise occurs in the 127-140 Hz frequency range and results from the forces transmitted to the body structure from the vibration of the engine on its mounts. The phenomenon is diagnosed as being caused by panel vibrations exciting the second longitudinal acoustic resonance of the passenger compartment. Several panels around the front of the compartment are identified as being significant to the excitation of this resonance, and weights are added to various panels to change their vibration characteristics. The noise in the compartment is thereby reduced by 8 dB, and the suggested change is, therefore, the modification of these panels.

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