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

TLDR: In this paper, a diagnostic technique for noise reduction based on the use of the finite element model together with experimental panel vibration data has been developed, and its application is described in this paper.

Abstract: This paper is No. 81011. Body "boom" is a structurally generated noise that can be excited in a passenger vehicle by road roughness or powertrain vibration. It typically occurs in a frequency band below 200 hz and results when the input forces to the body structure are transmitted to the wall panels around the passenger compartment which, in turn, vibrate and excite the acoustic modes of the compartment cavity. This paper concerns the diagnoiss of boom noise which is excited by engine vibration. Several approaches have been described in the literature for reducing engine induced boom noise. These include reducing the input excitation of the engine to the body structure by use of a vibration absorber, adjusting the engine mounts to tune the engine vibration for minimum acoustic participation, and the use of a Helmholtz resonator to modify the acoustic response of the compartment cavity. Another approach, which is the topic of this paper, is to identify and alter the structural wall panels which excite the boom noise. T his approach has been applied successfully to reduce boom noise generated by road input and is based on the use of a finite element model of the compartment cavity to determine the panel participations in exciting the acoustic modes. A diagnostic technique for noise reduction based on the use of the finite element model together with experimental panel vibration data has been developed, and its application is described in this paper. (Author/TRRL)