ASA 124th Meeting New Orleans 1992 October

4pSA1. Acoustic design for noise reduction (ADNR), a method and computer code based on the modelization of structural acoustic and vibration behavior for semicomplex structure.

J. Nicolas

N. Atalla

Y. Baubil

GAUS, Mech. Eng. Dept., Univ. of Sherbrooke, Sherbrooke, PQ J1K 2R1, Canada

Challenge of noise control in the nineties will be to introduce new tools in addition to classical ones (absorbing materials, enclosures, and mufflers) which have been used for several decades. For noise reduction at its source there are mainly two approaches: active noise control or passive noise control, based on a new mechanical design. This paper addresses the second possibility. To design and create a quieter product, an analytical model has been developed predicting the vibration and acoustic responses of a structure. The model is based on a variational method and the calculation of the Green's function. Specific developments have been introduced to decrease the total computation time. The main design indicators are the quadratic velocity, the modal and global structural shape, the radiation factor, and the sound power. These indicators serve to illustrate how the various design specifications (geometry, thickness, added extended of local mass, added stiffness, stiffener, damping, excitation type, and location) can or cannot decrease the radiated noise. The implemented code appears to be a unique, powerful, and helpful tool for taking the right decision, as far as radiated noise is concerned, at the very beginning of the design stage.