DEVELOPMENT OF AN INVERSE BOUNDARY ELEMENT TECHNIQUE FOR PARTIAL NOISE SOURCE IDENTIFICATION OF TIRES Fülöp Augusztinovicz, Ferenc Márki and János Granát 1 Wim Hendricx and H. Van der Auweraer 2 1 Technical Univ. of Budapest, Dept. of Telecommunications, H-1111 Budapest, Sztoczek u. 2. 2 LMS International, B-3001 Leuven, Interleuvenlaan 68. INTRODUCTION The identification of noise generation mechanisms inherent in tire/road interaction phenomena requires sophisticated instrumentation and measuring techniques. Due to the nature of the prob- lem, the application of conventional vibration sensors is largely limited, hence those methods making use of acoustic sensing are of primary importance. Nearfield Acoustic Holography (NAH, [1, 2]) is one of these techniques. Other useful techniques are, among others, the Air- borne Source Quantification (ASQ) method [3] and a whole group of inverse FRF methods [4,5], originally developed for excitation force identification in pure mechanical systems [6]. This paper reports on an inverse FRF method which makes use of numerically calculated transfer functions between the radiating (or source) and sensing (or measurement/holography) surface. The technique, originally proposed in this form by Mas et al. [7], can be considered as a generalization of the AH technique. Unlike NAH though, it is not burdened by the limitation that both the source and the measurement surface must be plane or of some other elementary shape, which is of vital importance from the tire analyst’s point of view. Its close relationship with the Boundary Element Method implies that it is usually denoted as an inverse BE method (I-BEM). SUMMARY OF THE UNDERLYING THEORY The inverse BEM method is based on the discrete form of the governing equation of a general radiation problem [ ] ( { } [ ] ( 29 { } ( { } y p x v B x p A s s = - (1) relating the sound pressure s p and particle velocity s v in any arbitrary node x along the source surface mesh to any arbitrary point y outside of the surface through the influence matrices [A] and [B]. Solving the problem by using the collocational method, the pressure m p to be measured along the measurement plane, usually selected in the vicinity of the source, can be expressed as { } [ ] [ ] [ ] [ ] [ ] { } [ ]{ } s s m v c v b B A a p = + = -1 (2) The matrix [c] is referred to as the transfer matrix of the system and {v s } is the vector of sought surface velocities. The solution of Eq. (2) is in principle rather straightforward, provided that the INTERNOISE 99 1 Ft. Lauderdale, Florida USA