Affiliations: General Motors do Brasil Ltda., Campo de Provas da
Cruz Alta, Indaiatuba, SP, Brazil | Universidade Estadual de Campinas, Depatamento de
Mecânica Computacional, Barão Geraldo, Campinas, SP, Brazil
Abstract: Vibro-acoustic Transfer Path Analysis (TPA) is a tool to evaluate
the contribution of different energy propagation paths between a source and a
receiver, linked to each other by a number of connections. TPA is typically
used to quantify and rank the relative importance of these paths in a given
frequency band, determining the most significant one to the receiver.
Basically, two quantities have to be determined for TPA: the operational forces
at each transfer path and the Frequency Response Functions (FRF) of these
paths. The FRF are obtained either experimentally or analytically, and the
influence of the mechanical impedance of the source can be taken into account
or not. The operational forces can be directly obtained from measurements using
force transducers or indirectly estimated from auxiliary response measurements.
Two methods to obtain the operational forces indirectly – the Complex
Stiffness Method (CSM) and the Matrix Inversion Method (MIM) – associated
with two possible configurations to determine the FRF – including and
excluding the source impedance – are presented and discussed in this
paper. The effect of weak and strong coupling among the paths is also commented
considering the techniques previously presented. The main conclusion is that,
with the source removed, CSM gives more accurate results. On the other hand,
with the source present, MIM is preferable. In the latter case, CSM should be
used only if there is a high impedance mismatch between the source and the
receiver. Both methods are not affected by a higher or lower degree of coupling
among the transfer paths.
