Simplified methodology for pump acoustic field analysis: the effect of different excitation boundary conditions

Harmonic response methods and vibroacoustic analysis are considered as tools of a methodology aimed at computation and prediction of the acoustic field emitted by a gear pump. In particular, FFT acceleration spectra were experimentally acquired only in few positions of a 8.5 cc/rev external gear pump case in different operating conditions and considered as external excitation boundary conditions to a FE quite simplified vibroacoustic model. The emitted noise field was computed considering the pump as a 'black box', without taking into account the complex dynamics of gear tooth meshing process and consequent fluid pressure/load distribution. The potentiality of this approach was confirmed and a good compromise was found between noise prediction accuracy and reduction of experimental and modelling requirements. Nevertheless the reduction of the FFT acceleration spectra from 8 to 5 caused some method reliability problems and unsatisfactory results. This paper presents a further investigation aimed at improving the vibroacoustic analysis based on five FFT acceleration spectra as excitation boundary conditions. The choice of the measurement positions was driven by a careful consideration of the spectra energy contribution.