Acoustic holographic analysis of vehicle side mirror power-fold actuator for sound quality control

The possibility of application of acoustic holographic analysis with statistical envelope analysis algorithm for vehicle side mirror power-fold (PF) noise diagnostic is explored. The aim of this paper is to establish whether the sound visualization contours derived from the measurements can be used as a basis for the power-fold quality differentiation, and whether the results of noise source localization can suggest the best locations for signal sensor placement(s). With use of the acoustic camera, the diagnostic algorithm of the statistical envelope analysis is developed and validated using a large number of power-fold actuators comprising of subjectively ‘good’ and ‘bad’ samples. These power-fold actuators were tested and measured for the sound pressure spectra over the 1/3rd octave band over the frequency range up to 6300 Hz. Power-fold noise was measured by use of the microphone array. For given frequency limits of 1/3rd octave bands, sound pressure levels are measured on given power-fold actuators, an envelope algorithm was formed for the subjectively ‘good’ actuators, thus allowing to develop a quality control acceptance boundary envelope, with which, sound pressure spectrum amplitude of each individual actuator was compared. When the actuators have sound pressure spectrum amplitude curves falling within this boundary envelope, a pass status is obtained, and when the sound pressure spectrum amplitude curves stay outside of this envelope, a fail status is given.