Investigation of the perceived sound quality of an automotive HVAC system

The noise emitted by the heating, ventilation and air conditioning system (HVAC) has a great influence on the car acoustical comfort and quality perception. To improve its sound quality, physical properties which determine the subjective perception have to be identified. The HVAC-noise of twelve cars in different arrangements of fan speed and direction of air flow was recorded for later objective and subjective analysis. All cars were of the same model, but with three different types of HVAC-systems, and had just been manufactured. Objective analysis with sound quality software and subjective evaluations was carried out. Using multiple linear regressions on the subjective data, relations between subjective results and psychoacoustic metrics were determined and models to predict subjective response to HVAC sounds are proposed. It is shown that the annoyance caused by the HVAC-noise can be satisfactorily described by Zwicker's stationary loudness model.