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In assessing the sound quality of electric motors (e.g., seat, mirror, and adjustable pedal motors), the sensation of Fluctuation Strength - a measure of intensity or frequency variation - has become important. For electric motors, it is typically caused by variation in the load, creating frequency modulation in the sound. An existing method for calculating Fluctuation Strength proved useful initially, but more extensive testing identified unacceptable performance. There were unacceptable levels of both false positives and false negatives. A new method is presented, which shows improved correlation with perceived fluctuation in sounds. Comparisons are made to the previous method and improvement is shown through examples of objective-subjective correlation for both seat motor sounds and adjustable pedal motor sounds. The new method is also shown to match subjective data from which the original measure of Fluctuation Strength was derived.

The following document is a set of guidelines intended to be used as a reference for the practicing automotive sound quality (SQ) engineer with the potential for application to the field of general consumer product sound quality. Practicing automotive sound quality engineers are those individuals responsible for understanding and/or conducting the physical and perceptual measurement of automotive sound. This document draws upon the experience of the four authors and thus contains many “rules-of-thumb” which the authors have found to work well in their many automotive related sound quality projects over the past years. When necessary, more detailed publications are referenced. The intent of publication of this document is to provide a reference to assist in automotive sound quality work efforts and to solicit feedback from the general sound quality community as to the completeness of the material presented.

Sound data were recorded from a series of trucks that were operated in various powertrain conditions. The acquired sounds from both the steady state engine speed and second gear wide open throttle operation were then presented to a group of subjects as paired comparisons. Correlation between these subjective ratings to the objective measures of the engine sound were then done and a linear relationship developed.

This paper describes a method to quantify the subjective sound quality of vehicle windshield wiper systems (at both low and high speed) and to relate these subjective impressions to objective characteristics. The process starts with blind paired comparison evaluations of wiper preference for eight wiper systems followed by annoyance ratings of the individual wiper components (blade scrape, motor whine, and reversal thud). For each of the individual component ratings, objective measures were found which correlated with the subjective annoyance ratings. For the overall wiper sound quality, merit values, derived from the paired comparison results were well explained by a three variable regression equation containing the objective measures for blade scrape, motor whine and reversal thud. The results showed that motor whine dominated the sound quality impression at high speed while reversal thud was the major factor at low speed.