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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.

Transient automotive sounds often possess a complex internal structure resulting from one or more impacts combined with mechanical and acoustic cavity resonances. This structure can be revealed by a new technique for obtaining translation-invariant scalograms from orthogonal discrete wavelet transforms. These scalograms are particularly well suited to the visualization of complex sound transients which span a wide dynamic range in time (ms to s) and frequency (∼100Hz to ∼10kHz). As examples, scalograms and spectrograms of door latch closing events from a variety of automotive platforms are discussed and compared in light of the subjective rankings of the sounds.