Component sound quality: a power window study

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The Noise and Vibration Center (NVC) at Volvo Cars Corporation (VCC) Torslanda needs to develop its requirements regarding component sounds, such as the sounds of electric motor systems. At present, component sound requirements are generally stated as A-weighted sound pressure levels in 1/3-octave bands. Components which produce the same level in dB(A) may sound very different and therefore NVC wishes to define measures that better describe the character of the sound. The aim of this master's thesis project was to define a homogeneous Volvo sound for electric motor components in the complete vehicle. Another object was to find measures that describe the quality and character of the sound and propose requirement levels for these measures. In the project the above mentioned was investigated by studying power window sounds. Power window sounds from nine different vehicles were recorded and then assessed in two listening tests. According to the results of the listening tests, a good Volvo sound for components with electric motor systems should be dull and steady. The subjective evaluation also showed that a loud power window sound and a weak sounding motor are regarded as annoying. Additionally, the listening tests proved that in the sound quality assessment of a power window, the starting and stopping events are less important than the travelling phase. The result of this thesis is a proposal for a new requirement regarding power window sound in the complete vehicle. The statistical analysis of the subjective assessments led to the conclusion that a requirement containing measures that correlates with the perceptions of loud and steady are desirable. Comprehensive acoustical analysis in combination with further statistical investigations res...