Perception of Sound and Vibration in Heavy Trucks

Doktorsavhandling, 2008

Interior truck cabin sound has for some time been a concern for manufacturers. Today reasonably low sound pressure levels have been achieved using passive absorption. However low frequency sound is difficult to passively absorb and will hence dominate the interior sound. The question is thus ”How can we make the sound better if we cannot, or do not want to, lower the level further?”. The aim of this thesis was to take a sound quality approach to the interior sound and vibration environment in truck cabins by investigating influences from listener experience meaning of the sound and vibrations. In general, taking the entire sound and vibration environment into account, as opposed to targeted measures, has been found to be important when designing for good product sound quality in heavy trucks. Changing one thing makes all others appear differently to the listener, be it sound or vibrations. Continuously reducing prominent sounds contributing to a negative impression will finally end up in a noise-like sound which inherently will lack meaning. How people react to sounds depends on their experience and hence measuring emotional reactions and grouping listeners according to their emotional reactions can be a useful way of creating focus groups for expert ratings. Instead of focusing on specific levels as such, except for means of avoiding e.g. hearing damage, a target sound and vibration environment based on what information should be salient in a certain driving situation could be defined using judgements by such focus groups, defined by common emotional responses to key reference sounds and vibrations.