A study was carried out to provide some background data on how acoustical seat belt reminder signals are perceived in a car. 19 subjects listened to 9 test sounds and one neutral reference sound while sitting in a stationary car and being exposed to a background noise corresponding to driving 50 km/h at top gear. Their task was to adjust the loudness level of each sound to make it “just audible”, “loud and clear” or “definitely annoying”. After the test session the subjects were also interviewed about which sounds they preferred or rejected. The results indicate that the more complex sounds are set at fairly uniform levels, but that two of the tested sounds were set consistently lower for the same perceived audibility. For one of these sounds the explanation to the deviation is assumed to be that the sound consisted of pure tones. For the other sound, a “ticking” with rather brief pulses and an instantaneous onset, the very low dB(A) values are hypothesized to be an artefact of the measurement mode. The interview gave rather conflicting results concerning the “popularity” of the sounds. This finding is explained by the widely differing criteria used by the subjects when preferring or rejecting a sound, which pinpoints the necessity of explicit specifications of the purpose of a seat belt reminder system. (Author/publisher)
Abstract