The influence of tone length and S/N-ratio on the perception of tonal content: An application of probabilistic choice models in car acoustics

Abstract

The rating of tonal content is not just a prevalent issue in the context of sound design but also in annoyance/noise problems. Two physical parameters influencing the evaluated tonal content are tone length and S/N-ratio. In order to integrate these parameters into a reliable, objective measure of the perceived tonal content of interior car noises the following experiments were conducted: Realistic ''howling,'' i.e. the tonal content, in interior car noise were presented with variations in tone length and S/N ratio. Thirteen stimuli were judged by 41 subjects in a complete pair comparison. It was shown that subjective judgments can be modeled by probabilistic choice models quite well. An one-dimensional choice model, i.e. the BTL model, must be rejected in favor of a more general elimination-by-aspect model. The results are the following: (1) The subject's decision aspects are identified by modeling the choice behavior: A non-howling aspect describes the sound evoking a sensation not described by the howling adjective and a pitch-salience aspect indicates the equivalent S/N-ratio of a tonal component. No subjective duration aspect was found. (2) The log-ratio scale obtained yields a constant factor for doubling the length in an interval from 250 ms to 2,000 ms with equal level as well as a constant factor for each increase by 3 dB. Furthermore, the tonal content conception and implications thereof are introduced and discussed.