Study on New Parameters for Tonal Noise Evaluation in Small Fan Noise

2.4 Psychoacoustics

In the fields of sound quality evaluation in information technology (IT) equipment, parameters for tonal components such as TNR (Tone to Noise Ratio) and PR (Prominence Ratio) are standardized in ISO 7779, ECMA-74 and so on. TNR and PR are mainly focused to detect abnormal tonal noise in products for quality control. On the other hand, psychoacoustic parameter so called as Tonality was established by Terhardt and Aures. Tonality expresses a kind of tonal feeling for sound, however, it doesn't focus specific peak component.
The present study is an attempt to establish new parameters for tonal noise evaluation in small fan noise and other IT noise. The TTNR (Total Tone to Noise Ratio) and TPR (Total Prominence Ratio) are presented and calculation tool were developed. In the paper, relationships between subjective tonal feeling and these parameters calculated by various methodologies to pick up tonal components were examined. Sensory test was done by using a paired comparison method and method of limits.