The experiments were examined to clarify the effects of pure tone on human autonomic nervous system and subjective impression on pleasantness. The activities of sympathetic nervous system and parasympathetic nervous system were estimated using the low-frequency component (LF) and the high-frequency component (HF) in the power spectrum of heart rate variability, respectively, in addition to heart rate (HR). As a result, 80 phon tones are evaluated to be significantly more unpleasant than 60 phon tones in all frequency conditions (125 Hz, 500Hz, 1 kHz and 8 kHz). On the other hand, there are no statistically significant differences between both loudness levels in any autonomic indices. With regard to the effect of frequency, HR is significantly lower in the presentation of 8 kHz tone than 125 Hz tone. Furthermore, HF is higher in the presentation of 8 kHz tone than 125 Hz tone. However, there is no statistically significant difference between them. At the same time, 8 kHz tone is evaluated to be slightly more unpleasant than 125 Hz tone at each loudness level. These results suggest that parasympathetic nervous system activate against the activity of sympathetic nervous system induced by high frequency stimuli evaluated to be unpleasant.
