Spectral loudness summation and simple reaction time

The present study evaluates the relation between loudness and simple reaction time (RT). Loudness matches between a narrowband noise (125 Hz wide) and a broadband noise (1500 Hz) were made at levels from near threshold to near 100 dB SPL. Over a similarly wide range of levels, RT to each of the noise bands was also measured. As reported often in previous loudness-matching studies, loudness summation depended strongly on level. With increasing SPL, the level difference between the noises needed to keep them equally loud first increased, to around 10 dB at moderate levels, and then decreased. Except for one listener, the RT data show the same pattern. The level difference needed to keep RT to the two noises the same first increased and then decreased. These results show that RT is closely related to loudness, but not to sensation level. If RT depended on sensation level, the level difference between the two noises needed to achieve equal RT would not change with SPL because the difference in sensation level between two sounds is a constant. Overall, the average results provide strong support for the contention that simple RT and loudness are closely related.