CONTOURS OF EQUAL PERCEIVED AMPLITUDE AND EQUAL PERCEIVED FREQUENCY FOR ELECTROCUTANEOUS STIMULI

Previous measurements of equal-sensation contours for electrocutaneous stimuli consisting of repeated bursts of biphasic pulses have shown t hat stimulus frequency has little effect on perceived amplitude, and t hat stimulus amplitude has no effect on perceived frequency. These ear lier contours, however, were measured over a very restricted range of amplitude and frequency or for a single perceived amplitude or perceiv ed frequency. Contours of equal perceived amplitude and equal perceive d frequency were measured in the present study for stimuli covering mo st of the useable range of amplitudes and frequencies: 3-12 dB SL and 4-64 Hz. Eight naive subjects generated contours of equal perceived am plitude at four reference amplitudes via Bekesy tracking, and 8 additi onal subjects generated contours of equal perceived frequency at three reference frequencies. The contours of equal perceived amplitude decl ined slightly but significantly with increases in stimulus frequency, consistent with previous results. The shape of the contours was also s lightly dependent on the amplitude of the reference stimulus. Contours of equal perceived frequency were unaffected by stimulus amplitude on the average, but the contour shape did vary modestly though erratical ly: with reference frequency.