Independence of pitch and loudness of an electrocutaneous stimulus for sensory feedback

Three experiments were performed to determine if: 1) perceived intensity (loudness) is dependent on stimulus frequency, and 2) perceived pitch is dependent on stimulus amplitude for an electrocutaneous stimulus used for sensory feedback. The electrocutaneous stimuli consisted of repetitive bursts of rectangular, charge-balanced, biphasic pulses applied through a concentric surface electrode on the lateral aspect of the upper arm. In the first experiment, subjects matched the pitch of two electrocutaneous stimuli with different charges (per pulse phase). In the second and third experiments, objects matched the loudness of stimuli with; burst periods that varied over a narrow range (30-50 ms) or a broad range (15.6-500 ms). Burst period and charge were independent over the range of stimulus parameters used; that is, subjects´ pitch matches depended only on burst period and were not affected by discriminable differences in charge of ±0.5 dB and ±1.0 dB. Subject´ loudness matches depended primarily on charge, were not affected by discriminable differences in burst periods of ±10 ms, and depended only slightly on burst period over the range of 15.6 to 500 ms (2.0 to 64.1 Hz)