Analogous to threshold of hearing measurements, we can characterize tactile perception by sensory threshold, the minimum amplitude above which vibration is felt. This amplitude threshold varies with:
- vibration frequency
- body place
- sensory adaptation
- etc.
Understanding tactile perceptual limits is important for building effective interfaces.
First, here is a summary of the sensory thresholds. The values shown are the average sensory threshold over the 100–300 dB band (where sensitivity tends to be best) in units of dB relative to full scale (dBFS). Smaller values indicate greater sensitivity:
These are measurements I made on myself using Bekesy's tracking method with the Tactometer program. I used a single Tectonic TEAX13C02-8/RH tactor. Body places measured are the scapula acromion, dorsal and volar sides of the forearm, ulnar and radial sides of the wrist joint, lateral side of the ankle, and the index finger. Contact with the skin should be secure but light, since putting pressure distorts the transducer's response. I used tape as needed to keep the tactor in place.
In more detail, here are threshold vs. vibration frequency curves. Lower points in the plot mean greater sensitivity.
Measurements are over 12.5 to 600 Hz. Each point is the average of at least 4 measurements.