Physiological noise and the determination of vibro‐tactile perception thresholds

Several physically different configurations are frequently used to couple sinusoidal vibration to the finger or palm for the determination of vibro‐tactile perception thresholds (viz: exciter diameter and contact surface curvature, contact force and skin indentation, and the presence or absence of a surround). Vibration of physiological origin (physiological noise) has been studied in the frequency range 0.025–1000 Hz for several common configurations. The acceleration spectrum consists of a broad plateau between 0.1 and 10 Hz, with peak amplitude ∼0.01 to 0.1 m/s² (with reference to 1‐Hz bandwidth) depending on the configuration and subject. The spectrum falls rapidly with increasing frequency above 10 Hz. Substantial contributions to the physiological noise can be identified from blood circulation (1–10 Hz) and respiration (0.2–1 Hz). Preliminary psychophysical results from three subjects, when combined with current knowledge of the masking of vibrotactile signals, suggest that vibrotactile thresholds at frequencies well above 10 Hz may be masked by this physiological noise under some conditions of flesh stimulation.