Spectral discrimination thresholds comparing audio and haptics for complex stimuli

Individuals with normal hearing are generally able to discriminate auditory stimuli that have the same fundamental frequency but different spectral content. This study concerns to what extent it is possible to perform the same differentiation considering vibratory tactile stimuli. Three perceptual experiments have been carried out in an attempt to compare discrimination thresholds in terms of spectral differences between auditory and vibratory tactile stimulations. The first test consists of assessing the subject’s ability in discriminating between three signals with distinct spectral content. The second test focuses on the measurement of the discrimination threshold between a pure tone signal and a signal composed of two pure tones, varying the amplitude and frequency of the second tone. Finally, in the third test the discrimination threshold is measured between a tone with even harmonic components and a tone with odd ones. The results show that it is indeed possible to discriminate between haptic signals having the same fundamental frequency but different spectral. The threshold of sensitivity for detection is markedly less than for audio stimuli.