Spectral peak picking improves tactile speech perception

Abstract Individual differences in speech perception often arise from disparities in access to acoustic–phonetic cues, particularly among those with hearing loss. Haptic hearing aids, which convey speech information through the sense of touch, offer a complementary pathway to improve speech understanding. However, effectively transmitting critical speech features through vibrotactile stimulation remains challenging. To address this challenge, we introduce a tactile spectral peak picking (tSPP) approach, integrated into a vocoder-based audio-to-tactile conversion algorithm to enhance vibrotactile phoneme discrimination. The tactile vocoder decomposes audio into eight frequency bands, with tSPP selectively transmitting only the most energetic bands to emphasise dominant spectral features. Tactile phoneme discrimination on the wrist was tested in 26 participants using either the tactile vocoder alone or with the tSPP algorithm selecting one, two, or four peaks. Discrimination improved significantly when one, two, or four peaks were selected relative to the vocoder alone, with the greatest benefits observed for one- and two-peak tSPP (average improvement: 7.5%). These findings demonstrate that selective enhancement of spectrally salient features can improve tactile speech perception. The algorithm is suitable for real-time use in wearable sensory substitution devices and could aid the development of effective haptic hearing aids.