Acoustics Research Unit
Vibrotactile concerns the perception of vibration through touch. It can be used either as a substitute for other senses (e.g. hearing, vision) or to enhance the information content.
The above video summarises interdisciplinary research involving collaboration between acousticians in the Acoustics Research Unit (ARU) at the University of Liverpool and music psychologists in the Centre for Music Performance Research at the Royal Northern College of Music. The research was initiated by Professor Hopkins (Principal Investigator) and was inspired by Dame Evelyn Glennie who describes feeling and using vibration when playing percussion instruments. The aim was to investigate the potential for vibrotactile feedback to facilitate interactive group performance with deaf musicians to compensate for the lack of auditory cues, and to avoid reliance on visual cues. The intention was to open up new opportunities for people with a hearing impairment to become musicians and perform with other musicians [1,2,3,4].
There were three components to the underpinning research.
The first component established the limits for perceiving vibration (vibrotactile thresholds) on the glabrous skin of the fingertips and feet over a range of musical notes from C1 to C6 [1,4]. A key finding was that there is no statistically significant difference between vibrotactile thresholds for people with a severe/profound hearing impairment and normal hearing. These thresholds helped define the usable dynamic range that would avoid vascular symptoms from exposure to vibration because musicians typically practise/perform for several hours each day. Practical implementation of vibrotactile technology poses no issues for pop/rock although classical music might require some compression to increase the level of quiet music (e.g. pianissimo) and decrease the level of loud music (e.g. fortissimo). Another key finding was that it is not possible to perceive pitch information reliably above the note A5 (almost two octaves above middle C).
The second component concerned the perception and learning of basic relative pitch through the skin . Normal and hearing impaired participants undertook a pitch discrimination experiment with a full test before and after a 16-session training period which indicated a high success rate for basic relative pitch with and without training. This has important implications as it was postulated that hearing impaired participants might be better at the task due to neural plasticity (where the brain re-organises the sensory processing) such that some somatosensory processing takes place in the auditory cortex. This implies that everyone has a basic ability to perceive relative pitch. Tests also identified an important limitation of vibrotactile feedback as it was shown to be difficult to distinguish intervals smaller than three semitones.
The third component provided ‘proof of principle’ through audio and video recording of a group musical performance using vibrotactile feedback. For this performance, the acoustic laboratories were used to ensure that all auditory cues from other musicians were removed and there was no visual contact between the musicians. The video promoted the research findings to a much wider audience and had more than 1000 views in its first week online.
To promote the research aims of social inclusion and to challenge public perceptions of what is possible with a hearing impairment, public engagement activities have taken place with the deaf community through a one-day dissemination conference and internet video.
The research was funded by the Arts and Humanities Research Council (Grant No. AH/H008926/1), included in the Universities UK initiative ‘Big Ideas for the Future’ and was shortlisted for the Times Higher Education (THE) 2013 Award for ‘Research Project of the Year’.
 Hopkins C, Mate-Cid S, Seiffert G, Fulford R, Ginsborg J (2012) Measurement of vibrotactile thresholds on the fingertip to assess vibrotactile presentation of musical notes to people with and without a hearing impairment. Proceedings of Internoise 2012. I-INCE, New York.
 Hopkins C, Ginsborg J, Mate-Cid S, Fulford R, Seiffert G (2012) On the potential for vibrotactile technology to facilitate interactive performance for musicians with a hearing impairment. Proceedings of LIPAM 2012, Leeds.
 Hopkins C, Mate-Cid S, Seiffert G, Fulford R, Ginsborg J (2013) Inherent and learnt abilities for relative pitch in the vibrotactile domain using the fingertip. Proceedings of ICSV 20. International Congress on Sound and Vibration, Bangkok.
 Hopkins C, Mate-Cid S, Fulford R, , Seiffert G, Ginsborg J (2016). Vibrotactile presentation of musical notes to the glabrous skin for adults with normal hearing or a hearing impairment: Thresholds, dynamic range and high-frequency perception. PLOS ONE http://dx.doi.org/10.1371/journal.pone.0155807 .