The first research papers which underpin the Musical Vibrations project were published in 2011. The research was funded by the Arts and Humanities Research Council (AHRC) and combined the psychology of musical performance, the physics of structureborne sound and acoustics, and the physiology of touch.
At this early stage, researchers aimed to gain an understanding of the musical cues needed by hearing-impaired musicians to facilitate group performance, and to create a technological solution based on vibration to provide the required cues.
The research gave insight into how vibration signals could be tailored to suit different musicians and different types of music and examined the potential for using individual vibrating performance decks on which each musician could stand or sit, vibration pads that could be attached to the body and arrays of vibrating bars that would transmit vibration signals from different musical instruments.
Vibration thresholds
The first component of the research 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.
Compared to the fingertip, it was found that low levels of vibration could be perceived on the forefoot and the heel for the lowest notes; hence there are potential advantages in using the forefoot and the heel for bass notes to increase the available dynamic range. Another 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 also 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. Another key finding was that it is not possible to perceive pitch information in the form of continuous vibration above the note G5 (slightly less than two octaves above middle C / C4.
Pitch
The second component concerned the perception and learning of basic relative pitch through the skin. Both participants with normative hearing and with a hearing impairment 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). 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 (minor third):
Proof of principle
The third component provided ‘proof of principle’ through audio and video recording of a group musical performance using vibrotactile feedback: https://stream.liv.ac.uk/kgfymdz4
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 date, it has been viewed over 6,000 times.
To promote the research aims of social inclusion and to challenge public perceptions of what is possible with a hearing impairment, public engagement activities took place with the deaf community through a one-day AHRC Dissemination Conference in 2013.
Awards
The research was 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’.
Funding
This research was funded by the Arts and Humanities Research Council (AHRC) in the United Kingdom under project AH/H008926/1 “Interactive performance for musicians with a hearing impairment”. Professor Carl Hopkins (University of Liverpool) was the principal investigator and Professor Jane Ginsborg (Royal Northern College of Music) was the co-investigator.
