Haptic display of melodic intervals for musical applications

The focus of this study was to investigate the ability to discriminate between melodic intervals of the equal tempered scale based solely on vibrotactile stimulation. In music, a melodic interval is the musical distance between two pitches, or notes, that are played sequentially. This paper tests the hypothesis that people can detect melodic intervals that are presented to different body sites such as the fingertip of the index finger of the non-dominant hand, as well as to the flank, the lateral region between the ribcage and the hip bone. Vibrotactile stimuli on the flank were displayed through voice coils of different diameters (0 13 mm and 0 25 mm respectively), while those at the finger were displayed with a 0 13 mm diameter voice coil. Six melodic intervals ranging from a minor second (A/=100 cents) to a perfect fifth (A/=700 cents) were compared to the reference interval of a perfect prime (A/=0 cents) at a fundamental frequency (/) of 65 Hz. Discrimination was significant for intervals as small as a major second (A/=200 cents; i.e. 8Hz, or 12.3%), depending on the location of the body. Overall, results tend to suggest that larger intervals are less difficult to detect than smaller intervals.