Fig 1.
Experimental set-up for Experiments I and II.
Fig 2.
Distal phalanx of the middle finger (A) placed on the contactor and (B) showing hand position.
Fig 3.
Electrodynamic shakers and contactor discs used to present vibration to the forefoot or the heel.
Fig 4.
Vibrotactile thresholds on the fingertip from 32 participants with normal hearing for notes between C1 and C6.
The median is indicated by the red line. The 25th and 75th percentiles of the values form the lower and upper bounds of the blue box which contains the middle 50% of the values. The black whiskers indicate values within ±3 standard deviations from the mean and the blue circles represent the outliers outside this range.
Fig 5.
Comparison of vibrotactile thresholds on the fingertip from the present experiment with other published data without a contactor surround from participants with normal hearing.
The number of participants is indicated in brackets. The results from the present experiment are shown as mean values with 95% confidence intervals.
Fig 6.
Vibrotactile thresholds on the fingertip from 14 participants with normal hearing for notes between G4 and C6.
Fig 7.
Vibrotactile thresholds on the fingertip from 32 participants with normal hearing (left-hand box in red) and 8 participants with hearing impairments (right-hand box in blue) for notes between C1 and C6.
Table 1.
Mann-Whitney test results to compare thresholds on the middle fingertip from participants with normal hearing and with a severe or profound hearing loss.
Fig 8.
Vibrotactile thresholds on the forefoot (left-hand box in red) and heel (right-hand box in blue) from 20 participants with normal hearing for notes between C1 and C6.
Table 2.
Independent t-test results to compare thresholds on the heel and forefoot.
Fig 9.
Comparison of vibrotactile thresholds on the forefoot and heel from the present experiment with other published data from participants with normal hearing.
The number of participants is indicated in brackets. The results from the present experiment are shown as mean values with 95% confidence intervals, and the results from Morioka and Griffin are median values.
Fig 10.
Comparison of the median threshold values from fingertip, forefoot and heel for notes between C1 and C6 from participants with normal hearing.
Table 3.
Mann-Whitney test results to compare thresholds on the middle fingertip and forefoot.
Table 4.
Independent t-test results to compare thresholds on the middle fingertip and heel.
Fig 11.
Vibrotactile thresholds on the fingertip from 32 participants with normal hearing for notes between C1 and C6 in terms of the frequency-weighted acceleration for comparison with values of 1m/s2 rms (equivalent to 120dB), 2.5m/s2 rms (equivalent to 128dB) and 5m/s2 rms (equivalent to 134dB).
Fig 12.
Vibrotactile thresholds on the forefoot (left-hand box in red) and heel (right-hand box in blue) from 20 participants with normal hearing for notes between C1 and C6 in terms of the frequency-weighted acceleration for comparison with values of 0.5m/s2 rms (equivalent to 114dB) and 1.15 m/s2 rms (equivalent to 121.2dB).
Fig 13.
Percentage of 14 participants with normal hearing responding positively that (A) transient vibration at the beginning or end of the note could be felt and (B) continuous vibration of the note could be felt via the middle fingertip.