Improving Tactile Codes for Increased Speech Communication Rates in a Phonemic-Based Tactile Display

Previous research has shown evidence of tactile speech acquisition of up to 500 English words presented as tactile phonemic patterns using a 4-by-6 tactor array worn on the forearm. This article describes modifications to some of the tactile codes encoding the 39 English phonemes, and ten additional codes as abbreviated patterns for the ten most frequent phoneme pairs in spoken English. The re-design aimed to reduce the duration of phonemes and phoneme pairs that occur most frequently, with the goal to increase tactile speech transmission rates. Code identification experiments were conducted with ten participants over three weeks using a video game. The average identification rate of the 49 modified codes (39 phonemes plus 10 phoneme pairs) was 83.3% with an average learning time of 6.2 hours. The average identification rate of the 49 codes in a retention test with 7 of the 10 participants after more than 90 days of no exposure to the tactile codes was 75.7%. An analysis using ideal transmission rates showed a 58% increase in transmission rate with the modified tactile codes as compared to the original codes, demonstrating that the improved codes can speed up tactile speech communication.