Researchers have been studying effects of tactile sound on people with hearing loss (PWHL) for decades. Most of this research emphasizes speech comprehension for practical reasons (day to day life) and the application of lower frequencies.
Hearing involves sound moving as vibrations through the eardrum, outer ear, to the middle ear and on to the inner ear, or cochlea, with its 16,000 hair cells, which process sounds. Hearing loss is often related to damaged hair cells.
Bone conduction is a vibration of the skull that creates an audio impact that gets around the outer and middle ears and affects the cochlea directly.
Tactile sound affects perception of sound through touch, apparently affecting a portion of the brain dedicated to touch, not audio input, but combining with audio input on PWHL to compensate for some of the frequencies they cannot perceive through sound.
At MIT a recent experiment using three fingers with a high frequency and low frequency inputs showed lip-reading comprehension improvement. After speaking to the creator of their device, I learned that they focus on frequencies under 1000Hz because vibrations become too challenging to interpret at higher frequencies.
Music has a broader range of frequencies than speech, especially electronic music such as rock. People with hearing loss experience difficulties interpreting music because of limitations with higher frequencies and deficits with perception of melody, of timbre, which helps discriminate instruments and voice, and of pitch, which helps discriminate among sequences and patterns of the musical notes.
Cochlear implants have eight to twenty four channels and while unable to replicate normal-range hearing, they improve speech perception for PWHL. They don’t help as much with music because the frequencies tend to be different than for speech. The PWHL deficits in defining timbre and pitch are not improved sufficiently with cochlear implants.
Hearing aids tend to be used by people with moderate to severe hearing loss who do not meet criteria or have the financial ability to get cochlear implant surgery. Hearing aids, although boosting volume, do not offer frequency discrimination of cochlear implants.
People with normal-range hearing do not benefit from tactile sound with speech or music interpretation because the brain eliminates tactile frequency input that matches audio frequency input. People with hearing loss may benefit from tactile sound because they may not hear certain frequencies which tactile sound is providing for them.
Tactile senses begin to diminish with age, especially as people enter their 50s.
This project asks "what haven’t researchers done?"
· It emphasizes music, not speech.
· It introduces a broader range of frequencies than most previous tactile sound research, as high as 10,000 Hz.
· It breaks down the sound spectrum into frequency ranges.
· It explores sensitivity to tactile sound of various parts of the body.
· It seeks optimal combination of these body parts for music perception.
· It emphasizes cochlear implant users as primary beneficiaries of this technology.
· It suggests that age affects the results.