While most people listen to music, deaf people feel it. Specifically, they can feel the vibrations produced by the sound waves, which are distinctive enough for them to process and translate into their own version of music. Deaf people often hold balloons at concerts to feel the acoustic vibrations, perceiving the rhythm of the music through the vibrotactile sense in their fingertips.
People who are born deaf or become deaf early on in life naturally develop enhanced sensitivity to touch that manifests in different ways. The neuroplasticity of the brain helps to accommodate hearing loss by repurposing the auditory cortex to process other information in place of sound. Dr. Dean Shiabta’s research demonstrates this phenomenon. He used functional magnetic resonance imaging (fMRI) to scan the brains of 10 deaf volunteers and 11 normal-hearing volunteers while they felt intermittent vibrations on their hands. All of them showed activity in the part of the brain that usually processes vibrations, but the deaf students also showed activity in the auditory cortex.
Every deaf or hard-of-hearing person is different, so their auditory cortex and vibrotactile sense adapt uniquely, changing the way they experience vibrations and music. Despite variations, there is definitely an overlap between senses that allows deaf people to rely on their touch to experience the sounds around them. The sensory systems for hearing and touch have a lot of similarities. Both hearing and touch are facilitated by sensory nerves called mechanoreceptors that bend in response to pressure changes, resulting in a neural impulse sent to the brain. In both normal-hearing and deaf people, signals from vibrotactile stimuli are detected by the auditory cortex and can be confused by the brain when both modalities are processed together. As vibrational information has the same features as sound information, for deaf people, one form of waves essentially replaces another form to be processed by the auditory cortex.
Through vibrations, it is even possible for people to distinguish differences in timbre, a characteristic that contributes to the “color” of a sound. While the vibrotactile sense cannot detect high frequencies typically within the range of human hearing, it can detect low frequencies even when they are not audible. This is how both hearing and deaf people have been able to distinguish between different instruments, as well as dull or bright sounds, by touching a vibrating device.
Although the vibrotactile sense plays a large role in the musical experience of deaf people, there is still a lot to learn. A current study being conducted by Mario Prsa and his colleagues at the University of Fribourg in Switzerland looks to explore whether certain combinations of frequencies are more pleasing to experience through the vibrotactile sensory system than others. For example, the group is exploring if there is a possibility of having harmonious vibrations, a vibrotactile octave, or even dissonance that would be equivalent to sounds. Prsa’s recent experiment involved observing how easily both deaf and normal-hearing participants could identify simple melodies, such as “Happy Birthday,” through their vibrotactile sense. Converting audio into vibrations is a flawed process that inevitably produces some alterations of the notes, and Prsa wants to determine whether these changes would influence the participants’ ability to recognize the tune. The results of the study are still in progress, but it opens up a new realm of sensory processing and communication.
Though some aspects may be fundamentally different, with vibrotactile sense, deaf people can enjoy music and even become artists and performers. Exposing deaf children to music would likely help develop their brains to process that information early on and encourage them to explore music. Either way, it seems that music remains universal in its ability to be heard.
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