Development Of Tactile Auditory Substitution System Based On Gammatone Filter

According to the statistics of the World Health Organization, the number of deaf people all over the world is about420million. In China, there are about20.75million hearing impaired people, according to the latest census statistics. At present, Audio-phone and Cochlear Implant are the two most popular equipment using for helping deaf people with their hearing disability. However, neither of them can radically solve the problem. Therefore, it remains to be a difficult problem in China and even a worldwide problem. The United States professor Paul Bach-y-Rita put forward the sensory substitution theory in Nature in1969. The theory suggests that one sensory organ can be substituted by another one, which has opened up a new way for deaf people to regain their auditory information, with the propose, development and application of the theory in recent years.On the basis of the sensory substitution theory, this paper has designed and implemented the experiment of Tactical Auditory Substitution System(TASS), which mainly tries to stimulate the skin to get tactical sense by transforming the information fetched by the speech signal into electrode array. And the brain will integrate those information and get auditory information with additional training and learning. TASS is formed by the speech collecting module, the speech features extracting module, the electrode driving module and the electric tactical array module. We obtain the features of the speech signal by using the16channel Gammatone filters. Every channel will correspond to one electrode to produce electro-tactile stimulation. It can produce216different signals that can be expressed65536characters which can cover the Chinese characters we usually use. In addition, the Gammatone filter can simulate cochlear hearing filtering characteristics well by using a few parameters. The electrode driving module adopts multiplex and timesharing technology to supply the high voltage pulse stimulation for the electrode array so that we just need one constant current high voltage power supply, it greatly simplifies the circuit design. And we adopt the photoelectric isolation circuit to protect the front-end weak current control system.The result of the experiment shows that the simulation threshold of the finger to the electric pulse is about130V, and different simulation pulse width will result in different simulation thresholds and effects. When the pulse width is50us, the finger will get comfortable electric tactical sense with the voltage around170V. It has been proved that with the help of TASS, people will obtain some simple voice information after the learning and training of a certain period of time.