How does Electric Acoustic Stimulation works (EAS)?
The cochlear implant component stimulates the part of your cochlea which is responsible for high-frequency sounds, while the ‘hearing aid part’ takes advantage of your natural residual hearing by turning up the volume on the low-frequency sounds. Together, it covers the full hearing range.
As with a cochlear implant, a small audio processor is worn behind your ear. It is connected with a cable to a transmitter coil, which sits on the outside of your head, over the implant. The coil stays in position with the help of magnets.
During surgery a thin, flexible electrode is inserted at the base of your cochlea in the inner ear. This part is responsible for hearing high-pitched sounds. The inner (apical) part of the cochlea, which is responsible for the low-pitched sounds, remains intact.
An ear mould, which directs sound into your ear canal, is connected to the audio processor.
How EAS works:
- A microphone inside the audio processor picks up sound. Both high and low frequency sounds are processed simultaneously.
- Low-frequency tones are amplified and sent through the ear mould into your ear canal.
- These low tones take the natural path to your cochlea. The hair cells in the apical region, which deals with low-frequency tones, receive the amplified sound signals.
- The audio processor digitally analyses and codes sound into a special pattern of coded electrical signals.
- These signals are sent to the coil and transmitted through your skin to the implant.
- The implant creates electrical pulses from the coded signals.
- These pulses are relayed via the electrode contacts to the different parts of the cochlea.
- The hearing nerve receives both acoustic and electric sound information at the same time and transfers it to the hearing part of your brain, where it is processed.