The wide range of hearing implants
Hearing implants were originally designed solely for the understanding of speech, which today works almost flawlessly. Now it is music’s turn to come under the spotlight. Hearing music properly requires sophisticated technology, because of the abundance of subtle details contained in it, as compared with speech. MED-EL produces implant systems that supply the best-possible perception of both speech and music – such as the classic cochlear implant (CI) and the Electric Acoustic Stimulation (EAS) system.
MED-EL's Product Management explains: “The cochlear implant substitutes for natural hearing in people with severe or profound hearing loss, once a hearing aid cannot improve hearing anymore.” The Electric Acoustic Stimulation (EAS) combines both an implant and a hearing aid.
Cochlear Implant: Electric impulses
The cochlear implant (CI) consists of two parts – the actual implant (which is placed under the skin behind the ear) and the external removable processor with its software and microphone. The implant has a flexible electrode array, which looks like a very thin cable. It is fed deep into the cochlea inside the inner ear, where it does the work of inactive auditory cells. The external processor converts incoming sound into digital signals and sends them to the implant. From here, the signals are sent via the electrodes inside the cochlea, to the acoustic nerve. The brain receives the sound information and the implant user is able to hear.
EAS: Two in one
MED-EL's Product Management explains: “The EAS system was developed especially for people with partial hearing loss.” EAS (like the CI) also consists of an external processor and an implant placed under the skin. It differs from the cochlear implant in the way it processes sound. Where a certain amount of natural hearing remains, the sound is simply amplified. Where sounds are inaudible for that individual, the implant steps in. The Product Management at MED-EL says: “This combination of implant and hearing aid makes it possible for EAS users to hear sounds that appear very close to natural, because use is made of their partial hearing.”
Enjoying music with an implant
An implant needs to be able to do four things to convey music well:
- Low frequencies are only reproduced well when the electrode array is long enough to employ the whole cochlea. Because low frequencies support the detailed structure of sound, speech and music are perceived more richly.
- It is vital that the implant sends the incoming sound information to the specific location inside the cochlea where this particular frequency is processed. Only then is it possible to distinguish between pitches of notes.
- The implant should also stimulate the nerves corresponding with the correct frequency. When a sound with a frequency of 100 Hertz comes in, the electrode pulsates exactly 100 times per second, in the area naturally corresponding to this specific frequency. This allows the complex and detailed structure of sound to be transmitted – a prerequisite for sound that seems natural.
- Any remaining natural hearing should be preserved, because it contributes to a richer sound. It can be protected by using soft electrode arrays and gentle surgical techniques. MED-EL's Product Management: “Implants by MED-EL fulfil all these requirements, so that not only does speech sound almost natural, but music does too.”