|
|
|
|
Cochlear implantsCochlear implants (note that the noun is "cochlea" and the adjective is "cochlear") work rather differently from hearing aids, although in some ways they do much the same thing. Hearing aids just increase the sound, so that the ear can do the best it can with louder sound. Cochlear implants actually stimulate the inner ear electrically, making the signals that hair cells would make if they could. The external microphone is the same as on a hearing aid, but instead of having a receiver to turn the electrical signals back into sound, electrodes carry the signal into the ear. The electrodes may stop outside the round window, or may actually penetrate the ear. There is much foolish talk of bionic ears in the press. Cochlear implants are not any more like corrective glasses than hearing aids are. The hearing restored is very limited. The maximum number of frequencies that can be simulated is twenty-two at the moment. However, there are several things it can do: a) it permits the perception of some sound. This is of some practical value, but also of psychological value. Deafened people usually long to hear just something, because they miss their hearing so much. It can also provide relief from tinnitus, because there is something else to listen to. b) it can work quite well in conjunction with lip-reading. However, you have to know what things should sound like, so this is only really much use for post-lingually deafened people. c) some people can distinguish between male and female voices (although this seems are rather minor ability, for the fuss that is made of it) After operations, many adults can follow speech without lip-reading. After nine months of training with an implant, 80% of adults can follow some speech without lip-reading (I have been unable to find out what "some" means here). Twenty percent of adults cannot distinguish any speech at all after an implant, and some score 100% in these tests. Most people can hear and identify 50% of the environmental sounds in a test, although some can identify very few. (Again, the cynic in me would like to know which 50% are heard by most people. Jet aeroplanes, car alarms and police sirens just might score higher than mewing kittens and hissing gas....). Implantees skills at identifying environmental sounds, and their speech skills are not correlated, and teams find it very hard to predict who will do well at what, before the implant. "All implantees report increased quality of life". (That sounds good. All? Did the 14 month-old baby report this, I wonder?). We will consider the ethics of implants, and their implications for the big issues of hearingness and deafness in the next session. For now, however, we will simply consider what happens when an implant is made. |
|
The course is copyright
Back to
Social Issues Homepage |
