Science Questions

I’m suffering from Meniere’s disease , and so I’m 85% deaf in my right ear. I do have a hearing aid provided by the National Health Service. I have pretty good hearing in my left ear. I’ve been wearing this hearing aid for 18 months, but what I’ve found out through trial and error is that when I block off my good ear I can hear nothing. I’ve had the hearing aid tested, and it works. Dave, Bradwell

What could be happening is the fact that you are blocking the sound that you can hear when you put your finger in your good ear suggests that your good ear is working perfectly and it’s working perfectly for the normal way in which sounds are conducted into the ears: Vibrations in the air go onto your ear drum, make your ear drum move and that’s turned into electrical signals in your inner ear that your brain can understand.

Your hearing aid on the other side ought to be just working by amplifying the sound that you’re hearing and making bigger movements in the ear on that side so that the signals that go into the inner ear and get converted into electrical signals. Even though the ear doesn’t work as well, the signals from the hearing aid are so much louder it allows what hearing is there to work a bit better.  
The fact that your hearing is lost when you put your finger into the other ear and block off the conduction of the sound suggests that the hearing aid is just not succeeding on that side in managing to make what’s left of your hearing there actually register anything that you can physically hear.  I think that’s the problem. I don’t think the hearing aid’s faulty necessarily. If it’s been checked, it’s been checked. I think it’s possibly that your ear’s not working as well as it could.

There are various therapies that are in the pipeline now to help people who’ve lost the ability of the inner ear to detect sound and turn it into electrical signals.  What scientists are now exploring is the idea of stimulating the nerves that connect the inner ear directly to the brain and you can get quite good discrimination of sounds that way.  A bit like a cochlear implant but a bit more advanced.

January 2008