Saturday, February 28, 2009

Two plus two equals ... five?

The last few days, the cochlear implant has come to seem more natural and less, well, freaky. It's less distracting; instead of thinking about it constantly, I'm simply using it. I even forgot to plug in its charger one night. Fortunately, I had three more cells on standby.

Bananas
I'm also starting to hear more low frequencies. Not very low frequencies but the ones centred around, say, 500Hz which is where many of the speech sounds occur. I'm still having trouble distinguishing between m, b, v but I'm getting there. No trouble at all with the sounds above 1,000Hz which is where I was having difficulty before the CI operation. Here's a diagram called the "speech banana" showing where the main speech sounds are centred and at approximately the volume level in normal speech:

Speech Banana (borrowed from http://quietsong.net)

If you read the previous post, I mentioned that I was able to understand an audio book recording by listening to it with both ears via my FM transmitter. Now the odd thing is this:
  • if I listen to it with just my left ear (hearing aid), I can't understand it at all. It sounds like the teacher in the Charlie Brown cartoons (blah blah blah-blah blah);
  • if I listen to it with just my right ear (CI), I can understand it quite well but something is missing;
  • but if I listen to it with both ears, I can understand it almost perfectly!
This is strange. Somehow, the brain picks up bits from both ears, adds them together and ends up with a bit more than the sum of the parts. Thus 2+2 =5!

Telephone
For the past year, I've pretty much stopped using the telephone except for brief conversations with people I know well. For example, asking Barb what things I should pick up from No Frills on the way home from work. Sometimes, I'd get it wrong and we'd end up with, say, two jars of marmalade but no margarine!

Early phone use

Since getting the CI, I haven't been too optimistic about the telephone. At first, I was unable to even hear the dial tone using the CI. But now, the dial tone is starting to come through. Not loudly but it is there. I played around a bit with various configurations of headphones and listened to a few recorded phone messages. I found I could understand what was being said even if it sounded a bit unnatural.

I took the plunge and called Clare who is usually happy to have a chat on the phone at the end of the day! We talked for about 15 minutes and I could understand most of what she said. Not 100% but enough to follow the conversation and fill in some of the gaps from the context. So that's encouraging. I'll have to keep working at this and try some more formal exercises with her and some other willing victims - lists of words and phrases from the workbook, etc.

The telephone obviously conveys a lot less sound information than other sources such as FM radio or cassette tapes. From what I've read, it's limited to frequencies between about 300Hz and 3,000Hz. Looking at the speech banana above, that band encompasses most of the speech sounds but j, f, s, th and ch fall outside its range. Is it possible to really hear the word this on the phone? Does it sound any different from fith or do we just know that fith isn't a word in English?

5 comments:

  1. The picture made me smile.... reminds me so much of Oliver when he was little.
    How about speaker phone - is that any easier to understand? Monica

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  2. you should get barb to write a post here talking about how shes adjusting to you and your new hearing experiences

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  3. Thats good news Steve, very encouraging that the phone is going to happen for you.

    Also, very interesting info about the dynamic range of a phone. I suppose even if you had a fancy phone it would still depend on the quality of the phone that the other person was using.

    Anyway great news, you are going great guns with the CI

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  4. The limiting factor is supposed to be the phone lines themselves. They are 'artificially' constrained to these frequencies for various reasons, mostly historical. The lines are actually capable of carrying a much wider range of frequencies and that's what happens with Bell's ADSL home internet service.

    I should try a VOIP phone (Skype or similar) and see it that's more clear. Ditto cellphones - in principle, they should carry more sound info.

    Steve

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  5. Hi Steve,
    Thanks for commenting on my blog post. I'm adding you to my regular reads! You seem to be the elusive hearing aid and CI wearer that I've been hunting for. That's my plan post CI is to wear both. I may even get an in the ear aid to help with the low frequencies in my implanted ear. My surgeon's goal is hearing preservation using a special electrode that Med-El has developed. No guarantees, but he thinks it is worth a try for me. I need to blog about that still.

    I had no idea about the phone losing frequencies but it makes total sense and it will help when explaining why making things louder doesn't always help.

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