Mapping No. 2

I had my 2nd mapping two days ago, which was one week after activation. I had been running all three programs at a volume level at the 3 o'clock position (12 o'clock is the normal setting), which means I was ready for another level boost. I also reported that everything was sounding deeper in pitch than normal. To combat that we boosted the level of the high frequencies a bit and changed from an Extended Lows setting to Standard. We changed the additional magnet from strong to weak since it was adhering a little too snuggly and could begin to irritate the skin over my implant. Lastly, we changed my program #3 100% T-mic from HiRes-P to HiRes-S. My audiologist had planned to run the NRI (Neural Response Imaging), but decided to put it off until my next mapping in early January.

NRI is an automated testing function that uses the bi-directional capability of the implant to read actual nerve pulses using electrodes adjacent to a fired electrode. Not only does the processor use AM radio waves to power and signal the implant, the implant also communicates back to the processor on an FM band. I think a new map can be created using the NRI results, but I'm not sure about that -- I'll follow-up later when I find out.

The new map has helped quite a bit. Voices sound more natural and everything is crisper. I went a little overboard on the levels so I am currently running at a volume level of 10 o'clock to quiet things down. But that's good for now and leaves me more room to boost it between now and my next mapping if necessary.

I still perceive sounds as deeper in pitch. Adjusting the levels of the bands helped, but that's not the same as shifting pitch. For example, you can adjust the emphasis of particular frequencies with a graphic equalizer, but a 1000 Hz tone will still be a 1000 Hz tone -- just softer or louder. There doesn't appear to be any capability in the processor software to actually alter which center frequencies are mapped to which electrode. Maybe that's something my brain will compensate for over time. To get a reference for where I am at now, I fired up my audio editing software which has the capability to generate sine wave tones. My right (unimplanted) ear has a fairly flat 75 dB loss, so I can still hear a broad range of tones if loud enough. My test involved playing tones to my implanted ear, memorizing the pitch, then playing tones to my other ear and adjusting the frequency until I found a match. Sure enough, I am perceiving sound in my implanted ear about 1/2 octave below the source. For example, a 4 kHz tone played to my implant sounds like a 3 kHz tone to my other ear. I measured about a dozen tones from 50 Hz to 8 kHz. All were shifted down about the same percentage. Also found that the low cutoff is below 50 Hz, and that source frequencies between 50 and 80 Hz cause a buzzy low pitch. At about 90 Hz the buzzing stops. Between 90 and 200 Hz it's a little fuzzy. The first pure tone is 220 Hz. I noticed that some tones in the 50 to 300 Hz range have a phasing, undulating characteristic which might be the cause of the "wooshiness" I get with traffic noise and other continuous sounds. At the top end, the high cutoff is above 8 kHz. Source tones from 6 kHz to 8 kHz sound the same, probably mapping to the same last (outermost) electrode. Due to the shifting down of pitch, the highest actual frequency I hear at this time is about 4500 Hz. I am very interested to see if this changes over time.

The pitch thing is interesting to me. It seems that most people report the opposite -- that everything sounds higher, tinnier. It makes me wonder if it has to do with the position of the electrode array. I don't know for sure, but I would think there is some kind of reference point for the surgeon to know how deep to place the array. But given differences in physiology from one person to the next it seems like that would only be an approximation. A millimeter or two one way or another from the actual "true" match of a place-code frequency would cause the sound to be perceived higher or lower -- at least initially. In my imagination I see mine being just a tad deep, which I believe would map frequencies lower. I am just conjecturing here because I've never run across the issue in my readings.

One week into this I am extremely happy where I am at. I had a 45 minute conversation with my sister on the phone this morning using my CI - my first! I understood almost everything she said. Bit by bit it's getting better and better. Listening to NPR radio in my car I can understand everything when it is one of the female reporters. It's more iffy with the men -- it depends on their voice. If their voice is deep and less crisp I struggle. I still take my processor off for an hour or two in the middle of the day. The top of my ear where the ear hook hangs is still tender, but getting more tolerant. By the evening, a little before bedtime, I am ready for an auditory break. It's a lot of work listening at this stage. It's nice to take it off, put my hearing aid in my other ear and go back to a quieter world. By morning I'm ready for the full sound load again!

This is probably my last post before Christmas. We'll be leaving in couple of days -- off to see the families for a few days. It should be an especially Merry Christmas this year! I'm looking forward to being able to catch dinner table conversation again!

Happy holidays to you all!