Hi Ralph,

My 87 year old mother has two digital hearing aids, both of which fit in her ear canal (not BTE). The cheap one is $1500, and the expensive one is over $5000.

I remember years ago seeing people wear hearing aids that they clipped to their belt or carried in their shirt pocket (with a wire going up to their ear). The difference between those and your's and my mom's is just as someone mentioned, scaling down to chip-scale packaging. In the case of in the canal aids, the chip and printed wiring can be bonded directly to the molded plastic housing unit.

But the issue of performance is independent of package scale. I believe it was Steve who mentioned the inverse of your hearing graph. That is essentially the breakthrough of the digital hearing aid. You need to understand that neither hearing nor hearing loss is linear. Normal hearing is logrithmic as a function of frequency. In other words, a sound wave of a given dB level at 5000 Hz will sound softer than a sound wave at the same dB level at 1000 Hz. Also, your hearing loss will depend upon the frequency of the sound. In general, you lose higher frequency hearing as you age, but your actual loss will be greater at some frequencies than at others. A digital hearing aid can be calibrated to amplify sounds more at the frequencies where your hearing loss is greatest, less at those frequencies where you hearing loss is least pronounced, and over the whole spectrum to model the natural logrithymic response of normal hearing. And that is regardless of package scale.

Now for my own theory about the cost. I believe that two things are going to bring down the cost of digital hearing aids in the future. And you're demonstrating the first of them here and now. If one is willing to accept the cigarette-pack style of hearing aid, programming a DSP to compensate for your hearing loss is just a matter of plugging the right coefficients into the right equation. Really, it's just a matter of learning the math, and there are people who will do just that. The electronics are no more difficult than any other non-linear amplifier. I dare say that if you can design and build an MP3 player, you can build a digital hearing aid.

But the most signinficant thing that will bring down the cost of hearing aids in general is that the first generation of rock-concert-going, car-stereo-blasting, louder-is-better rock-and-roll hippies is getting old enough to need them now. There are literally tens of millions of middle-aged people, right now, who are only a few short years away from regretting all of that unbearably loud music.