What Percentage?

I’ve always been more of a words person. Math wasn’t my thing. In high school I blew through chemistry, geometry, geotrig, biochemistry, and chemistry. But math, not so much. If you’re living with hearing loss, percentages are a problem. Well, they’re not a problem, but they come up a lot. A lot a lot.

When people find out you’re hearing impaired, they immediately 1) apologize, and then 2) ask what percentage of hearing you have. The problem is, no one really deals in percentages.

Percentages are used in audiology, but not to measure how much you can hear. Percentages are generally used to express comprehension. That’s because you can hear something without knowing what it is (just think of ANY time you’ve heard a bump in the night or some other sound you had to stop and think about – now do that with every word you hear). So, you may hear 100% but only comprehend or understand a fraction of that.

Bear with me as we do a very quick tech update: Sound is just waves of air, and sound is measured by sound pressure. Volume (amplitude) is measured by decibels. Silence would be 0 decibels, or 0db. A loud sound would be over 100db. Caroline’s hearing loss is 70db. Look at this chart:

If Caroline is sitting in a quiet room WITHOUT hearing aids, she can hear everything BELOW the red line. We can even put a finer point on it: in a quiet room without her hearing aids, everything above the red line is silence. To recap: with hearing aids Caroline can hear almost everything, but understands about 75% of it. Without hearing aids, she’s deaf; it’s just a lot of work to hear or understand anything.

The solution to the problem is to pump up the volume. But at 70db of loss, there’s simply a limit to how much volume you can push into the ear: prolonged exposure to loud noise causes hearing damage. It’s an irony of hearing aids: they help, and over time they do damage. It’s a trade-off that every hearing impaired person understands and accepts. Not happily, but they accept it.

Caroline is at a stage where turning it up to eleven isn’t enough. She’s reached the end of conventional hearing aids.

Caroline’s middle ear (the ear drum and bones) work fine. The problem is that the 30,000 hairs in her ear have malfunctioned in some way. Instead of using a mechanical process (more volume/sound pressure)

The alternative for Caroline’s kind of hearing loss is using direct stimulation of the hearing cells in the inner ear (cochlea). Literally, a cochlear implant is an electrode which stimulates the hearing organ directly. Volume is based on the strength of the electrical signal.

In all of human history – thousands of years – we’ve been able to replace the inner ear for just 35 years.

Talk about good timing.