Acoustical feedback when the mic can hear the earphone and the sound goes around and around. The gain at high frequencies of my hearing aids is 40dB (100 times) or more so the standard anti-feedback system in the hearing aids was usually used to eliminate the feedback (high frequency squealing if an earplug becomes loose or if a sound reflecting window or something is close to a hearing aid). The anti-feedback system causes high sound frequencies to flutter that makes music or the beeps from my test equipment sound bad. Some cheap anti-feedback systems simply cut all high frequencies that is a very poor way to do it.
My hearing aids are Starkey Destiny 400 BTE (Behind The Ear) and implement a anti-feedback algorithm where the output is frequency shifted (up or down, don't remember which), so that each time it re-enters, it's continually shifted until nulled. It's quite effective, as one of the more embarrassing things that can happen is having your aids hanging off your ear or in your pocket while still turned on and people looking at you like WTH is going on with you?
Not anymore with these. These are the first digital ones I stuck with, as I hadn't had good experiences with digital. Really prefer the old analog.
I'm 52 and have worn aids all my life, as I was born with profound hearing loss from birth, like my twin brother. My frequency loss starts at 500Hz, yes, really. And, is off the chart at 2KHz (below -110db), so no amount of amplification is going to help there.
We always wear BTE, as they are the only types that usually have the power needed with the large enough battery to last.
Funny story: Hearing loss got me started in electronics and sound. I started tinkering with amplifiers as a kid and entered a regional Science Fair at age 13 and won first place in Physics with a telephone amplifier I hacked together from a radio and a magnetic pickup coil. I still had a lot to learn, as I used a linear pot for the volume control and demonstrated that there was still plenty of volume when turned all the way down. LOL.
I'm a digital guy through and through, however, building digital circuits and programming MCUs and such.
Anyhow, I'm enjoying this thread and applaud any efforts in this field. As much as I enjoy technology and having the latest of the greatest, my experience with aids has exposed many problems in this field. The aids offer so many features and options that my main aid seller, as well as several other "professionals" that offered to fine tune these aids and fix my issues, were baffled for hours trying to figure out what to do and what to change on the software connected to the aids. This took many visits and I was left giving up on having some issues ever resolved.
One of the issues was the hearing aid confusing music as noise and always tuning it out. This was a problem I had many years prior when I was testing out a digital aid. I worked in a printing plant and needed to hear the equipment running, including pressurized air or vacuum, and drive motors. Having the aids constantly trying to tune out the sounds was extremely annoying, so I returned them. I needed to hear the noise! This was finally fixed, however, by finding a way to turn it OFF. Probably a disappointment to the team of DSP programmers who spend weeks/months making this "work."
The other issue was just simply having the telephone pickup work. This was supposed to work automatically or you could switch it manually. But, no. Unlike any hearing aid in the past, I cannot use these on any hearing-aid compatible phone. What's the point offering all these bells and whistles if no one knows how to make it all work? Inexcusable for a $3000/aid system.
Now, I like the idea of BT enabled aids and other features, but when it really comes down to it, all we really need is a good, low-power, sensitive mic, amplifier, and transducer, coupled with a 2 or 3-band filter. Everything else is gravy.
MAJ