Specifically I'm curious if in below drawing does sound somehow travel down the long S shaped tube (that connects the behind the ear section to the in the ear section) or is it really just one
wire in there that does the actual transmitting from the BTE part to the in ear part ?
How do hearing aids work? | Oticon
Or if wire, maybe more than one wire ? If so, seems like they would have to be some seriously tiny wires !
And is the BTE part really a sort of microphone and the in ear part is a tiny "speaker" ?
With a behind-the-ear (or an eyeglass-mount) the part in the ear is an "earmold".
Passive. A resilient "plug" to seal the ear channel so the boosted sound does not escape and feed back to the microphone, a mere inch or so away. The actual reproducer is closer-yet.
Inside the BTE case, opposite end from the microphone.
Resilient mounts that work, and last a year or more, are ..." challenging" at the dB of gain involved.
So are the wires to each that are meant to not carry sound. Even fifty years back, we were already "weaving" them in de-coupled ladder-loops from 64 wire gauge.
The tube carries sound over...the air inside it.
"Fast forward" nearly fifty years and a better solution as to de-coupling feedback IS to use the now-tinier (for their power output) reproducer at greater distance, flexible human flesh the isolator. Some reproducers ARE now down INSIDE the ear-canal. for these, the flexible tube protects very tiny wires.
These run off a "baby" aspirin-sized battery, so the power is relative. Very low in absolute terms. DEAFEN a person with normal hearing. Radioear was hitting 134 dB over fifty years ago, Model 990 BTE.
BTW ..Oticon (Danmark) is one of "substantially less than 100%" of hearing aid suppliers with genuine credibility. Or at least they WERE.
Bill
(formerly.. National Service Manager, Radioear Division, Esterline Medical, dawn of the 1970's).