A DIY Audio Induction Loop for the Hard of Hearing(spectrum.ieee.org)
spectrum.ieee.org
A DIY Audio Induction Loop for the Hard of Hearing
https://spectrum.ieee.org/geek-life/hands-on/a-diy-audio-induction-loop-for-the-hard-of-hearing
6 comments
You will almost certainly need a neural accelerator for this, neural networks are currently the only known effective solution for cocktail party problems.
How did the world arrive to this, that we think that NNs solve everything? Beamforming requires zero NNs and works wonderfully (it is all math).
Induction loop disadvantages:
* Poor frequency response
* Only one channel
* They pick up mains 50/60Hz hum and other disturbances from power electronics
* works best when whole room is inside the wire loop, which isn't always possible. Portable "wireless" systems exist but have range at most few meters.
Advantages:
* technically very simple, reliable, not encumbered by patents
* most hearing aids have the receiver coil
...and this is why hearing aid manufacturers hate it. They prefer to sell proprietary devices. There were attempts to move to FM radio but as everyone does it differently and both transmitters and receivers are expensive, it isn't widely used. Newest hearing aids come with bluetooth, I've no idea whether it can be reliably used this way (simultaneous streaming to multiple bluetooth devices).
* Poor frequency response
* Only one channel
* They pick up mains 50/60Hz hum and other disturbances from power electronics
* works best when whole room is inside the wire loop, which isn't always possible. Portable "wireless" systems exist but have range at most few meters.
Advantages:
* technically very simple, reliable, not encumbered by patents
* most hearing aids have the receiver coil
...and this is why hearing aid manufacturers hate it. They prefer to sell proprietary devices. There were attempts to move to FM radio but as everyone does it differently and both transmitters and receivers are expensive, it isn't widely used. Newest hearing aids come with bluetooth, I've no idea whether it can be reliably used this way (simultaneous streaming to multiple bluetooth devices).
What I am about to write here is similar to third hand information.
I do not have first hand experience.
I looked into putting an audio loop into a venue. I asked an audiologist
about the prevalence of T-coil equipped hearing aids. She told me most
users prefer small and rechargeable. There is not much space in the unit
and rechargeable would likely be selected. So, the T-coil does not get
included. She thought T-coil units were common in Europe.
There are special amplifiers to drive the audio loop. The makers don't
tell us much about them. I think we would call those transconductance
amplifiers. Reading the subject article is encouraging. Perhaps we
will just try this after the virus is not such a threat.From first hand: No special transconductance(no idea what that means) amplifiers are necessary, just a wire loop that matches output impedance of usual audio amplifier, as described in the article. Hearing aid manufacturers and audiologists prefer their proprietary solutions so they push for removal of T-coil.
In my recent experience in churches in New Zealand, newer hearing aids either don't have T-coils, or the audiologist has to turn them on (and hasn't), or the hearing aid owner does but doesn't know how.
10-20 years ago everyone had a T-coil and loop systems were a great option. Now they're not.
10-20 years ago everyone had a T-coil and loop systems were a great option. Now they're not.
You will be a complete hero if you write up how to do "blind signal separation" with an economical microphone array. Such a device can be ceiling mounted and use copious heaps of mathematics to locate speaking people and isolate just their voice, attenuating other room noise and echos.
There are likely affordable hardware candidates, the $55 ESP32-Lyra-TD development board with 3 microphones or the MATRIX Voice with 8 at $75. Both have special hardware for the signal processing.