Here’s a quick and terrible pic of the prototype.
The box contains a Teensy 4, Teensy sound shield, two mic pre-amps and a 3 watt stereo amp. All are modular components wired together (no custom PC board required), cheap and readily available. At the moment power is external and fed into the Teensy USB jack. I want quick battery swapping to be possible, with battery modules snapping to the rear of the box magnetically. The headphone set is 3D printed and contains two transducers. The headset mimics the popular design of consumer bluetooth bone conduction headphones. It’s light, comfortable and the wiring is internal. I’ve worn it long enough to forget I have it on. The transducers are enclosed in soft TPU, while the rest is ABS. The temporary mic carrier is attached to the wearer’s shirt magnetically. I want the mics on the headset, but there are feedback issues to be worked out.
The amp can output 3 watts and the current transducers max out and begin to distort at 1 watt. This is more than enough for typical age related hearing loss. As the ear canal remains open, the transducers output the needed amplification based on audiogram results, plus additional amplification to bring results to normal or – if desired – above normal. This results in a more normal hearing experience and eliminates occlusion.
I have transducers on the way that can handle 3 watts. I have single sided deafness. With the current setup I can hear partially out of by deaf side and identify which side sounds are originating from – something I’ve not been able to do in decades. The new transducers should be able to restore normal level hearing on my deaf side (the hearing loss is conductive, but my cochlea seems to be more or less intact).
Balance (left/right) is currently adjustable via trimmer pots on the pre-amps, accessible from outside to box. - as this tends to be a one-time adjustment. All of the above will be or already is under revision. I want the box to have a self contained rechargeable battery, but there’s a fair amount of current draw involved in driving the transducers. I’m thinking the internal battery will minimize size, while snap on larger battery modules will override the internal (or perhaps charge it) and provide longer use.
Of course there’s no reason you couldn’t plug a standard set of earbuds into this thing and use a suitably smaller amp, but I’m a big fan of bone conduction for a lot of reasons.!
OK, here’s my dream. As the Tympan board is unavailable, some wonderful soul will port the Tympan library over to the Teensy sound shield. My programming skills are basic. Although I 've taken a stab at this the learning curve will be long and steep for me to do on my own. This entire project will be open-sourced once V1 is ready. My other dream is to encourage folks like me (retired) to build these and donate or sell at a minimal price to folks who cannot afford the other very pricey options.
