[AudioI] Hearing aids project

[Matt Flax]

Hi there,

Great to hear from you on this topic.

There is an open master hearing aid project which you may be interested 
in, have a look here :

http://www.openmha.org/userproject/2017/12/21/openMHA-on-raspberry-pi.html

Interestingly they seem to be using an external preamplifier for the ear 
receiver shells. It is possible you could get the headphone output from 
the soundcard to generate enough power for hearing aid shells, but not 
sure - I guess it depends on the gain prescription and the ear receiver 
impedance plus required power output from the receivers.

 From what I see they describe a way to get the NAL-NL2 prescription 
running on the device too, which is pretty much still state of the art 
in hearing aid prescription.

You can probably look at the hardware they use and extrapolate out from 
there.

Regarding the phono preamplifier, I am not sure that would work for a 
hearing aid because the input frequency response matches the RIAA 
transfer function. That frequency response would alter a hearing aid 
prescription for gains too much and not be useful.

What do you make of the openMHA project ? Do you think it would be 
useful for you ?

Regarding hardware options,

The ultra 2 has 2 electret microphone inputs which is good, you could 
alter the output preamplifier to suit your power requirements or in an 
even more simple situation you could use the existing preamplifier 
output to a second amplifier, like they do with the openMHA project. 
This second amplifier would be responsible for generating enough 
acoustic power for your hearing aid receivers.

An alternative is to use the Pro. sound card and create a new 
preamplifier PCB which has the capability to power and receive signals 
from electret microphones and do a significant power output for the ear 
receivers. I think the Pro souncard can drive a maximum of around 2w 
from its +-12V power rails. How many watts of power are consumed in 
profound gain prescribed hearing aids ?

Matt


On 5/3/22 13:32, Emmanuel Perez via People wrote:
> Hello AI community 🙂
>
> I'm hard of hearing and I wanna make hearing aids ( very loud because 
> I've -80 dB hearing loss each ear ).
>
> It seems it's possible to build that with a Raspberry.
>
> I don't have a lot of knowledge about electronics, so may someone help 
> me to choose the right components in order to build a hearing aid please ?
>
> Pi 3 + ultarsound card seem accurate. Do I need a DAC , DCA and DSP ?
> The preamp provided into the ultra 2 sound card works for output only?
> Do I need a phono amp ?
> Can I add more components ?
> I'm quite confused...
>
> I would like a device which can :
> - capture, DSP , reproduce in less than 5 ms
> - able to work on ultra HD sound
> - allow to equalize the signal with parametric equalizer and another 
> effects if needed
> - One way each ear ( different hearing profile between right and left )
>
> 2 Microphones will be miniatures.
> IEMs will be low impedance ( nearly 16 ohms ).
> The volume I need is very loud, for example I listen to music with 
> FiiO Q3 DAC ( which drives 300 ohms headphones ) with 16 ohms IEMs and 
> I turn the volume to 80%.
>
> A big thank in advance for your enlightenments 🙂
>
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