Ok, so I've been doing some research trying to find something like an audio MCU\DSP with a built in audio filter; for instance, something that I could manipulate audio with to get a final filtered output. So if I put audio through it, maybe the output will only be 5khz+, and 5khz- will be completely cut.

Basically, I'm going deaf in one ear (I had brain surgery to remove a tumor like 8 years ago, and the nerve is slowly dying continually taking more and more high tones with it), and insurance won't pay for a hearing aid to help boost the frequencies I'm losing back up to more normal levels. This all sucks too because I'm a musician with a very huge background in audio engineering.

Bottom line: I'm going to build my own hearing aid that does exactly what I need and want it to do. But I'm a little lost where to start and what IC's to get that will allow me to manipulate and filter the audio easily. I found one through TI, but I'm still looking into it. Plus size; it needs to be tiny. Thoughts?

  • \$\begingroup\$ Most small microcontrollers will be able to do this filtering in software, although you could do it with just an amplifier and appropriate analog filters? \$\endgroup\$
    – pjc50
    Feb 27, 2015 at 23:01
  • \$\begingroup\$ I'd prefer to do it in software so I can change the filter to exactly match my hearing tests, and then tweak it from there\if it worsens, you know? The way I see it, it would go like: microphone > amplifier > MCU > output speaker, or microphone > MCU > amplifier> output speaker. So then I can use an AVR to do this? No special MCU needed? What about an amplifier; do you have a recommendation? \$\endgroup\$ Feb 27, 2015 at 23:50
  • \$\begingroup\$ Look at sigmadsp from analog mic in headphone out graphically design filters, change in real time etc. very cool for audio could probably design what you want in a day with an eval board. \$\endgroup\$ Feb 28, 2015 at 0:04
  • \$\begingroup\$ Oh those are beautiful little machines. But the only thing I'd be worried about is size; they're a 10mmx10mm package. \$\endgroup\$ Feb 28, 2015 at 0:25

1 Answer 1


For doing audio filtering, I recommend using a DSP (Digital Signal Processor). I wear hearing aids and know there is a DSP hidden somewhere inside the case. Mine are the kind that have a minimal speaker unit that fits in the ear, and the electronics sits on the top of my ear. After an audiologist performs a hearing test, the results are uploaded to my hearing aids where it programs a graphic equalizer.

Microchip makes a line of chips that combine a DSP with one of their PIC24 microcontrollers. For example, the dsPIC33FJ128GP802 is available in a 6mm x 6mm QFN-S package. It is also available in a 5 mm x 5 mm VTLA package, but Digi-Key doesn't appear to stock it. You can also get it in a DIP package, which would be useful for prototyping.

Microchip has two libraries available for designing filters, a Digital Filter Design for $250, and a Digital Filter Design Lite for $30.

  • \$\begingroup\$ Yes! Perfect! I know AVR's and PIC's quite well, so this is gold. I also know how the audiologist tweaks the hearing aid itself with the results from the hearing test, and I wanted a similar design as well. I was going to write a .NET program that I can stick my results into and it will generate a hex file with the appropriate changes, and then I just upload it to the MCU in the aid. That was the concept I was hoping for which gives me simple tweakability and concept. The next hurdle is the non-MCU components... \$\endgroup\$ Feb 28, 2015 at 2:45
  • \$\begingroup\$ I found these microphones (st.com/web/en/catalog/sense_power/FM125/SC1564?sc=memsmics) that I feel would work well for this project. They are digital, so they offer a PDM interface (I'm still working that one out). I'm assuming an amplifier isn't needed \$\endgroup\$ Feb 28, 2015 at 2:46
  • \$\begingroup\$ @DominicLuciano Before you go off and spend a lot of time designing your own, I did want to make you aware of these digital hearing aids for $600 (for 2) -- about 15% of what brand-name digital hearing aids cost. The main drawback is they have only three equalizer profiles. They have a 100% guarantee, maybe you should try them first. With PCBs, assembly, and a 3D printed case, you're going to spend that much making your own. \$\endgroup\$
    – tcrosley
    Feb 28, 2015 at 4:15
  • \$\begingroup\$ I do understand completely what you are saying because I know how expensive and time consuming developing products can be (I've been inventing since I was a kid). Since I have the necessary skills as well as friends that fabricate anything you can think of for me for cheap, I can usually get off with a quality finished product on the bottom dollar. I will, however, check out that link for sure! But since I have a very specific need and hearing loss, it limits what I can buy off the shelf because I need total control for best results. \$\endgroup\$ Feb 28, 2015 at 5:11
  • \$\begingroup\$ I would love to hear more on your thoughts though! I'm out of my depth just a little on this one because DSP and audio electronics aren't my normal deals (robotics and MCU's are my electrical engineering strong points). So anything you might like to add, products, thoughts, anything, it would be very, very welcomed and helpful! PS: I ordered a few variants\samples of the dsPIC33 lines in a DIP for prototyping. Great call on those chips! \$\endgroup\$ Feb 28, 2015 at 5:13

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