At the Carl von Ossietzky University in Oldenburg we developed a mobile hearing aid prototype with a Raspberry Pi 3. Therefore, we used mainly consumer hardware with a combined value of about 250€ and only open source software. It is based on the open Master Hearing Aid (open source hearing aid software) and we will use it for teaching and research. We provide instructions to build the prototype as well as an SD card image which comes with a fully functional pre-configured setup.
- Efficient real-time implementations of research-approved hearing algorithms
- Looks like wearing in-ear headphones
- Competitively low delays
- Whole setup fits in a belt bag
Some cool features:
- Pre-configured SD-card image
- Several hours of autonomy
- Connect via wifi to the hearing aid prototype
- Fit it to a specific hearing profile using openMHA's graphical fitting interface
Check out our project at GitHub for more information, if you are interested.
Today I added a few script to measure and evaluate some basic properties of the setup: Feedback and amplification.
Feedback can be measured by playing back white noise and recording which part of it is recorded by the microphones. The instructions are detailed in the GitHub Wiki
The impulse responses are shown in the upper panel, the frequency responses in the lower panel. You can see that there is substantial feedback and that is far worse on one side (which probably indicates headphone-lottery).
Amplification in terms of output level vs. input level can be measured similarly, by feeding signals with determined level and frequency (e.g., sine sweeps) into the signal processing block and recording the corresponding output signals. The instructions are detailed in the GitHub Wiki