Parabolic Microphone Dish (Customizable)

This creates a bowl shaped model where the interior shape is parabolic with a specific focal point exactly where the top of the microphone is defined. The parabola is configured so that the microphone points forward. This does create a much smaller bowl to pickup the sound, but I was able to build mine to a height of 250mm which made a decent size and worked well.
If you set the microphone height greater than the total height then you could make the parabola larger - but then you'll need to point the microphone backwards.

Using a small cylinder shaped microphone that would insert to the exact length specified.
It will need to be adjusted for each microphone type.

I used a splitter on my Android to separate the mic and headset and then used an hearing aid app to amplify the microphone input back into the headset.

It worked pretty well.

PS: I used it to listen to my family's heartbeat just by placing the cup on each of our chests. It was considerably louder than the ste