Make an electronic Stethoscope
According to a project in University of Victoria , they use a Microphone with a chamber of silicon .

Here is the main Source : iHeart Project

But it seems a very odd way to capture sound of muscels using an acoustic microphone. It's exactly same as non-electronic stethoscopes, and main LNA is a commonly two stage amplifier with inbuilt filters.

What I've seen in recent commericaly stethoscopes is far away this way. They're using more advanced ways to capture its signal than using an acoustic Mic.