Why is it that pilots, when addressing the fliers over intercom always have terrible sound quality? You'd think that airlines could afford a high-quality microphone considering the cost of the plane and the pilot's time. Air traffic control should appreciate quality audio as well.
There could be some ruggedness requirement to these microphones that takes precedence over audio quality. Maybe they must withstand decompression?
EDIT: if you're interested, you can go right here! http://www.liveatc.net/ I transcribed hours of this stuff as part of a research project. The first 4 or so hours were really rough. After that, it got easier, with the majority of issues being that seemingly one in 20 aircraft actually have horrendous audio pickup, and accents.