Exactly what SRD said. There are off the shelf solutions used in flexwing microlights, that integrate helmet, headset, microphone and intercom - they work very well. Don't re-invent the wheel.
G
P.S. I notice that Sam Rutherford's last post was 5 year ago and he's now banned. Not obsessing too much about La Curtis-Taylor was he? Anyhow, probably all a bit irrelevant now.