Definition
A microphone that converts sound into an electrical signal using a piezoelectric crystal. Sound waves vibrate the crystal, which produces a small voltage that varies with the sound. Crystal microphones have high output and high impedance, and were once common in older aircraft intercom and radio systems.
Plain English
A microphone that turns your voice into an electrical signal by vibrating a special crystal inside it. The vibrations produce a tiny voltage that the radio can transmit.
Context Anchor
Seen in older aircraft radio systems, radio maintenance notes, and microphone troubleshooting or replacement discussions.
Derivation
From the Greek krystallos, meaning 'clear ice' or 'rock crystal.' The name refers to the piezoelectric crystal element inside the microphone, which is the part that does the actual conversion of sound to electricity.
Why Pilots Care
Most modern aircraft no longer use crystal microphones, but pilots flying older aircraft may still encounter them. They are sensitive to heat and humidity, and can degrade or fail in cockpit conditions, which matters when clear radio communication is required.
Intuition Check
Do not read “crystal” here as a clear stone or as a radio tuning crystal. In this term, the crystal is the sound-sensing part of the microphone that helps turn voice vibration into an electrical signal.
Example Sentence 1
The vintage trainer was still fitted with a crystal microphone, which gave a strong but somewhat scratchy signal on the radio.
Example Sentence 2
Mechanics replaced the aging crystal microphone during the radio overhaul.