Oscillations and Waves > Sound Reproduction > Microphones
DCS# 3E30.xx

CARBON MICROPHONE



APPARATUS
carbon microphone
202-19-B6
1.5 V battery
202-02-D1
audio transformer
214-01-D
amplifier/speaker or digital video recorder
202-20-B2


DESCRIPTION
This is a model of an early microphone invented by David Edward Hughes.

The carbon rod rests between brass contacts.  As the rod vibrates in response to sound, the resistance and thus the current varies.  The signal can be sent to the speaker/amplifier or recorded and played back.  The audio quality is not good but spoken words are discernible.

NOTES

The quality of the sound is very sensitive to how tightly the rod is held.