The sound waves hit the microphone - The changes in air pressure related to the sound wave cause the microphone diaphragm to oscillate - The microphone diaphragm and coil vibrate at the same frequency as the incoming sound wave (bigger the amplitude of sound, bigger the amplitude of vibration) - This induces a potential difference and current in the coil with the same frequency as the incoming sound wave (and an amplitude dependent on the amplitude of the incoming sound wave)
