Why won't my external microphone work on my Mac?
When selecting an input device on
Macintosh, please be aware that not all external microphones
will work.
Macs require a line-level signal, so plugging
a conventional microphone into the audio input jack will not
work.
If the Mac does not have an internal microphone,
the user will need to use a USB or FireWire microphone (the
FireWire iSight camera has a microphone, for example).