Can anyone tell me if the output voltage of a microphone (like the type on a webcam) is an AC voltage? And whatever it is, can it be measured on a standard voltmeter?

Thank you.

  • \$\begingroup\$ The output of a webcam is usually (digital) USB. Please elaborate. \$\endgroup\$ – Turbo J Oct 15 '15 at 16:28
  • \$\begingroup\$ OK, thank you. Just consider a microphone, then. You attach a battery, you speak, and this gets converted into an output electrical signal which is connected to a speaker. Is this output DC or AC (in that it is a varying signal which depends on the sound or voice)? \$\endgroup\$ – Amygdala Oct 15 '15 at 16:31
  • \$\begingroup\$ Powered microphones (such as electrets) usually have a DC content on which the AC signal is superimposed. \$\endgroup\$ – Andy aka Oct 15 '15 at 16:39
  • \$\begingroup\$ @Andyaka Thank you. So, could this be measured by a standard multimeter or must you use an oscilloscope? \$\endgroup\$ – Amygdala Oct 15 '15 at 17:04
  • 1
    \$\begingroup\$ Use an oscilloscope if you want to capture any signal worth looking at. A standard voltmeter will not give you anything useful. \$\endgroup\$ – KyranF Oct 15 '15 at 17:46

The audio signal from a microphone will be AC, with the frequency and amplitude (voltage) of the signal depending on the sound that the microphone is picking up.

For electret microphones, the audio signal will usually also have a DC bias, which can be removed with an AC coupling capacitor.


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