$AudioInputDevices
gives the list of available audio input devices.
Examples
Wolfram Research (2017), $AudioInputDevices, Wolfram Language function, https://reference.wolfram.com/language/ref/$AudioInputDevices.html.
Text
Wolfram Research (2017), $AudioInputDevices, Wolfram Language function, https://reference.wolfram.com/language/ref/$AudioInputDevices.html.
CMS
Wolfram Language. 2017. "$AudioInputDevices." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/$AudioInputDevices.html.
APA
Wolfram Language. (2017). $AudioInputDevices. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/$AudioInputDevices.html