If the audio cannot be detected, or if there is no audio device, an exception will be raised (the program will crash), but due to try statements elsewhere, the private key will not be generated.
What is wrong with simply using /dev/urandom for entropy gathering? Maybe even /dev/random if you are wary of the pseudo-generated bits, but that is not really necessary as minikeys are much smaller and normal private keys.
Most servers do not have audio devices on-board and the ones that do (in the rare case), are not utilizing them so you will not be getting any data from them.