This application relates to microphone authentication apparatus for verifying whether or not an audio signal originated at a microphone (101, 102). The microphone authentication apparatus (300) has a comparison block (301) configured to receive a first signal (A*) indicative of one or more spectral parameters of at least part of an audio signal to be verified, and compare the one or more spectral parameters to one or more predetermined characteristic microphone parameters relating to a characteristic resonance associated with an acoustic port of a microphone. The first signal (A*) may be an audio signal (A) and the microphone authentication apparatus may have a feature extract module (303) for determining the spectral parameters. Based on the comparison determination block (304) may whether the audio signal originated from a microphone and may send a verification signal (VMIC) to a voice biometric module 111.