Audio signal verification methods and apparatus for video/audio production equipment are disclosed. An audio signal and a video signal are input into production equipment. The audio signal has one or more known frequencies, and the video signal has a known video frame to which the audio signal is to be synchronized by the equipment. Based on the known frequency or frequencies and a frequency or frequencies of an output audio signal that is output by the equipment with the video frame, a determination can be made as to whether the output audio signal corresponds to the input audio signal. Respective values could be assigned to a number of frequencies, to enable values to be encoded in the input audio signal. The correspondence determination could then be made based on whether the values encoded by frequencies in the output audio signal match the values encoded in the input audio signal.