I am using four voice recorders to record the audio of a group interview. Three of them are Sony IC Recorder ICD-PX440 (stereo) and one is a Phillips Voice Tracker (mono). I synced the four tracks in Audacity around a clapping sound towards the middle of the recording. However, I find that whereas the three tracks coming from the Sony recorders sync perfectly, the Phillips track is out of sync as I move away from the clap. That is to say, the mono track is synced with the stereo ones around the clap, but is off by milliseconds towards the start and end of the track. Is this to do with the encoding of the audio? Can I do something to correct it in Audacity?
Check the sampling rate that each of the recorders are using. For example, you could be running into issues importing a 48kHz digital recording into a 44.1kHz DAW project.