A recording being classified as “poor” is preferable to one that is deemed to be “not viable for transcription”. Unfortunately though, a “poor” quality of audio can cost more to transcribe as it will take longer to complete the transcription.
One of the most important factors would be the presence of background noise contained in a recording. While white noise or air conditioners may cause minimal disturbance, the presence of noisy machinery or groups of patrons in a restaurant will severely impact the clarity of the recorded voice input.
Another factor is the format used to record the audio file. Formats such as “.dss” or “.dct” are better suited to the recording of dictation while uncompressed file formats such “.wav” or “.aiff” are appropriate formats for recording groups of speakers or interviews.