Audio dropout is a brief reduction or loss of signal that occurs during playback, and it can be found in both analog and digital audio tape sources. Read about analog audio dropout here: Audio Dropout. Dropout is the result of a defect in the carrier or playback mechanism.
Digital Audio Tape (DAT) is particularly susceptible to dropout. Digital audio dropout is caused by a non-uniform magnetic surface, or a malfunctioning tape deck. However, because the magnetically recorded information is in binary code, it results in a momentary loss of data and can produce a loud transient click or worse, muted audio, if the error correction scheme in the playback equipment cannot correct the error.
Can it be fixed?
Digital dropouts can be very difficult to eliminate. If you encounter a digital recording with dropout, try cleaning the playback head and re-transferring, or try re-transferring on a different deck. If the deck the tape was originally recorded on is still available and in good working order, try using it instead. Bear in mind that the dropout may have been recorded into the source; in these cases, switching decks or cleaning the heads will not solve the problem.
Should dropouts persist, production or access copies of files can be remediated using software tools (for example, Izotope Spectral Repair) that use digital signal processing (DSP) techniques to resynthesize gaps in audio content.
Listen to Digital Dropout in a DAT on Soundcloud