A type of frequency modulation distortion which manifests itself as aof relatively slow variation in frequency of reproduced sound caused by slow speed variations in the transports of turntablesrecords, tape recorders, etc. Pitch fluctuations of 1Hz-2Hz are classed as wow, while faster variations are called flutter.
Wow and Flutter caused by any variation in the speed of the tape transport. The lower the figure the better and hence the lower the level of variation through the speakers.