Wow and flutter measurement
Wow and flutter measurement is carried out on audio tape machines or cassette recorder and players in order to quantify the amount of 'frequency wobble' present in subjectively valid terms. It is also used on turntables (for vinyl recordings) which tend to suffer mainly slow Wow.
While the terms Wow and Flutter used to be used separately (for wobbles at a rate below and above 4Hz respectively), they tend to be combined now that universal standards exist for measurement which take both into account. Listeners find flutter most objectionable when the actual frequency of wobble is 4Hz, and less audible above and below this. This fact forms the basis for the weighting curve used in various standards, as shown here. The standards also require a special quasi-peak rectifier to be used.
High frequency flutter, above 100Hz can sometimes result from scraping of tape across a head, and is termed 'scrape flutter'. It adds a rougness to the sound that is not typical of Wow & flutter, and damping devices or rollers are sometimes employed on professional tape machines to prevent it.
See also
- Audio quality measurement
- Noise measurement
- Headroom
- Rumble measurement
- ITU-R 468 noise weighting
- A-weighting
- Weighting filter
- Equal-loudness contour
- Fletcher-Munson curves