The Physics Factbook™
Edited by Glenn Elert -- Written by his students
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|Bibliographic Entry||Result |
|Alten, Stanley R. Audio in Media. Belmont, CA: Wadsworth, 1999: 98.||"30 ips, 15 ips, 7½ ips, 3¾ ips"||76 cm/s |
|Encyclopedia Americana. Grolier, 1999: V26, 279.||"Typical home or professional audio recorders operating at 7½ inches and 15 inches per second …. Cassette recorders which operate at 1⅞ inches per second"||38 cm/s |
|Daily, Jay E. Cataloging Phonorecordings Problems and Possibilities. Marcel Dekker, Inc., 1975: V1, 5||"The fastest speed … is 15 inches per second or 38 cm per second. Most tape decks include 7½, 3¾, and 1⅞ ips speed …. so that the slowest speed is 1⅞ ips."||38 cm/s |
|Earl, John. Cassette Tape Recorders. New York: Fountain, 1977: 34.||"… at a tape speed of 4.75 cm/s (the cassette tape)"||4.75 cm/s|
|Tape Speed. Zen Audio Project (ZAP). Simon Fraser University.||"Cassettes run at 1.875 inches per second (4.75 cm/second) while some 4 track cassette devices ("portastudios") run at 3.75 i/s (9.5 cm/s). Reel to reel tape runs at 7.5 i/s (or 19 cm/s) and 15 i/s (38 cm/s)- the latter being the professional standard. Occasionally one may find analogue machines set to run at 30 i/s (76 cm/s)."||38 cm/s |
Analog tape systems run at a variety of speeds depending ontype. There are two basic types of audio tape: open reel and cassette.
The larger open reel-to-reel tapes typically run at 7½inches per second (19 cm/s) and 15 inches per second (38 cm/s)-- the later being the professional standard. Occasionally, youmay find analog machines set at 30 inches per second (76 cm/s).The fastest speeds are reserved for professional use because theyhave the greatest range due to less wow and flutter and greaterfrequency response. Wow is a relatively slow variation in thefrequency of reproduced sound caused by slow speed variationsin records, tape recorders, etc. Pitch fluctuations of one ortwo per second are classified as wow, while faster variationsare called flutter. Wow and flutter are almost never an issuein digital recorders because tape speed has no direct effect onthe pitch of the audio playback or recording.
The quality of sound decreases as speed is reduced. Reproductionquality also fades as speed decreases so that the slowest tapespeed of 1⅞ inches per second (4.8 cm/s) is unsuitablefor professional use. However, only a very sophisticated devicecan detect the difference between 15 inches per second and 7½inches per second. For almost every kind of music one is justas good as the other. Also, a minimum of 7½ inches persecond is required to physically cut or edit tape.
Cassette tapes on the other hand are much smaller in size.They typically run at 1⅞ inches per second (4.8 cm/s),however, some four track cassette devices run at 3¾ inchesper second (9.5 cm/s).
Tien-Huey Heh -- 2000
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