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Buchmann-Meyer effect
10 Apr 08
These two German physicists discovered during experiments with sound recordings in the 1920s that, if a beam of light is thrown onto a disc record, the grooves produce an effect suggesting the branches of a Christmas tree, with the root at the last groove. They further discovered that the length of the “branches” is in direct proportion to the amount of sound recorded in that particular groove or grouping of grooves, and that the brightness and clarity of definition of the “branches” is also in direct ratio to the brightness and clarity of the sound from the relative grooves. Thus, a recording depicting a sharply defined image of a Christmas tree will give an excellent performance, no matter how improbable this might seem from a cursory examination of its surface in normal or subnormal light. And, if part of the “Christmas tree” image is dull and the rest bright, the bright part will provide an excellent reproduction of the recorded sound. A record giving only a vague, blurred outline, barely recognizable as a Christmas tree, will thus give only a very poor sound reproduction, and some records have been found with the grooves so badly worn by constant playing with blunted needles or styli, probably with heavy pickups or soundboxes, that they are almost ground smooth and give no Christmas tree (Buchmann-Meyer effect) at all. (Rust 108)
According to Foreman, the effect is “best seen from a 45° angle across the diameter of the record with a small but bright source of light on the same side as the viewer” (29).
Posted by pzed on April 10, 2008 at 7.39pm
Categories: none of the above
