The Record Microgroove
The microgroove record
(what it was originally called when first produced in 1949) is played by placing a stylus, a highly polished and specially shaped piece of diamond mounted on the end of a fine rod called the cantilever, into the record groove.
The vibrations — caused by the force developed between the stylus tip and the three dimensional engravings on the sidewalls of the record groove — travel up the cantilever into the tonearm cartridge are turned into minute electrical impulses, which are then transformed into sound by the system amplifiers and speakers.
The Wear and Care of Records and Styli by Harold D. Weiler was a study conducted to determine the effective life of phonograph styli and the effect of worn styli and dust on record life and quality of reproduction. The work remains the pre-eminent study on the topic. Check out the original study here.
In Weiler’s words, the proper relationship between the stylus tip and the record groove is extremely important. The impressions on the walls of the record groove are microscopic, three-dimensional duplicates of the sound waves which created them. The pickup stylus must follow with extreme exactitude the variations of these impressions. This can only be accomplished if the original shape of the stylus tip is maintained. Anything that comes between the stylus and the groove walls will degrade the sound.
Writing about the new technology, Weiler observed that the new microgroove was so small that brushes and cloths would be ineffectual in properly cleaning the tiny depression. Worse, cloths were simply likely to push particles deeper into the groove with damage the likely result.