Our Great Spherical Friend, Part Three

by Frederick C. Lyman, Jr.

Originally published in American Lutherie #9, 1987 and Big Red Book of American Lutherie Volume One, 2000

See also,
Our Great Spherical Friend, Part One by Frederick C. Lyman, Jr.
Our Great Spherical Friend, Part Two by Frederick C. Lyman, Jr.
Improving the Plywood Bass by Frederick C. Lyman, Jr.



Our great spherical friend, the Earth’s atmosphere, is the medium through which sound waves are transmitted from the source to whatever auditor may be present. The relative frequency of the waves, in the audible spectrum, is influenced by the physical characteristics of the sound source, for example, its size. A low-pitched sound may be most efficiently propagated by a relatively large surface area that can exert relatively small forces (per unit of area) onto a wide atmospheric front, which offers the correct amount of resistance to this kind of push. As the sounds go up in pitch, the source becomes smaller, faster-moving, and more forceful per unit of area. But there must always be some area of atmospheric contact.

The physical energy that is put into a stringed musical instrument, whether by finger, plectrum, bow, or whatever, is not at that stage in the form that is needed to agitate the atmosphere in the desired musical way. It has to be converted to this form (or forms) by the intervening action and reaction of the instrument. For example, the stretching and releasing of a string by the act of plucking, does not in itself accomplish much in the way of compressions and rarefactions in the surrounding air. Feeble sounds may be detected by listening very closely to the event; but for us to have musically useful sounds, more vibrating surface area must contact the atmosphere. In our sophisticated violin-type instruments, the energy undergoes a rather complex series of conversions.