Experiments in Audio Spectroscopy

by John C. Moore

Originally published in American Lutherie #80, 2004 and Big Red Book of American Lutherie Volume Seven, 2015



R.M. Mottola’s interesting article in American Lutherie #70 (Big Red Book of American Lutherie Volume Six) described the use of audio spectroscopy, with a simple home setup, for the analysis of bass guitars. I had read about a spectrum comparison of a Martin D-28 with a Kaman AA 14-4 in An Introduction to Scientific Guitar Design by Donald Brosnac, and have always been intrigued with the idea of capturing in an objective way the “quality” of the sound of different acoustic guitars. Also, my experience has been that seeing colors of nature is enhanced by having tried to paint them, and tasting beer is enhanced by having brewed some. I felt that analyzing sounds from a guitar would heighten the senses here as well.

When I read the Brosnac book, written in 1978, the equipment utilized for the guitar comparison sounded exotic and expensive, and certainly beyond the capability of the casual hobbyist. In Mottola’s article, it was clear that the technology of the PC had brought the potential for such experiments within reach. In fact, I already had hardware that could get me started: a digital camcorder that I could extract wave files from and a Sony Vaio laptop. So I decided to have a go at some audio trials.