Questions: Measuring Soundboard Vibration

by Alan Carruth

Originally published in American Lutherie #73, 2003 and Big Red Book of American Lutherie Volume Seven, 2015



Gregory Furan of Toronto, Ontario, Canada asks:

Over the past several years there have been numerous articles written in many different guitar mags regarding measuring soundboard vibration, that is, tuning tops. Can you give me a reference for where all of the different elements can purchased?


Al Carruth of Newport, New Hampshire responds:

For tuning plates on guitars or violins, the equipment you need is fairly simple:
 a signal generator capable of producing a reasonably “clean” sine wave signal over the range from about 20Hz to 1000Hz,
 an accurate frequency counter,
 an amplifier that can boost the output of your signal generator to around 12w or more, and
 a loudspeaker that is matched to the amp and rated for the power. To be on the safe side, I’d get a speaker that was rated for about 1½ times the nominal power of the amp: sine waves have high peak-to-peak voltages.