Experimental investigation of an American five-string banjo

An experimental investigation of an American five-string banjo is reported. The acoustic spectra of the strings are analyzed and it is found that in many ways banjo strings behave in a manner similar to those on a piano. The terminating impedance presented to the strings at the bridge is reported and it is found to be generally much lower than the characteristic impedance of the strings. It is also shown that, for a properly tuned banjo, the mode shapes of the membrane are symmetric about the center even though there is a large asymmetric force due to the off-center placement of the bridge. Finally, high-speed electronic speckle-pattern interferometry was used to study the motion of the membranic head after a string is plucked, and it is found that the motion is dominated by a rocking motion of the bridge.