Sounding out the qin

The Chinese zither, the qin, is ancient in origin. Construction of the instrument became standardized in the Tang dynasty (618–907 CE), a thousand years after it was celebrated in poems compiled by Confucius. A qin’s body consists of a 1.2-meter-long hollow box made from two pieces of lacquer-covered wood. To play a qin, the musician lays the instrument on a special table and plucks or strums its seven strings, which run the length of the box. All the strings are tuned in the bass register. When played unstopped, the qin sounds deeply sonorous, like the low strings of a cello or a guitar. Higher notes sound more like a banjo. Despite its long prominence in Chinese culture, the qin has not been subjected to acoustical study—until now. Chris Waltham, Yang Lan, and Evert Koster of the University of British Columbia obtained five qin and suspended each of them in an anechoic chamber. Using accelerometers, microphones, and other devices, the researchers determined the vibrational modes of the instruments’ wooden shells and internal cavities. They also measured the frequency dependence of the radiated sound. Although the acoustical properties differed from instrument to instrument, a consistent picture emerged. Low-frequency notes arise from the bending modes of the frame, whereas high-frequency notes arise from cavity modes. In follow-up experiments, Waltham, Lan, and Koster plan to examine how the two types of modes interact. (C. Waltham, Y. Lan, E. Koster, J. Acoust. Soc. Am. 139, 1592, 2016, doi:10.1121/1.4944874 .)