Abstract:

In 1990, the ``Mendelssohn'' Stradivarius violin sold for $1,686,700. A good violin sells for around $2000. What is it about the Stradivarius that makes it cost almost 1000 times as much? The structure and geometry of the two instruments are similar, yet subtle differences in structural dynamics cause them to vibrate differently in response to a violinist's bow. This, in turn, causes differences in the sound produced by the two instruments, which ultimately determines quality and, to a large extent, price. If it were possible to force the less expensive violin to vibrate like the Stradivarius, the legendary sound would follow. This paper explores the potential for the use of active structural/acoustic control to obtain a desired acoustic response in an acoustic guitar. Detailed information on the desired acoustic response of guitars is available, and experimental specimens are relatively easy to obtain. The model developed is an elastic plate with piezoceramic sensors and actuators backed by a rigid, vented cavity. The sensors and actuators are used with active feedback control to influence the vibration and acoustics of the guitar. The feasibility of favorably changing acoustic guitar vibration and acoustics is examined in detail, including analytical and experimental results.