Gregory H. Canfield
Thomas D. Rossing
Phys. Dept., Northern Illinois Univ., DeKalb, IL 60115
Tuning-fork resonators, useful in acoustics lecture demonstrations [T. D. Rossing, J. Acoust. Soc. Am. 92, 2401 (1992)], can vibrate in a wide variety of modes. The Malmark Choirchime(trademark), consisting of a closed-end tuning-fork resonator with an attached handbell clapper, has become a popular musical instrument. The modes of vibration of two Choirchimes(trademark), tuned to A[sub 3] and A[sub 4], are described. The observed modes can be classified into five categories: parallel bending, symmetric bending, out-of-plane bending, parallel torsional, and symmetric torsional. The lowest symmetric bending mode radiates a strong fundamental, which is greatly enhanced by the resonance of the tube, resulting in a sound spectrum in which the fundamental dominates (the next partial is generally 20 dB or more below the level of the fundamental).