Short sound decay of ancient Chinese music bells

Ancient Chinese music bells, which have oval-like cross sections, possess the unique feature of a short sound-decay time that is especially suitable for music with fast tempo. Although recorded in the literature nearly 1000 years ago, this feature has never been truly understood. Recent damping measurement of oval pipes with different axial ratios suggested a challenging task for acousticians as the increase of the modal damping with the pipe's axial ratio is significant only when the pipe response is measured in air but not in vacuum. In this paper, the decrease of sound-decay time of oval pipes with the increased cross-section ovality is investigated. This is the first time that such short sound-decay feature is explained in terms of the rich sound radiation characteristics of the symmetric modes of music bells and the oval pipes. Finite element and boundary element methods are employed to explain how axial ratio significantly affects the normal velocity distribution, radiation efficiency, and directivity of acoustic modes. (C) 2002 Acoustical Society of America.