Geometrical effects on the tuning of Chinese and Korean stone chimes.

The vibrational mode frequencies and mode shapes of ancient stone chimes are analyzed and their dependence on stone shapes are discussed. Mode shapes and frequencies of several chime models are determined by using finite element methods, and these show good agreement with mode shapes and frequencies observed in Korean pyeongyeong chime stones using holographic interferometry and experimental modal testing. The dependence of mode shapes and frequencies on vertex angle and base curvature suggests that the geometries used in late Chinese bianqing and Korean pyeongyeong may have been selected to give the best sound.

Sound radiation from Caribbean steelpans.

Besides radiating sound from the note area being struck, a steelpan radiates from neighboring note areas that vibrate sympathetically, from the areas between notes, and from the skirt [Rossing et al., Phys. Today 49(3), 24-29 (1996)]. Measurements were taken in an anechoic chamber using a four-microphone intensity probe to visualize the acoustic radiation from selected notes on a double second and a low tenor steelpan. Swept sinusoidal excitation was effected using an electromagnet. Sound intensity maps were drawn for the first three harmonics.

Reed vibration in lingual organ pipes without the resonators.

Vibrations of plucked and blown reeds of lingual organ pipes without the resonators have been investigated. Three rather surprising phenomena are observed: the frequency of the reed plucked by hand is shifted upwards for large-amplitude plucking, the blown frequency is significantly higher than the plucked one, and peaks halfway between the harmonics of the fundamental frequency appear in the spectrum of the reed velocity. The dependence of the plucked frequency on the length of the reed reveals that the vibrating length at small vibrations is 3 mm shorter than the apparent free length. The frequency shift for large-amplitude plucking is explained by the periodic change of the vibrating length during the oscillation. Reed vibrations of the blown pipe can be described by a physical model based on the assumption of air flow between the reed and the shallot. Aerodynamic effects may generate and sustain the oscillation of the reed without acoustic feedback. The appearance of subharmonics is explained by taking into account the periodic modulation of the stress in the reed material by the sound field. Therefore, a parametric instability appears in the differential equation of vibration, leading to the appearance of subharmonics.