Thomas D. Rossing,
Rossing@physics.niu.edu
Physics Department
Norhtern Illinois University
DeKalb, IL 60115
Uwe J. Hansen
Department of Physics
Indiana State Univeristy
Terre Haute, IN 47809
Felix Rohner and Sabina Scharer
Panart
Engehaldenstrasse 131
CH-3012 Bern, Switzerland
Popular Version of Paper
4pMU4
Friday Afternoon, June 2, 2000
139th ASA Meeting, Atlanta, GA
The Caribbean steelpan is probabaly the most important new acoustical musical instrument to develop in the 20th centruy. In addition to being the foremost musical instrument in its home country, Trinidad and Tobago, steel bands are becoming increasingly popular in Europe, North America and some Asian countries as well.
Being a new instrument, steelpans are still evolving. The original steelpans were fabricated from empty 55-gallon oil drums, thousands of which were left on the beaches of Trinidad after World War II. Later, steelpan makers began to prefer new drums to used drums, and now many makers are using custom-made drums and materials. Panart has pioneered the use of "sandwich-hardened" steel which has a pliable interior but a very high surface hardness to make a durable playing surface and stabilize the tuning of the pan.
In this paper we report on studies of vibrational modes in a totally new instrument, called a PING. The playing surface is drawn to a uniform thickness of 0.9 mm and sandwich hardened. Each note area has an appropriately sized elliptical dome, which forms a durable strike point and stabilizes the overtones. The stainless steel skirt has a thickness of 1.25 mm. A ping is shown below.
By means of electronic (TV) holography, we have studied the vibrational mods of both the playing surface and the skirt. Electronic holography offers an accurate maps of modal shapes, which can serve as guides to the maker and player alike. An important consideration is how the vibrations in one note area excite sympathetic vibrations of other note areas. From previous studies, it is known that these sympathetic vibrations are an important factor in determining the timbre or quality of a steelpan (see Chapter 20 in Physics of Musical Instruments by N.H. Fletcher and T.D. Rossing).
Hologrpahic interferograms showing the first four vibrational modes of the C4 note area are shown below. The second mode has been tuned to twice the frequency of the fundamental, and the third mode to three times the frequency. Sound spectra of the played note show strong harmonics corresponding to these modes.
Two vibrational modes of the skirt are shown below. Each mode consists of bending waves that propagate around the skirt. These bending waves are excited by mechanical coupling to the note areas, and contribute to the sound radiation by the steelpan.
