Uwe J. Hansen

Music from Oil Drums: The Acoustics of the Steel Pan

The steel pan—made from the end of an oil drum—is probably the most important new acoustical (that is, nonelectronic) musical instrument developed in the 20th century. In addition to being the foremost musical instrument in its home country, Trinidad and Tobago, the steel pan is becoming increasingly popular in North America and Europe. (See figure 1). The modern family of steel pans now covers a five‐octave range, and steel bands of today use them to perform calypso, jazz, and popular and classical music.

Vibrational mode shapes in Caribbean steelpans. I. Tenor and double second

Vibrational mode shapes have been studied in several tenor (soprano range) and double-second (alto range) steelpans by three well-known makers. Normal modes are determined from operating deflection shapes recorded by means of electronic TV holography. Vibrational modes of the various note areas are designated by the number of radial and circumferential nodal lines. Tuners generally tune one mode an octave above the fundamental and, if possible, a third mode is tuned either a twelfth or two octaves above the fundamental. Note dimensions follow an approximate scaling law L=Kf(213), and the larger note areas can be roughly modeled as rectangular plates with simply supported edges. Modal shapes in the skirt correspond to standing bending waves propagating around the ring.

The HANG: A hand played steel drum

The HANG is a new steel instrument consisting of two spherical shells of steel, suitable for playing with the hands. Seven to nine notes are harmonically tuned around a central deep note which is formed by the Helmholtz resonance. Elliptical note areas are formed on the upper shell and tuned so that the (1,1)a and (1,1)b modes of each note area have frequencies that are in the ratios of 3:2:1 with respect to the fundamental, except in the highest notes where they are in the ratio of 2.5:2:1 or 2.4:2:1. Holographic studies show the modal shapes and also the extent of coupling between note areas.

Air column resonance demonstrations

An impedance head designed and constructed at the Physikalisch Technische Bundesanstalt in Braunschweig, Germany is used to illustrate the pattern of resonances in an air column confined to a cylindrical tube closed on one end and open on the other. This is compared to the pattern observed for a tube closed on both ends. The effect observed when adding a mouthpiece is demonstrated, as is the effect when adding a bell. Finally the resonance patterns associated with a number of brass instruments will be demonstrated.

Relating the radiated piano sound field to the vibrational modes of the soundboard

The sound field near a piano sound board is determined by moving a microphone over a grid of points above and below the sound board as well as in a plane in front of the piano using the experimental techniques of modal analysis with soundboard excitation at a bridge point by a swept sine signal. Since the standard modal analysis signal processing technique relies on tracking phase relations between excitation and response, it is possible to relate the sound field in terms of the vibrating structure which radiated it. Animations of sound board motion and sound field pressure variations are shown for the lowest four modes. It is noted that in all modes the locations of maximal excursion correlate with the sound pressure maxima or minima, respectively.

Music: A vehicle for science—Workshop for teachers

With ASA technical initiative support, approximately ten acoustics workshops for teachers have been conducted by members of the technical committee on musical acoustics in the past six years. Workshop content emphasizes laboratory and demonstration skills for high school and college level teachers. The workshops for elementary teachers have been more concerned with generating excitement for science. Music is an ideal vehicle to accomplish that. Elementary teachers in the workshops participate in monochord construction and receive training in the use of a number of pieces of equipment which they take back to the classroom. Basic wave properties are illustrated and related to string harmonics and musical intervals. Workshop content and training approaches will be discussed.

Holography in the high school laboratory

During the past ten years a number of workshops were conducted which introduced holography into about 25 high schools in central Indiana. Sand box systems were constructed. Participants were provided with minimal equipment including a 5 mW laser and associated optics. both reflection and transmission holograms were produced. The workshops included several phases. During the first phase teachers were introduced to basic principles and gained hands-on experience with their systems. During the second phase staff visits to the classes assisted teachers in implementation. During the third phase teachers brought selected students for training and review. Second year workshops utilized first year participants as workshop trainers. Workshops were concluded with a review session which included a section on curriculum design to include holography in the physics lesson planning. Continuing enthusiasm for optics and specifically holography suggests that this is a great way to generate science interest in the secondary schools. The workshops were supported with Eisenhower funds administered by the Indiana Commission for Higher Education.

Modal analysis of classical and folk guitars

The mechanical responses of three freely supported guitars have been studied both under impulsive excitation and under excitation with a sinusoidal force [J. Popp and T. D. Rossing, J. Acoust. Soc. Am. Suppl. 1 76, S26 (1984)]. The normal modes of vibration as determined by the two different methods have been compared, and the agreement is found to be quite good. A comparison is made with the modes of vibration recorded in one of the guitars with the ribs fixed using time‐average holographic interferometry.

“Mode studies in musical instruments,” a journey with Tom

For me, that journey began when Tom agreed to have me work with him in 1984. While Tom was busy at the Minneapolis ASA meeting, I learned about holographic interferometry at Dick Petersons laboratory at Bethel College, while mode mapping a guitar, for which Tom had designed a support rack which isolated the front and back plates, enabling us to record their principle resonances. Immediately following that experience, we went on a whirlwind tour, meeting with some of the “Greats” in musical acoustics. Starting with Carleen Hutchins, we then met with Norman Pickering in Southampton, did some modal analysis guitar studies at the Steinway laboratories with William Y. Strong, and later visited with Gaby Weinreich. We concluded the tour with a visit to Gila Eba,s guitar building studio. In the course of studying two-tone Chinese bells, we used judicious mirror placements to observe the bell modes in three dimensions. Eventually, the wet plates were replaced by Karl Stetsons computer based device, enabling us...

Finite element illustrations in the classroom

“You hear, you forget. You see, you remember. You do, you understand.” This is Tom Rossings favorite education quote. Solutions to wave equations generally result in traveling waves. Imposing boundary conditions usually limits these solutions to discrete normal modes. The one dimensional elastic string is an easy, accessible example, illustrated frequently with a long spring. The two dimensional example of a rectangular stiff plate is a little more complex, and the normal modes are often illustrated with Lissajous figures on a plate driven by a shaker. Whille full blown FEA programs are prohibitively expensive, ANSYS has an educational package available to students at nominal cost with sufficient memory to demonstrate normal mode vibrations in moderately complex structures. Normal mode vibrations in a rectangular plate with a number of different boundary conditions will be illustrated.