DESIGN AND MEASUREMENTS OF VARIABLY NONUNIFORM ACOUSTIC RESONATORS

We describe the design, construction, and acoustical measurements of r esonators with nonuniform cross-sectional areas that are easily altere d to yield different resonance frequencies. These resonators are usefu l as educational demonstrations of symmetry breaking and of an effect of nonuniformity upon standing waves. Resonators that yield two, three , and four pitches are considered, where the relative frequencies are designed to correspond to musical intervals. Agreement is within 2% in all cases and 1% for most. The data reveal a breakdown of the theory, which is shown to be a result of additional kinetic energy, and thus effective inertia, near a discontinuity in cross-sectional area. The d ata also reveal that it is more accurate accurate to employ the end co rrection of an infinite flange rather than that of a thin-walled tube. (C) 1996 American Association of Physics Teachers.