29th Annual Student Research Conference
An Acoustical Impedance Head for the Study of Tone Hole Lattices
Colin A. Justice
Dr. Ian Lindevald, Faculty Mentor
Woodwind instruments are acoustic wave guides of varying cross-sectional area punctuated with open or closed tone holes. The input impedance, which is the frequency-dependent ratio of pressure to flow at the input end of the system, is a vital quantity for determining its acoustical properties such as its resonances. Pressure is measured with a microphone, but there is no simple device to measure flow. However, if the amplitude of the flow is held constant with respect to frequency, then impedance is directly proportional to the measured pressure. Thus, in a constant-flow device, a measurement of pressure as it varies with frequency reveals the dependence of impedance on frequency. A low-cost impedance head was constructed using a piezo-electric transducer driven through an integrator circuit in order to ensure a constant flow rate. The impedance head was tested using pipes whose impedances are well-known theoretically.
Keywords: acoustic, physics, tone holes
Topic(s):Physics
Presentation Type: Oral Paper
Session: -4
Location: MG 1096
Time: 1:45