Abstract
The measurement of acoustic impedance of acoustic materials and networks often requires a rather laborious impedance tube measurement. Other methods have been evolved, but these usually rely on two microphone measurements. The single microphone system reported here utilizes the incident and reflected pulse in a circular impedance tube. The pulse is generated by a suitably damped loudspeaker driven by a low-frequency square wave. A two-channel Fast Fourier Transform analyzer captures the pressure-time history. The signal is then conditioned leaving only replicates of the incident and the reflected pulses suitably shifted in time to simulate conditions at the sample surface. Using the various features of modern FFT analyzers, the reflection (absorption) coefficient as well as the complex valued impedance are readily available from a single measurement. At present the usable frequency range is 5 kHz. [Work supported by the Natural Science and Engineering Council, Canada.]
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