In Fall of 2017, a series of measurement laboratory exercises, built around a microphone preampifier and filter, were used in teaching an engineering measurement techniques course. The microphone circuit included a preamplifier that introduced JFETs, a virtual ground and buffer to illustrate loading effects, a high pass filter and a low pass filter, and a zener-diode-based limiter. The data was sampled using a beaglebone microcontroller’s built-in analog-to-digital converter. The data was transmitted to matlab for post-processing and analysis. The microphone was then used in the Spring 2018 acoustics class. A variety of projects, including a Kundt’s tube, a driven closed-open pipe, a 3D printed horn for a blue-tooth speaker, and an absorptivity measurement for a restaurant’s wall treatment tiles, were completed in the course. It was observed that students showed improved interest in the material (increased in-class and out-of-class questions about specifics of the course material related to the project, increased exploration of material outside the provided course materials, full participation by all members of the class in the project) and learning (improved test scores after the project began relative to scores before the project began) relative to earlier classes where no experimental component was included.
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March 04 2019
A measurements laboratory using a digitally-sampled microphone circuit
Andrew Wright, Amanda Nolen, Ann Wright; A measurements laboratory using a digitally-sampled microphone circuit. Proc. Mtgs. Acoust. 5 November 2018; 35 (1): 025001. https://doi.org/10.1121/2.0000987
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