Fundamental acoustics concepts taught through the development of an impedance tube

As part of its mission to educate students, Applied Research Laboratories, The University of Texas at Austin (ARL:UT) employs student technicians to assist on a variety of ongoing research projects. Recently, an undergraduate student technician was tasked with the design and fabrication of a low-cost impedance tube for use in characterizing acoustic materials. To assist the student in developing a set of design requirements, and to determine whether preliminary data were being accurately collected and processed, a set of homework problems were developed to teach the student the fundamental concepts in acoustics necessary for impedance tube development. Homework problems required utilizing both travelling- and standing-wave solutions to the one-dimensional (1D) Helmholtz equation, as well as a basic understanding of the relationships between pressure, particle velocity, and acoustic impedance. Homework solutions were compared with 3D finite element simulations and with experimental data collected using the impedance tube. We felt that these homework problems were effective at conveying basic ideas in acoustics to a student with no prior knowledge in the subject, and how those concepts could be used to solve real-world problems.