Work in progress - Using a "cigar box" guitar to teach waves and sound in a high school physics program

NASA-Threads is a full length high school physics program developed by Louisiana Tech University faculty with support from NASA. NASAThreads is a partnership between K-12 schools and Louisiana Tech University that aims to improve high school student achievement in mathematics and science. This partnership will result in better prepared students entering science, technology, engineering, and mathematics (STEM) programs at the university level. Our previous experiences with K-12 program development have shown that long-term impact on students comes through close collaborative relationships between their teachers and university faculty. This paper presents how mathematics and science fundamentals are shown through the construction of a cigar box guitar. Tuning the guitar further develops the physics concepts of sounds, frequency, and waves. Index Terms – curriculum, guitar, high school, NASAThreads, physics, sound NASA-THREADS CURRICULUM Louisiana Tech University has partnered with the Lincoln Parish School Board to develop a physics curriculum for 11th and 12th grade students [1]. The curriculum adopts a non-traditional ordering of topics beginning with “electricity and magnetism” content which utilizes a robotics platform to facilitate hands-on projects. The curriculum then moves to “work and mechanics,” and then on to “thermal fluids” and “waves and optics.” The NASA-Threads curriculum is designed to motivate and deepen student learning of STEM fundamentals using a project-based approach. LEADING INTO THE CIGAR BOX GUITAR Musical instruments are a natural way of showing physics concepts such as frequency, sounds, and waves. Some use musical instruments as a way of engaging students in the STEM topics [2] while others use instruments as a way of teaching manufacturing processes [3]. This low-cost project requires K12 students to build and test their cigar box guitars as a way of showcasing the STEM fundamentals. Students are naturally engaged because it does not come across as an academic exercise, and allows them to easily relate. The cigar box guitar project described within is used as a hands-on application of concepts related to sound and waves. The NASA-Threads curriculum has been created to provide flexibility for the individual instructor, and as such the material leading up to the cigar box guitar project will be different from class to class. The guitar project itself is used to demonstrate sound and wave topics such as the relationships between tension, frequency, pitch, and mass in a vibrating string. Examples of topics that have been used to lead into the guitar project include: resonance, open & closed-pipe resonators, beat frequency, geometric sequence for chromatic scale, and Doppler shift. Additionally, the project is used to reinforce topics such as force equilibrium, spreadsheet use, and digital signal processing. The project described in this paper is centered on a cigar box guitar. These three-string guitars can be built for under $5.00 each and produce a respectable sound. During this project, students learn topics such as harmonic series, sound propagation, how sound is produced through vibration, and how tension affects pitch. Students also learn about spreadsheet programming, and use free signal analysis software to “view” the sound produced by their guitar. The guitar is initially tuned through a simple statics evaluation of the tension in the strings.