We present a modernization of the undergraduate physical chemistry laboratory experiment for determining the speed of sound in various gases from resonant frequencies in a spherical resonator. The resonator (schematic IR = 7.5 cm) is constructed by 3D printing with eco-friendly poly(lactic acid), a commercially viable alternative to traditional construction methods. We provide a schematic stereolithographic CAD file for printing the cavity and Octave (or MATLAB) code for the fast Fourier transform of time-based signals to the frequency domain. Student results for argon, air, carbon dioxide, and R-134A refrigerant show excellent agreement with published values, with less than ±0.2% error in most cases. This module provides an introduction to and practical example of the use of 3D printing technology and fast Fourier transform algorithms in the undergraduate chemistry lab.