This text is intended as a student guide for hands-on exploration of physical layer communication. Through a sequence of guided explorations, students design and implement a digital communication system with modulation to an acoustic carrier frequency. The acoustic operation allows students to hear, see, and wirelessly transmit signals using readily available, low-cost hardware, such as a PC with sound card or a smartphone. Acoustic wireless transmission, while readily accessible, nonetheless presents a student with the channel impairments and synchronization issues encountered in radio frequency systems. An accompanying smartphone app is available for free download; supplementary software for Matlabª and Octave is freely available at OpenStax CNXª, iTunesU, and Mathworks¨ Matlabª Courseware.