Sound fields forever: Mapping 3D sound fields using position-aware smartphone technology

Abstract

Google Project Tango is a suite of built-in sensors and libraries allowing certain mobile devices to track their motion and orientation in three dimensions, without the need for any external hardware. Our new Android app, “Sound Fields Forever,“ combines position information with sound intensity data for multiple frequency bands obtained from a comoving external microphone plugged into the phone's analog audio jack, and filtered digitally. These data are sent wirelessly via a WebSockets connection to a visualization server running in a web browser. This system is intended for multiple roles: (1) education, providing visual representations of introductory acoustics laboratory phenomena such as interference patterns and room modes; (2) live sound reinforcement, providing front-of-house engineers real-time maps of a loudspeaker system's effects throughout the venue; (3) architectural acoustics, aiding builders and designers in evaluating acoustical properties of halls. The relatively low cost of our approach (∼$400 for the smartphone) compared to more sophisticated 3D acoustical mapping systems could make it an accessible option for such applications. We present visualizations of various sound field measurements and intend to demonstrate how the bandpass filters make it suitable for use even in the presence of nontrivial ambient noise.