[Edward] and [Tom] managed to build an actual phased array speaker system capable of steering sound around a room. Powered by an Atmega 644, this impressive final project uses 12 independently controllable speakers that each have a variable delay. By adjusting the delay at precise intervals, the angle of maximum intensity of the output wave can be shifted, there by “steering” the sound.
Phased arrays are usually associated with EM applications, such as radar. But the same principles can be applied to sound waveforms. The math is a little scary, but we’ll walk you through only what you need to know in case you’re ever in need to steer sound with a
speaker and a servo phased array sound system.
The physics of a phased array system can be demonstrated with a diffraction grating.
The above animation shows what happens to a waveform as it passes through openings in a barrier. By counting the number of openings, obtaining the distance between the openings and combining this knowledge with the properties of the incoming waveform, one can find the area of most intensity.
This is the phased array setup. If you consider each speaker as openings, you can apply the same technique. [Edward] and [Tom] hammered it out, and found that the output intensity can be calculated by the following equation:
Where vs = speed of sound, d = distance between speakers, and td = a time delay. By varying the time delay, you vary the angle of maximum intensity. [Edward] and [Tom] tested their theory in MATLAB, and it worked!
Below is the theorized output of several frequencies with no delay.
This is the output with a .3ms delay.
Be sure to check out [Edward] and [Tom's] project for complete details, source code, schematics, ext. Below is a video showing the project working in real-time.