I'm writing a program that will determine sound directionality by measuring the time difference from left and right acoustic triggers (with two additional triggers to determine if the sound is coming from the front or back). Here's the math I derived: dt = measured time interval between left and right microphones dt_max = maximum possible time interval (i.e., source is directly to the left or right, 90 or 270 degrees) r = spacing between microphones c = speed of sound (temperature compensated) a = relative bearing of sound source dt_max = r/c a = asin(dt/dt_max) So I sketched a the system up in CAD and entered the distances to the left and right "ears" into a spreadsheet which spat out the predicted value, and then I measured the angle in CAD and compared the two. The predicted value is pretty close, but there's a periodic level of error which peaks at 1.5 degrees error at 45 degrees and 0 degrees error at 0 and 90. It's not a huge amount of error, but I can't figure out where it's coming from. Any thoughts?