Headphones required. This app plays different signals to your two ears; through loudspeakers the effect disappears.
Move a sound around your head and listen to the two cues the brain uses to locate it: the tiny arrival-time difference between the ears (ITD, up to about 0.7 ms) and the level difference caused by the head’s shadow (ILD). Switch the cues on and off to hear what each one does on its own. Press Start audio first.
What to notice: the low clicks localise mainly by timing (switch to ITD only and they still move), while the hissy noise localises mainly by level. Angles behind you sound the same as the mirrored front angle, since headphones give none of the spectral cues that normally resolve front from back.