Acoustics – How to Focus Sound Waves Effectively?

Question

I saw this TED talk and I am curious as to how the sound is focused on the general level. Can anyone explain this or does anyone have any good articles?

Answer 1

I don't think anyone here has really answered your question. In this case, the sound is "focused" using phased arrays. The face of the audio spotlight has multiple transducers:

Flickr

The same signal is output from each of them, but delayed slightly by different amounts, so that the wavefronts all reach the same point in front of the device at the same time. This "virtual focus" is called beamforming.

ref ref

This is how modern radars focus their beams, too. Instead of spinning a satellite dish around, they have lots of little elements that don't move, but the signals are delayed to produce different beam shapes.