OT: Sound spotlight

[Andy Main]

Hi all,

I was watching the end of Tommorows World (UK science prog) last night, when
it mentioned that in next weeks show they were going to show a new sound
spotlight.  Now I've been thinking about this ever since, and still can't
work out how the interferance pattern required could be obtained, to give a
true spotlight.

Any ideas? (I generally don't watch TV so I doubt I will ever see it)

Andy