Can sound be broadcast in a channel or beam as light can, like a flashlight and be contained in that beam?

Question

When a train travels through a neighborhood, the mandatory warning horns disturbs people for miles around. Would it be possible to direct, restrict, the loud noise to an area directly in front of the train in the danger zone, leaving the rest of of the area in blissful peace.

Answer 1

Sound can be partially 'focused', but not in the same way as a beam of light or electromagnetic energy. Sound travels through the air and air causes the sound to 'disperse' in all directions.

Doug

Answer 2

Actually, light isn't "contained" to a beam in a flashlight. A laser pointer, yes, the light is contained to a beam because you can't see the red light unless looking at it head on.
In a flashlight, you can see the "beam" of light from the side, you don't have to look at it head on to see it, that means that the light from the flashlight is actually propagating to the sides as well. So if you can see the light, then its going in the direction of your eye.
Yes sound can be concentrated to a beam, I believe machines exist where it produces a sound that can only be heard if you stand directly in front of it.

Answer 3

Yep. The most common method is to have a sound source at the focus of a parabolic reflector, then use a second parabola to collect the sound. You'll find a setup like this at most science museums, and we've got one in the Physics Department at K-State.

Answer 4

You can send sound through a light beam too:
http://home.earthlink.net/~lenyr/modlitbm.htm