Originally posted by JB88
so its the hz that determines the size of the wave?
The hz is the length of the wave. It also determines the tone. This is where subwoofers come in.
The lowest tone (hz) a human can hear has a wave length of 17 feet. If you're not outside of 17 feet from the source, you won't actually hear it. So subwoofers were invented. With these, they try to reproduce low frequency sounds by vibrating the air.
The amplitude of the wave is from the amount of energy creating it. The size is determined by how loud you make it.
But I don't really see a solution to your problem. Sound is pressure waves. Unless there's something confining it, it'll radiate in any direction it wants. You can't really focus it, because once it leaves it's confinement, it tries to move towards lower pressure areas.
You've heard about the domes and sound. This works because it redirects sound. Same with reflective surfaces. Both the dome and a pipe could work, but having a 100 foot pipe escapes your purpose, I believe. As well as having an immovable dome.
Only other solution I see is electrical reproduction at the target.