Stuart wrote:
Actually, its what we've been doing with sonar equipment for the last forty years. Using signal processing to compress the transmission pulse to as brief and intense a level as possible, tightening it up so that it is spread over the smallest possible range of frequences and eliminating sidelobes and harmonics. All of that with teh specific intent of concentrating as much energy as possible into the smallest possible pulse in terms of frequency coverage. I've just pushed it to the ultimate level where the energy in the pulse is concentrated into a single frequency spike with no spread or harmonics.
But you
can't do that. Physics does not work that way.
First off, it's literally impossible to make a pure note; unless it happens to have infinite duration, you'll get harmonics at the start and end, decreasing (but never hitting zero) as you near the middle. That's with perfect speakers, too.
Second, these are sound waves, not light. They travel through the medium of air, which is a heck of a lot more grainy than the quantum vacuum - it'd mess up the frequency spectrum too.
Third, and most problematic, the degree to which a wave spreads out is an (inverse) function of its frequency, not its purity. If you want a sound "laser", the simplest way to do this is to give it a frequency that is more commonly associated with light. In fact, one way we're "beaming" sound today is to use multiple speakers, each of which produces a high-ultrasound beam; due to its frequency it won't spread out. We then have them interfering at the target site to produce sound we can actually hear. Kind of inefficient, but it works.
For your story, all you need to do is specify that it's a bloody loud noise at an enormous frequency. Oh, and you can make it unusually pure too, if you want, but that doesn't really matter; you're smashing stuff up with pure force here, not trying to hit a resonant frequency.
Unless you are. That would be nifty.
"
- PeZook
[