Is there any way to "soundproof" an open air space?

Factual Questions
1

For parties! I know it’s unlikely, but figured if anyone knew how it’d be the Dope. Details - It’s an open air area that can hold around 300 people comfortably, and the closest building is about 300 meters away. Is there any way to prevent loud music from getting out?

2

You need to create sound waves that are the inverse what is there and that will cancel out the sound.

See http://www-personal.umich.edu/~gowtham/bellala_EECS452report.pdf for a starting point

3

I know about active noise cancellation, but doubt that it is feasible for the application I had in mind. As far as I know, it is useful only for localised noise cancellation - earphones and such like.

4

Exactly. The problem in an open air environment is that the soundfield is completely different from one inch to the next. That’s why active noise cancellation only works (well) in headphones, because you can concentrate it on a very small space. If someone figured out a way to not have noises travel through open air, he would become very, very rich. Think of the possibilities: plane noises, highways, open air music festivals close to residential areas - if it could be done today, it would.

5

Nope. It actually quite difficult to soundproof rooms inexpensively, let alone outdoors.

6

Trial and error in placement of things can be used to reduce sound levels in a particular direction. Though it is difficult to scale up to what you are proposing. I would suggest you look into sound deading walls used for highways, not to construct one but to get a idea of the principals involved and methods used to help arrange what you will have such as parked vechicals, outhouses etc.

Also note that high pitched sound doesn’t carry as far as base so if possible tune the base down if you don’t want it to carry far.

7

outdoor music venues use earth berms or are placed in holes.

8

Actually you can use noise cancellation, the right configuration of loudspeakers will dramatically reduce the volume outside your perimeter. The downsides: it only really works for bass, you need a shitload of gear and the sound/music really sounds like crap outside your perimeter.

I know some large venues that use it for raves (Gelredome in Arnhem for example).