[ed]

Sound decays exponentially as a function of distance, so speakers close to you don't need to be loud. Also most speakers are also fairly directional, so i'd expect any extra energy to be absorbed by the room (as heat).

Edit: more importantly these are destructive waves, so if anything you’d actually reduce reflections back out into the world.

[hwillis]

quadratically (proportional to x^2, the surface of an expanding sphere) as opposed to cubically (x^3, the volume of an expanding sphere) or exponentially (2^x, objects that multiply over time)

[ed]

ah yeah, thanks!

[Robotbeat]

Not exactly exponentially.

[vages]

Yes, it's not exponential. The sound level is inversely proportional to the square of the distance.

[gmantg]

This is 1/d^2. Exponential would be 1/2^d.

[anticensor]

It is actually between the two because sound is a material wave and air has friction.

[hwillis]

depends how far away you are.

https://upload.wikimedia.org/wikipedia/commons/thumb/6/64/Ex...