[PD] Re: multi-speaker panning.. problamtic maths

Charles Henry czhenry at gmail.com
Fri Oct 27 01:43:43 CEST 2006

> I made this mistake again last thursday - I computed sound amplitude of
> some kind of omnidirectional source as being r^-2 where r is the distance.
> However, I believe that it's energy that should be r^-2, therefore
> amplitude should be r^-1. That's assuming ideal 3-D dispersion (no
> ceilings and no walls). Is that right?

Exactly right.  For that ideal environment, we have the intensity
(W/m^2) distributed evenly on the surface of a sphere at radius r.
So, since the surface area of the sphere varies as r^2, the intensity
falls off at a rate of r^-2.  The energy of the wave is (mostly)
conserved, it just gets spread out over a larger area.


More information about the Pd-list mailing list