The power for a sound wave is give by P = 1/2*p*A*(w*s)^2*v...in which p is density (rho), A is cross-sectional area, w is angular frequency, s is maximum displacement (amplitude), and v is speed of propagation. The intensity is given by P/A...the intensity for a spherical sound wave is supposed to decrease over time (according to experience)...but I'm not seeing it in the equations. The power is proportional to the area over some region and the intensity is inversely proportional to the area over some region. Therefore...the Intensity at a given point shouldn't depend on A (the area)...that would make the intensity constant throughout the wave. Where am I wrong in the reasoning? Oh wait...never mind...the source determines the power...I shift to a new question: the A (area) in the equations is the cross-sectional area immediately "touching" the source, right?