The basic difference between Acoustic Power Level and Surface Acoustic Power Level is the nature of source being quadrapole or dipole. Acoustic Power Level (dB) is useful for estimating the local quadrapole contribution to the total acoustics. W[dB] = 10 log10 [Integral(Acoustic Power*dV)/10^-12] Surface Acoustic Power (dB) is useful for estimating the local dipole contribution to the total acoustic power. W[dB] = 10 log10[Integral(Surface Acoustic Power* dA)/10^-12]