Root Mean Square amplitude
For simple periodic waves, the Root Mean Square amplitude is equal to the peak amplitude multiplied by 0.707. For complex periodic waves, RMS amplitude cannot be derived directly from peak measurements. Peak measurements differ from RMS amplitude in that they give a measure of acoustic amplitude, whereas RMS amplitude is a measure of acoustic intensity (because perceived loudness is linked more closely to acoustic intensity than to acoustic amplitude). To calculate RMS amplitude, each sample in a waveform window is squared; then the average of the squares is calculated; and then, the square root is taken.