Hi all, First of all, thank u for ur time and sorry about my english. I have measured a loudspeaker's Sound Pressure Level from a distance of 1 m. At the same time, i've measured, with a accelerometer, the displacement, velocity and acceleration of the loudspeaker's diaphragm. I've found that when the SPL is 60 dB and the frequency is 80 Hz (loudspeaker radiating a pure tone) the displacement is 0,034 mm, the velocity is 190 mm/s and the acceleration 9,76 mm/s^2. 1) First wrong that i found is that, i know the magnitude of displacement is d=A, so d=0,034 mm, then the velocity is v=w·A=17,1 mm/s, and acceleration is a=w^2·A, so a=8,59 mm/s^2. The most different is about the velocity (17,1 mm/s so far from 190 mm/s).. any idea? 2) i start slowing the SPL, and i find that the velocity and displacement decreasing also, however, the acceleration keep constant.. about 9,7 - 9,8 mm/s^2. When the SPL is 42 more or less, the acceleration start decreasing (at 42 dB is 2,1 mm/s^2) until almost zero at 39 dB.. is not a bit rare? Thank u very much.