What properties of sound determine the volume of sound? Is this affected by the motion of the sound source?

Question

anonymous · Answer

Only the 'size' of vibrations affect the volume of a sound (hit something harder, it will be louder). This is the amplitude of the wave. It is a measure of how far the particles move back and forth, or if you represent it graphically as a trace, the height of the wave from the centre line. 

Motion of the sound source will only affect the frequency (as per the Doppler effect) and not the volume (apart from the fact that a sound which is closer will be louder because the intensity [energy] of the waves has not decreased as much).