Answer the following question given this paragraph: 

Amplitude is a measure of the size of sound waves. It depends on the amount of energy that started the waves. Greater amplitude waves have more energy and greater intensity, so they sound louder. For a video demonstration of the amplitude and loudness of sounds, go to this URL: http://www. youtube. com/watch?v=irqfGYD2UKw.


Q: What is a measure of the size of sound waves?


A:
amplitude