The more energy a sound wave carries, the louder the sound and the bigger its amplitude.
Explanation
The amplitude of a sound wave is the key factor that increases with the energy the wave carries. A larger amplitude means the wave causes greater vibrations in the medium (such as air particles), which translates to a louder perceived sound. Intensity, which relates to the amount of energy passing through a unit area per unit time, increases with amplitude and is measured in decibels (dB). Thus, louder sounds correspond to bigger amplitudes and higher energy in the sound wave.
In summary, the answer to the question is that the bigger characteristic of the sound wave is its amplitude.
