Question

Which best describes the energy of a sound wave as it travels through a medium?

It increases.
It decreases.
It remains the same.
It depends on the medium.

Answer 1

It decreases.

As a sound wave travels it loses energy to the medium via absorption (converted to heat), scattering, and geometric spreading, so its intensity and energy diminish with distance (in an ideal lossless medium it would remain constant, but real media attenuate sound).