As to the perennial question of whether a tree falling in the forest makes a sound if no one is there to hear it (first posed by Irish philosopher George Berkeley), the answer is technically no. There is no sound apart from a sentient brain’s interpretation of molecules vibrating through air or water. The brain turns those molecules hitting the eardrums and pinnae into a mental idea of sound. Birds will hear the toppling tree, and fish will hear it too. But there is no thing called sound unless the vibrating molecules are processed into pitch.