If a tree falls in a forest

This tree in the River Wear made me think of the famous old question: "If a tree falls in a forest and there is no one there, does it make a sound?". My take on it is that it must make the air molecules vibrate but that in order to call it a sound, there must be an ear to detect the vibrations and a brain to interpret it. To me, it seems similar to ideas in quantum physics. Detection is everything. We don't know what is going on between observations. We end up summing the probabilities of different possibilities.