Everyone knows this riddle: If a tree falls in a forest and nobody is there to hear it, does it make a sound? Here is the good news – I will answer the question. – However, the bigger question is will you agree?
The key is in the definition of two key words: sound and sound waves. The question is whether one considers these two terms as the same or different.
Sounds waves are sequence of a repeating pattern of high and low pressure waves passing through a solid, liquid, gas, or plasma. Waves can be of different frequencies, the number of repeated waves over a period of time (usually seconds). Think of different musical notes having different frequencies.
Sound is the interpretation of sound waves. From an organism’s point of view, in order for sound to occur, the organism needs a mechanism that converts sound waves into nerve impulses that are another mechanism translates them into a sound.
Does a dog whistle make sound waves? Unquestionably yes. Does it make sound? To a dog, yes – but to humans, no.
Does the symphony make sound waves? Yes. Does a totally deaf person in attendance hear the sound? No – not to them; but to one with healthy hearing, yes.
Therefore, the falling tree unquestionably produces sound waves – but if nothing is there that is capable of translating sound waves, there is no sound.