If a tree falls and no one hears it, is sound made?

While our class scribes work on the scribe reports, I think a good question to ask is on the topic of Appearance VS. Reality.

Earlier today, we were posed this question that if a tree falls and no one hears it, is sound made?

Some of us (including me) agreed that indeed, sound was made. But Mr Shyam then posed the argument (well, not his argument, but he showed it to us): Sound is defined as sound, when the disturbances in air reach out ears and interpret the signals as SOUND. Therefore, when the tree falls and no one hears it, it basically means that disturbances in the air are created, but no sound, since there is no human ear (or animal ear) to listen to it.

Then I posed this counter-argument: Then what about sound we cannot hear and detect, like infra-sound and ultra-sound? Just because we cannot hear it, does it mean that it does not exist. This is thus very contradictory, as saying that things we cannot hear are not sound would mean that many technology applications would not be able to exist!!! What about ultra-sound scanners used to check foetuses growth? What about ultra-sound that is used to check the integrity of construction? What then about INFRA-SOUND which animals like elephants use to communicate over long-distances? Are they not sound?

This epitomises the conflict and the conundrum between appearance versus reality.

Share with me your views. You can always agree or disagree with me. My verdict is: Physical reality is undeniable. In the example above, sound is indeed made and present.

What do you think?