SOUNDS AND TREES

The other day, I overheard someone on a bus talking about the famous, philosophical point, "If a tree falls in a forest and no one is around to hear it, does it make a sound?" It got me thinking about the nature of sound in general - can a sound exist without it being heard? We know recorded sounds exist but if the recording isn't played then maybe the sound doesn't exist....

You can look at an instrument that isn't being played and imagine the sound it would make if it was being played .....

For those of us that can see and hear, it's possible to 'hear' with the eyes and 'see' with the ears. Like many people, I've learnt to read a music score and 'hear' the notated sounds without the music playing. 
With this in mind, it's also possible to hear a sound and know how it would be written as notated music.

Wikipedia says, 'The Music Of The Spheres is an ancient philosophical concept that regards proportions in the movements of the Sun, Moon and planets as a form of music'. 
You can't actually hear this 'music', but maybe that's because we've always heard it and would only notice it if it wasn't there! I often only notice the hum of the fridge was ever there when it turns off.

Does visual art only become art when the viewer looks at it....
arghh, I don't know the answers to any of this, I think I need to get out more!