If a tree falls in the forest, and nobody is there, does it make a sound?
If we not rush to reflexive conclusions, we find that this age-old question unearths a fascinating look at the nature of sound, of hearing, and further still, our place in reality.
How is sound produced? It is a disturbance, a ripple in some medium, whether air or water, earth or steel. Branches and tree parts falling through the air and hitting the ground create pulses of air. Rapid pressure variations that spread in ripples at 750 miles per hour. There is no sound implicit in them – it is just wind moving.
Yet if someone armed with an ear and an auditory cortex happens to be nearby, these puffs of air will hit their eardrum, vibrating it and setting off a cascade of mechanical and electrical activity down the auditory nerve and into the brain, resulting in the perception of a noise. For the sound to be perceived, however, the frequency of the air puffs must fall between 20 and 20,000 times a second – the particular range for which the ear and neural system are designed. Either side of this – there is just silence.
So an observer is every bit as essential to create the sound experience. When a tree falls in the forest and no one is there, there are just silent pulses of air. Sound is a shared experience, a symbiosis between the world outside and our conscious perception. They are indivisible. Indeed this is one of the most fundamental and puzzling discoveries of Quantum Physics – that reality is a process, which involves, and is even influenced by, our consciousness.
When we are immersed in the sonic landscape of our lives, replete with songs and sirens, we are full participants in the process of creating it. When music stirs our emotions, the little puffs of air stimulate ancient neural pathways, conjuring memories and emotions both personal and universal. Perhaps this is what makes life all the more remarkable: that while everything is ultimately in our heads, what we feel in a song or a sound can be so deeply shared by other people, who we may have never even met. Music and sound forge a bridge from our individual experience to the individual experiences of countless others. Now that is magic.
And if you still believe in the firm reality of sound outside of your brain, check out some of these bewildering Sonic Illusions.
Joel Douek is Creative Director + Sonic Strategist at Man Made Music. Talk to him on Twitter @joeldouek.