What is this thing called “Sound”
In our first two chapters we examined how we are affected by the sounds in our surroundings, and how we affect our surroundings with sound. The bridge in this transaction is the phenomena of sound itself; how it is created, how we receive it, and ultimately what happens to it once it impinges on our bodies and thus our minds.
Unlike smell, texture or taste, sound is not a property of something; and while we can see an object that hasn’t moved in a million years, for sound to exist, something has to happen. For us to hear it, quite a few things need to happen. As we examine these things, it is important to make the distinction between ‘sound’ – what we hear, and ‘acoustical energy’ – the physical phenomena that we perceive.
For the sake of this clarification, ‘acoustical energy’ is considered the physical displacement within matter that is a result of a mechanical action imposed on that matter. The matter does not need to be something inhabited, like air or water that we inhabit, or the wood that termites inhabit; it can be any matter – from lead to ether.
Acoustical energy needs matter to exist. It does not pass through a vacuum because there is no matter in a vacuum. If a brick is thrown in a vacuum you would not hear any sound when it hits its target. Nonetheless there would be acoustical energy within the brick once it strikes because the brick is matter; but it would stop at the boundaries of the brick without transferring this energy into the surrounding vacuum. Acoustical energy is a product of mechanical energy transmitting through matter. If the matter is something we are submerged in, like air, water, or molasses, we can sense or feel the energy through our ears and bodies. This is what we call ‘hearing.’ ‘Sound’ is what we hear.
Most animals can perceive acoustical energy through their bodies by way of ‘proprioceptors’ and ‘mechanoreceptors’ – sense organs that respond to body position and mechanical stimulus, respectively. Many animals, including humans, also have phonoreceptor organs – ears in our case – that are finely tuned to receive acoustical energy and transform it into neural impulses. In a broad sense, these phonoreceptors are the organs that translate acoustical energy into sound.
Understanding the distinction between these two independent phenomena –‘acoustical energy transmission’ and ‘sound perception,’ has long contributed to the confusion about how we think of, or imagine sound. ‘Acoustical energy’ can behave in ways that are hard to perceive, and we can perceive sound in ways that seem inconsistent with our understanding of the material world. Our increasingly refined grasp of physics and our broadening concepts of perception are bridging the gaps in our understanding to a degree, but I find that most people’s innate comprehension of how sound works has not progressed much since the 18th century – perhaps earlier. Some of these notions seem quaint to an informed reader, but they remain persistent to this day
In this chapter we examine the physics and physiology of sound, looking at the transformative path which acoustical energy passes from source to our hearing; through vibrating matter into air, enveloping our bodies reaching into our ears channeling through our nervous system to become “sound perception.”