Today we’ll be looking into how we as humans hear sound as well as how sound travels, the speed of sound and also touch on the Fletcher Munson Equal Loudness Contours (which I will go more into more depth tomorrow).
So, here is a question: “What is the most important gear that a sound engineer has?”
Take some time to think about it, as there are many possibilities…
Right, most of you would have jumped to things such as “the mixer”, “the microphone”, “the speakers”, “the amp” etc etc etc
Well, you’d all be wrong. THE most important piece of gear that a sound engineer has is his/her ears. Yes, your ears. The little piece of flesh on the side of your head. Without these, your brain would not be able to interpret sound, or give you spacial awareness. The ear may look simple from the outside (“a little piece of flesh on the side of your head” as I said earlier), but inside, it is one of the most complex parts of the body.
Below are two pictures. The first one is of the outside of the ear, while below is a picture of the inside of the ear. See how complex it actually is.
Don’t worry, we will be discussing the inside in detail later on. First though, we must understand how sound travels in order to get to our ear.
Sound travels in waves through any medium that it can vibrate. Mediums such as air, water, concrete etc spring to mind. Any medium that is a solid, a liquid or a gas has the ability to be vibrated. The less of the medium that exists, the less vibrations are going to take place. Also the medium affects the speed at which sound can travel. Solids have particles that are more dense that liquids and gasses so can therefore handle more vibrations. Normally, sound travels through air for us to hear where at 18°C it travels at 342.376 meters per second. This is calculated with a fairly simple calculations:
c = 331.45 + (0.607 x Dc) Where: c = the speed of sound & Dc = the temperature in 18°C.
So the calculation would come out as:
c = 331.45 + (0.607 * 18)
c = 331.45 + 10.926
c = 342.376
Sound is usually measured at 18°C.
Now that we understand how sound moves, we can start to understand how our ears receive the vibrations in the air.
If we go back to the picture of the ear:
We can see here that vibrations come into the auditory canal in the form of vibrations. These vibrations vibrate the ear drum which is a skin membrane stretched across the end of the auditory canal. This in turn moves 3 bones (the smallest in the human body) the Hammer, the Anvil and finally the Stirrup. The stirrup will vibrate another membrane, behind which is the cochlea. The cochlea is filled with a liquid which will cause waves, similar to dropping a stone in a pond. Lining the cochlea are over 30,000 microscopic hairs, whose ends connect to nerves which go to the brain. These hairs each pick up a different frequencies, and amongst them, they make up the frequency range which we hear. So our ears are fairly similar to a microphone – The air vibrates a membrane which sends an electronic signal.
I was going to touch on the Fletcher Munson Equal Loudness Contours today, but I think I will leave that for tomorrow.