You’re watching TV on a saturday night in your underwear with the remote in one hand, and a cold drink in the other. You’ve had a rough week behind you and now it’s time to relax and enjoy the precious spare time you have. But there’s always someone to ruin it for you. “Take out the trash. Do your homework. I want some attention. Do this. Do that. Whine, whine, whine.” Some people just don’t know when to shut up, so now I will teach you how to stop that white noise from spoiling your weekend.
It won’t surprise you that the key factor here is sound, or rather the propagation of sound. In more or less technical terms, sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid or gas. So, what we eventually hear in our ears is nothing more than the vibrations of the air molecules. Sound can be visually represented as a line going up and down (sinusoidal waves) at various frequencies. When the peak of a single wave is high, so is your voice, when it’s low and outstretched, you sound like James Earl Jones.
The propagation of sounds is affected by three things: density of the medium, motion of the medium and viscosity of the medium.
Simply put, sound waves travel by tapping molecules and passing the message along. Each molecule taps the next in a chain of molecules, until the sound reaches your ear. The denser the medium, the faster the waves will go. This is because in a dense medium the space between each molecule is smaller, making it easier to tap the next molecule in line. It’s like being at a crowded party, it’s much easier to grope people.
If the medium itself is moving, like wind, the sound waves within it will travel along, going further than they normally would. If the wind is going in the opposite direction as the waves, the sound can drown out if the wind is louder. This can be shown in numbers: if you have -1 coming from the left, and +5 from the right, they will smash into each other and combine to form +4 going to the left.
Finally, there is viscosity. This is the measure of the resistance of a fluid when you throw something into it. Honey has more viscosity than water and will offer more resistance to the sound waves, thus limiting their range.
Well that was a long lecture wasn’t it! But it was worth it because now your weekends will once again be sacred. All you have to do is stop the molecules from moving, or introduce a vibration of your own to counteract the nagging. And if all else fails, you can always try earplugs.
Fun fact: the speed of sound in dry air at 20 °C is 340 metres per second, or 1,236 kilometres per hour (768 mph).