6.1 Introduction to Waves and Sound

There is a secret about waves. It is the kind of secret that, if you fully understand it and its implications, may well blow your mind and leave you scribbling paranoid manifestos on attic walls.

Or worse, you might only think you understand this secret, and go off and make some horrible and misleading movie like What The Bleep Do We Know[1. Just don’t even bother googling it, seriously.] based on your flawed understanding.

What the bleep do we know
Augh, I wish I could un-see this movie

It is the kind of secret that has a lot in common with some of the best conspiracy theories: it’s far-fetched and far-reaching, and for many years it attracted only a small handful of dedicated believers trying in vain to convince everyone else that it was true.

The secret is fairly simple: everything is a wave.

Every chunky, solid object around you, every apple and lamp and floorboard and, yes, every particle of your very body is not nearly as solid as it looks, but is instead a kind of wave interacting with other waves using (believe it or don’t) waves.

Unfortunately, it takes some careful work in order to understand what that even means, let alone to start talking about the implications of such an outlandish theory. But rest assured that it is completely true. In Chapter 9, we’ll see how scientists made a series of baffling discoveries throughout the last two hundred years that eventually led to the theory of Quantum Mechanics, which now stands as one of the most thoroughly experimentally-proven theories we’ve got.

To begin looking at waves, it is much more useful to pretend at first that quantum mechanics doesn’t exist at all, and that waves and solid objects are two very different things. In this way, we can understand all of the fascinating properties of wave behaviour without getting bogged down by the insanity that is modern physics. Once we know exactly what waves can and can’t do, we’ll be much better prepared to face Chapter 9.

And in the meantime, we get to learn about more classical types of waves, which are cool enough in their own right. The big star of this chapter is the sound wave, but this will set us up nicely to discuss light waves in the next chapter, and we’ll also mention things like earthquake waves and water waves, too.

To whet your appetite for an in-depth discussion of sound, I’d like to offer you the following thought. Consider the image below. Look it over for a few seconds. What information can you get out of it?

Hard Days Night waveform
If you cross your eyes, you can see a sailboat.

Granted, this isn’t the most detail-rich sound visualization, but surely we can glean some information out of it. Is this music? Barking dogs? A whispered conversation? Radio static? Someone dropping a microwave oven onto a stack of Belgian waffles?

It’s impossible to say! And yet if you took this image and moved the air near your ears back and forth in time to all of those bumps, you would hear the first few words of “Hard Day’s Night” by the Beatles.

Now consider just how extraordinary that is: from this mess of densely-packed data that was mostly meaningless to your sophisticated visual senses, you could clearly distinguish two vocalists, even though they’re singing the same words at the same time with the same Liverpool accents. If you were familiar with the band, you would know which voice belonged to which singer. You could also distinguish four different instruments, even though three are only minor variations on the same stringed theme. If you understood enough English, you could quickly and effortlessly decode the meaning of the song’s lyrics, even if you’ve never heard that exact combination of words before in your life. And if someone walked into the room and spoke to you while the music was playing, you could understand them just fine as well, despite all of the other information entering your relatively small ear canals at the same time.

All this from a little squiggly line that can really only do two things – go up or down. How can we be so skilled at getting information from sounds? What’s so special about a sound wave that allows us to analyze it so much more easily than its equivalent visual representation?

To understand the answers, we’ll need to see just what makes a wave a wave. It’ll quickly become apparent what makes them so special.

Next: 6.2 – Waves

Previous: 5.7 – Entropy, Part 2: Efficiency