Fundamentals of Sound - part 1

Welcome back! Hope you had a restful/exciting break and are ready to get back into the wonderful world of audio.

So far we've discussed a bunch of different topics, from music theory to hip hop history to navigating software. Today we're going to talk a little about some fundamental audio concepts.

What is sound?

On the most basic level, sound is the vibration of molecules. Since we live in an air-filled atmosphere, sound for us is usually the vibration of air molecules.

Whenever there is any kind of movement or friction or impact in our air-filled environment, the air molecules get compressed and are pushed out of their normal position. They then react by springing back in the other direction. Same concept as a pulling a piece of string tight and then plucking it; the molecules swing back and forth.

It's important to understand that these vibrations don't just stay fixed in one place; as the vibrating molecules get pushed out of place they bump into their neighbor molecules and cause those molecules to vibrate, causing their neighbors to vibrate, then those molecules bump into their neighbors, and so on. Basically, the vibrations spread out in all directions in waves, sort of like dropping a rock in a pool of water. This is how the sound gets to your ears. The waves move outward at a steady rate, but get weaker and weaker as they move farther and farther away from the source...


If we try to draw a picture of a sound vibration, we get something like this:
A picture like this is called a waveform.

If we zoom in really close, then we see somthing like this:



What this diagram is showing you is a single cycle of a sound, and in this picture we can see the two basic aspects of sound, which brings us to the main point of today's lesson...

FREQUENCY and AMPLITUDE!!!

On the most basic level, here is what you need to understand:

Frequency = pitch (Hz)

Amplitude = loudness (dB)

Now, more specifically, frequency is the number of cycles that happen in a single second. The faster the vibrations are, the more cycles are happening per second, the higher the pitch. In the waveform diagram above, the horizontal axis is showing frequency. The closer the cycles are to each other, the higher the pitch and vice versa.

The unit of measurement of cycles per second is the Hertz (Hz).

Amplitude is a little trickier to explain, but basically it is the amount of energy that is going into making the sound. In a waveform diagram like above, the height of the wave is showing you how loud the sound is.

The unit of measurement of amplitude is the decibel (dB).

Last and SUPER IMPORTANT thing to know for today:

The human range of hearing is approximately 20Hz to 20,000Hz.

With this information, we can start to get into really working with sound. Tune in next time for the wonderful world of harmonics, folks!