– Or: Someone is asking someone named Kenneth this somewhere and he’s fed up with it
You know? The REM song? Frequency and …. Yeah. Moving on.
Welcome to the start of all kinds of wackery and funnery where audio stuff is concerned. Today’s episode is going to be a deep(ish) dig into some audio basics. Starting with the most basic of all things: the waveform.
This has nothing to do with your hand. Or water. Or being some kind of disruptor in some kind of industry doing some kind of disruption.
Sound waves are the order of business today and I’m going to do my UTMOST to make this worth reading if you’ve ever been curious about what makes sound tick. Almost literally. Probably going to repeat some ideas or say them in different ways here and there to throw everything at the wall and see what sticks*. Hopefully it doesn’t get too boring
(* spaghetti sticks to the wall. can confirm.)
What is sound and how does it happen and where can I buy one
The first step to figuring out the ins and outs and sidewayses of the world of things we hear is to know what sound is and how it’s measured.
It all starts with what we call frequency. Frequency – outside of the context of audio – is how often something happens. How frequent something happens is the measurement of occurrences within a time period. We can measure how many times a day we eat (anywhere between one and seven per twenty-four hour period). Or be super nerdy and measure how many times a cyclist has to pedal a complete circle in order to cross a distance within a certain time. We can measure the number of stomps it takes for a child to make it to their bedroom from the bottom of the stairs and how long it takes.
(that last one we probably can rattle off quickly. 19 stomps : 6 seconds)
So take all that and now let’s apply it to audio. Sound in its purest form is a measure of frequency.
To up your audio frequency game, it is measured in Hertz. Not the rental car company. Named after Heinrich Rudolf Hertz who is credited as having shown proof of electro-magnetic waves. Frequency and hertz (hz) are the measurement of cycles per second.
I’m going to try to keep this as un-mathy as possible but there will be a few numbers here and there. A sound wave will consist of the number of times it cycles through a period of time along with how much power it has. It’s generally referred to as Amplitude but we know it better as Volume.
Figure 1.0 – Basic Sound Wave
What is an amplitude and you c–
IT WASN’T FUNNY THE FIRST TIME, MR BALD GUY AUTHOR.
As stated above, it’s all about how much of the sound wave you’re getting. In the picture above, I selected an arbitrary number of +1 and -1. Why? I dunno, it worked for the illustration. If I changed that picture to say +2 and -2, then we would have a larger sound wave which means it’s “louder.” See? Volume. Boost. Gain. Things that make it hurt our ears more vs less.
The larger the amplitude, the further a speaker has to move in order to create the sound.
Once again in the picture above, the beep and boop are the peaks of a full sound wave that occurs over the space of one second. This is 1hz.
If we had a GIANT SPEAKER and we could power it up and look at the magnetic coil that makes it move (the driver), you would see that over the course of that second, the paper would move up to a peak (+1), and then retract to a peak (-1) and then return to a neutral position (0).
A complete and total sound wave!
That you couldn’t hear!
WASN’T THAT EXCITING???
Familiarizing frequency into something that makes sense
So now that we know what 1hz looks like, what would, say, 4hz look like? I have drawn yet another picture for your viewing (dis)pleasure!
Figure 2.0 – Example of Four Cycles Per Second (4hz)
Look. I’m not an artist. I can’t even draw stick people right. I’m a musician. I make the waves, I can’t draw them. Forgive me.
That is 4hz. Four full positive to negative cycles. That speaker cone would complete a cycle of movement four times in that single second.
Still can’t hear anything.
It is considered to be a “sub bass” frequency. The air moves too slow for our feeble earth ears to perceive in a way that makes sense.
For any of you who were, at some point, introduced to the playing of the piano in your childhood days – potentially by a very strict teacher who would bonk your hands with a ruler if you misplayed which is why you’re not a piano player anymore – you likely remember where Middle C is. You probably can almost visualize what it sounds like.
Middle C on the standard piano scale is 256hz. Two hundred fifty six cycles per second.
I’m not going to try to draw that. It would look like this: ▓▓▓▓▓▓▓▓▓▓▓▓▓▓
And I’m left handed to boot so there would be smudges and smears and LOOK JUST TAKE MY WORD FOR IT.
Frequency in the realm of what we are familiar with
As alluded to above, there are frequencies that we just cannot hear. For example, anything about twenty thousand hertz is – for the most part – outside of the realm of what our earth human ears are capable of hearing. You know what -can- hear frequencies above that range? Dogs. The conventional dog whistle is a whistle that produces a loud sound at a frequency that we are unable to perceive but sounds like a high pitched shriek to a canine.
Sometimes they are frequencies that we cannot exactly hear but can certainly feel! Sub-bass frequencies (higher than 4hz though) can rumble around and while we are unable to perceive what the actual note or notes are, our bodies will feel them because of the way sound travels. Sound travel and penetration is probably a completely different blog topic but for the moment we’ll leave it at that. Been to a rock concert and felt the kick drum and bass guitar punch you in the gut? Low frequencies can be felt in a way that high frequencies cannot*. Amplitude/volume helps with that. Those volume levels are designed to fill massive rooms with sound so that everybody can go deaf/hear from anywhere. Please wear ear plugs. You won’t thank me later because your hearing will be preserved and you’ll never know.
Specific frequency examples
Between the sub bass frequencies and the high pitched stuff that dogs give us the side-eye over is all the stuff that we CAN hear. Like Middle C. Fingernails on the chalkboard are a very loud sound between 2000hz and 4000hz and make us want to claw our faces off. Ambient airplane noise covers a huge range of 50hz to 5000hz. The meat and potatoes of my voice lives in the realm between 100-500hz (next time we’ll talk about how we can use tools to stealthily mute me without muting me! 😀 )
*I have to mention sonic weaponry. Briefly. Refined directional huge blasts of audio that have been used in crowd control scenarios without needing to cause bodily harm. I suspect that damage to hearing during those blasts is irreparable and I have opinions about their use and they’re not good but we’ll just move along.
So now what?
Sound waves are the ground floor level of everything that I’m planning on brain-dumping about coming up. This first entry was going to be all about Equalizers and spent over a thousand words just talking about frequency. SO! This is its own post. Equalizers are going to come later and how we use those things to manipulate what sounds actually sound like. That’ll be a bucket of fun!
I’m super excited to share as much of this as I possibly can. I’m also going to get quite a bit of this wrong and I’m always open to correction! If I’m messing something up, please let me know.
Talk to you soon!
-= george =-