Okay, so you might have seen me teach on this in some of my, some of my other training courses, but let's just go over it quickly right now, at its core sound is changes in air pressure. If I snap my fingers it sends out waves in all directions of air pressure. Those waves of pressure make their way to your ears and vibrate your eardrum in sympathy with those waves and you just perceive that as sound if there was no air in here, we wouldn't be able to hear a thing. Because sound is changes in air pressure. And that's why in space no one can hear scream that's a reference to the original alien movie if any of you are old enough to remember that one. Okay, so at is can also detect the rate of those sound waves.

If I play this sound right now, as the fattest sound on acoustic Guitar we perceive that as being a musical scalp, but what really happened is your ear drum was pushed back and forth in sympathy with that sound and get this your brand counted as happening at 2.41 times a second, can you believe that it counts those waves, and you just perceived it as an eight. So the next string as your rank counting exactly 110 times a second or an A and then all these other rates for the other strings. By the way, a shortcut for saying 110 compressions of airwaves per second is just to say 110 hertz. So whenever you I say something like a 440 hertz, for example, I'm saying the sound vibrating is at 440 times a second. Once we get into thousands of hertz, we say kilohertz, okay? for short.

Humans hear roughly from 20 hertz to 20,000 hertz or 20 K, or waveforms that cycle between 20 times a second to 20,000 times per second. We tend to lose our top n as we age, but to hear some pictures and also know where they are, let's play a sweep from 20 hertz to 20,000 hertz It's kind of like how light is broken up into different wavelengths of color through a prism or, or rainbow, right? Sound lives in a certain area of the spectral bandwidth. And depending on how complex those sounds are, there are all sorts of overtones and harmonics to any sound. So keep in mind that that while it guitars fundamental pitch range is about 80 hertz to about 2000 hertz during many more overtones and harmonics that vibrate at higher pitches. On top of that, it's also worth noting that is human ears are more tuned to be sensitive at certain frequencies than others Fletcher and Munson did some acoustic research way back, I think was back in the 1930s that show that the human ear while it can perceive from 20 to 20 kilohertz like I mentioned before, it's specifically tuned to the band between about two to Five kilohertz, they actually did some tests where they would play a reference time of, say, one K, and then other frequencies at the same level.

The most other times were amped up until they were perceived by human ears to be the same loudness. As that reference 10 of one k ends up that we have trouble hearing outside that sweet area between two and five K, especially if the overall level is low. That's actually why you should never mix a song in the middle of the night at really low volumes. What you know, while you weren't wake up the names that that's a good thing. Your mix will be unnaturally bumped up in the low frequencies, because it's hard to hear them at very low volume. But I digress.

Okay. Here's another interesting fact. Because sound travels at a fairly constant speed, the lower the frequency, the longer The waveform is if you divide out the speed of sound, which is about 1100 feet per second, then a turn at the 1100 hertz will have a wave length of about one foot. Now, if you do the math and 100 hertz time will be about 11 feet long. And really high frequencies can only just be inches long. Now, why am I telling you this?

Why am I going into wavelengths, all that stuff? Because you're a geek, right? No offense, I'm a geek too. Now actually, there's there's probably no reason to really think about this stuff unless you're designing rooms that have standing waves or positioning multiple mics on a sound source. Actually, just a quick factoid to kind of keep you on your toes right here. By the way, he his his one for extra credit, what the exact speed of sound.

That's actually a trick question. Because there is none for all situations. The exact speed is 1100 and 26 feet Second with dry air at sea level at 20 degrees Celsius or about 68 degrees Fahrenheit. Anyway, all this noise is kind of fun. The next time that you have a thunderstorm and you count the seconds between the lightning and the thunder, but for an EQ course, let's just zero in on just the frequency spectrum and have a really close look at the fundamental frequency chart. So here's a frequency spectrum chart that shows all the fundamental frequencies of various instruments.

But rather than going through all this right now let's start off with something we're all very familiar with. And that is a piano and the very lowest a on a piano a one vibrates at 27.5. next octave up is 55 hertz followed by 110 hertz. A four is 228. A five is 440. Now you might have noticed those various tuning forks, we're using them less less now that we can bring up a tuning fork on our phones, things like that. But certainly when I was growing up when you're tuning things, a tuning fork would be the way that you would tune up to something and quite often you'd see the initials a 440.

On those tuning forks, that's because if you struck that tuning fork, the the I think they called tines the the two kind of tongues of that tuning fork would vibrate exactly for 40 which is a five let's go next octave at 1760 and 3520. Now can I direct your attention to the numbers at each successive a everytime you go up an octave generis, do anything about those numbers? Do you see what happens every time that you go up an octave. So for example, check out what happens on a guitar, I'll play an open a, which is the second fatter string on a guitar. Now when I press down on the 12th fret here, what I'm actually doing is having the length of the string, the 12th fret has that little double dots that you might see on here. It's exactly the halfway point between the nut here and the bridge, right here.

It's the halfway point. So if we press down here and interesting thing happens. The string vibrates twice as fast. This is 110 hertz, 110 times a second, and up an octave is 220 hertz or twice as fast. That's the relationship between octaves and hertz. Let's look at this again.

Look at all those numbers. They all double every octave. Now if you weren't sleeping through math class back end High School you could say is the octave relationship. That is a one, a two, a three, a four, up to eight, that is a linear relationship, octave one octave to octave three and so on. But the Hertz relationship is exponential, it doubles every octave. So here's where it gets really interesting.

Imagine that I can hit basically from zero kilohertz. I mean, I know I start from 20. But let's pray argument's sake, it's zero to 20, K, zero to 20. Where would the mid range be smack dab in between zero and 20, you would think it would be 10 K, right? split any measurement between zero and 20 down the middle, and it's going to be around 10. But if we thought that we'd be dead wrong, let's look at our keyboard again.

So at that frequency, or hertz doubles every octave and it would stand to reason that the very top octave of our hearing would be 20 K or 20,000 hertz, then the next octave down would be 10 K would be half that right? If it doubles every octave, then one octave shy of top octave octave nine would be 10 K. So 10 K is not the midpoint, but only one octave from the very top frequency that we can hear. If you have that again and again and again, then you see the midpoint is actually about 1000 hertz or about one kilohertz that the mid range of human hearing dough linear and logarithmic scales. I like totally different right. Now, if you're you're probably screaming at your computer or your TV right now just shut up with all these numbers and this mumbo jumbo I flunked math years ago, right?

Well, let's actually lay this all out and make it very practical, okay, and see where most instruments live in the town spectrum. So here's that tonal spectrum and I said before that the fundamental frequencies of Can I go around From Around 27 and a half hertz to little over 4k. Now we can break up the range of human hearing into four basic sections, which are the lows from about 20 to 200 hertz, the low mids from 200 to about one k, then the high mids from one to five K, and then the highest from five to 20 K. And all of these instruments, the fundamental frequencies are the darker parts of that bar. So, bass is 31 to 500. And then beyond that there's harmonics that go all the way up to around probably three case like that, then kick drum, and so on and so forth.

So all of these you can see that I've got the fundamental of symbols don't really get started till about 200 hertz, here are some with guitar and also male and female vocals. We'll see and hear plenty of examples when we get into the into the actual URL. Examples of EQ. But suffice to say that active EQ is nothing more than just boosting or cutting certain bands or parts of the frequency neighborhoods. And we'll use a few related tools to do it. In fact, let's quickly go to a graphic EQ example and see how it's done.

Before we go on, we'll look at many examples later on. But I just wanted to quickly show you something tangible. Lest we get kind of bogged down into, you know, a lot of this theory. This is a software version of a graphic equalizer basically, is sometimes called a 31, or 30 band or third octave EQ. Now, why do we call a third octave EQ? Well, it has 30 bands across here.

And as we learned before, with 10 octaves of frequencies that we can hear 30 bands ends up being basically one slider every third of an octave. So if that was, this was 10 divided by three that would be every time we skipped a couple that was Be new octave and then that would be a new, a new octave and we could check the math down here 25 we skip a couple, this should be double, right, we talked about every doubling frequencies every octave, so 25 to 50 to 100 to 200 to 400 801 K to four, eight k 16 k and so on. And, well basically what a graphic EQ does is it slices up this entire frequency range into little third of an octave slices so that we could boost for example, just the area around one kindness. In this instance, I'll flatten that out again or we could scoop out an area around one K. And because all these sliders are dealing with octaves rather than frequencies, that means that the slice around here is basically the same amount as the slice around here.

So for example, look at this, this one from here. This One at say 40. That's boosting around 40. And then it goes down to maybe around 30 and around 50. So it's, it's, it's boosting, basically a range of property around 20 hertz, a range of 20 hertz around 40 hertz, look up here at 16 K, and we boost that up here, that is boosting everything from around 12 K to 20 K, which is about 8000 cycles per second range over there, versus what I say about 20 over here, so you can really that certainly, you understand that this is an exponential. When we talk about octave that is a linear thing, that's octave one octave to octave, three octave for you know, every time you skip over three, but the frequencies double and up here it gets really crazy, right between this fader and misfire, that's 4000 hertz, right there.

And as we hear a little bit later on, we start listening up at the very top end, you'll find that, you know, there's not a lot going on above 10 K, and if it is, you know, I kind of roll my eyes when people sort of say, I think I need to, you know, boost a little air around 13 K, or maybe maybe 13.2 K, well, you know, there's not a lot of difference out there, down here, there's a big difference. I mean, if someone says, I'm gonna, you know, boost my subs around 100 Well, as we'll learn a little bit later on, you know, 100 is really not subs, you know, the subs are really down here. This is kind of around the, you know, the top end of the base, if you like, kind of the boxing, so we'll get into all of that stuff there.

But anyway, I just wanted to get given an idea of what a graphic EQ does. And that way you know, as you know, we boost things around, creating better A graphic EQ is that it shows you basically graphically what is going on under the hood. So you can see that this EQ gives us a graphical view of add changes to the frequency spectrum. And so that's why they call it a graphic EQ, that every EQ we'll look at basically tweets the spectrum in some sort of similar way. And depending on what we're putting through that EQ, I mean, we could be doing things like rolling off the lower end of a hi hat track or maybe boosting the high end on a vocal track, maybe even notching out just a thin slice of a mixer on stage in life situation to reduce feedback, lots of very cool things to do.

Okay, so you're probably thinking that there's got to be a better way to define the range of frequencies on the kick drum to help us attack it's actually from about two to six K, but a great way to refer It is just something like smack you know that snack. As we go along, we're going to refer to certain frequency ranges within a, with a shortcut name that we can use that it's much more kind of a descriptive word than just those cold numbers. Like the body of an acoustic guitar or the Clank have a hi hat or the air of vocals. Once you start to kind of know these neighborhoods of frequencies, you can start to have kind of a shorthand method to talk to other engineers or musicians who are trying to understand what you were trying to achieve. You might end up saying something to another engineer, you know, I think the bass needs a little bit more bite or the snare is a little bit too touchy.

And the way that we're going to understand, you know, why we need to develop these kinds of descriptive words is that you can't just have a favorite set of frequencies that you boost all the time for all of the instruments. I've been asked more than a few times to name my family. frequencies. And I always have a hard time. You know, kind of explain it because I really can't have those, you know, hard and fast rules on EQ. Until I created this analogy of fat thighs and boldness.

What? Let's take this generic stick figure of a person not knowing who this person is, would you think would be a good idea to have the upper arms in largest pumps, super big, big old guns. This might look good on a guy but maybe not so much on a woman. A lot of gals try to have arms. The opposite might be said of the other region as evidence by the success of cosmetic surgeon and the cosmetic surgeon industry if you know what I mean, and you probably know what I mean. Okay, what I'm trying to get across here is that you can't just generally say that then arms a great or a big bar is not desirable.

It really depends on the individual and generally, we know As an individual how to accentuate the areas that we think are desirable and hide the areas that we're not so proud of. So if you have a big belly, you soon learn not to wear horizontal stripes. Okay, so well, in the same way, every sound source has great segments of the frequency spectrum that we want to highlight, and maybe a few that we may want to hide, for example, say in a kick drum, there's a boxiness quality around the 200 hertz mark that we might want to just pull back a little bit. But there's a really cool sweet spot around two k that if we boost creates a real smack of that attack, that can really cut through a mix rather than boosting the fundamental of that kick drum down. It's a 60 hertz, or so it takes a lot of air to move those very low frequencies.

So if you want to boost the perceived loudness of a kick drum, a two k boost can really, really help. So yeah, to get that done, Stupid analogy that each and every person might want to increase the attributes or hide their flaws, you know, depending on the individual Same thing with audio, look at each sound individually and highlight the good stuff and scoop out the stuff that's you know, kind of not so great. We'll look at specific examples in the EQ in action section later on. Now before we look at all of the tools available, there are also very natural ways that we can EQ things without using any electronics at all. I mean, just think about when you make sounds with your mouth when you go out. Wow, wow, wow.

When you close your mouth down, you are filtering out the high frequencies right? Ah, it gets duller. As you close your mouth, that's something you can naturally do with with your voice. Now other things do is mic position with a cardioid microphone is the thing called the proximity effect. And when you get a microphone a cardioid microphone and bring it closer to you, the low end starts to ramp up a lot. It's called a proximity, you know, the closer the proximity to the sound source, then the low end will get much more pronounced.

We haven't tweaked an EQ knob anywhere, right? But the simple movement of a microphone towards the sorry towards the sound source will have that natural EQ thing. Same thing with where you place microphones near a guitar, typically on an acoustic guitar placed around the 12th fret about maybe a foot away from the guitar. But if you place it more towards a sound Hall, you'll get a more of a boomy sound more towards the bridge, and you'll get a more treble sound. So there's lots of different ways that you can EQ in terms of the mic position, and the best way to do that is through some headphones on so you're listening to that microphone, and then just start moving that microphone around and get the sound that you're after. If you can EQ that way without tweaking anything on your mixer or in plugins or anything like that.

It's a better way to do that right at the sound source, then, you know, using a million different EQ tools, but having that being said, let's look at the tools that we can use in EQ.