As we start talking about the dynamic processors that we have available,

they're going to be our, expanders, gates, compressors and limiters.

And all of these have really the same basic fundamental, functional components,

in that they're all split up into two segments.

we saw with the vocal riding example that you have to kind of listen to the vocal,

analyze it and respond to it. And all these devices are doing just

that. They have one section that's designed to

analyze the input signal, that's called the side chain section, or the key

section. And the other section of it, is really

just a volume fader, it just brings it up and down.

So the first thing I'd like to look at is that kind of, key, or side chain section.

Its role is to analyze the signal and calculate the envelope of the audio, and

the envelope is kind of a signal that represents the average level at any point

in time. And though it seems like a simple thing

to do, it actually is kind of complicated, and the, the way it happens

is, and you, you've seen this term, I'm sure, is RMS, which stands for root mean

squared. And so it's trying to calculate the

average level over a little bit of time of that signal.

But sound, as we saw, is alternating it's gong up and down and up and down.

So if we were just to average out the sound, it would always end up with zero.

Because it sends, it spends just as much time as above as below zero.

So we need a mathematical process to kind of give us the average level over time.

So what we do is first square the signal. We take every sample and multiply it by

itself. Any time you multiply something by

itself, you get a positive number, right? A negative times a negative is a

positive. And a positive times a positive is a

positive. So every single sample is multiplied by

itself, giving us a compltely positive version of the signal.

And then we can take an average. So then we might say that over 30

samples, or 50, or 100 samples, we take an average of it.

Which gives us a nice slowly moving envelope, and then we take the square

root of that, to get it back into a reasonable range.

So we see the RMS all the time, and really all RMS is kind of a average

level, of what's going on in the signal. Once we have that information, once we

have that envelope we can use it to control the volume fader right?

So in our vocal writing example we saw when the signal got loud we brought the

level down and that's functioning like a compressor does.

So compressor has that volume fader, and whenever the envelope goes up, the volume

fader goes down, same thing we were doing with vocal riding.

Now when we're kind of programming this, this robot that's going to help us move a

volume fader, we have a couple of parameters that we're going to need to

configure. The first is at what point does he start

bringing down the level? And that's going to be our threshold and

all these dynamic devices are going to have a specific threshold.

And in a compressor when we're below that threshold the compressor does nothing.

It's completely linear below the threshold.

Once the emblem gets above that threshold which we can set at any point we like,

then the level will start coming down. Now, how much it comes down, is the

ratio. The ratio will always be expressed as a

number to one, something over one. And that's going to be input to output

above the threshold. So, if we have a one to one ratio Above

the threshold, nothing happens. Input equals output.

If I had a two-to-one ratio, that's saying if the input goes up two decibels,

the output only goes up one decibel. So above the threshold, the, the output

will be half the level of the input. And we can keep on going up with that

ratio. In fact, a limiter is a compressor with a

very high ration, usually considered above ten to one to be limiting instead

of compression. So they are really the same device a

compressor and a limiter, with that one thing changed.

So threshold will always need to be adjusted.

No matter what signal you're going through.

You can't rely on a preset to set your threshold.

because threshold has to be related to the underlying musical material.

If you have someone playing quite quietly, they'll never hit that

threshold. So the compressor won't do anything.

If you have someone that's always playing loud, you might always be a thre, above

the threshold. Maybe not what you want.

So you'll always have to adjust that. Ratio.

You're going to adjust for how much reduction you really want the compressor

to give you. The other parameters we're going to have

to address are how fast that volume fader moves.