Use the Scientific Filter effect
Explore the advanced manipulation of audio using the Scientific Filter effect — especially useful for producing audio evidence in legal cases as well as working with analog electronic equipment.
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This lesson is about one effect inside Audition, the Scientific Filter.
Why do a lesson about one effect?
Well, for two reasons.
First of all, it's a new effect in the latest version of Audition.
And secondly, it has a very narrow purpose and very few people will use it.
Let me show you where it resides.
Let's go to Effects, Filter and EQ, and it's inside this group, the FFT Filter..., the Graphic Equalizer, the Notch Filter..., the Parametric Equalizer..., and then there's the Scientific Filter...
I've covered these guys up here in a separate lesson, but let me remind you about them.
Let's go to the Graphic Equalizer... here.
What this does, it allows you to control the amplitude within certain frequency bands.
Right now, we're at the (Default), which is sort of neutral.
I'll just click Play here.
Let's change that, let's go to let's say a Hi-Pass, where we're passing the high frequencies through, or we'll go to a Low-Pass, where we're passing the low frequencies through.
I'll go back to the (Default) here and I'll just set these guys individually, I'll increase the bass, bring the treble down here, like so.
And this is how the Graphic Equalizer works.
You control frequencies within these bands.
But what folks don't know is exactly how the curve looks between these two sliders.
What that little line would be like if you saw it on a graph, and how it's defined.
Well, it's defined by the Adobe engineers who created this.
They created it to make things sound as good as possible, but the exact way it's created is not something that is known to the public.
It's not really a secret necessarily, but this is not something that's known to the public.
And so, let's say you're presenting evidence at a trial and you've recorded something and then you've adjusted the audio using an equalizer like this, well, the opposing side will say "well, you manipulated the sound in some way and there's no way that we really know that's exactly how it sounded."
So, to avoid that kind of an argument, you use something called the Scientific Filter, where the exact behavior is known to all.
So, I'll close this down, I'll take a look at the Scientific Filter.
So, go to Effects, go to Filer and EQ there, go to Scientific Filter... and it is a graph.
And if you worked with the Parametric Equalizer, you've seen this before - I'll close this down for a second - go to Effects, Filter and EQ, and go to Parametric Equalizer...
And it is a graph, looks like so.
Let's change this to let's say Generic Hi-Pass.
See, we cut off the low frequencies and the high frequencies are going through.
Let's close this and take a look at the Scientific Filter then.
Effects, Filter and EQ, Scientific Filter...
I'll do a HighPass here, same kind of a thing where high frequencies go through and the low frequencies are cut off.
So, what's the difference?
The difference is these curves, these shapes, the behavior, are defined mathematically using various types of filters.
The types are down here, there are four types: Bessel, Butterworth, Chebychev and Elliptical.
These are all defined by mathematicians or engineers many years ago.
Bessel was created in the 1800s by a German mathematician.
Tends to be a linear response across the frequencies.
Butterworth was created by an English engineer and it tends to be a flatter response.
Chebychev was created by a Russian mathematician, has a steeper roll-off when these things are done.
And then finally, Elliptical was created by a German engineer, Wilhelm Cauer.
Actually, it's Chebychev going in, Chebychev going out, and Butterworth at the connection of the two.
So, these are all well-defined reproducible ways to filter audio.
And if you use these in court, you could say, "OK, I used the Elliptical filter, with a Cutoff set to so and so, the Order set to 3, the Stop here, all set to these numbers, so both sides know exactly how this was done.
Now, depending on what you select here, you get different options.
For example, if I go to Bessel, this will change in terms of what you can select.
And if you are accustomed to working with this, you're going to know about all these things and I certainly can't explain all of them.
But the thing is, it's not only used for forensic purposes, it's also used by audio engineers who harken back to the electronic analog days and they know exactly how things sounded when they use a Bessel or a Butterworth or a Chebychev.
And they like the way it sounds, they like the way it works and they're accustomed to that.
So, if you fall into that category, then this filter is for you.
But in general, most folks won't use this, they use the Parametric or the Graphic Equalizers.
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