Duck Volume Audio Effect - Unity Official Tutorials

In Unity it's possible to control the

volume of one element in your audio mix

based on the volume of another.

This is called ducking and we achieve this

using the Duck Volume effect.

I've got a simple scene setup here with

three musical parts, a kick drum,

bass line and arpeggio, these are all assigned

to game object which have

audio source component which are assigned

to different outputs in our audio mixer.

The kick has it's own group

and the synthesisers, the bass line and

arpeggio are both routed

to the synthesiser group.

What we're going to do is we're going to cause

the volume of the synthesisers to duck

based on the volume of the kick drum when it strikes.

This is also called side chain compression.

To begin I'm going to add a duck volume effect

using the Add drop down menu.

Now that the duck volume effect has been added

I'm going to send some audio signal to it

and I'm going to do this using the Send effect.

I'm going to click Add and choose Send.

Now in the inspector

I'm going to choose the bus

for the send to be routed to.

In this case that's going to be

synthesisers duck volume.

Now that we've setup our routing

we're going to set the send level.

Because the input

on the duck volume effect does not route

it's signal back to the main volume

we can turn up this send without

adding any volume to our mix.

This is a typical behaviour for a side

chain input on a compressor.

With the volume turned all the way up

now the full amplitude of our

kick will reach the duck volume effect when it plays.

Let's listen to the scene first.

Now even though we've configured our scene

we're still not hearing any gain reduction

from the duck volume.

If we click on the duck volume effect

we can configure it's parameters.

The threshold is the volume at which

gain reduction will begin to occur.

So our input signal, in this case

our kick drum, will need to exceed a

threshold of -10 decibels

before we start to apply any gain reduction.

Let's listen to that in action.

We're going to play

turn on Edit In Play Mode so that we can

change the parameters

and we're going to slowly reduce the threshold.

And so you can hear as we reduce the

threshold we start to hear that

pumping breathing effect

because the amplitude of the kick drum

is now causing our duck volume effect

to lower the amplitude

or volume of the synthesiser group.

Now we can move on to our next parameter,

which is called the ratio.

The ratio determines how much gain reduction

will be applied once

the threshold is triggered.

One easy way to think about this is that

it's the amount of gain reduction which is

applied once the threshold is exceeded.

Next we have the attack time and the release time.

The attack time is once the threshold

has been triggered, how quick is the onset

of the gain reduction?

The release time is the opposite.

Once the attack phase is completed,

so in this case after 26 milliseconds,

the release time begins to release

the compression or the gain reduction.

And so in this case after 100 milliseconds

we will no longer be reducing volume

so we'll be back to our original signal strength.

The makeup gain is simply an

additional volume control

that allows us to make back up

some of the gain that we've reduced.

In this case because we want to have a

pronounced ducking effect where we hear the volume

getting quieter we're going to leave the makeup

gain at 0, which means that no change

in volume is going to be applied.

The knee controls the behaviour of the threshold.

At a very low or hard knee

we're going to get a linear transition

from once the threshold is crossed

we're going to begin applying gain.

If we increase the knee value or soften it,

we're going to see that we're going to have a

much more smooth transition

as the gain reduction is applied.

And it's actually possible at high knee values,

as you can see from the graph changing,

to begin reducing gain even before

the threshold has been tripped.

As we approach the threshold at a soft knee value

we're going to begin to see some gain reduction

even before we've exceeded the threshold.

The side chain mix allows us to blend

between the effected

and the unaffected signal.

At 100% we're listening to

only the signal which is being

processed by the duck volume.

At 0 we're going to be listening to

only the original signal.

In addition to being able to adjust the parameters

via the sliders we can also

adjust the parameters by clicking directly

on the graphic.

If we click on the white line here representing

threshold we can actually drag horizontally

to adjust the threshold value.

By dragging vertically we can adjust the knee

and you'll see we have this nice representation

of how the knee is effecting the threshold.

If we drag to the left of the line we can

adjust the makeup gain

and if we drag to the right of the line we can

adjust the ratio.