Send and Receive Audio Effects - Unity Official Tutorials

In Unity's audio mixer

the send and receive effects

give us a great deal of control

over how our signals are routed

through the mix and particularly to effects.

In this scene we have four game objects,

each with an audio source and an audio clip

loaded that's a loop of a music track.

In our mixer we've setup two effect return tracks.

These are normal groups which have respectively a reverb

on reverb return and an echo effect

on echo return.

Currently they are not receiving

signal from any other the other tracks in the mixer.

But if we want to get a signal to them

we can do that using the send and receive effects.

Let's start with our arpeggio sound,

which sounds like this.

What we're going to do is that we're going to use

a send effect to split the signal so that our

arpeggio will continue to be routed

through the master output but will

also have a duplicate of it's signal

with a controllable volume sent

in this case to the reverb return.

So first we're going to go to our reverb return track

and we're going to setup our destination, our receive.

We're going to choose Add - Receive.

Now it's important to note that the

sequence of these effects in the channel strip

is very important.

In this case the signal from the receive effect is

coming in to the chain after the reverb,

meaning that it's signal will not be processed

by the reverb effect.

What we're going to do is move the reverb down

so it's in the chain after the receive.

Now we're going to go to our arpeggio and we're going to

apply a send effect, we're going to choose

Add - Send.

Now we'll see over in the inspector

that we have a choice for what bus to route the send to.

The term bus comes from the world of

audio mixers in which a bus can be used

to route signal from one channel

to another or two multiple other channels.

In this case the choice is between

routing to a receive effect

or to a duck volume effect.

For more on duck volume effects

check out the information linked below.

We're going to choose our reverb return receive effect.

Now we'll notice that a send level becomes visible.

This is how much duplicated signal

is being routed to the receive effect.

We're going to start playing and turn that up

so we can hear the effect happen.

And you can hear when I stop it we get

that nice reverb tail

tailing off there because now the arpeggio sound

has been routed through the receive effect,

through the SFX reverb plugin

and that's creating that nice cycle acoustic impression

of our sound being played in a large space.

What reverb effects do is they simulate

the reflections of sound

bouncing off of surfaces and returning to the listener

in an acoustic space.

Our synthesiser sound never occurred in an acoustic

space so it has no natural reflection

and we're adding those using the reverb effect.

It's worth noting when we work with

reverb effects via sends and receives

that the dry level should be turned all the way down

so that we don't duplicate the unaffected signal.

It's also worth noting that the order

of the attenuation and the send in our group is important.

Currently the attenuation effect is before the send,

meaning if we turn down volume

using the attenuation effect the signal will stop

passing to the send, let's give that a try.

We can hear the trail trails off

and the sound ends.

If we reorder these effects we'll get a different effect.

We're going to place the attenuation after the end

and what you'll hear is that by

placing the send before the attenuation effect

the send is not going to have it's volume turned down,

it will still receive volume

before the attenuation turns the signal down.

The result is that the send is going to continue sending

signal out even though the main channel is turned off.

What we can hear in this case is that whether or not

the volume is turned down the send is still

getting it's volume out to the reverb return

and not what we're hearing is only

the wet signal of the reverb

coming back in to the main mix via the reverb return.

This can be interesting for some non-traditional effects

but typically you're going to prefer

attenuation followed by your send.

It's also worth noting as I mentioned earlier

that if the receive effect is after,

for example the reverb in this case,

we're going to receive no effect, so it's important for any effects

that you want to process your signal to be

placed in the chain after the receive effect.

Now one of the other major uses of sends

is that we can use it to process

multiple channels with the same effect.

So in this track we also have

a percussion element.

And what we can do, by adding a send

to that and routing that also to the reverb,

we can add reverb, the same reverb

to both of our tracks.

So we can hear this gives us a very

consistent psycho-acoustic impression,

which is especially important if we're aiming for realism.

To have things passing in to the same reverbs

so that they feel like they're emanating in the same environment.

It's also possible to use send and receive effects

to route one signal to multiple effects.

What we're going to do is we're going to send our

arpeggio additionally to our

echo effect on our echo return group.

We're going to add a receive effect

to the echo return and move it up in the

chain so that it's signal will pass through the echo.

Then on the arpeggio we're going to add a send

and assign it's output to

the echo return receive.

once that's assigned we can test.

And you can hear with that nice tail

that our arpeggio is now being passed to both

the reverb return and the echo return

groups that we've created here via the two receive effects.

What's great about this setup is that we can

control the levels individually using the send volumes

and we can really achieve a lot of flexibility

in our mix this way.

It's also worth noting that this is a common

audio industry best practice because

processing audio signals, especially with reverb can

be very processor intense.

Having a reverb on each of these tracks

could have a serious CPU resource cost at run time.

So minimising our use of effects

by sending multiple effects to the same

reverb on a return track

is going to save us some CPU

resources that we'll probably need elsewhere in our game.