Send and Receive Audio Effects
Checked with version: 5
In this lesson we'll look at controlling our signal flow using Send and Receive effects. Send effects allow us to route a duplicate of an audio signal to another group or effect in our mixer enabling complex signal flows. We'll look at using sends to route signal to a reverb audio effect.
Send and Receive Audio Effects
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In Unity's audio mixer
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the send and receive effects
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give us a great deal of control
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over how our signals are routed
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through the mix and particularly to effects.
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In this scene we have four game objects,
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each with an audio source and an audio clip
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loaded that's a loop of a music track.
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In our mixer we've setup two effect return tracks.
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These are normal groups which have respectively a reverb
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on reverb return and an echo effect
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on echo return.
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Currently they are not receiving
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signal from any other the other tracks in the mixer.
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But if we want to get a signal to them
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we can do that using the send and receive effects.
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Let's start with our arpeggio sound,
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which sounds like this.
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What we're going to do is that we're going to use
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a send effect to split the signal so that our
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arpeggio will continue to be routed
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through the master output but will
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also have a duplicate of it's signal
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with a controllable volume sent
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in this case to the reverb return.
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So first we're going to go to our reverb return track
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and we're going to setup our destination, our receive.
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We're going to choose Add - Receive.
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Now it's important to note that the
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sequence of these effects in the channel strip
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is very important.
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In this case the signal from the receive effect is
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coming in to the chain after the reverb,
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meaning that it's signal will not be processed
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by the reverb effect.
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What we're going to do is move the reverb down
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so it's in the chain after the receive.
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Now we're going to go to our arpeggio and we're going to
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apply a send effect, we're going to choose
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Add - Send.
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Now we'll see over in the inspector
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that we have a choice for what bus to route the send to.
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The term bus comes from the world of
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audio mixers in which a bus can be used
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to route signal from one channel
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to another or two multiple other channels.
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In this case the choice is between
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routing to a receive effect
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or to a duck volume effect.
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For more on duck volume effects
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check out the information linked below.
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We're going to choose our reverb return receive effect.
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Now we'll notice that a send level becomes visible.
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This is how much duplicated signal
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is being routed to the receive effect.
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We're going to start playing and turn that up
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so we can hear the effect happen.
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And you can hear when I stop it we get
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that nice reverb tail
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tailing off there because now the arpeggio sound
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has been routed through the receive effect,
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through the SFX reverb plugin
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and that's creating that nice cycle acoustic impression
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of our sound being played in a large space.
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What reverb effects do is they simulate
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the reflections of sound
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bouncing off of surfaces and returning to the listener
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in an acoustic space.
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Our synthesiser sound never occurred in an acoustic
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space so it has no natural reflection
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and we're adding those using the reverb effect.
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It's worth noting when we work with
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reverb effects via sends and receives
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that the dry level should be turned all the way down
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so that we don't duplicate the unaffected signal.
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It's also worth noting that the order
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of the attenuation and the send in our group is important.
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Currently the attenuation effect is before the send,
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meaning if we turn down volume
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using the attenuation effect the signal will stop
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passing to the send, let's give that a try.
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We can hear the trail trails off
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and the sound ends.
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If we reorder these effects we'll get a different effect.
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We're going to place the attenuation after the end
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and what you'll hear is that by
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placing the send before the attenuation effect
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the send is not going to have it's volume turned down,
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it will still receive volume
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before the attenuation turns the signal down.
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The result is that the send is going to continue sending
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signal out even though the main channel is turned off.
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What we can hear in this case is that whether or not
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the volume is turned down the send is still
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getting it's volume out to the reverb return
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and not what we're hearing is only
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the wet signal of the reverb
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coming back in to the main mix via the reverb return.
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This can be interesting for some non-traditional effects
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but typically you're going to prefer
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attenuation followed by your send.
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It's also worth noting as I mentioned earlier
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that if the receive effect is after,
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for example the reverb in this case,
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we're going to receive no effect, so it's important for any effects
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that you want to process your signal to be
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placed in the chain after the receive effect.
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Now one of the other major uses of sends
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is that we can use it to process
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multiple channels with the same effect.
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So in this track we also have
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a percussion element.
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And what we can do, by adding a send
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to that and routing that also to the reverb,
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we can add reverb, the same reverb
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to both of our tracks.
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So we can hear this gives us a very
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consistent psycho-acoustic impression,
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which is especially important if we're aiming for realism.
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To have things passing in to the same reverbs
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so that they feel like they're emanating in the same environment.
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It's also possible to use send and receive effects
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to route one signal to multiple effects.
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What we're going to do is we're going to send our
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arpeggio additionally to our
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echo effect on our echo return group.
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We're going to add a receive effect
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to the echo return and move it up in the
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chain so that it's signal will pass through the echo.
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Then on the arpeggio we're going to add a send
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and assign it's output to
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the echo return receive.
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once that's assigned we can test.
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And you can hear with that nice tail
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that our arpeggio is now being passed to both
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the reverb return and the echo return
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groups that we've created here via the two receive effects.
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What's great about this setup is that we can
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control the levels individually using the send volumes
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and we can really achieve a lot of flexibility
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in our mix this way.
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It's also worth noting that this is a common
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audio industry best practice because
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processing audio signals, especially with reverb can
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be very processor intense.
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Having a reverb on each of these tracks
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could have a serious CPU resource cost at run time.
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So minimising our use of effects
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by sending multiple effects to the same
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reverb on a return track
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is going to save us some CPU
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resources that we'll probably need elsewhere in our game.