The audio mixer asset in Unity allows us a great deal of control over the signal flow of audio in our projects. By default our main camera is assigned an audio listener component. The audio listener component is where audio is output from the scene to the headphones or the speakers of the listener In Unity all audio starts at an audio source. Here we have a game object called Base and it's got an audio source on it which has a clip of a baseline loaded, which is also set to play on awake and loop. There are 3 other objects which contain other musical parts including an arpeggio kick and percussion. When we play the scene we're going to hear these first 3 parts play directly through the audio listener component. If we want to get more control over how our audio is processed we can create an audio mixer asset, so choose Create Audio Mixer and then we can either double click on it to make it visible or we can go to Window - Audio Mixer or choose command-8 on Mac or control-8 on PC. The audio mixer can be docked like many of the other windows, I'm going to dock it down here on the bottom of my screen and I'm going to expand to give myself a little bit more real estate. The default state for an audio mixer is that it's created only with a master group here. In Unity's audio system we refer to channels as groups because they provide a little bit of additional audio functionality that a normal mixer channel would not. Now, we've got our master and currently nothing is assigned to it. If we play we'll see no movement in the meters. If we choose our game objects here we can edit for all of them the output parameter here and we can assign it by clicking on it to the master channel of audio mixer 1. Now when we play we've setup some signal flow, our signal is now passing from our audio sources through the master to the audio listener on the main camera. By default the master group is created with an attenuation effect applied to it. The attenuation effect is what allows us to control the volume of the signal passing through the master group. If we want to adjust that while we're playing we're going to need to click Edit In Play Mode. Now we can adjust the volume and we can see in the inspector on the right that the change is being reflected. Changes made while editing during play mode will be saved to the audio mixer asset. Unlike scene changes, which will revert when exiting play mode. Currently audio mixer 1 has only 1 group the master. To create a more flexible signal flow we're going to go over here to the Groups area and click the + button twice. When we click the + button a new group will be created that is the child of the currently selected group. Notice that in the channel strip view group A and group B have appeared. With multiple groups in our mixer we can now assign some of our parts to different groups Let's assign the kick drum by clicking on the output parameter to group A. Now if we play activate Edit In Play Mode. You'll notice that when we turn down group A we can turn down the kick drum independently because it's now on it's own group. And when we turn down the master we can turn down everything. This is because group A is routed through the master so the master controls everything which is routed through it.. That's because of the way that the groups are arranged in the groups area down here. We can see that group A is a child of the master group and group B is in turn a child of group A. So if we assign our arpeggio using it's output to group B we can now test again and we'll see that turning down group A now turns down both the kick and the arpeggio because group B is a child of group A. So here we have what's called a serial signal flow routing, meaning group B passes through group A and then passes through the master. We can also create a parallel signal flow by changing the routing of group B. If we click on group B in the groups area and drag it's name on to the master we can now make group B a child of the master and pass it's signal directly to the master, and we can test that out. So now we have the kick in group A. The arpeggio in group B. And everything being run through the master. While we're working in the mixer we may want to check parts of our mix individually. We can do this using the solo, mute and bypass buttons on each of the groups. When we click solo all the other tracks are temporarily muted so that we can hear that track by itself and make any changes we need to make. When we click mute the opposite happens. The one track we've muted becomes silent and we can hear anything else that we need to hear. Bypass allows us to bypass any audio effects that we've applied to the channel. Let's go down and click Add Low Pass Simple. This is a low pass filter which will remove high frequencies from our arpeggio sound. Here's the arpeggio soloed. Here's the bypass. So if we're having problems with one of our effects or we want to check something we can bypass. It's worth noting that solo, mute and bypass are not intended to be used at runtime they're supposed to be used in setting up your mix and designing your sounds. But not to be controlled by the engine while the game is playing. Additionally each group has it's own pitch control. If we look in the inspector we'll see that the pitch is currently set to 100 for this group, our arpeggio, let's set it to 50%. So we can adjust the pitch not just at the individual sound level using audio source pitch control but also at the group level. In addition to controlling signal flow with groups we can also control signal flow with multiple mixers. By using multiple mixers for each category of sounds in our mix we can then route those mixers to groups in audio mixer 1 to control the overall balance of the mix. If we create another mixer by clicking the + button, we'll call this one Drum Mixer. We can now create two groups within this. We'll configure this in a parallel routing and we will assign our kick to the drum mixer kick channel and we'll activate our percussion source here and assign that to the percussion channel. In order to be able to control the volume balance between those two sets of elements let's create a third group and route it to the master output. Now if we grab our drum mixer and drop it on to audio mixer 1 we can choose drum group as an input. When we play the scene We can see that our entire drum mixer is now being routed through drum group to the master output. As you're working in the mixer and your project's grow more complex you may find that you want to manage the view of the mixer. This can be done using the visibility controls down here, let's say we want to make groups A and B invisible and just view the drum group and the master, we can do that by clicking these eye icons beside the group names. Once we've made them visible we can save that in a view. Here we currently only have one view, let's click the + button to make another. Now in view View Simple we have these two groups turned off and in our main view we could have them turned back on by clicking on the view name we can toggle between different views of the mixer. Snapshots allow us to store and recall the state of the mixer. We'll cover snapshots in their own dedicated lesson. Please see the link below for more information. So far we've taken a look at controlling our signal flow for our game music. Let's take a look at an example which includes some sound effects as well. Here we have the Nightmares project which is available for download on the asset store. What we've done is we've setup two mixers. One is the master mixer and another is a sound effects mixer. In the master mixer we have two groups, one for music and one for our sound effects. We've also got our vocal effects for when the player gets hurt routed to a vocal effects group also on the sound effects mixer. Our background music is routed directly to the music channel of the master mixer since there's only one channel for the music in this case. If we play our scene we can see this in action. Using this approach we can then balance each separate set of effects, gun shots, vocal effects against our music easily using one overall volume for sound effects and one overall volume for music. Subtitles by the Amara.org community
