If you drag either a Sound Wave or a Sound Cue into your Level, it will create what’s called an Ambient Sound Actor (Figure 9-3).

It will automatically assign whatever asset you dragged in, as the asset for that Actor’s Sound property (Figure 9-4).

If you want to preview the sound, you can use the Play and Stop buttons, located above the Sound property. For Sound Cues, you can use the Edit button to open the Sound Cue in the Sound Cue Editor . If you want to create a new Sound Cue to use for the Actor, you can use the New button.

Below, you’ll see four properties with “Priority” in their name. These properties are used when this Actor is playing multiple instances of its sound concurrently. The concept of concurrency will be covered later in the section.

You can use the Volume Multiplier property to increase or decrease the volume of the sound. Note, however, that setting the volume too high could cause clipping in your waveform which will cause distortion in the audio.

The Envelope Follower Attack Time property will set the amount of time, in milliseconds, that it takes for the sound to reach its peak amplitude. Conversely, the Envelope Follower Release Time property sets how long it takes for the sound to decay back to silence. Note that these properties only apply when the Sound Cue or Sound Wave is used in the audio mixer.

The Pitch Multiplier property can be used to increase or decrease the pitch of the sound.

Down in the Activation category is the Auto Activate property. By default, an Ambient Sound Actor’s Auto Activate property is set to True. With it set to True, the sound will play as soon as the Actor is created.

By default, the Ambient Sound Actor will only play its sound once. If you want the sound to be continuous, you will need to set it to loop. With a Sound Wave, this can be accomplished by setting its Looping property to True. With a Sound Cue, this is done by using a Looping Node. The Looping property can be found on the Sound Wave Properties page.

If you want to edit the properties of a Sound Wave, you simply need to double-click it in the Content Browser.

Starting at the top in the Format category (Figure 9-5) is the Is Ambisonics property. Ambisonics is a specific type of surround sound format. If your wave file is in that format, you would want to set this to True.

First, you can set the compression of the wave using the Compression property. This can have a value from 1 to 100, where lower numbers represent more compression and higher numbers represent better quality. So if you want the sound to sound as good as it can, and you’re not worried about the file size, you would want to set this to a high number. If you don’t care about the quality of the sound and you just need to save space somewhere, you could set this to a low number.

If you need to lower the file size even more, you can use the Sample Rate property to lower the sample rate of the wave; otherwise you should just leave the value at Max.

In the Sound category (Figure 9-6), you can adjust the volume and pitch of the Sound Wave, and you can also place it into a Group. So you can specify if it should go in Effects, UI, Music, or Voice. Or, if it doesn’t fit into any of those categories, you can just leave it in the Default group. Groups are useful for being able to apply a setting to an entire group of related Sound Waves, instead of having to apply that setting to each individual one.

In the Subtitles category (Figure 9-7), you can add subtitles to the Sound Wave and edit their properties. To add a subtitle, go to the Subtitles property and click the plus sign. Then you enter the text of the subtitle in the Text property and the time it should appear on the screen in the Time property. The Time property refers to the amount of time that has elapsed since the Sound Wave began playing.

There is also a Spoken Text property. The difference between the Spoken Text property and the Text property is that the Text property is for the text that should appear on the screen, while the Spoken Text property is for the dialogue that was actually spoken. For example, there might be the word “angrily” in brackets indicating that the speaker is speaking in an angry tone. Or if the subtitles are in a different language, then obviously the two texts will be different.

The Mature property is used to flag a piece of audio that contains mature content, such as adult language. This can be used to more easily create a “clean” version of your game later, by having the ability to filter out all mature content.

By default, the Engine will automatically wrap your subtitles to the next line if they get too long, but if you don’t want the Engine to do this – for example, if you have already split the subtitles manually – you can set Manual Word Wrap to True to disable automatic wrapping. If you want to force all subtitles to only display on one line, you can set the Single Line property to True.

Next is the Subtitle Priority property . If two pieces of audio are playing at the same time and both have subtitles, which subtitle will appear on the screen will be determined by the Subtitle Priority, with higher numbers representing a higher priority. You will remember that there were two properties on an instance of a sound – Override Subtitle Priority and Subtitle Priority. The Subtitle Priority property on the Sound Wave Properties page will, by default, be used for all instances of that sound. But you can override this on an individual basis by setting the instance’s Override Subtitle Priority to True and then entering a new value in the instance’s Subtitle Priority property.

A few categories down is the Voice Management category (Figure 9-8). Within that, under the Concurrency sub-category, there are several properties used to specify what should happen when multiple instances of the Sound Wave are played at the same time. If you want to use preexisting Concurrency Settings, you will need to set the Override Concurrency property to False and then select the settings using the dropdown. If you want to specify new concurrency settings, then you need to set Override Concurrency to True, and then you will be able to expand the Concurrency Overrides property.

The Max Count property specifies how many instances of the sound are allowed to be playing at once. The Limit to Owner property specifies if the Max Count should only be applied per sound Actor, or if it should be applied to all instances of the Sound Wave that are being played from any sound Actor.

If the Max Count is reached and another instance of the sound tries to play, you can set how the conflict should be resolved using the Resolution Rule property. For example, you could set it to prevent the new instance from being played, or set it so that the oldest instance is stopped to make room for the new instance, and so on.

If the Can Release property is set to True, an instance that has gone quieter can get louder again if another instance stops playing. The amount of time that this takes to happen after the other instance stops playing is determined by the Release Time property.

In addition to there being a limit to the number of the same sounds that can play at once, there is also a limit to the number of sounds in general that can play at once. If this limit is met, by default, the Priority property, combined with the volume of the sound, will be used to determine which sound is stopped and which keeps playing. If the Bypass Volume Scale for Priority property is set to True, then the Priority property alone will be used to make that determination, and the volume of the sound will be ignored.

In the Details Panel of an individual instance of a sound, there is an Override Priority property you can use to override the priority on an individual basis, which allows you to set a new value in the instance’s Priority property.

We already saw how to have a sound play immediately when the Level begins, but oftentimes, you won’t want a sound to be played until certain conditions are met or a certain event is triggered. In these cases, you can use Blueprints to specify when the sound should be played.

If you go into the Level Blueprint, open the Node Menu, and type “Play Sound,” you will see several Nodes available for playing a sound, as seen in Figure 9-9. For one thing, you can choose to either play a sound or spawn a sound. The difference is that when you spawn a sound, you have control over it. You can choose to stop playing the sound at any point or modify its properties. But when you play a sound, you don’t have any control over it. You can’t modify it or stop it. It will continue playing until it’s finished, and if it’s set to loop, it will continue playing repeatedly.

You can also choose to have a sound come from a certain location in the game or make it a 2D sound which will be heard at the same volume, and the same stereo position, regardless of your location in the game. If you use one of the location Nodes, such as Play Sound at Location, you will need to pass in the location where you want the sound to play from. If you wanted it to play from the location of a certain Actor, you could use the GetActorLocation Node to get that Actor’s location, as shown in Figure 9-10. Or, with the Spawn Sound Attached Node, you can attach a sound to an Actor directly and the sound will travel with that Actor.

A Wave Player Node , shown in Figure 9-14, is used to output Sound Waves. If you select it, you can edit its properties in the Details Panel on the left. The Sound Wave property will specify which Sound Wave the Node should output (Figure 9-15).

A Looping Node (Figure 9-16) will take a sound as input and output that sound as a loop. In the Details Panel, you can choose to have it loop a specific amount of times or have it loop continuously (Figure 9-17).

The Delay Node (Figure 9-18) can be used to add a delay before a sound is played. Each time the Delay Node is activated, the amount of delay will be a random value between the Delay Min and Delay Max (Figure 9-19). So if you set this to 1 and 3, for example, each time the sound is played, the delay will be between 1 and 3 seconds. If you wanted the delay to always be the same value, you would need to enter that value for both the Min and Max properties.

The Doppler Node (Figure 9-20) can be used to add the Doppler effect to a sound. This is the effect that occurs when sounds, such as the siren of an ambulance, increase in pitch as they move toward you and decrease in pitch as they move away. The Doppler Intensity property (Figure 9-21) can be used to specify how pronounced this effect should be, with higher values increasing the effect.

The Modulator Node (Figure 9-22) can be used to play a sound at a random pitch and volume each time it’s played. This can be used to make the audio sound slightly different each time so as not to get repetitive. The range of the random values generated can be set in the Details Panel (Figure 9-23).

The Oscillator Node (Figure 9-24) can be used to add a continuous modulation of volume and pitch within a single instance of a sound being played. The first two properties are used to enable the modulation of the volume and/or pitch (Figure 9-25). Amplitude refers to the height of the Sound Wave, with larger waves producing louder volumes. Frequency affects the pitch of a sound, with higher frequencies resulting in higher pitches. The remaining properties deal with more advanced wave physics, with the Offset properties controlling the wave’s phase and the Center properties controlling the center of oscillation.

In addition to Nodes that alter sounds, the Palette also contains many useful Nodes for combining sounds. A Mixer Node , shown in Figure 9-26, takes two or more sounds as input and outputs all of those sounds being played simultaneously. In the Details Panel, you can adjust the volumes of each input (Figure 9-27).

The Concatenator Node (Figure 9-28) is just like the Mixer Node, except that instead of playing its input sounds simultaneously, it plays them one after the other.

A Random Node (Figure 9-29) will randomly output just one of its input sounds each time it’s activated. By default, each sound has an equal chance of being played each time, but you can change this using the Weights property (Figure 9-30). For example, if you set the weight of the first sound to 2 and leave the weight of the second sound at 1, then the first sound has twice the chance of being played each time.

You can use the Preselect at Level Load property to trim down the number of possible inputs that can be selected from. For example, if the Random Node has ten inputs and Preselect at Level Load is set to 5, then as soon as the Level loaded, it would randomly select five of the inputs and then only randomly select from those five each time the Sound Cue was played. This can be used to trim down memory usage for Random Nodes that have several inputs. Note that this Node doesn’t have any effect when simulating your game, it will only work when playing a build outside of the Editor.

The Branch Node (Figure 9-31) will output one of its input sounds based on the value of a Boolean variable. In the Details Panel, you use the Bool Parameter Name property to specify the name of the Boolean variable that should be evaluated (Figure 9-32). If that Boolean has a value of True, whatever sound is connected to the True pin will be outputted. If the value is False, the sound connected to the False pin will be outputted, and if the Boolean has a value of Null, then the sound connected to the Parameter Unset pin will be used.

The Switch Node (Figure 9-33) is just like the Branch Node, except it outputs a sound based on the value of an Integer variable instead of a Boolean variable.

As mentioned already, in the area described by the Falloff Distance, the sound will go from 100% volume to zero. But the rate at which this occurs can be adjusted, by setting the Attenuation Function that should be used to define the Attenuation Curve . By default, this will use a Linear curve, meaning the volume will decrease evenly.

Using the Logarithmic curve, the volume will decrease more rapidly at first, then the rate of decrease will slow as the sound approaches the bounds of the attenuation shape. The LogReverse curve, as its name indicates, is the reverse of that. The volume will decrease slowly at first, then more rapidly.

The Inverse curve is similar to the Logarithmic curve except the volume decreases extremely rapidly at first, then very slowly for the remainder of the distance. The NaturalSound curve is somewhere in between the Logarithmic curve and the Inverse curve and is supposed to represent the most natural attenuation curve that sounds have in the real world.

Finally, you can create your own custom attenuation curves, using the tool of the Custom Attenuation Curve property (Figure 9-37), which creates curves the same way the Timeline Editor did in the section on Timelines. So you hold down the Shift key and left-click the graph to add a new point on the curve. Then you can click and drag those points, or manually adjust their locations, to change the shape of the curve.

At the highest level, you can create an Attenuation asset that can be saved and applied to multiple sound assets. To create a new Sound Attenuation asset , click Add New, go to Sounds, then select Sound Attenuation (Figure 9-38). You can double-click it to edit its properties, which are the standard set of attenuation properties that were just covered.

You can apply this Sound Attenuation to as many sound objects as you want, and then you only need to make changes for the entire group in one place. For example, if you open a Sound Cue, under the Attenuation Settings property, you can select the Sound Attenuation asset you created, and it will apply those attenuation properties to the Sound Cue.

But if you decide you want to set different settings for the Sound Cue, you can check the Override Attenuation property, and that will cause the Attenuation Settings property to be ignored and will instead use the settings defined in the Sound Cue itself.

Now let’s say you drag several instances of the Sound Cue into your Level and you want to change the settings for just one of the instances, without changing the settings of the Sound Cue itself. You can select that instance and then edit its Attenuation properties directly in the Details Panel by checking the Override Attenuation property. Or you can choose an existing Sound Attenuation asset to use just for that instance.

To get the file into the proper format so that the Engine can import it, you simply need to open the file in an application that can read it and then export it back out in the proper format. One program that can do this is Audacity, shown in Figure 9-39. It is free to download and use, can read many different types of audio files in various formats, and can export those files in a format which the Unreal Engine can read.

To download Audacity, go to www.fosshub.com/Audacity.html. If you have Windows, you can click the “Audacity Windows Installer” link and then run the .exe file that is downloaded. If you have a Mac, you’ll need to download the .dmg file, and if you have Linux, you will have to download the source code and compile it yourself.

Once you have Audacity installed, converting your audio files into the proper formatting is pretty simple. First, go to “File ➤ Open,” and open the file you want converted. Now, go back up to the File menu and choose “Export ➤ Export As WAV.” Now click “Save,” and when the Edit Metadata box pops up, you can simply press OK without making any changes.