Nested Reverbs and Prioritization

When you start the level you are in the *Sewer Pipe* (Bookmark 1), which leads into a basement room in a bank. From here you can make your way up across the debris into the bank lobby.

The sewer pipe and basement room are straightforward [AudioVolume] s, but the lobby and back room in the lobby are more problematic. We could make a series of volumes, but the main L-shape of the lobby is clearly the same space, and the crossover of the [AudioVolume]s could lead to some audio artifacts.

Sometimes it is useful to enter geometry edit mode (Shift + 5, and then Shift + 1 to return to place mode) to see the [AudioVolume]s more clearly, and we can use this mode to edit the shape of the volumes to better suit the environment (hold shift while selecting a corner of the volume to move it). You can also choose different brush shapes as starting points when creating your reverbs.

In this case (as is often the case), the lobby room sits within (or is nested within) the larger volume that covers the whole of the ground floor of the bank, and so another thing we can do is to set its Priority to override the large one that it sits within.

The audio volume [Small_Back_Room] of the lobby has a priority setting of 3.0 (in its Details panel) whereas the main lobby [Lobby] Audio Volume has a priority of 2.0.

In fact the reverbs of both of these large rooms and the smaller back room actually already sit within a larger reverb that covers the entire street. There’s a hierarchy of priorities: street reverb priority 1.0, lobby reverb priority 2.0, and small back room reverb priority 3.0.

In order to more clearly hear the effect your reverb settings have, you can use a Console command when playing the game. Go to Bookmark 1 and start the game from the *Sewer Pipe*. Call up the Console with the ¬ (PC) or ~ (Mac) key and type “IsolateReverb” (type “ResetSoundState” to turn this off). This removes the dry audio to isolate the reverb (you can also type “IsolateDryAudio” to remove the reverb to isolate the dry audio). Now play through this area up to the street and listen to the reverb changes. You can also see which reverb effect is currently active by using the Console command “Stat Reverb” (see Appendix A: Core Concepts/Console Commands for more on Console commands).

Reverb: Prebake

Sometimes you’ll want greater control over the quality of the reverb applied since real time reverb isn’t always the best quality. You can prebake your reverbs into the sounds and then use volumes to decide which sample to play or layer to apply. We’ll go into more detail on this when looking at weapons in Chapter 09.

Sound Source Types

Mono

Generally used for spatialized point sources such as the diesel generator in the street outside the bank.

Multichannel Audio: Quad, 5.1, and 7.1

Multichannel sound sources are sometimes used for music but are increasingly becoming the norm for long ambient area loops. Quad, or 4-channel, loops are common since they leave the center speaker free for dialogue.

By using a specific naming convention, you can import multichannel files into a multichannel asset to use in the game. In the *Warehouse* (Bookmark 3) at the end of the street, there are two quad files: a warehouse ambience on the ground floor ([Quad-Warehouse]) and a quad music file on the first floor ([Quad-Music]).

Since both of these are quad, the source files were renamed according to the convention below:

Front-left:	Factory_Amb_fl.wav
Front-right:	Factory_Amb_fr.wav
Side-left:	Factory_Amb_sl.wav
Side-right:	Factory_Amb_sr.wav

All these multichannel files play back directly to the speakers and so do not spatialize, which is what you’d generally want for looping ambiences or music.

There may be specific circumstances where you want to use a multichannel file for sources that are located in game (for example if you had a group of musicians or musical sources in game). You could of course simply implement these as separate ambient sounds, but then they would not be in sync. On the roof of the warehouse is an example using our <GAB_Quad_Sounds> macro. (You can press ‘T’ to toggle the background ambience off/on.)

Four [Notes] have been created that are used for the location of each sound (which now need to be imported as separate mono files). By using the <GAB_Quad_Sounds> (from the right-click Graph Action Menu), you can assign 4 targets for the sounds and define their fall off distances. Once you trigger the node to start (when the player enters the area), the sounds will be spatially located but will stay in sync. This macro is installed here when you install the levels:

• PC: C:Program FilesEpic GamesEngine VersionEngineContentGAB_Resources
• Mac: /Users/Shared/Epic Games/Engine Version/Engine/Content/GAB_Resources

In order to spatialize the Sound Waves must have an {Attenuation} defined with its Spatialize checked. You can assign an {Attenuation} through the Sound Wave’s Generic Asset Editor.

Directional and Diffuse Sources

Directional Sources

Although we’ve looked at the spatialized properties of mono sounds in the game, sounds often have a particular direction in which they are loudest/unfiltered rather than simply attenuating evenly in all directions from a central point. Many sound sources have a front where the sound is clear and back where the sound may be attenuated or filtered. Think of your voice, for example, or a megaphone. Using these controls can greatly support the reality of your soundscape.

In the street outside the bank, there is a public address system spouting propaganda (Bookmark 2). As you move around it, you can hear that this source is directional since the [Ambient Sound] is using a Cone attenuation shape.

Within the inside cone the sound is at its maximum volume, then it attenuates to 0.0 at the outer cone position.

Diffuse Sources

In some cases a sound source will not come from a very specific point but from a larger source of sound, for example a large piece of machinery or a waterfall. In these cases you would then want to spatialize the sound when heard from quite a distance, but as you get closer you want the sounds to be more enveloping and the panning of the sound as a point source begins to sound wrong.

For the Tank 01 [Tank_Diesel] in the street, we’ve made use of the non-spatialized radius function of the ambient sound’s attenuation settings. When the player is within this radius, the sound will no longer pan. This feels a lot more convincing for larger sound sources.

Exercise 07_02: Quad, Directional, and Diffuse Sound Sources

In this exercise we are going to explore adding sound with different source and spatialization properties to your exercise level.

1. Try the following:
   1. Add a quad ambience as an area loop to one of the areas of your level. There are two ambiences (cave and oasis) supplied in the exercise folder.
   2. These are set up already with the correct file naming convention, and so when you import them they will form a single quad Sound Wave asset that you can treat in the same way you would when setting up a normal area loop.
   3. If you want to import your own quad assets, then be sure to follow the naming convention outlined above.
   4. Try using the Cone attenuation shape on an [Ambient Sound] for some more directional sound sources.
   5. Add an [Ambient Sound] that uses a non-spatialized radius. For example you could edit one of the music sources in the *Mountain Village* area so that when you approached the house, the music would become less directional and pan less wildly.

Filter over Distance

Applying a low-pass filter over distance is very effective for creating a sense of distance, making sounds appear far away or close by through an imitation of the way that high frequency elements of sound are absorbed by air over distance (although obviously in reality it is a lot more complicated than this!) We already looked at implementing this filter over distance in Chapter 01, but you can hear another example of this effect here by listening to the fire blazing around the Tank 02 [Tank_02_Detail_Distance].

In some other game engines, you may need to fake the way that sound is filtered by the air over distance. You might do this by applying filtering in your DAW and then crossfading between the normal (dry) sound and the filtered (wet) one over distance using different attenuation settings for each Sound Wave in your Sound Cue. If you were going to get slightly obsessive about it, you could even have different versions of Sound Cues (using the same Sound Wave but with different low-pass filter settings) played depending on atmospheric conditions such as hot sunshine or dense fog (you can dynamically adjust the attenuation settings of an [Ambient Sound] by using the <Adjust Attenuation> node in a Blueprint).

Detail over Distance

While effective, the application of a simple low-pass filter over distance does not really capture the subtleties of how the different sound elements of some sources attenuate over distance. You can add a lot of depth and character to your objects in the game by applying different attenuations over distance to the different elements of the sound. You may have noticed in the above example that the attenuation settings for the fire are not defined in the ambient sound itself. They are actually defined by an -Attenuation- node in the Sound Cue {Tank_02_Detail_Distance}.

In addition to this, there are the three other layers that make up the complete tank source sound, each part of which has a different attenuation setting so that as the player approaches the vehicle, more details of the sound are revealed. Typically you’d be adding smaller, higher frequency elements the closer you get to the source. This approach is also good for weapons, although we need to implement it in a slightly different way—see Chapter 09.

In theory you could use the -Crossfade by Distance- node in the Sound Cue for this, but since this, at the time of writing, actually retriggers the sounds as you cross the cut-off points, it is only really useful for short one-shot sounds, not loops, and even then you need to use with caution!

Occlusion

When we enter the *Offices and Factory* (Bookmark 4) building at the end of the street, we would naturally expect the outside sounds to be attenuated and filtered as these sounds are occluded by the brick walls.

The extent to which the sound is attenuated in volume and altered in frequency content will be dependent on the material of the obstacle. Brick has a pretty significant effect as you can imagine, whereas if the sound were occluded by the paper walls of a traditional Japanese house, the effect would be rather different. As an illustration of the problem, consider a city block in the rain. With no occlusion implemented, you would hear the rain sound inside all the buildings.

If you carefully placed a number of rain instances using ambient sounds, you might be able to arrange these so that they were only heard outside, but this would be quite a lot of work and also would be liable to phasing issues as multiple instances of the same sound overlapped.

We would also have the same issue of ambient sounds overlapping into areas they should not be in terms of the different vertical floors of a building.

Toggle for Occlusion

The way we’ve dealt with this up until now has been to either carefully construct our ambient sounds’ Falloff Distances or to toggle on or off the inside and outside ambience with [Trigger]s as we cross a threshold.

We have seen this triggered switching approach in Chapter 01 but have included another example here. As we enter the office ground floor, a [Box Trigger] toggles off the outside ambient sounds and switches on the sounds inside the lobby.

Of course there are a number of drawbacks with this approach:

• Unless you’re going to make your own filtered/attenuated versions of the inside and outside sounds, then you will either hear only the inside ones or only the outside ones, which is not very realistic. This can be fine for some environments where due to the noise levels, or the degree of occlusion, you wouldn’t hear these anyway.
• If the player is quickly entering and exiting rooms, then they can become aware of this trickery and this can affect their immersion in the game.
• The nature of a switch is that it is either one or the other—there is no midpoint. So a player hovering in the doorway is going to have a pretty odd experience of constantly switching between the two states.

Many modern game audio engines use what is called ray tracing for detecting occlusion. A simple path is traced between the sound emitters and the listener. If any geometry or objects interrupt this path, then a filtered version of the sound is played (either by filtering in real time or by playing a prerendered filtered version of the sound). Other engines, such as the Unreal Engine, require us to define the geometry for them.

Ambient Zones

It is often the case that the game engine does not have any awareness of the positions of walls in regard to occluding sound, so even if you do have a built-in occlusion system, you will have to do some work to define rooms for this system to work. The Unreal Engine provides a system for occlusion called Ambient Zones, a functionality available as a subsection within the [Audio Volume]s that we’ve already come across. In the case of our city block rain example, we could box out the buildings with ambient zones so that the rain was no longer heard inside.

An important note to remember is that the effects of the ambient zones will only be heard if the sounds belong to a Sound Class that has Apply Ambient Volumes enabled.

In this level the affected sounds are set to belong to the {Ambient}sound Class (in the Details panel of a Sound Wave or through the -Output- node of a Sound Cue). We will be looking at Sound Classes in more detail in the next chapter.

The settings of the ambient zones work as follows:

Interior Volume

The volume of things inside when heard from the outside

Interior LPF

The amount of filtering to apply to things inside when heard from the outside

Exterior volume

The volume of things outside when heard from the inside

Exterior LPF

The amount of filtering to apply to things outside when heard from the inside

The first room on the left (*Room 01*) has an [Audio Volume] around it with its ambient zone set to attenuate any sounds outside of the room by 0.5. As you enter this room, you can hear the generator in the main lobby getting quieter as the zone’s Exterior Volume is set to 0.5. (Given the toggling of exterior ambience method we used when first entering the building you will need to start outside the building (Bookmark ‘4’) in order to accurately preview all of the following Ambient Zone examples on the ground floor.)

Prioritization of Zones

Like the reverb, [Ambient Zone]s also have a priority system so you can nest zones inside one another. In *Room 02* there is an [Ambient Zone] for the room, and then another smaller [Ambient Zone] for the inner vault room. The inner vault has a higher priority, and so it will override the general room zone when you enter it (it is also set to attenuate the outside sounds further as you might expect).

Filtering

*Room 04* has a window looking onto the lobby, and this room has two zones in it. When you are by the window, the outside sounds are filtered less than when you are hearing them through the wall.

Obstructions and Exclusions

In addition to occlusion (where both the direct and reflected sounds are blocked), we must also consider two other scenarios. Obstructions are where there is an obstacle between the listener and the sound object, but the reflected sound emanating from the object and bouncing off the walls still reaches the listener. This obviously has a different sound from when all the sounds are on the other side of a wall for instance.

In this instance pillars are obviously blocking the direct path of the sound, so an [Ambient Zone] is created behind the wall with a filter applied to exterior sounds. This produces a very rough approximation of an obstruction effect.

Exclusions are where the sound reaches the listener directly from the sound source, but the reflections hit the obstacle. This would be typical of a sound and listener lined up through a doorway for example. You can hear this as you enter the elevator lobby at the back of the room.

Dynamic Occlusion

Having destructible buildings is quite common in games, and obviously when the geometry and nature of a space changes like this, we need to update the reverb and occlusion settings. In the room to the left of the elevator lobby is a button that you can use to blow up the outer wall—which is fun!

We could simply create a reference to the [Audio Volume] in the [Level Blueprint] to disable it using the <Set Enabled> node (shown top right in the image below, but unused), but a better approach is to give it some new settings for both its reverb and ambient zone properties. In the “Destructible Wall” section of the [Level Blueprint], you can see this in action.

When the game starts, the audio volume has a {BunkerHall} reverb setting, and its ambient zones settings are set to attenuate any exterior sounds to 0.05 (since they are outside of this brick building). When the player uses the button to explode the wall, the ambient zone settings are changed to 0.8 (since now the external sounds will be heard through the hole in the wall). The reverberant nature of the space will also change with this wall missing, so we have applied a different reverb setting: {City}.

The elevators nearby also apply a similar system to change the occlusion operating when you are inside the elevator depending on whether the doors are open or closed.

Moving Sound Sources with Matinee

Matinee is the system in the Unreal Engine for getting things to move, and in this case we’ve just created a flies Sound Cue and then used a Matinee to animate its movement. If you select the Matinee Actor that’s near to the trash [Flies] and open it (Open Matinee in the Details panel), you can see the Matinee Editor. The sound’s movement is animated by setting up a number of keys. These are the locations for the ambient sound at different points in time.

Try playing or looping the Matinee, and you can see the sound moving around in the Viewport.

You’ll also hear some hawks flying around this rooftop, and this [Ambient Sound] is being animated by the Matinee [Hawks]. Both these Matinees are set to Play on Level Load and to be Looping.

Creating Movement

Given that this is an urban warfare environment and explosions are pretty important elements, we’ve created a Blueprint [GAB_ExplosionMovingSound] to add a bit of life and movement to these. This is particularly effective on a surround sound system.

While on the roof (Bookmark 6), try pressing M and you will see an explosion based around the public address system. No matter how good your explosions sounds might be, if they are just spatialized mono or stereo assets, they are going to lack the dynamic impact of explosions in the real world because in the real world sound moves!

If you select the [GAB_ExplosionMovingSound] Blueprint, you’ll see in the Details panel that you can add explosion core, right perpendicular, left perpendicular, left swoosh, and right swoosh sounds. This is triggered in the Level Blueprint by setting it the <Activate>—see the “Moving explosions” section.

The core is your basic explosion sound, the perpendicular sounds shoot off right and left from the explosion source (suited to explosion bloom type sounds), and the swooshes whizz towards and then past and behind you (suited to tails). As you can hopefully hear, this movement makes the experience a lot more impressive than a simple static sound and is an idea you could develop for a number of other applications (edit the Blueprint, from the Details panel, to see how it works).

Rotating Doors

Go back down the elevator to the *1st Floor* (Bookmark 5) and open (by pressing E) the door at the end.

Like the moving ambient sounds above, this door is controlled by a Matinee, and it is from this Matinee that we can get timed events to sync the sound to the movement. We could just create one sound that is timed to match the full opening (creak) and opened (clunk), but animations often change, so breaking up your audio into smaller events that can be triggered is a good habit to get into.

In this instance the E command that starts the Matinee immediately plays the creak of the gate movement, and then we get a Finished event from a <Matinee Controller> to trigger the clunk.

It is important to note that the Finished event derives from the red end marker in the Matinee (the small red triangle). Sometimes you may find that an animation has finished but your sound has not triggered. An incorrectly placed end marker is most likely the cause. See the “Rotating Door” section of the Level Blueprint.

Open/Opening Loops

The metal grill in this first warehouse room (after Bookmark 5) is operated by the control panel on the wall. Pressing E starts the grill opening, but releasing E will pause it.

Because the opening of the grill might last an indefinite amount of time, we cannot just prerender a wave. Instead we use a looping wave that plays for as long as the grill is still moving (i.e., for as long as the Matinee is still playing). The <Gate>s are just to make sure that the player is in proximity to the control panel. E starts the Matinee then plays an open sound and the opening loop. This loop continues until either the player releases E (then it plays a stopped sound and stops the opening loop) or the Matinee finishes. See the “Grill—Button Held” section of the Level Blueprint.

Matinee Events for Mechanical Systems

Often there are events within a Matinee that you want to sync sound to, but so far we’ve only been getting notifications when a Matinee plays or finishes. The [Crane] Matinee in the *Warehouse Room* contains an Event Track.

This Matinee will pick up the metal girders that block the entrance to this side of the roof and move them out of the way. This time the movements are more complex, so we have added an Event Track to trigger our sounds. These are created in the same way you create movement keys, only this time you give each event a unique name.

Then when you create a <Matinee Controller>, you don’t just get the Finished event from which to trigger your sounds, but also a list of the other events.

Compared to embedding the sounds in the Matinee itself, as we will see below with the Matinee Sound Track, this may seem like a hassle, but the advantage of this approach is that you can use looping sounds like we have here for the {Crane_Moving} cue. This means that with any in-game animation from a Matinee, it does not matter if the designers decide to change the speed of it (the Play Rate of the Matinee)—our sounds will remain in sync.

Matinee Sound Track

You can start the final machine, to the rear of the next room, with E as usual, but then speed it up or slow it down using the + or − keys. Here it is crucial that the audio remains synced, and so we have used the Sound Track functionality of the Matinee to embed our sounds.

As you can see, the Sound Track in the Matinee is very useful for closely synchronizing sounds to movement events; however as we have noted above, you can’t use loops in these tracks, so depending on your needs you may want to use a combination of Sound Tracks and Event Tracks as outlined above.

Doppler: Faking It

Pressing L gives you an alternative approach using prerecorded flyby sounds. As we discussed in Chapter 02, the best results are often from a combination of system approaches and just using great recordings where appropriate.

The cube in the illustration above is attached to the plane [EuroFighter_Doppler_Fake] and has a tag (Details /Tags) with the name “PlaneSound”. Whenever anything overlaps with a box we have set up around the player (see it in the Viewport of [MyCharacter]), the [MyCharacter] Blueprint checks whether it carries this tag. If it does then it triggers the <CallFakeDoppler> event, which is picked up in our case in the [Level Blueprint] (in the “Doppler” section).

Since our flyby sound peaks at 3.0 seconds and we want this to coincide exactly with the moment when the plane flies past the player, we have set the box around the player that triggers this sound to be 500UU large. With the speed that the plane is traveling, this will trigger the sound to start at the right time.

Simple Object Collisions

In the *Physics Room* (Bookmark 9), there are some objects that produce a sound when the player collides with them. These are implemented using simple trigger on overlap (collision) events, and since these objects are likely to be reused, we’ve made them into Blueprints that have the collision triggers and sounds embedded.

Select the [WarehousePipes01_Blueprint] and click on Edit Blueprint/Open Blueprint Editor in the Blueprint section of its Details panel. Here you can see that we have created an <Event Hit> event that triggers a collision sound. Because you can sometimes get a very quick series of triggers from these kinds of collisions, we have blocked this temporarily with a <DoOnce> node that is only reset after a given <Delay>.

Since we have made the variables for the Sound and the Retrigger Delay time public (indicated by the highlighted eye icon below), these are editable in the Details panel of the Blueprint in level.

Velocity to Collision Sounds

What the game system is attempting to do here is to somehow replicate the interactions of different materials that produce sound. There is a great deal of research available on the physical processes that create sounds, and there is an increasingly important branch of game audio research that looks at how these can be implemented in games without the vast processing overheads of truly accurate simulations. The details of this subject, sometimes termed procedural audio, are for another book (see the further reading section of the website for a good one!) The reality is that within the processing power currently available for game audio, we are at the early stages of this brave new world and so often there is still the need to fake it.

The most important thing when dealing with variables arising from games physics is to be able to scale these variables into a useful and meaningful range of numbers for your audio. In addition to scaling the variables from physics events, it’s also often useful to set thresholds (to clamp or cap the numbers) so that the sometimes extreme numbers that might appear unpredictably do not result in an extreme audio event.

Velocity to Volume

The first control panel in the *Physics Room* controls the height of the first barrel (use + and − to control the height and E to release the barrel).

The first barrel is the Blueprint [Barrels_Vol] and has a simple relationship between the velocity at which the barrel impacts with the floor and the volume of the collision sound played. When this Actor collides with something, the <Hit Event> in the Blueprint is triggered and this causes a sound to be played, but instead of the simple collision above, we now get a Normal Impulse from the hit event that gives the velocity of the impact (this is converted from a vector to a float) and is then normalized (to a 0.0–1.0 range) to set the <Volume Multiplier> for the sound. Select the [Barrels_Vol] Blueprint or the barrel in game and Edit Blueprint to see the system.

Velocity Reading through Curves

Since the sound of a collision will differ significantly with the velocity of the impact, the second barrel ([Barrel_Curves]) uses the velocity to read through a set of curves. We could have used switches within a Sound Cue to change the sounds, but this would have been a little binary with abrupt changes on the thresholds, so using curves gives us more flexibility.

The velocity of the impact (taken from Normal Impulse) is normalized then used to read out the curve values at that point. The figure below illustrates the velocity (X) to volume (Y) relationships for the three different metal impact sounds: light, medium, and heavy.

These are then used to modulate the volume of the different elements (you could also send the curve output to <Set Float Parameter>s and -Continuous Modulator-s in the Sound Cue to achieve the same effect). We looked at this concept of reading through curves in the Parameterization = Interactivitysection of Chapter 02 and in the Curves to Volumesection of Chapter 04. Go back and read Appendix A: Core Concepts/Transforming and Constraining Variables and Parameters/Reading through Curves if you’d like to refresh your memory.

Sliding, Rolling, and Scraping

In order to work out if an object is rolling or scraping, we need to analyze the pattern of hit events received. If it’s above a given threshold, then we’ll treat it as a normal impact, but if we’re getting lots of low velocity impacts within a given time frame (in this case 4 low impacts within 0.2 seconds), then we can assume that it’s continuously in contact with a surface while still moving (i.e., sliding, scraping, or rolling).

For the blue barrels [Barrels_Roll], press + or − to increment or decrement the angle of the ramp, and E to release. You can also push the freestanding barrels in this area with R and hold the RMB while focused on them to implement a gravity gun type system to pick them up.

If we get the required number of low impact hits, we trigger a different sound and use the impact velocity to change the Volume Multiplier. A <DoOnce> node is used so that we only trigger one instance of this sound at a time (an <OnAudioFinished> event is used to reset the <DoOnce>).

You will notice that you need to build in lots of belt and braces systems (i.e., double checking and limiting systems just to be sure, like the <DoOnce> above) for physics events since they can occasionally send out some extreme values outside of their normal range. See Appendix A: Core Concepts/Transforming and Constraining Variables and Parameters.

Physics-based Collisions: Cascading Physics

You’d imagine that if you take the sound of one rock falling or one pane of glass breaking and applied it to 20 rocks or 20 panes of glass that when multiplied this might produce the appropriate sound for a group of these objects, but this isn’t the case. The complex interference of Sound Waves when many collisions are occurring simultaneously means that any attempts to recreate 20 rocks falling or 20 shards of glass by playing back 20 individual impact sounds is doomed to failure.

When responding to physics, it’s also very easy for your sound system to get overwhelmed with the number of events. Simply reusing the same sound for each individual collision does not work beyond a certain density of events because it can lead to too many voices being used, it can lead to phasing, and it just doesn’t sound right. You could limit the number of occurrences of this sound to stop it taking up too many channels (using the {SoundCue} Voice Instance Limiting discussed later in the Prioritization: Number of Voices Controlsection), but this would not improve the sound beyond perhaps eliminating some of the phasing.

Go over to the window in the *Physics Room* (Bookmark 9) and shoot it, first as spaced single shots and then with a burst of fire. You will hear that after a certain rate of fire, the sound changes from single small glass breaking sounds to a larger glass breaking sound.

What we have done here is to set up a cascading physics system. If more than a certain number of events are happening within a given time frame, then change the sound to a recording of a larger event. This helps to keep the number of simultaneous sounds to a minimum as well as producing a more realistic effect. Consider this approach to any circumstance where you have a potentially large number of sound events (e.g., glass breaking, bricks falling, etc.)

For each hit event, we increment the Window Shot Count variable, and if this reaches more than 5, then we <Branch> to play the larger sound. This is reset after 0.3 seconds to set the timeframe.

In theory this is how the -Group Control- node in a Sound Cue should work. You can assign sizes for each of the inputs, and as soon as the number of active sounds exceeds that size, it will choose to play a sound from the next input down so you can set up a series of prerecorded small to large sound events. At the time of writing, this node doesn’t actually work, so this is why we thought we would build our own!

Recap:

After working through this chapter you should now be able to:

• Use nested reverbs and prioritize these;
• Use appropriate distance algorithms for a variety of sources;
• Create obstruction, occlusion, and exclusion systems using ambient zones;
• Move sounds and objects using Matinee;
• Implement physics-based audio systems such as the speed of sound, Doppler, and collisions;
• Add sounds to animations and implement footstep and Foley systems;
• Use cameras for cutscenes and control the listener position.