7.3) Loudness and Dynamic Range
You now have a professional way to mix the complete Soundscape of your game, but how loud should it be? What does loud or Loudness even mean; how is it measured? What is the Dynamic Range of your mix? Why is this an issue? In the end, you need to use your ears to make the final decisions when balancing the various sounds. Sometimes this is easier said than done. It’s easy to get too focused on one part of the soundscape, skewing your perception of exactly how loud it is. Even the listening environment can skew the perception of volume in favor of one part versus another. This is why it’s important to have the visual feedback of Audio Meters to help confirm your understanding of a program’s volume or perhaps bring your attention to an issue you might not be aware of.
By default, Wwise provides a Volume Meter on the Master Audio Bus which appears in the Meter View to the right in the Designer Layout and Mixer Layout. While this gives you a sense of the final Output Volume when playing Objects, it would be helpful to have a visual Metering available for each of the Busses in the Music Mixing Desk. In Wwise, Master-Mixer Hierarchy Busses are handled under the hood as Non-Mixing Busses, unless they need to be converted to a true Mixing Bus. You can acquire a Meter for an Audio Bus by forcing it to sum the Audio Signals that are contributing to it, by inserting an Audio Effect across the Audio Bus. The Plug-in that uses the least amount of CPU processes is the Wwise Gain Plug-in, so inserting it into an Audio Bus is a way to get the Meter.
Scroll back to the top of the Mixing Desk to show the Meter Section. (Pic01 Meter Section)
In the Audio Tab, right-click the four Bus Objects and choose Show in Multi Editor. (Pic02 Show in Multi Editor)
Expand Audio > Effects > Effect 3, then right-click to the right and choose Set Effect 3 > Wwise Gain > New.
In the New Effect pop-up window, select your Default Work Unit for Effects, name your Effect and click OK. You’ve now inserted a Wwise Gain Plug-in across all of the Busses displayed in the Mixing Desk, so you are now able to see a Meter displaying the level of sound being routed to the Busses. (Pic03 New Effect Window)
When the mix is complete, you should remove the Gain Plug-ins to save Memory and CPU processing at runtime.
Play some Events in the Soundcaster View, simulate gameplay and watch the Meters. (Pic04 Audio Meters)
The Meter View displayed on right side of the Mixer Layout provides features not available to the Meters displayed in the Mixing Desk. For example, there are various types of Meter responses such as Peak and RMS that differ in how the visual reacts to the input. All of the Meters displayed in the Mixing Desk use a Peak Response Type Meter which shows you an instantaneous volume value. This type of Meter can sometimes be a bit deceptive when it comes to evaluating how loud a track is playing. Sounds with a lot of transient energy can cause Meters to react with high levels, even though your ear doesn’t necessarily perceive it that way.
Now look at the Meter View. At the top you can see the number 1 displayed in a box.
This is the Sync Group the Meter is displaying. A Sync Group is like a preset for a Meter assignment as well as its Response Type. There are four Sync Groups available, so you can quickly switch between Metering four preferred Objects in the Master Mixer Hierarchy. Because the Master Audio Bus represents the final output including Cinematic, Music, Sfx and Dialogue, it makes sense to assign it to Sync Group 1.
Click the Sync Group button, choose Meter Sync Group 2.
Choose the Sfx Audio Bus and adjust the Meter mode to RMS. (Pic05 Sync Group 2)
Play some Sfx Objects in the Soudcaster View and observe the differences between the Sfx Audio Bus Meter displayed in the Mixing Desk and the Meter View. (Pic06 Metering)
While the RMS Meter mode helps to better reflect on how we hear the volume of sound, it isn’t without limitations. RMS Meters react visually the same way to any frequencies that pass through it. An RMS Meter doesn’t distinguish between a high frequency or a low frequency sound, unlike humans who have different sensitivities to sound at varying frequencies. For example, we perceive changes in mid-range frequencies much more acutely than volume changes at lower frequencies. To account for this, an entirely new Metering scale has been created to specifically account for how human beings perceive Loudness. The scale is called LUFS - Loudness Units Full Scale. LUFS is a refinement of the scale called LKFS. The LUFS scale is used extensively in the broadcast television industry. To help ensure consistent volumes as you switch between channels, there are government standards that mandate programs adhere to an average LUFS level over the course of the program. Using the LUFS scale as a reference for understanding volume has spilled over to web delivery and even video games. It’s very possible that a game company might request that a mix falls within a defined average LUFS level in order to make a game’s audio more predictable in Loudness. The Meters in the Mixing Desk do not have an LUFS option, but Wwise does provide a specific LUFS Loudness Meter with four Sync Groups that can be assigned to Objects in the Master Mixer Hierarchy in a way similar to what you did with the Meter View in the last exercise.
Choose View > Loudness Meter > Sync Group 1.
Pin the Loudness Meter right under the normal Meter and adjust the Mixer Layout, so you can see all important Loudness Metering options, like Momentary, Short-term and Integrated Loudness. (Pic07 Loudness Meter)
Now, play some Objects and watch the Loudness Meter. (Pic08 Momentary and Short-term Loudness)
You can see how the Short-term Meter reacts more slowly than the Momentary Meter. This is because the Momentary Meter reacts quickly averaging the perceived Loudness over 0.4 seconds while the Short-term Meter averages over the last 3 seconds. The larger Integrated section of the Meter isn’t displaying anything. The Integrated measurement is used to understand Loudness over a longer timespan, but it isn’t activated until you click Capture. Also, levels that drop below -70 LUFS are not factored into the Integrated Meter’s average. This lets you stop and start playback without having the silence impact the Integrated Meter’s reading.
Now, launch the game and before you start running, start a new Profiling Session by pressing the Capture button in the Menu Bar and also press the Capture button in the Loudness Meter. Once you’ve finished one complete play-through, look at the Integrated Loudness value in the Meter. (Pic09 Integrated Loudness)
The Integrated Meter will continue to average the Loudness until the Reset button is pressed. This is helpful to get a feel for the overall Loudness of the soundscape, when played for a longer period of time. You can also see a value in the upper right corner called LRA, which represents Loudness Range. Loudness Range is a calculation of the material's Dynamic Range in LU–Loudness Units. It helps to understand how much perceived Loudness change there is between the quietest and loudest sounds of your soundscape.
You’ve no doubt noticed that segments of the various Loudness Meter appear blue, yellow, or green. The green area is referred to as the Target Zone, or the ideal Loudness Level. In broadcasting, the target for the average level over the course of a television show is around -23 to -24 LUFS depending on the governing agency. For web delivered content, that target is commonly set around -16 to -18 LUFS. In other words, the target could be different depending on the application. For video games, there is no standard, but there are a few game companies, publishers or technology providers, for example Playstation’s Sony Interactive Entertainment Group (SIE), that mandate that mixes must be delivered at a defined Target Level of -23 LUFS with a tolerance of +/- 2 LUFS over a measurement period of about 30 minutes. The Target value can be adjusted by using the View Settings available for the Loudness Meter.
Look at the Integrated Loudness Meter one more time. You can clearly see that your mix as it is now is too hot, meaning too loud. It has to be mixed about 7 LUFS or 7 dBFS quieter (one Unit of LUFS is equal to one dBFS).
Now let’s clarify the term Dynamic Range in detail. Dynamic Range means the difference between the quietest and loudest sound in either dBFS or LUFS. In a game-context, the quietest sound could be a distant enemy’s footstep, the loudest sound could be an explosion right next to the Player Character. Just like in real life, there has to be a believable difference between the intensity and level of these two sounds, in order for them to have a somewhat realistic relationship. What the Technical Sound Designer has to do is think about how to translate such differences from the real to the game world.
If all gamers were audio people playing on high-end sound systems and in perfect listening environments, nobody would probably see this option in games and the Dynamic Range would most likely be very wide, as it is at cinemas for example. Yet, most gamers do not have high-end sound systems nor great environments. For example, if a person plays on Laptop Speakers, having a very wide Dynamic Range would be rather inconvenient because the volume of the game would be too low because of the limited output gain of their sound system. Furthermore, the width of the Dynamic Range would make the quiet sounds too quiet to be audible. On the contrary, having a Dynamic Range that is too narrow would be very frustrating for a player with a High-end Sound System and a good listening environment. Consequently, in the last five years more and more games include a Dynamic Range option. But most commonly, the Dynamic Range option is hidden or included in other settings like Output or Speaker Type. Most games provide four settings like Headphones, TV Speakers, Stereo Speaker, Surround (5.1) Speakers.
Now, how could the most common Dynamic Range Calibration System be implemented in this game? The answer is by either setting up a new State Group with a State for each listening scenario, or an RTPC that drives Bus Volumes depending on which Dynamic Range preset is being used. For this particular Platformer Game, a headphone mix is sufficient enough. If you look at the Loudness Meter once again, you can see that the current mix has a LRA of around 12.0 LU, meaning that there are 12.0 LU difference between the quietest and loudest part of the game. (Pic10 LRA - Loudness Range) An audio mix for television is recommended to have around 8 LU as LRA, to be convenient enough to the home listener. Gamers might not always have better headphones than television sets have built-in speakers, so a LRA of 12.0 LU could be a bit too high.