FAQ

Basic Concepts

What is the resting level in HDR and why is it set to 80?

The resting level of 80 isn't arbitrary - it corresponds to where the stapedius reflex naturally occurs in human hearing (around 80 dB SPL at 1 meter). When sounds are at this level, the HDR system will not have any effect on your mix, making it an ideal baseline. Think of it as your natural "home base" for sound levels.

What's the default loudness when a sound is created?

80 is the default value, and the default resting level of the system. Then playback will be the same as without HDR, which is often a good starting point.

What kind of loudness ranges should I work with?

For most sounds, working within a range of 80-100 is very reasonable. While the system can handle values up to 150, these extreme levels are best reserved for special dramatic effects. What's interesting is that even small changes can be very effective - just 6dB of headroom above resting can create impactful ducking behavior.

Implementation

Do I need to change the way I put sounds in the game?

If all your sounds are at 80 (default resting level) loudness, and none of them go above full scale output signal, playback will be the same as without HDR. So, not necessarily! But when you want certain sounds to duck other sounds, you start a balancing act between loudness, attenuation, and audio signal.

Do I need to normalize all content in order for them to work with HDR?

Not really. The level of your sound sources will affect the resulting loudness of the HDR. For example, boosting a sound 20 dB should give you the same result whether you do it in the wav file, the sound's Volume property, or DefinedLoudness.
The DefinedLoudness of a sound sets a baseline, and adding the metered audio signal you get a resulting loudness, which is compared to the current loudness of the system.

How should I handle sustained or looping sounds?

Sustained sounds need careful attention. They should generally stay near or below resting level to avoid constant mix movement. Consider using different loudness levels for different states of the same sound, e.g. first person vs third person perspectives.

What release speed should I use?

Release speed typically works well between 20-60 dB/second. Think of it as a balance: faster release creates snappier response but risks more pumping, while slower release sounds smoother but can hold the mix down longer. The key is matching your sound tail lengths to your release speed for natural results.

Technical Considerations

How do HDR modes actually behave? I'm confused about Write mode.

Full Mode affects and is affected by system loudness. The sound affects system loudness calculations based on its defined loudness, and its volume is adjusted based on the current system loudness. Overshoot applies when the metered amplitude pushes the resulting level above 0dB, and distance attenuation affects the "distanced loudness" used in calculations.

Write Mode affects but is not affected by system loudness. The critical behavior here is that the loudness value is ignored for this sound's playback volume - it only plays at its base volume without any HDR boost. However, the sound still affects system loudness calculations, influencing other sounds. No overshoot applies, and distance attenuation directly lowers the playback volume rather than affecting loudness calculations. This mode is perfect for sounds that must always be heard, like artillery warnings or critical UI sounds.

Read Mode is affected by but does not affect system loudness. The sound volume is adjusted based on system loudness, but it doesn't contribute to system loudness calculations. Overshoot applies normally. This is ideal for ambient layers that should duck when important sounds play but shouldn't duck other sounds themselves.

The most common confusion with Write mode is that sounds seem quieter than expected. This happens because the loudness value doesn't boost the playback volume - only the base audio level plays. Adjust your attenuation curves accordingly if needed.

Right now I think my sound is a bit too loud compared to my other sound, although they are ducking each other as I wish

This is what we use Post Gain for! Since it's a constant push and pull between loudness and metered audio signal, it can be difficult to control the final signal strength. This gain is applied after all HDR calculations.

HDR and clipping

Since submixes clip at 0dB FS, it is often a good idea to add some headroom for transients and louder sounds to play without clipping. If you for example feel like the overshoot is not emphasizing the attack enough, you can try setting your submix to e.g. -6.

How do attenuation and HDR work together?

HDR calculations happen after attenuation, which creates some interesting behaviors. Very loud sounds can override normal attenuation behavior - when a sound's loudness exceeds resting level, it won't attenuate normally until it falls below resting. Using steeper attenuation curves for loud sounds helps maintain control over this interaction.

What performance benefits does HDR offer?

HDR isn't just about mixing - it also offers valuable optimization opportunities. The system can automatically stop distant quiet sounds from playing and cull low-loudness ambient sounds when appropriate. It helps manage voice counts and can be particularly efficient when working with reverb and complex spaces. Think of it as getting mixing and optimization benefits in one package.

How should I handle dialog and voice content in HDR?

Dialog presents unique challenges in HDR due to frequent pauses and silence between words, which can cause noticeable pumping between spoken words. Fast release times create obvious pumping effects, while slow release times may prevent gameplay audio from returning naturally.

For critical dialog like player character voices and important narrative content, you might consider keeping them outside the HDR system entirely. Alternatively, ambient dialog can work well in Read mode, allowing it to be ducked by important sounds while not affecting others. Background chatter can potentially work within HDR with careful tuning, though traditional submix ducking may be more predictable for dialog in some cases.

Since HDR reads amplitude before mixing, changing submix levels won't affect HDR calculations. You can still use traditional mix automation on submixes alongside HDR. Consider using a final limiter with adequate headroom to handle overshoot behavior. The approach is often to let HDR manage your gameplay audio dynamics while using proven techniques for dialog management where needed.

Best Practices

How should I approach my first HDR implementation?

You could start by setting all sounds to 80 dB loudness (resting level) and lower your final submix output volume to create headroom and avoid clipping. Verify the mix sounds similar with and without HDR enabled as your baseline.

Check the HDR Envelope window during system verification. If the RestingLevel moves, you have high amplitude signals. These aren't problematic but they do affect HDR since a 6dB hot signal adds 6dB to loudness. Test with Allowed Overshoot set to 0 if you're experiencing unexpected volume increases.

For incremental tuning, start adjusting one sound category at a time, like weapons. Increase loudness in 6dB steps to observe effects on other sounds. Use mute in the HDR Authoring window to isolate how other sounds are affected, and build your loudness hierarchy gradually.

Maintain good mix hygiene by keeping headroom throughout your mix chain, not just at the final stage. Keep individual sound outputs under 0dBFS for clean HDR operation and use a final limiter to handle overshoot behavior safely. Document your loudness ranges and reasoning as your project grows.

The philosophy is simple: start with everything in HDR, then exclude only what specifically doesn't work. Establish your ambient sound design as a foundation, then adjust loudness values upward for sounds that need to create space in the mix.

What are common pitfalls to avoid?

The biggest pitfall is over-complication. Avoid combining too many mixing systems or adding excessive modulation on top of HDR, as this can make it impossible to predict final volume levels. Keep your approach consistent and maintainable. Always test with real gameplay scenarios - behavior can change significantly in full gameplay conditions.

How should I approach sound design for HDR?

Design your sounds with HDR in mind from the start. Consider how amplitude variations within a sound will interact with the system, and how different sounds will layer in dense scenarios. Pay particular attention to sustained sounds and how their timing relates to your HDR release speeds. The goal is to work with the system rather than trying to force it to behave differently.

My authoring inclusion/exclusion is not working

Make sure to specify the /Game/ path of the folder you wish to include or exclude, without including the /All/ at the beginning of the path.

Creative Uses

Is HDR only for dramatic moments?

While HDR is excellent for managing peak moments, it's equally valuable for subtle mix movements. Using gentle 6dB changes with slower release speeds can create beautiful, nuanced transitions. The system is incredibly versatile - it's as much about delicate mixing as it is about managing dramatic moments.

One powerful creative use example is a low health state. You can use high loudness values, 50+ dB above resting level, to create a suppressed feeling - imagine playing a loud muffled sound that pushes other sounds away. By carefully shaping the release curve, you can control how sounds return to normal. This creates sophisticated state changes without relying on traditional filtering techniques.