We recently had a great call with one of our HDR users that turned into an in-depth discussion about implementation approaches and creative uses. The conversation helped us expand our FAQ documentation, making it clearer for everyone using the system.

If you haven’t seen it already, a feature set overview video for SweejTech HDR can be found here

HDR Audio - An Overview of SweejTech 004 in Unreal Engine 5  / SweejTech 004 HDR

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 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.

How should I approach HDR implementation?

Start with all sounds in HDR at resting level (default 80) and consistent reference monitoring levels. Establish your ambient sound design as a foundation, then adjust loudness values upward for sounds that need to create space in the mix.

While music and dialogue often need special consideration, it's better to start with everything in the system and switch HDR modes or bypass HDR only if they specifically don't work well. Document your loudness ranges and reasoning - this becomes crucial as your project grows.

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.

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.

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.

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.

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, where many sounds can compete for space in ways that are difficult to test in isolation.

What works in small tests might behave very differently at scale with many sound sources. Mix throughout development rather than treating it as a final phase. Start early to understand the tools and workflow, and regularly test with multiple sound sources in real 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.

Whether you're creating subtle transitions or dramatic gameplay moments, understanding how to work with SweejTech HDR will help you achieve more sophisticated and maintainable mixes.

Want to give it a test? Contact us at hello@sweej.tech to arrange your free trial license! 


Got questions about HDR, SweejTech, or anything game audio? Join our Discord for in-depth technical discussions together with other developers!

While technical features often take center stage, we love hearing how our tools impact real production workflows. At SweejTech, while we pride ourselves on building powerful audio technology, we're equally committed to enhancing developers' daily workflows. HDR exemplifies this approach - advanced audio capabilities paired with thoughtful, practical tools that make a real difference in production.

Here's the experience of John Tennant, Technical Sound Designer at Sweet Justice, after working several months with SweejTech HDR.

Sometimes, a tool surprises you—not just by doing the job it’s meant to do, but by changing how you work. That’s been my experience with SweejTech’s HDR. While I could talk at length about how effortlessly it implements the ‘High Dynamic Range concept’ to an existing Unreal Engine audio project, I’m going to instead shine a spotlight on the unexpected workflow benefits I’ve been enjoying on a daily basis. 

UE Audio Without the Content Browser? Yes, Please.

Using the Unreal Engine, the Content Browser can end up quite quickly like the junk drawer of your kitchen—essential, but chaotic. Coming into my current project after it was in development for over a year, our audio assets were a mishmash of Marketplace Sound Packs, custom SoundCues & Metasounds, and random wave assets all scattered across various Plugin Content folders. These were all hooked up using a variety of techniques by well-meaning programmers, designers, and technical artists. Organising that? A nightmare. Rebuilding it all from scratch? Not feasible. 

Enter Loudness Definitions in HDR. At first glance, these seem like just another audio organisation tool, but they’ve become my go-to system for wrangling typical fast-paced game development chaos. Once I sorted all our sounds into logical Loudness Definitions, something magical happened: the HDR Authoring Window became my new audio home base.

The HDR Authoring Window: My New “Audio Hub”

Of course I still use the Content Browser, but with HDR, the Authoring Window replaces it for many tasks. It’s not just a utility for HDR mixing—it’s a streamlined command centre for making audio changes quickly and efficiently. Here’s why:

Direct editing of Loudness and dB offset without opening Metasound, SoundCue, or wave asset editors. 

Snappy filtering-by-string (including subtractive strings) for only the audio assets in the project. 

Mute/Solo buttons for HDR Loudness Definitions and individual assets. 

Full/Write/Read HDR modes per Loudness Group with per-asset overrides make it that much faster to translate the mix in my head into actual sound. 

The irony here is that my favourite part of SweejTech’s HDR actually has little to do with the core HDR system itself–though this all works beautifully. It’s the workflow enhancements—the way the Authoring Window creates a space where I can focus on the big picture sound of a project and individual sounds at the same time. 

For me, SweejTech HDR doesn’t just solve the HDR problem; it’s changing my entire process by eliminating friction from my daily tasks. 

SweejTech HDR pairs powerful audio technology with thoughtful workflow enhancements, making a real difference in daily game audio production. By focusing on both technical excellence and practical usability, it helps developers work more efficiently while delivering exceptional sound.

SweejTech HDR: Come for the Sound, Stay for the Workflow

Building Next-Gen Audio: The Technical Foundation of SweejTech

At SweejTech, we're building our audio DSP stack from the ground up to take full advantage of modern hardware capabilities. Here’s the thinking behind some of the technology we’re working on.

At the core of SweejTech is a custom-built audio specific DSP mathematics library. While many solutions build directly on more general-purpose game engine math libraries, we've developed a platform-agnostic foundation that allows for precise control over performance-critical operations. Audio processing demands consistent, fast and predictable performance - requirements that shaped our mathematical foundation from day one.

One area where this foundation proves crucial is in our convolution reverb implementation. Modern game engines haven’t taken full advantage of the performance capabilities of modern hardware in their convolution implementations, resulting in restrictions on reverb usage due to CPU constraints. We're challenging this limitation.

By rethinking how data is stored and processed, we've achieved significant performance gains. This means games can use more reverb instances in more contexts than previously allowed for, opening new possibilities for sound designers.

A key challenge in game audio is maintaining consistent performance and signal output across different platforms. Our technology is designed to deliver identical results whether running on a PS5, high-end PC, or Xbox Series. This predictability is crucial for game developers who need to ensure consistent audio quality across their entire player base.

Future developments include exploring real-time acoustic simulation and advanced binaural rendering. While these features are still in development, they represent our commitment to pushing the boundaries of what's possible in game audio.

By building our technology stack from first principles, we're creating solutions that don't just work within current constraints, but help define what's possible for the next generation of game audio.

While we’re hard at work on audio features, we’re also building out a foundational layer that will ensure we’re always making the most of the hardware we use, and using it to enhance the quality and performance of everything we do.

We've added an impressive new set of features for the latest release of Audio Inspector (for Unreal Engine 5). The feedback and response to the original release was very positive, and we've been impressed with the breadth and scope of projects using the tool.


The new Audio Inspector is included as part of our SweejTech suite licence - https://sweej.tech/license/

Let's take you through some of its new features.

Display Origin Distance: Now showing the distance from the origin

Audio Inspector: Display distance from origin

New Owner Column: We've added a dedicated column to identify the owner of each 'Active Sound'

Audio Inspector: New owner column

Sound Highlighting: Selecting a sound in the list will now highlight its corresponding location in the world

Audio Inspector: Select active sound to highlight owner instance

Asset Type Icons: Rows now display sound type icons to easily identify different sound asset types

Audio Inspector: Show asset type icons

Quick Access to Assets: You can now Shift+Double-click on an active sound to instantly locate it in the 'Content Browser'

Audio Inspector: shift+doubleclick to show asset in 'Content Browser'

Footer Enhancements: Added a footer displaying the total voice count and current 'Master Volume' output for quick reference

Audio Inspector: footer with total voice count and 'Master Volume' output

Viewport Selection: Clicking a row in the list will select the corresponding owner instance directly in the viewport

Audio Inspector: display selected active sounds in viewport

Performance Improvements: Various optimizations have been implemented to enhance overall performance.

We've added an impressive new set of features for the latest release of Audio Inspector (for Unreal Engine 5). 
The feedback and response to the original release was very positive, and we've been impressed with the breadth and scope of projects using the tool.

When working on game projects, we have seen a need to easily access a few specific values in a large number of sounds. Therefore we created this Global Parameter utility. It enables you to set a value in one place and then easily get that value from anywhere. 

Maybe you want to be able to get the player's campaign progress in your music systems? Or do you want the health, velocity or height above ground from your player? Maybe you need the wind and rain amount or time of day in your spot sounds? Or the distance to your companion for voice line selection?

Let's take the rain amount as an example. We want that value to affect different spots sounds, like tarps or barrels. The higher the rain amount, the more we fade in the rain layer sound.

We send the amount via a suitable blueprint.

In our MetaSound we add the SweejTech.GlobalParameters interface.

Then we fetch the value using the interfaces and the Get Global Parameters Value node.

This utility is still work in progress, but if this would be of interest to you please let us know. 

When working on game projects, we have seen a need to easily access a few specific values in a large number of sounds. Therefore we created this Global Parameter utility, an interface that receives parameters set from anywhere in the game!

The SweejTech Audio Inspector allows sound designers, programmers and anyone working with Unreal Audio to view active sounds in a compact, dockable tab window. It displays a table list view with configurable columns that show each active sound and important information about it. It slots neatly into your Unreal Editor audio content creation workflows and debug sessions without obscuring the game viewport. Enjoy inspecting your audio!

 See detailed, useful info about all active sounds in game in a compact editor tab window.

Mixing is essential to ensure player agency; when we hear better, we play better. Too many competing sounds and the message is obfuscated; reason and meaning are lost. HDR mixing enhances the gameplay experience by making each sound impactful, and ensuring that all your hard work is heard and appreciated. 

HDR prioritises more important, or generally ‘louder’ sounds. It preserves relationships between adjacent sounds and scales the output signal to the ‘loudest’ perceived sound. A moving HDR window maps the active sounds to the dynamic range of the playback system, automatically culling sounds that are below its lower threshold. HDR makes loud sounds sound louder, and quieter sounds sound as loud as loud sounds sound!

High Dynamic Range audio for UE5, enabling automated mixing and prioritisation, for delivering an immersive audio experience.

The SweejTech MetaSound MIDI plugin is a versatile solution that enables sound designers, musicians, and anyone working with Unreal Audio to use MIDI devices within the MetaSound editor. It features MetaSound interfaces for receiving MIDI events, such as keypresses, pitch bend, and control changes, which can be used to trigger events and parameters within your MetaSound. Users can customize their experience through adjustable settings, MIDI device management, and real-time MIDI monitoring, while also having access to console commands and example content to explore creative possibilities. Whether building synthesizers and samplers, or prototyping and debugging MetaSound graphs, this plugin provides an exciting playground for MIDI and MetaSounds enthusiasts alike.

Effortlessly use MIDI devices in the MetaSound editor, and build innovative graphs.

Find out more about our current and upcoming technologies.

SweejTech Blog

Common Questions about HDR

SweejTech HDR: Come for the Sound, Stay for the Workflow

Building Solid Foundations

New features for Audio Inspector

First look at Global Parameters