Standardizing Loudness in Virtual Reality

Loudness is a way to control how loud the mix of a media is perceived by human ears (sensation of sound intensity), which includes volume, frequency and duration.

Back in the days, regulatory authorities received complaints because of the audio volume playback jumps when changing TV channels or programs. This then led the regulatory authorities to create the Loudness standards legislation and thus forcing broadcasters to comply with audio normalization standards.

Loudness standardization has started for regular console games based on broadcast standards (-23LUFS, Loudness Units relative to Full Scale). As those standards have been primarily set for television, should VR games, as part of a new form of media, adopt its own legislated standard(s)?

Safe and consistent consumer experience

As with any form of media, VR audio needs to be controlled in terms of consistency between experiences (movies, games, apps), different types of VR experience should all have a similar perceived volume, so that when the consumers switch from one to another, they won’t have any drastic changes in their auditory experience. Nothing revolutionary here, but this is of great importance considering VR audio playback configuration: adjusting volume is complicated with a VR headset sitting on your face and the audio should be even more safe and consistent because of being played on headphones (and earbuds), which due to their close proximity to the eardrums, require less power to possibly damage people’s ears. In other words, we don’t want to hurt consumers or have them adjusting their volume control over and over again with the risk of taking them away from the experience.

With that in mind, output power of the VR devices along with headphones sensitivities are important elements to take into consideration when defining loudness standard for VR. With a Target at -23LUFS, if the output power is too low, the games will not sound loud enough to serve their engagement purpose, but if the power is too high, consumers could experience ear fatigue. While engagement is important for immersion, avoiding ear fatigue can let the players stay in a game longer, and the longer a player stays in a virtual world without interruption, the more real and immersive it will feel, and thus it increase the chances to simulate the sense of presence in a virtual environment.

Loudness Range

While Integrated Loudness with Target at -23LUFS could possibly affect the players’ engagement, Loudness Range is the factor that affects how impactful the mix will sound.

The Loudness Range (or LRA) is a statistical measure of the difference in loudness level between the soft and loud part of a program.

“The measure Loudness Range shall be used to help decide if dynamic compression is needed (dependent on genre, target audience and transmission platform)” - EBU R128 Recommendation

Loudness Range needs to be monitored and adapted to fit different audio playback systems and different games genre.

Mixing with a high LRA is generally preferred, providing good difference in loudness between the quiet and loud part of your program. However, we don’t want the players to turn down volume during loud passages of the game, or turning up volume on the soft ones. Those situations would mean your LRA is too high for your playback system. In contrary, if loud passages seem not loud enough and soft ones not quiet enough, it would mean your LRA is too narrow. A game with a low LRA and integrated loudness at  -23LUFS will cause more fatigue compared to a game with larger LRA and a possibly higher integrated loudness. It depends of course on the game genre and its audio aesthetic direction (first-person shooter, narrative, social, etc.). Because VR is made to play at home, in a quiet environment and with headphones, VR audio allows a relatively high LRA.

Conclusion

Harmonizing audio levels for a media is fundamental, and the primary purpose is to improve the consumer experience. Although current Loudness standards for broadcast audio production set a great benchmark to define how consumers perceive a mix, it might have to be adjusted or optimized for VR.

Loudness can and should also be used to create presence in Virtual worlds. While we want VR media to be played at a comfortable volume to avoid ear fatigue, we also want it to sound loud enough to serve engagement and to help create a more immersive experience.

With VR contents made to play in good playback condition, VR Loudness Recommendation should allow for high quality playback without unnecessary dynamic processing, medium to high Loudness Range, as well as high but yet still comfortable Sound Pressure Level (SPL).

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