While there is a lot that goes into delivering a high quality, immersive VR experience, audio is an element that is sometimes overlooked in regards to how essential it is in delivering that heightened sense of immersion.

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Creative Control

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When it comes to sound design for immersive experiences, it may come as a surprise, but realism is not necessarily the end goal. Keep this in mind at all times. As with lighting in computer environments, what is consistent and/or “correct” may not be aesthetically desirable. Audio teams must be careful not to back themselves into a corner by enforcing rigid notions of lifelike accuracy on a VR experience. This is especially true when considering issues such as dynamic range, attenuation curves, and direct time of arrival.

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Mono

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Most spatialization techniques model sound sources as infinitely small point sources; that is, sound is treated as if it were coming from a single point in space as opposed to a large area, or a pair of discrete speakers. As a result, sounds should be authored as monophonic (single channel) sources.

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Head-Locked Audio

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A great deal of content, such as music, is mixed in stereo. Since VR is using stereo headphones, it’s tempting to play stereo sounds without spatialization. The drawback is these stereo sounds will not be positioned in the virtual world and will not respond to head tracking. This makes the sounds appear “head locked”, as they follow the users head movements rather than feeling grounded in the virtual world. This can detract from the spatial audio experience and should generally be avoided when possible.  For original compositions it’s best to mix to ambisonics which can be rotated and won’t be head-locked. If that is not an option then try to be mindful of how the music impacts the spatial audio.

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HRTF Spatialization

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For more traditional mediums, sound is positioned on the horizontal plane with 3D panning. So sound designers working on non-VR don’t need to concern themselves with the height of sounds, and can simply place sound emitters on the root node of the object. HRTF (Head Related Transfer Function) spatialization provides much more accurate spatial cues, including height, and with this improved accuracy, it is especially noticeable if sound is emanating from the wrong part of a character. It is important to position the sound emitter at the correct location on a character (e.g. footsteps from the feet, voices from the mouth) to avoid weird phenomena like “crotch steps” or “foot voices”.

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Doppler Effect

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The Doppler effect is the apparent change of a sound’s pitch as the source approaches or recedes. VR experiences can emulate this by altering the playback based on the relative speed of a sound source and the listener, however, it is very easy to introduce artifacts inadvertently in the process.

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Virtual Reality has come a long way and is a metaphysical transportation to an altered state. Born of technology, virtual reality at its core is an organic experience.