Sound in gaming: latency, spatial audio and the mic

Latency: the delay between picture and sound

Between the instant the game produces a sound and the moment it reaches your ears, there is always a delay. Over a cable, it is a few milliseconds, which is to say none. Over wireless, the sound has to be digitised, compressed, transmitted by radio, buffered to absorb packet loss, then decompressed: each step adds delay.

Recommendation ITU-R BT.1359, the reference in broadcasting, puts the detection threshold for sound lagging behind the picture at around 125 ms. In games, where you react to what you hear, the trouble starts sooner: beyond about 100 ms, gunfire feels sluggish and footsteps are located too late.

Classic Bluetooth, with the SBC or AAC codecs, sits between 150 and 250 ms. Video players compensate for this delay by shifting the picture, which is impossible in an interactive game. Low-latency codecs (aptX Adaptive, the LC3 of Bluetooth LE Audio) come down to around 50 to 90 ms, provided the transmitter and the headset both support them. The details are in the guide to Bluetooth codecs and latency.

That is why wireless gaming headsets come with a 2.4 GHz dongle: a proprietary radio link, optimised for delay rather than for saving energy, which holds at around 20 to 30 ms.

3D audio: how two speakers place a sound in space

We have only two ears, and yet we can tell whether a noise is in front of us, behind us or above us. The brain uses three cues: the difference in arrival time between the two ears, the difference in intensity, and the way the outer ear and the head filter sound according to its direction. Together, these filters have a name: the head-related transfer function, or HRTF.

3D audio in games consists of applying these filters by computation. The game engine knows the position of every source; it applies the corresponding HRTF and produces a simple stereo signal that already contains all the spatial information. This is what Tempest 3D on PlayStation 5, Windows Sonic, Dolby Atmos for Headphones and DTS Headphone:X do.

Two practical consequences follow:

• Any good stereo headphones can reproduce 3D audio. The processing is done upstream, by the console or the PC.
• The “7.1” printed on the box is a sales pitch. It refers either to software processing equivalent to the console's or, more rarely, to several small speakers per ear, a solution since abandoned because it is less precise than a single good driver.

What really improves localisation is the quality of the headphones themselves: a balanced response, with no excess bass to mask the detail, and a wide soundstage. That is the advantage of open-back headphones, much loved by competitive players when they play in a quiet room.

The mic: distance makes the quality

The quality of a voice pickup depends first on the ratio between the voice and the ambient noise, and therefore on the distance between mouth and mic. A boom mic sits two or three centimetres from your lips; a mic built into the earcup is more than ten centimetres away, and picks up the keyboard and the room as much as your voice.

Two features deserve attention. Sidetone feeds your own voice back into the headset: without it, you tend to shout when wearing closed-back headphones. And a physical mute, triggered by flipping up the boom, avoids open-mic mishaps.

Over classic Bluetooth, switching on the mic drops the link into a “hands-free” mode of telephone quality: the game audio becomes muffled and mono. That is one more reason to prefer the dongle or the cable.

Compatibility: every platform has its own rules

The Xbox is the special case: its wireless protocol is proprietary, and a dongle headset designed for PC and PlayStation will not work with it, unless there is a specific version.

What to remember when choosing

• Competitive gaming: wired or 2.4 GHz, a balanced signature, a boom mic.
• Single-player and immersion: comfort and sound quality come first; good hi-fi headphones do the job perfectly.
• Long sessions: under 330 g, fabric ear pads, a suspension headband.
• Several platforms: check Xbox compatibility, and favour a 2.4 GHz model that also has a jack.

Benchmark models and a selector already set up for gaming can be found in the gaming headset buying guide.

Sources and references

1. Bluetooth SIG — LE Audio
2. ITU-R BT.1359 — Relative timing of sound and vision for broadcasting