Gaming audio: latency, spatial sound and the mic

Latency: the delay between picture and sound

Between the instant a game produces a sound and the moment it reaches your ears, there is always a delay. Over a wire, it's a few milliseconds, which is to say nothing. Over a wireless link, the audio has to be digitized, compressed, transmitted by radio, buffered to absorb packet loss, then decompressed: every step adds delay.

ITU-R Recommendation BT.1359, a reference in broadcasting, puts the threshold for detecting sound that lags 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 mushy 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 lag by delaying the picture, which is impossible in an interactive game. Low-latency codecs (aptX Adaptive, and the LC3 of Bluetooth LE Audio) get down to around 50 to 90 ms, provided the transmitter and the headphones both support them. The details are in the guide to Bluetooth codecs and latency.

That's why wireless gaming headsets ship with a 2.4 GHz dongle: a proprietary radio link, optimized for delay rather than power savings, that 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 the sound depending on its direction. Together, these filters have a name: the head-related transfer function, or HRTF.

3D audio in games consists of applying those filters by computation. The game engine knows the position of every sound source; it applies the matching HRTF and outputs an ordinary stereo signal that already contains all the spatial information. That's 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 marketing claim. It refers either to software processing equivalent to the console's or, more rarely, to several small speakers per ear, an approach that has been abandoned because it is less precise than one good driver.

What really improves positional accuracy is the quality of the headphones themselves: a balanced response, with no excess bass to mask the details, and a wide soundstage. That is the advantage of open-back headphones, a favorite of 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 of voice to ambient noise, and therefore on the distance between mouth and mic. A boom mic sits two or three centimeters (about an inch) from your lips; a mic built into the ear cup is more than ten centimeters 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, people tend to shout when wearing closed-back headphones. And a physical mute, triggered by flipping up the boom, prevents hot-mic mishaps.

Over classic Bluetooth, turning on the mic switches the link to a "hands-free" mode with phone-call quality: the game audio turns muffled and mono. One more reason to prefer the dongle or the cable.

Compatibility: every platform has its rules

Xbox is the special case: its wireless protocol is proprietary, and a dongle headset designed for PC and PlayStation won't work with it unless there is a dedicated Xbox 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.
• Multiple platforms: check Xbox compatibility, and favor a 2.4 GHz model that also has a 3.5 mm jack.

Benchmark models and a selector preset for gaming are 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