Footsteps in CS2: what stereo audio can tell you, and what it cannot

What the Ears Can Resolve

The human brain localizes sound sources using two main cues: interaural time difference (ITD) and interaural level difference (ILD). For sounds below 1500 Hz, ITD is the stronger localizing cue. This is simply the difference in arrival time of the sound at each ear. At ±90º, ITD is about 0.7 ms. The interaural level difference is better for sounds above 1000 Hz, where the human head creates an acoustic shadow and causes a greater difference in sound pressure.

These binaural cues are the basis of spatial hearing. One handbook chapter calls them fundamental to nearly all spatial hearing. ITD and ILD are also the cues spatial audio researchers use to model the internal "head-related transfer functions" that create the sense of sound coming from 3D space.

What Valve is Actually Shipping in CS2

Counter-Strike 2 is a first-person shooter video game developed by Valve and available on Steam. The game is published by Valve, as indicated on its Valve store page, and began release on 2023-09-27.

However, the available Valve store snippets for Counter-Strike 2 and its soundtrack extension product do not expose the exact details of the in-game audio settings. Gamer-to-gamer advice on forums and YouTube may discuss features like stereo/pseudo-surround toggles, headphone/elevated speaker modes, EQ presets, or other spatial-sound features, but this documentation is not yet available in Valve's own published counterstrike content.

Why the Stereo Signal Can Work for Footsteps

The human auditory system resolves elevation and front/back cues less well than horizontal localisation. ITD and ILD are weaker for front-back positioning than for left-right perception.

In-game sound design can preserve directional cues as long as they're strong enough to be perceived. ITD and ILD can pick up the difference between left and right footfalls, putting you in an advantageous listening position. Richer surround processing, or more complex HRTF spatialization, could be more informative. However, CS2 is processed as stereo bilateral audio.

It seems reasonable that a spatial sound feature would add more position fidelity. But there's no concrete documentation of what additional processing Valve uses in CS2 and whether it rotates input, adds a third plane, or preserves the HRTF cues of stereo.

The Limits of Stereo

Headphones don't solve front/back confusion or weakness on elevation. Above about 1000 Hz ILD is the stronger cue, but ILD is weaker than ITD for localisation of spatial cues. ITD is more precise than ILD for lower frequencies. ITD is best for lateral, less so for elevation. For stereo signal, left/right ambiguity is the key strength.

So while stereo delivers some directionality, the diagram of ILD and ITD across frequencies points to the limitations. The horizontal plane is the most accessible field for binaural localisation. Stereo spatial information is not enough for perfect 3D positioning.

CS2 Audio Settings the Reader Can Change Tonight

Which is why manual tweaks are critical. CS2 visual audio indicators show exactly where sounds originate, a sort of built-in training cue. But turning up and down sliders, according to players on forums, can increase how much directional information is accessible from the mix.

Unfortunately, Valve's own published materials don't specify which sliders to change. Patch notes and release announcements sometimes cover sound balancing or how sounds are weighted, but specifics on CS2 audio settings are not yet found in Valve's publicly accessible CS2 content.

Looking at forum advice, advice on audio settings includes using headphone-specific presets, raising high-frequency audio to better localise weapons, and manually lowering "lead" balance to get more spatial cues. But this information is not published by Valve, and may or may not endure with updates.

Why This Audio Angle to CS2 Matters

As Counter-Strike retakes the esports crown, player grades may turn on audio fidelity and skill, not just buying better quality headphones. But acting on bad advice is expensive and ineffective. The large, competing audiophile headset market means gaming and audio-enthusiast forums are high on self-promotion, while official game documentation is often thin.

A quality set of headphones gets a leg up through engineering innovation, but the baseline behavioral data is how stereo spatial hearing works. Valve's CS2 sound design builds on that otological foundation. But the developer has not yet published information about CS2 audio settings. That makes the game's chief competitive advantage, under certain play styles, opaque even to players who will be relying on it.

If Valve has an authoritative guide on CS2 audio options, it deserves the last word in its own guide to Counter-Strike's chief advantage.