The Audio Mixer & Basic Filters

OBS Studio

Chapter 3 · The Audio Mixer & Basic Filters

Chapter 2 introduced Audio Input Capture as one Source type among several. This chapter gives audio Sources their own dedicated treatment — the Audio Mixer, and the filters that clean up a microphone's own sound live, during recording or streaming itself.

The Audio Mixer: Per-Source Volume

Every audio-producing Source — a microphone, desktop audio — gets its own independent fader in the Audio Mixer panel, entirely separate from the operating system's own system volume. Each source also has its own mute button, a quick, commonly used action during a live workflow.

Noise Gate

A Noise Gate automatically mutes a source once it drops below a set volume threshold — used on a microphone to silence background hum or keyboard clatter during pauses in speech, without needing to manually mute and unmute constantly. The threshold needs careful tuning: set too aggressively, it cuts off quiet speech; set too leniently, background noise slips through during pauses.

Noise Suppression

Noise Suppression actively reduces steady background noise — fan hum, AC noise — while you're speaking, not just during silence the way Noise Gate does. Two algorithms are commonly offered: Speex (older, lighter) and RNNoise (newer, AI-based, generally higher quality). Noise Suppression is genuinely complementary to Noise Gate, not a replacement for it — Noise Gate handles silence, Noise Suppression handles noise present during actual speech.

Filter Order Matters

Filters applied to a given Source run in the order they're listed — Noise Suppression applied before a Compressor versus after produces genuinely different results, not an arbitrary cosmetic difference. Reordering filters is a legitimate, real way to fix an audio chain that isn't sounding quite right, worth knowing rather than treating filter order as unimportant.

Basic Compressor

OBS's own built-in Compressor filter can even out microphone volume live — a first mention here, since full production-level compression technique belongs to Audio Editing & Production Basics' own dedicated chapter. A dedicated tool used in post-production, like Audacity or Resolve's own Fairlight page, offers considerably deeper control than OBS's own live-focused version.

Filter	What it does	Active when
Noise Gate	Mutes below a volume threshold	During silence/pauses
Noise Suppression	Reduces steady background noise	Continuously, including while speaking
Compressor	Evens out volume differences	Continuously

Two different tools solving a similar-sounding problem

Noise Gate and Noise Suppression here are live, real-time filters applied during actual recording or streaming. Audio Editing & Production Basics' own Noise Reduction effect works differently — it analyzes a sampled noise profile from an already-recorded file and removes it after the fact, in post-production. Two genuinely different tools for two different stages of the same underlying problem.

Maximum Noise Suppression isn't the cleanest setting

It's tempting to assume cranking Noise Suppression to its maximum setting produces the cleanest possible audio. Aggressive settings can introduce audible artifacts — an "underwater" or robotic-sounding voice — by removing too much of the actual voice signal along with the noise, especially with the AI-based RNNoise option pushed to an extreme. Moderate settings tuned carefully by ear usually sound genuinely better than maximum settings pushed as far as they'll go.

Hands-On Exercises

Exercise 1

A streamer's microphone picks up constant fan hum throughout their entire stream, even while they're actively talking. Which filter from this chapter directly addresses this, and why would Noise Gate alone not fully solve it?

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Exercise 2

A streamer sets Noise Suppression to its absolute maximum setting, hoping for the cleanest possible audio, and their voice starts sounding robotic and processed. Using this chapter's own warning box, explain what happened and the fix.

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Exercise 3

A creator asks why they'd bother with OBS's own live Noise Gate/Noise Suppression filters at all, when they already plan to use Audacity's own Noise Reduction effect on the audio afterward anyway. Using this chapter's own material, explain why both are still worth using together.

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Chapter 3 Quick Reference

The Audio Mixer gives every audio Source its own independent volume fader and mute button
Noise Gate mutes below a threshold during silence; Noise Suppression reduces steady noise continuously, even during speech — complementary, not interchangeable
Filter order matters — the same filters in a different order produce a genuinely different result
OBS's own live Compressor is a lighter-weight counterpart to a dedicated post-production tool's own deeper control
Maximum Noise Suppression is not the cleanest setting — aggressive settings introduce audible artifacts