- Michael Fay
Going Way Beyond
Complex automixing using a virtual digital mixing console
I was so tempted to give this piece a geeky marketing title or sub-header suggesting VR (virtual reality), AR (augmented reality), or AI (artificial intelligence). But the truth is, none of those modern terms are relevant. What’s relevant is: with a quality DSP engine, and some good old-fashioned RPI (real person intelligence), we can create a complex microphone mixer that pushes way beyond the traditional boundaries of automixing.
Per Wikipedia: “An automixer, or automatic microphone mixer, is a live sound mixing device that automatically reduces the strength of a microphone's audio signal when it is not being used. Automixers reduce extraneous noise picked up when several microphones operate simultaneously. Automixers are frequently employed in settings where it is expected that a live sound operator won't be present, such as courtrooms and city council chambers.”
Wikipedia’s definition is limited in scope. It describes the earliest form of automixing algorithms called NOM - an acronym for number of open mics. A NOM automixer simply applies a noise gate to each input channel. Inputs that don’t receive a strong enough signal to cross a preset threshold - and open the gate - stay closed, or off.
A more elegant solution is the gain-sharing, automix topology.
Per QSC’s Q-sys “help” page: “The Gain-Sharing Automatic Mic Mixer is primarily used for multiple live microphones operating in the same room together as a system, for example, in boardrooms, classrooms, churches, courtrooms, etc. The Gain-Sharing (GS) Automatic Mic Mixer controls the live microphones by turning up microphones when someone is talking, and turning down microphones that are not used. It is a voice-activated, real-time process without an operator. The Gain-Sharing Automatic Mic Mixer controls the additive effect of multiple microphones being on at the same time and adapts to changing background noise conditions. The gain of each microphone input is calculated as the ratio of its RMS level to the combined RMS levels of all inputs. This ensures unity system gain at all times.”
Traditionally, automixers, be they NOM or GS topologies, are meant for voice reinforcement, excluding musical instruments. This article introduces automixing concepts that provide recall, management, and control of both voice and musical instruments, while documenting the idea of using a DSP engine to custom-build virtual digital mixing consoles, with or without a graphic user interface.
Download the full paper pdf via the link below.