Overview; Noise Adaptive Threshold - Sound Devices 688 User Manual

MixAssist
™
The 688's powerful digital processing
engine delivers 12-channel auto-mixing
capability using the most sophisticated
algorithm on the market.
MixAssist automatically attenuates the
level of inputs that are not open and
helps maintain consistent background
sound levels regardless of the number
of open microphones. This automatic
attenuating function is commonly
referred to as "auto-mix".
MixAssist intelligently attenuates
redundant mics picking up the same
sound source which significantly helps
to reduce comb filtering and phasing
artifacts.

Overview

The MixAssist feature auto-mixes post-fade input signals to the L and R buses.
Other signals are not affected by MixAssist.
Inputs that are auto-mixed will be open (unattenuated) when a person talks
into the input's microphone and closed (attenuated) when the person stops
talking. Microphone channels open with ultra-sensitive responsiveness to voice
levels to ensure that no syllables are lost, and then will "gate off" smoothly over
500mS. This gating action is smooth and imperceptible when switching between
microphones. MixAssist is more sophisticated than a simple gate, and uses four
different principles to automix input signals.
MixAssist will allow several microphones to be open simultaneously if there are
several talkers, and MixAssist does not limit the number of open microphones.

Noise Adaptive Threshold

When an input's post-fade level surpasses the MixAssist threshold, it will be
opened. Unlike a simple limiter or gate, this threshold is dynamic: MixAssist
continuously analyzes all inputs assigned to it to determine an average noise
floor level and uses that level as the threshold. This prevents common back-
ground noise (fans, crowd murmur, etc) from causing the input to open, while
allowing normal sounds to open the mic.
Topics in this section include:
Overview
Noise Adaptive Threshold
One Mic Per Sound Source
Number of Open Microphone Attenuation
Last Mic Lock-On
MixAssist Setup Screen
Turning MixAssist On or Off
Assigning Inputs to MixAssist
LCD Views During MixAssist
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