True Voicelift is an algorithm that is designed for clear voice intelligibility across a room which works by amplifying a detected user's voice before the point of feeding back.
There is some user knowledge required in order for this work as intended, which this article aims to help clarify.
First things first: when the distance increases from a speaker, there will be a natural loss of level the further away a person is to the speaker.
Based on the graph below, someone 2m / 7 ft away from a speaker will notice no diminishing volume level, but as this is doubling in distance, you lose +6 dB of volume. This of course increases the further you get; at a distance of 8m / 26 feet, the direct sound level will have dropped to approximately 46 dB. This is where True Voicelift can come into play.
Zone Control
Zone Control allows for an even distribution of sound by splitting loudspeakers and TCC2's (or TCCMs) into different zones within the room. These zones can be defined within Control Cockpit on the Zones tab by carving out Exclusion Zones and also a Priority Zone, if desired.
An excluded area is displayed by a dark coloration and instructs the TCC2's beam not to go into this defined area.
Standard coverage is denoted and blue, and green is a designated priority zone. A Priority Zone may be established if there is a designated presenter or presentation area, for example.
Zones should be configured and tested prior to enabling True Voicelift.
True Voicelift Settings
The True Voicelift settings are as follows:
Mute Threshold - this triggers an automatic mute if the microphone level exceeds the Mute Threshold value. This parameter ranges from -50 dB to + 3dB
Mute Interval Time - how long the microphone is muted after the mute threshold has been exceeded.
There is also a Noisegate, which can be enabled to remove any low-level sources of noise during periods of silence.
Calculating the need for True Voicelift
Based on PAG / NAG (Potential Acoustic Gain - Needed Acoustic Gain), there is a formula and some measurements to help determine if True Voicelift may benefit a given situation.
The formula is: PAG = 20*log((D0 * D1)/(D2 * DS)) − 10*log(NOM) − FSM
Important Considerations
Ambient noise level - a background noise level exceeding 45 dBA or so should be addressed. Otherwise, noise will be pervasive in the in-room audio, or be overprocessed trying to remove its effects and in turn degrading the overall quality.
Acoustic conditions - room furnishings and construction such as glass panes can affect in room acoustics. This may introduce unwanted reverb or echoes, which can affect how True Voicelift behaves.
Management of speakers in the space / "zoned speakers" - reinforced audio for the back of the room so as to not strain to hear a presenter in the front of the room.
What this might look like:
Certain microphones are processed and sent to different portions/zones of the room.
The red mic in the Rear Zone is sent to green and blue loudspeaker zones (Front and Middle);
Green mic in the Middle Zone is sent to red and blue loudspeaker zones (Front and Rear);
Blue mic in the Front Zone is sent to red and green loudspeaker zones (Middle and Rear).