How to reduce ambient noise in conference and meeting rooms

Biamp's integrated Tesira audio and video processing and distribution platform, brand marketed in Spain by AVIT Vision, features a noise reduction function, whose application is described below.

Noise reduction is critical in most conference audio systems. Unless the room is exceptionally quiet, some of the natural background noise from this space will be picked up by the microphones and transmitted to the other end of the conference., which will increase distractions and reduce speech intelligibility.

Below is an overview of the noise reduction feature in the integrated Tesira audio and video processing and distribution platform Biamp, brand that markets in Spain AVIT Vision.

Available on all Acoustic Echo Cancellation tickets (Aec), Tesira provides great help for remote conferencing applications.

Noise reduction (NR) de tesira is a subset of the aec input block that is implemented using the dsp processing hardware of the aec input, where it is available on each input channel, even when the AEC is disabled.

This reduction is more effective in the management of cyclic and repetitive mechanical noises., such as projector fans or refrigerator motor noises, and it is not in random noises, like the air blowing through a microphone screen, closing doors, the crunch of papers, the sirens, barking dogs or the like.

When people are talking, the noise suppressed will be more audible, as NR filters relax to reduce the impact on conversation.

Profit structure

It is important to configure microphones with a proper input gain structure, which avoids creating an artificially high noise floor (it's about ambient background noise in a room, which is random and fully variable).

The interaction between the noise reduction process and the noise floor can result in audible artifacts, such as the dripping of water or whispering sounds, as the NR attempts to pursue random sounds with varying success.

Another element that should be taken into account are the settings. It is necessary to listen to the output of the microphones to adjust them correctly, what is often achieved by calling a conference room from a remote location.

Before applying the NR it is advisable to listen to the output of the microphones and increase the High Pass Filter until most of the 'rumble' of the low frequencies is removed. (this setting is located in the aec block > Ch Processing > Advanced Filters).

The default value is 70Hz, but most rooms benefit from a switch between 125Hz and 195Hz. Rarely does a room need to reach up to 250Hz, as it can adversely affect the tone of the interlocutors in the room.

there are four user-defined levels of nr: Deactivated, Low, Medium and High. The latter can reduce noise up to a few 12 Db; the average level does it up to a few 18 dB and the high achieves it up to a few 24 Db. Results vary depending on the unique properties of the noises to be reduced.

That is why it is convenient to listen with the NR function disabled, then move the setting to Low level and listen. As needed, the Medium and High level is used, choosing the best solution for each microphone in the room. Localized sound sources may motivate different levels of NR to be used for each microphone.

For example, if a mechanical noise is 10dB above the background noise on the micro No. 1, and 20dB above background noise on micro No. 2, then the low NR settings (about 12dB) for the first micro and medium (about 18dB) for the second, may be appropriate.

These settings use the NR to eliminate mechanical noise and prevent excessive interaction with background noise.. If you try to use NR to reduce ambient background noise, which is random, artifacts are produced, as there is no pattern present for the NR algorithm to predict and suppress.

Whether there are audible artifacts in the microphone output (often perceived as dripping water or whispering) there are two ways to try to resolve this issue.

The first is to lower the Noise Reduction that is applied in one step and listen to the output. Is it clear?? If not, it must be reduced again.. Whether the results are acceptable, no problem and, otherwise, you have to try it with the second way.

In this last one you have to reduce the input gain of the microphone to reduce the background noise. Listen again with NR function disabled, then move to the Low function and listen, and repeat if necessary with Medium and High level.

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