How to reduce ambient noise in conference and meeting rooms

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

Noise reduction is essential in most conference audio systems. Unless the room is exceptionally quiet, Some of the natural background noise in 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 functionality in Tesira's integrated audio and video processing and distribution platform. Biamp, brand that sells in Spain AVIT Vision.

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

noise reduction (NR) 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 AEC is disabled.

This reduction is more effective in managing cyclical and repetitive mechanical noise., such as projector fans or refrigerator motor noises, and it is not in random noises, like air blowing through the screen of a microphone, the closing of doors, the rustling of papers, the mermaids, dog barking or similar.

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

Earning structure

It is important to configure microphones with a proper input gain structure, which avoids creating an artificially high noise floor (This is the ambient background noise in a room, which is random and totally variable).

The interaction between the noise reduction process and the noise floor can result in audible artifacts, like dripping water or rustling sounds, since the NR attempts to chase random sounds with varying success.

Another element worth taking into account is the settings. It is necessary to listen to the output of the microphones to adjust them correctly, which is often accomplished by calling a conference room from a remote location.

Before applying NR it is advisable to listen to the output of the microphones and increase the High Pass Filter until most of the low frequency 'noise' is eliminated (This setting is found in the AEC block > Ch Processing > Advanced Filters).

The default value is 70Hz, but most rooms benefit from a switch between 125Hz and 195Hz. On rare occasions a room needs to go up to 250Hz, as it can negatively affect the tone of the interlocutors in the room.

There are four user-defined NR levels: Disabled, Low, Medium and High. The latter can reduce noise up to about 12 dB; the average level does it up to about 18 dB and the height reaches up to about 24 dB. Results vary depending on the unique properties of the noises you want to reduce..

Therefore it is convenient to listen with the NR function deactivated, then move the setting to Low level and listen. As necessary, the Medium and High level is used, choosing the best solution for each microphone in the room. Localized sound sources may cause different NR levels to be used for each microphone.

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

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

If there are audible artifacts at the microphone output (often perceived as dripping water or whispering) There are two ways to try to solve this problem.

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

In this last thing you have to reduce the input gain of the microphone to reduce background noise. You have to listen again with the NR function deactivated, then switch to the Low function and listen, and repeat if necessary with Medium and High level.