Headset Noise Cancelling Technology Explained

Noise Is All Around Us

Headsets are used in the most demanding of environments where clear audio is critical, such as in contact centres, emergency dispatch, and command and control applications, just to name a few.

When considering noise cancelling headsets it is important to understand that distinctly different technology is used to reduce noise for the headset wearer acting on the receive side (typically this is active noise cancelling) compared to noise cancelling for the far end, which acts on the microphone (transmitting) side.

How Headset Noise Cancelling Technology Works

Receive Noise Reduction

Passive Noise Reduction

The simplest form of receive noise reduction comes from the fact that any stereo headset provides a physical barrier to the ear canals and hence reduces the level of audio that can be heard.

The amount of noise reduction will depend on may factors. For example, a headset such as the Voyager Surround 80 UC, with six microphones for clear transmit audio, covers the ear completely in an adaptive over-the-ear design, providing better noise reduction compared to one that sits on the ear.

Slanted audio drivers and improved ear cushion material offer long-lasting comfort and a greater acoustic seal to the ear, hence advanced noise reduction compared to foam ear cushions.
Headsets with earbuds that sit inside the ear provide a greater isolation from external sounds.

An advantage of the Voyager Free 60+ UC is that the conical-shaped earbud tips are engineered to minimise pressure in the ear while also providing ideal audio isolation.

Active Noise Reduction

For greater noise reduction, passive noise isolation can be combined with active noise cancellation. Poly offers one of the largest ranges of Active Noise Cancelling headsets in the market.

There are three types of ANC:

• Feedback ANC: With Feedback ANC, microphones are placed inside the ear cup and monitor what the user hears.
• Feed-forward ANC: Feed-forward ANC is rarely used on its own in headsets as the ANC microphones are placed outside the ear cup and monitor the background noise, making it sensitive to wind noise.
• Hybrid ANC: ANC microphones are placed both inside and outside the ear cup (requires two times more microphones compared to feedback ANC) and monitors both what the user hears and the background noise.

Transmit Noise Reduction

Noise Cancelling Microphone

To ensure that background noise is not picked up by the headset microphone, which can interrupt the call, many Poly headsets include noise cancelling microphone booms.

These booms include a special directional microphone that picks up sound in a pattern that is focussed toward the user’s mouth.

Sounds that come from all directions, such as background noise, are picked up with less amplitude and therefore are heard by the far end at a reduced level.

To provide the best noise reduction, the optimum position for a noise cancelling microphone boom is directly in front of the user’s mouth.

Since this can be distracting to the user, as it’s in their eyeline, a compromise is made so that the microphone boom is typically located at the corner of the mouth.

The microphone booms can be bent so that the microphone is in the correct position. For the EncorePro 700 Series, an extendable microphone boom is used to provide the best placement.

Close Conversation Limiting

Using proprietary digital signal processing (DSP), Poly can further reduce any transmit noise. The Savi 8400 Series uses a noise cancelling microphone boom plus a feature called close conversation limiting, which is designed to reduce the level of nearby conversations. The actual level of noise reduction can be configured via Poly software.

Discrete Microphone Boom

The Voyager 5200 UC, designed as an on-the-go product, includes a discrete microphone boom that is great for indoor or outdoor use. Windsmart technology and a unique DSP is used to reduce disruptive wind noise for outdoor use.

Boomless Design Noise Cancelling

For products without a microphone boom, four microphones are used along with beam-forming technology to focus on the user’s voice while minimising background noise.

Acoustic Fence Technology

Transmit noise reduction can be enhanced when additional, physically separated microphones are added, such as those on headsets with Acoustic Fence technology.

Single Additional Microphone

Acoustic Fence technology uses a long noise cancelling microphone boom with an additional microphone located on the ear cup. This additional microphone picks up the background noise, and this noise is minimised from the user’s voice using DSP.

Multiple Additional Microphones

The Voyager Focus 2 provides even greater transmit noise reduction despite its shorter microphone boom. In this implementation Acoustic Fence technology uses four microphones in total, two microphones on the boom and one on each ear cup, to create a virtual pick-up bubble focused at the front of the user’s mouth. Anything outside of this bubble (noise) is ignored.

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