Noise-cancelling headsets: How exactly do they work?

You know that sound you hear when you walk onto a busy trade show floor? That loud, intense human buzzing? When you enter a busy contact center, you can hear the same thing. The difference is that when someone calls into that contact center, they don’t want to hear a trade show in the background. Enter noise-cancelling headsets.

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Let’s look at how this tech actually works, especially when it comes to noise-cancelling microphones.

“As employees become more mobile and businesses increasingly turn to UC solutions, the use cases for headsets utilizing noise-cancellation technologies are growing,” says Dennis Majikas, a service engineer with Jabra, “Whether that is a sales guy walking through a crowded airport, or a HIPAA regulated contact center making sure the customer never hears the agent in the next cubicle repeating credit card information, noise-cancelling tech is quickly becoming critical for businesses looking to deliver a professional call experience.”

Noise-cancelling microphones come in many flavors

Noise-cancelling headsets incorporate a lot of technology that can be scaled up to meet the needs of any knowledge worker.

Level 1 – Noise Cancellation: This is when the microphone is not equally sensitive to sounds from all directions. This type of headset is ideal for noisy open offices. It will filter out most background noise, as long as the microphone is relatively close to the mouth.

Here’s how it works: Background noise is relatively far away from the microphone. As a result, this noise puts the same pressure on both sides of the microphone’s diaphragm. Because the pressure is the same on each side, the diaphragm will not vibrate, so no sound is transmitted.

On the other hand, sound pressure from someone speaking into the mic is much higher on one specific side of the diaphragm. As a result, the diaphragm will vibrate and clearly transmit the speaker’s voice.

Level 2 – Ultra Noise Cancellation: This is when the microphone is designed to only pick up sound from your mouth and eliminate virtually all background noise. Such headsets are ideal for very noisy environments, like busy contact centers.

In this setup, the microphone’s components are placed away from the entrance to the diaphragm, making the openings on both sides of the diaphragm symmetrical. This essentially eliminates any noise from 270 degrees in front of and around the user. Only the speaker’s voice gets through. Great stuff for those contact centers that sound like a trade show.

Note: It’s usually necessary to place the mouth about two fingers away from the mic. Otherwise, your voice will get filtered out as well!

Level 3 – Noise Blackout: This is what you need if you are outside or on the road and are subject to wind, trucks rumbling by, jackhammers, and so on. This can be equally important for a utility worker up in a lift or a sales VP that spends 80 percent of his time out of the office.

“These devices have shorter – and in many cases much shorter – boom arms and take advantage of information picked up by two microphones,” explains Majikas. “By adding information from the second mic, it is possible to distinguish sounds from different directions, improve the clarity of transmitted speech, and eliminate the pickup of disturbing noise sources like wind or that super-loud colleague sitting right next to you.”

What you should know when rolling out noise-cancelling headsets

There are a few things you should know if you’re rolling out noise-cancelling headsets to your team.

First, microphone positioning. “If you have a good noise-cancelling headset, your mic needs to be right next to your mouth,” explained Majikas. “I can’t tell you how often I’ve seen team members with their mic boom flying way out to the side, and they wonder why people can’t hear them, not to mention that the noise suppression isn’t working effectively.”

Another thing to watch out for are the “transmit” levels. This dictates how loud your mic broadcasts your voice. Most of the time, the default should work fine, but the levels can be adjusted in many different ways – through your operating system, a softphone, a UC client, or the headset itself. “80 percent of the time we have an issue reported, it is because someone has set their transmit levels too high,” says Majikas, “This not only results in a hypersensitive mic picking up conversations three cubicles away, but ironically in the user not being heard well by the customer. The simple answer is to turn the transmit levels down.”

One of the reasons people can’t hear a you when your transmit levels are high is because of automatic gain control (AGC). AGC uses sampling to keep the conversation volume consistent. This becomes a problem when multiple devices with AGC are involved, like when a headset with AGC is plugged into a phone with AGC. According to Majikas, “Then one automatic gain controller will automatically lower the transmit level, while the other increases it. You don’t want to get in an AGC war. Sometimes, you have to lower the transmit levels to make everyone happy.”

As if that wasn’t enough, UC clients like Microsoft Skype for Business or Cisco, have their own approach to the transmit levels on calls going over their platform. That’s why it’s important to have headsets that are certified to work with specific UC platforms to avoid AGC conflicts. The last thing you need is to add another AGC to the struggle.