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Noise Cancelling Headsets: How The Microphones Work and What You Need to Know

Posted by Kevin Gulley

Nov 11, 2014

You know that sound you hear when you walk onto a busy tradeshow 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 tradeshow in the background.  Enter noise cancelling headsets.  noise_cancelling_headset_microphone_small

To learn more about how this tech works - specifically on the microphone end of things - and what businesses need to know about it, I spoke with Dennis Majikas, a Service Engineer with highend headset maker Jabra.  “As employees become more mobile and businesses increasingly turn to UC solutions, the use cases for headsets utilizing noise cancellation technologies are growing,” said Majikas. “Whether that is sales guy walking through the 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 significant amount of technology that can be scaled up to meet the use cases for various types of knowledge workers.  

Level 1 - Noise Cancelling:  This technology ensures that the microphone is not equally sensitive to sounds from all directions.  This type of headset is ideal for noisy, open offices and will filter out most background noise as long as the microphone is relatively close to the user’s mouth.  

In essence, the way they work is that background noise is relatively far away from the microphone and as a result generates the same pressure on both sides of the diaphragm.  When the pressure from both sides is the same, the diaphragm will not vibrate and no sound is transmitted.  On the other hand, when the user speaks the sound pressure from the user’s speech will be much higher on one side and the diaphragm will vibrate and clearly transmit the user’s voice.

Level 2 - Ultra Noise Cancelling:   This tech is designed to really only pick up noise from your mouth and eliminate virtually all background noise.  Note: Placement of the mic 2 fingers from your mouth is essential, or noise cancelling could become voice cancelling!  These headsets are ideal for very noisy environments, like busy contact centers. Noise_Cancelling_Microphone

In this situation, the microphone components have been moved away from the entrance to the diaphragm making the openings on both sides of the diaphragm symmetrical. This means that only the sound from the speaker’s voice is picked up and the noise from the 270 degrees in front and around the user is essentially eliminated.  Great stuff for those contact centers that sound like a tradeshow.  I’ve included a diagram of this one to provide more details on how it works.

Related:  Voice Communication Use Cases:  What Kind of Phone Worker Are You?

Level 3 -  Noise Blackout:  This is what you need if you are outside or on the road often and are subject to the wind, trucks rumbling by, jackhammers, etc..  This can be equally important  for a utility worker up in a lift, or a sales VP that spends 80% 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,” explained 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.”

I suggested they should bring tech to bear to eliminate the dog barking in the back of every conference call I’m on these days (usually mine).  He told me he’ll check what’s in the works.

Considerations When Implementing Noise Cancelling Technology

There are a number of things you should know about if you are 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 gotcha to be aware of is adjusting your transmit levels.  These are the levels dictating how loud your mic broadcasts your voice.  Most of the time the default should work fine, but they can be adjusted in many different ways (via a computer’s operating system, through a softphone, via a UC client or with the device).  “80% 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 3 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 speaker when their transmit level is very high is because of Automatic Gain Control, or AGC.  This technology uses sampling to ensure that the volume during a phone conversation stays consistent.  The challenge shows up when there are multiple devices involved that each have AGC capability, for example 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 a AGC war.  Sometimes you have to lower the transmit levels to make everyone happy.

”To add another layer to the stack, UC clients , like Microsoft Lync or Cisco, have their own perspective on the transmit levels associated with calls going over their platform. That is why it is important to have headsets that are certified to work with specific UC platforms and work together to eliminate the AGC conflicts.  The last thing you need is to add another AGC to the struggle.






Topics: Technology, Voice, Contact Center