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Demystifying noise cancelling headphones

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Published byTom Darnell

They’ve brought peace to long haul flights and calm to the daily commute but how does noise cancellation actually work, and with more people now wearing them in the office, are they actually the answer to a calmer, more productive workplace?

It was in 1978, on a return flight from Switzerland to America, that Dr. Amar Bose – who was fed up with not being able to hear the in-flight movie – had a lightbulb moment that led to the design of the first active noise cancelling headphones (ANC).

Other engineers had experimented with the concept previously. Dr Lawrence Jerome Fogel, an American pioneer of electrical and aerospace engineering, patented a system for protecting pilots’ hearing back in the 1950s, but it was Bose, who after testing his own system for pilots, released the first commercially available ANC headphones in 1989.

There are now countless ANC headphones available in all shapes, sizes and budgets, and I wouldn’t dream of travelling long-haul without mine, but just how do they work?

The science behind the silence

Sound travels in waves, which move molecules through the air and into your ear canal where they vibrate your eardrum. If however, a sound wave is met by an identical soundwave of the same frequency, the two will effectively cancel each other out. 

ANC headphones feature a number of microphones that analyse the sound coming towards your ears and instantly play the opposite phase of that sound through the headphone’s drivers (speakers). As a result, you can no longer hear that soundwave and background noise is significantly reduced.

This is obviously a massive simplification of a highly technical process. If you want to deep dive waveforms and kHz IRIS’s Chief Technical Officer, Rob Reng could keep you enthralled for a week, but one of the key things to remember about ANC technology is that it works best at reducing lower sound frequencies. 

Lower frequencies (between 10Hz and 1kHz) produce longer waveforms, which are easier to counteract using ANC technology. This is why they’re so good at quieting the din of persistent engine noise and general background hubbub, but are actually pretty useless at combating the higher frequency sound of screaming kids or that particularly grating voice in the office.

What is passive noise isolation?

If you want your headphones to reduce unwanted sounds across all sound frequencies the best current solution is known as ‘passive’ noise isolation – essentially soundproofing. Creating an effective seal either in or over the ear (depending on the style of headphone you choose) can do a fantastic job at blocking out higher frequency sounds. The combination of materials used, shape and various layers of foam insulation can block out a huge amount of unwanted noise. 

In fact when designing the IRIS Flow Headphones we actually chose to develop a better quality of passive noise isolation rather than use ANC technology. They still offer excellent protection from outside interference, but don’t suffer from any of the issues associated with active noise cancelling, including a reduction in sound quality and the strange pressure sensation some people experience when wearing them.

It’s an odd feeling, not dissimilar to when you want to pop your ears, and is actually caused by your brain perceiving the lack of low-frequency sound as a difference in pressure between your inner and outer ear. It’s a sensation some users find distracting and uncomfortable, which is hardly ideal if you’re using them at work and need to concentrate.

But, the combination of ANC and passive noise isolation can be extraordinary, and if the headphones also boast high quality drivers you’re in for an aural treat, whether you’re watching films or listening to music. They’re also great if you need quiet to work from a local cafe, or in a bustling open plan office, but wearing headphones all day isn’t always the best solution, especially if you’re having to make calls and interact with others. 

There’s no denying the importance in reducing unwanted noise though. This recent study has shown that open-plan office noise heightens negative mood by a whopping 25%. You don’t have to extrapolate too far to see how detrimental to your (or your staff’s) well-being and productivity this could be, and while it’s unreasonable (not to mention impractical) to expect everyone to wear headphones all day, they do offer respite from the noise when you do need to get your head down and concentrate.

The drawbacks to ANC headphones 

Headphones in the office are great, right up until the point I can’t get anybody’s attention. The cocooning effect of silence is addictive and aids concentration, but it kills any spontaneity, and does nothing for banter. Let’s face it, headphones are selfish.

I’m only half joking here, but in truth, even the finest ANC headphones have their limitations, especially in the modern workplace. Headphones can be tiring to wear for long periods, which is problematic if you work in a call centre or now find yourself on video calls all day. Have you ever heard someone in a noisy public space or open plan office take a phone call while wearing headphones? Of course you have, because they’re shouting to be heard. And only the wearer benefits from the reduction in background noise, everyone else has to put up with the cacophony. Finally, high-quality ANC can be expensive – especially if you need them for hundreds of employees.

So is there an alternative to noise cancelling headphones?

But there is another solution that works with or without your headphones, that actually removes all background noise from online meetings leaving just clear natural speech. IRIS Clarity is an advanced AI-based voice isolation app that vastly improves the sound quality of any digital conversation. It’s perfect for video conferencing, radio communications, call centres or anywhere users need to hear, and be heard, clearly.

And what makes it all the more remarkable is the fact Clarity works bi-directionally, which means that you won’t hear unwanted noise coming from other people on the call, and they won’t hear background noise from you.

How does Clarity’s voice isolation work? An excellent question, and definitely another one for Rob Reng to deep-dive, but Clarity’s AI algorithm has essentially been taught to differentiate between background sounds and human voice. And the results are remarkable.

Obviously Clarity doesn’t replace the need for Active Noise Cancelling headphones, particularly in a shared office space, but it does give the wearer the ability to focus on the content that really matters. Imagine actually being able to hear the manager who always dials into group calls from the back of a cab. No more, ‘sorry, say that again?,’ means more enjoyable, and productive meetings, improved customer engagement and ultimately greater profitability.