Behind the Buds, Volume 2: Clearing up Calls


Back in 2011, when we were the new, handsome and dashing kids on the block, the main function of a headphone was to "make sound" (preferably "sound good"). Fast forward to 2020 and the spec has increased wildly. Now it’s: "sound good, make calls, last all-day and contain tiny omnipotent Siri/Google-genie" - and that’s just the basic model. Technology has changed, life has changed, headphones have changed.

In Volume 1 of Behind the Buds, we discussed the challenges in designing true wireless earbuds for all of life's needs. In this volume we are focusing on call quality, specifically: eliminating background noise from phone/video calls. So how do we remove: "CAN YOU HEAR ME? I CAN HEAR YOU CAN YOU HEAR ME? THERE’S A BIT OF NOISE. CAN YOU MAYBE GO TO THE WINDOW?" from your life?

Block out the world

The first thing we can do is design something that blocks out as much noise as possible; physically cutting off the outside world from what you’re listening to. Both passive and active noise cancellation earbuds do this in a variety of ways – enjoy a non-disgusting tour around the inner ear here.

But this doesn’t solve the problem for other people who can hear your audio – namely your parents/partners/offspring/internet connectivity engineer on the other end of the phone-line. If you’ve got a good noise-isolating fit, often the person you’re talking to will know better than you what the traffic’s like outside your house or what TV show your colleagues are discussing or what your flatmates are arguing about – because your call microphone is telling them everything.

With wired headphones, there were a few things you could do to cut down on noise. For example our microphones are located more or less exactly in line with the mouth of an average human head (or your head, which we’re sure is a lot more beautiful than average), and are oriented towards the mouth, cutting wind noise right down.

Mix out the world

However, with the rise of Bluetooth headphones, there are more advanced methods. Even the most basic true wireless earbuds are a feat of design and engineering; all components that you’d find in any wireless headphone, including over-ear cans, are combined and positioned inside a housing about half the size of pack of chewing gum (or a thimble, or whatever else your standard unit of "this is really small" measurement is). They’re positioned in a way where the complex electronic processes: Bluetooth receiver, decoder, audio driver, microphones, flux capacitor, encoder, transmitter to the other earbud, quantum strangler (most of those were real) don’t interfere with the signal from your phone. If you showed it to someone in the year 1960 – hell, if you showed it to someone in 2010 – you might be burned as a witch (or a spy).

To cut down on background noise in calls, we added noise cancelling microphones to that bundle. Basically these are mics that face out into the wider world; towards your cats, kids, cars or Karen from accounting. They record and remove those sounds from your calls. You can (optionally) think of it as a simple sum:

(Your voice + outside noise) – outside noise = Your voice

It’s very similar to the tech you see in ANC headphones – and it’s for the benefit of the person on the other end of the phone line; so you can consider it a good deed for the day.

So there you have it, the RHA guide to making headphones capable of crystal clear calls!

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