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Nura, an Australian technology startup, has promoted Nura headphones on Kickstarter as a music-listening device that “automatically measures your hearing” and adjusts “to your unique hearing profile” – all in about 30 seconds.    Earlier today, Nura’s crowdfunding campaign was named the “best funded Australian Kickstarter campaign ever” by Business Insider Australia. Nura’s Kickstarter page currently shows over 4000 backers and over 900 thousand dollars in pledges. UPDATE July 14 2016: Nura has approaching $2M in pledges now.

Nura Headphones Kickstarter

As anyone with hearing loss will tell you, measuring hearing is a fairly painstaking process that requires listening to very soft beeps across many pitches, repeated across both ears. A typical hearing test can take anywhere from 5 minutes (for a very basic screening) to over half an hour (for a test that diagnoses the type and severity of loss, as well as underlying factors, such as ear infection). While Nura isn’t claiming their headphones diagnose hearing loss, they are throwing around words like “measure” and “assess” rather loosely.

The first time you put them on your head, they’ll measure your hearing – a process that takes about 30 seconds.

Kyle approached Luke to explore whether it would be possible to squeeze a hearing measurement machine into a pair of headphones and make a closed-loop music experience.

Sound and hearing are very hard to objectively self-assess […] Nura empowers everyone who loves music to find their perfect sound – automatically.

Check out their promotional video, which provides an overview of how the technology works.

Researchers have been looking for a convenient way to “automatically” measure hearing for a really, really long time. While there are fairly robust tests to measure hearing automatically (without a patient responding), such tests require expert training, special equipment, and an adequate testing environment to administer. You can have your hearing tested automatically, but expect the appointment to take anywhere from 60-120 minutes (source: Johns Hopkins).

So, how has Nura achieved the unachievable? How are they automatically measuring hearing in 30 seconds with an affordable consumer device – at home – and without a trained expert? Nura claims the following on their Kickstarter page:

Nura uses a microphone to know exactly what sound went in, and also uses the same microphone to listen to the faint sounds that return from the ear. This makes Nura very different from any other type of calibration. It actually knows the response of the inner ear. The inner ear detection is performed using an adaption of OAE (otoacoustic emission).

The sound that is produced by our ears and detected by our headphones’ internal microphone is encoded with information about how well you actually heard the sound that went in.

Nura headphones connect to your smartphone. You press go, and they sweep through a bunch of tones for about 30 seconds. At the same time, they listen to the sounds your ear is making. By processing these signals it works out how well specific frequencies of sound got through to your brain. Once they know this, they sonically mould to match your ears perfectly and provide rich, balanced sound for you.

We reached out to Nura’s “residing hearing scientist” and Chief Technology Officer, Luke Campbell, MD, PhD, with the following request:

A group of audiologists, including myself, have been discussing the feasibility of fine tuning audio based on the results of OAE measurements. We are primarily concerned with the accuracy of assessing hearing sensitivity with OAEs as OAEs generally only provide a rough approximation of hearing thresholds.

Luke responded to our email with the following very important points. Any consumer considering purchasing the Nura headphones should ensure they read these:

  • Nura is designed/optimized for normal or near normal hearing users.
  • Nura is not a substitute for an audiogram in people who need a hearing aid or ENT attention.
  • Nura is not attempting to act as a hearing aid, and the maximum gains (or attenuations) applied are more subtle.
  • Personalized headphone tuning using objective information of hearing provides a more complete sound that the majority of users prefer compared to headphones tuned as on one-size-fits-all.

He also responded specifically to our question about OAE measurements. What follows is an excerpt from Luke’s email, without any edits:

There are OAE measurement paradigms published (particularly coming out the University of Tubingen) achieving impressive relationships to hearing thresholds, especially at higher frequencies, and especially in subjects with normal or near norm hearing. However they simply take too long (~10min) to provide a reasonable user experience.

The main insight that allows nura to work is that with consumer audio headphone you do not need to know absolute thresholds, only the relative sensitivity at different frequencies. Furthermore, it is suprathreshold differences rather than threshold differences that are important, when listening to music (which is not listened to at threshold). We are not going to disclose exactly what we are doing with our OAEs but normal clinical paradigms aren’t quite good enough as their accuracy (depending on the exact device) is confounded by issues with fine structure and standing waves.

What is the best way to use the data-

Most flavours of OAEs can detect the normal decrease in high frequency sensitivity with age or loss of isolated frequencies. In our experience people overwhelmingly prefer when we apply our retuning to their music to account for this. Have you ever thought about why young people love bass heavy headphones and older users generally prefer headphones with more treble focus?

When we first started we were curious what the effect of using OAE data from normal hearing listeners would be. And we have spend enormous time and effort working out the best retuning to apply in this population (the details of which we wont share that this stage). Even we were surprised at how clearly “normal” hearing users prefer the sound we customize for them. The principle here is that the normal range of hearing is wide and even modest changes in EQ at a few frequencies completely changes the colour of the sound/music. Try it for yourself, turn a few frequencies up and down by 5 dB on an multiband EQ.

What about people with more more severe hearing loss? –

As you know OAEs become difficult to measure beyond mild hearing losses and for users with a significant conductive component. We have tried nura with a few hearing aid users and most like it, but most of the benefit or the OAE based retuning is mostly lost and results would vary. We certainly do not assert that nura will work well in these situations. If a hearing impaired user doesnt like the attempted OAE based retuning, they can simply disable it in the app and nura will revert to a default (one-size-fits-all) mode, such as that used by all other headphones on the market.

It seems the main goal of Nura headphones is to offer a custom-tailored listening experience for consumers with normal hearing sensitivity. Nura claims that their headphones automatically measure your hearing, but as we can see, there are limitations to this technology if your hearing is beyond the range of normal (worse than 20dB HL).

While Nura’s automatic hearing measurement technology isn’t quite the game-changer we had hoped, the technology is fascinating, and promises to bring an improved listening experience to thousands of normal-hearing consumers. I’m eager to test the technology out on myself, and hopeful that the listening experience is superior to experience I have after adjusting the bass and treble manually myself.

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