Regular concert goers will be familiar with the problem of trying to record a favourite song on your phone, only to find that the recorded sound quality is terrible, and certainly nothing like how you remember it!
As well as concerts, you can also add weddings, parties and sports events to the list. In fact, video recordings on your mobile phone are easily ruined by heavy distortion on the audio track whenever the ambient noise gets too loud.
Nokia’s engineers found a solution to this with a number of innovations, collectively called High Amplitude Audio Capture (HAAC), which enable you to record audio that sounds as good as when you first heard it.
We caught up with Antti Kangasaho and Teemu Rämö, audio specialists at Nokia, to find out more about HAAC and how it came about.
The problem explained
It was in 2007 that a Nokia team began thinking about how they could create a microphone that could handle high amplitude noises.
Together, Antti and Teemu explained the roots of the problem to me:
Most microphones have a certain dynamic range – one can be sensitive to the quietest sounds while another can tolerate extremely loud noises.
What is difficult to achieve, particularly in a mobile device where the component may only be 3-4 millimetres wide, is having a microphone that can be effective for both the quiet and loud parts of the sound.
The solution found
Following lots of test recordings and demonstrations, the Nokia team filed patent applications for key innovations in early 2009 and began working with suppliers to develop the first prototype HAAC microphones.
Nokia’s team continued to refine the technology before the first HAAC microphone was launched to the world, in the Nokia 808 PureView last summer.
The key innovation behind HAAC is a microphone that has two different sensitivity levels – two paths or channels for recording. The dual channel audio recording is then combined to give you a tremendously broad dynamic range. In other words, it is sensitive enough to pick up the quietest sounds, but still sounds great even during the really loud bits.
A rock concert can easily reach 120 decibels, which poses no trouble at all for Nokia’s HAAC microphone. It can record up to 140 decibels with no audible distortion. By contrast, most other mobile phone microphones struggle to handle anything above 110 decibels.
The eardrum for your mobile phone
Following the development of the dual channel HAAC microphones, the team looked at how to implement it in devices. First models used a single membrane, the part of the microphone that vibrates when sound passes through it – similar to the role the eardrum plays in the human ear.
Another way to implement HAAC is to have two membranes, one more sensitive than the other. Both ways of implementing HAAC microphones enable distortion-free audio capture across the same, broad dynamic range, they just offer different approaches to address the same challenge.
HAAC technology (with single or dual-membrane microphones) can be found in most Nokia Lumia smartphones running on Windows Phone 8.
Read Nokia’s HAAC white paper (PDF) for more information.