A scientific article I stumbled upon scanned subject’s brains using fMRI whilst they listened to voices being played over headphones. The voices were either played in stereo (inside the head) or using 3D audio (outside the head). The aim was to find the neural substrate for the perception of voices outside the head (in what we might call external auditory space) in an effort to better understand auditory hallucinations of that type. You can find the article for free here. Very interesting.

One other large emerging application of 3D audio that you might not be aware of is for hearing aids. People who require hearing aids at the moment have sounds simply amplified and they are unable to know the direction of where the sounds came from. This makes situations such as a dinner party almost impossible. Normal listeners at a dinner party are able to follow one conversation and ignore the other voices due largely to the fact that the brain knows where the sounds are coming from (this is the so-called Cocktail Phenomenon). Once this ability is lost, as with a hearing aid, all the voices are mashed together and it is impossible to follow a conversation. A hearing aid with 3D audio amplifies the sounds around the listener and at the same time provides a sense of where the sounds are coming from.

Have a listen to this demo (USING HEADPHONES ONLY) to see what it is like have a hearing aid with and without 3D audio. The demo starts without 3D audio and then 30 seconds in it switches to 3D audio, you will hear it don’t worry (think of what it’s like to have hallucinations of people talking while you listen). Focus on trying to understand the different talkers. Again, you must use headphones:

Visit the site and watch the short movie (or watch it below) for some amazing audio effects. Remember to wear your headphones.

Enjoy

It is an example of what is called a ‘binaural recording‘. A dummy head, with tiny microphones stuck inside its ears, is used to record an acoustic environment such as a person cutting your hair or a band playing in a room. You then listen to the binaural recording over headphones and it is as if you were sitting at the position of the dummy head at the moment of the recording. The best way to really understand the process is to just watch and listen to these examples:

YOU MUST USE HEADPHONES FOR THE FIRST EXAMPLE!

‘Snakecharmer-Binaural‘ by Ottmar Liebert

John Q. Walker’s talk (7 minutes 45 seconds in) entitled ‘Re-creating great performances’ from the EG 2007 conference posted on TED

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Have a look and subscribe to the channel.

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To explain very briefly the concept behind 3D audio:

• If you close your eyes and click your fingers in different locations around your head, you will notice that you are able to locate sounds in space with no more than the signals your two ears are receiving
• Imagine that you were to now insert a tiny microphone into each of your two ears, and then go and attend a concert of your favourite band and record the whole concert with these two microphones stuck in your ears
• If you now take the recording that you made at the concert and then put it on your mp3 player and play it using headphones, by effectively playing the exact signal that entered your ears at the concert back into your ears, you will hear the concert in 3D as if you were standing back in the crowd
• In short, all the information your brain needs to tell you that sounds are coming from outside of your head are embedded in the signals that arrive at the entrance of your two ear canals

YOU NEED TO LISTEN TO THIS MATERIAL WITH HEADPHONES!

Here is one such recording, accomplished with the use of tiny microphones as mentioned above that are inside the ears of the dummy head you can see in the middle of the people playing instruments. Watch the video below and listen.

Other sites dedicated to these types of recordings are: ‘through my ears’ blog, Duen Hsi Yen’s Binaural Sound Page, and Bird vs. Alligator.

These examples are great demonstrators of 3D audio. However, they are just recordings, known as binaural recordings. Arkamys is now dedicated to push the technology even further, by being able to synthesise any audio content that you may have on your mobile phone or mp3 player, so that it is rendered in 3D and is personalised.

Don’t forget to check the ‘3D Audio Showdown‘ page for more demos and the ‘Project Demo‘ page on this blog for an example of what the personalisation of 3D audio really is, and what it is like to listen through someone else’s ears…

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