Our ability to hear spatially, i.e. our ability to determine where the source of a particular sound is located, is often taken for granted, yet this is an extremely important aspect of our auditory system.
How exactly can we tell where a sound source is located relative to our own position? Well, our current understanding is that this ability largely rests upon three different mechanisms, which work together to produce a sense of direction. Two of these are related to the fact that we possess two, spatially seperated ears (described as a binaural cue) while the final cue is related to the distinct shape of our ears and head (a monaural cue).
Consider this example;
In this scenario, the sound of the bird will travel toward the head and reach the right ear first, before then arriving at the left ear. If the bird was positioned to the left side of the head, then the sound would arrive at the left ear first, and then at the right ear after a short delay.
In addition, as the sound can travel directly to the right ear, but has to travel around the head to reach the left ear, there will also be a slight difference in volume.
These two binaural cues allow us to determine if a sound is coming from the left or the right, but what happens in this example;
In this situation, the exact same time delay and amplitude differences will be present for both birds, so how can we tell which is which?
This confusion is resolved using our third perceptual cue, which is produced by the unique and non-symmetrical shape of the ears, head and shoulders. A sound coming from the rear will be filtered by the unique shape of the ears in a different way than if it was positioned in front of the listener.
Binaural recording techniques attempt to reproduce all three of these perceptual cues by placing two microphones inside a life sized, dummy-head. When recordings made with this microphone are listened to on headphones, the experience is quite unlike normal headphone listening and much closer to how we normally hear.
Have a listen to these two audio examples which were recorded using the Neumann KU-100 microphone shown to the right. Please ensure that you listen to these examples on headphones, and that the headphones are orientated correctly.
Example 1: Click to play, or right click to save.
Example 2: Click to play, or right click to save.
In the Remote Ears - Spatial Hearing installation, the binaural microphone is positioned in the centre of the gallery and routed to multiple sets of headphones suspended over cafe seating area, allowing particapents to experience remote hearing. More information can be found at the Science Gallery website here.