The importance of sound in our daily lives?

How sound connects us to the world around us?

Why music moves us in ways that the visual arts, perfumery and even gastronomy can’t?

Why tonal music is pleasing to the ear?

Do we learn to hear? How does this affect our acquisition of language?

What is the evolutionary advantage of the sense of hearing: Why did we develop the ability to detect mechanical energy in the atmosphere surrounding us?

Why we have two ears?

What happens when we can no longer hear the sounds around us?

I have! A lot!

In this blog I want to share some things I have found out in over more than 30 years in audio research and development, as a neuroscientist and psychophysicist as well as an inventor and developer in the areas of hearing impairment, virtual and augmented reality, games audio and as an amateur musician, sound designer and engineer .

I don’t want to blog long polemics that will take hours to digest – I have written enough of that stuff and I can link to those more technical and scholarly papers so you can check them out if you are interested. I want to discuss question like those above and similar sorts of questions I get from you.

A fundamental principal of perceptual neuroscience is that hearing is the only truly immersive sense that tells us about things that are away from us. By the time we can smell it or feel it it’s up real close – in some scenarios this might be quite pleasant but in others is spells certain death. So hearing has played a special role in keeping us alive along with all the other animals that have this marvellous capability.

Sight tells us what’s up ahead but not what’s behind us or even beside us. We peer at the world through the window of our visual field and the brain uses this information to build up a coherent picture of what’s going on around us. At least it feels pretty consistent and secure but the recent research on change blindness has demonstrated just how unreliable this can be – check out  Susan Greenfield’s cute take on this

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We see a similar phenomenon with hearing which is referred to as change deafness. In this case we are pretty good at identifying when two sample of the same auditory scene are the same but we need a pretty significant change in the scene before we can reliably detect a different sound (for example, a dog sound being replaced by the sound of a ships horn) (see http://scienceblogs.com/cognitivedaily/2009/09/beyond_change_blindness_change.php) and this is also affected by whether the we are directing our attention to the sound or the space that is occupies.  Other work has suggested, however, the way auditory memories are formed is different to visual memories and that this does make change detection easier for the auditory system than the visual system (see http://pss.sagepub.com/content/19/1/85.full WARNING- Seriously pointy head stuff). More of this later.

Unlike vision, hearing means that we are surrounded by the world. You don’t have eyes in the back of your head but your auditory system is able to very rapidly and accurately locate the source of a sound behind you. We are surrounded by sounds nearly all our waking hours and we use the locations of sources around us to continuously orientate us in our world.

We are immersed in sound nearly all the time. It helps us feel present in the space we are in. Walk down the street with your headphones in but turned off and you can feel the reduction in your sense of presence. With them on you are in another place: the physical space that you occupy combined with the aural space you are listening to. So this is a hybrid space. One where we can choose a particular emotional overlay that is transmitted in the music.

 I’ll return again and again to the idea of presence – this is one of the more important concepts to have emerged from the virtual reality research of the last few decades and has particularly important implications in the areas sound design in cinema and video games.

Your auditory system is also exquisitely tuned to change in that world. The auditory system is not really interested in things that are constant – you only notice the air conditioner when it turns off. We know that from looking at how the auditory nerve responds to sound: The neural responses have a very short latency and with a predominance of activity at the onset of a sound. In behavioural terms, unexpected sounds are extremely salient and grab your attention (an involuntary switch of what is called exogenous attention) – in evolutionary terms it’s a real advantage to not only know where the sound came from but to be able to identify it as a threat, an opportunity or simply a distraction to be ignored – at times the difference between eating dinner and being dinner!

The saliency of auditory change has obvious implications for sound design and understanding the role of attention but probably more importantly illustrates why audio can be so visceral. The saliency of the unexpected sound is in part driven by the same systems that drive the fright, flight, fight response of your nervous system. Not surprisingly this is also why sound can be so evocative. Musical perception plugs into these emotive systems in the brain, the architectural spaces in which we listen to music optimize the sense of envelopment (in the best seats at least) and so drives this sense of presence in the emotional landscape of the music.

So, next time you are playing a video game or watching a DVD try switching between stereo and surround (5.1 or 7.1 if you are lucky enough) and see which one makes you feel more part of the virtual world being created and how you identify with the narrative or action being portrayed. This is presence.