Listening For Change In Complex Soundscapes


Listening for change is something we do for both pleasure and survival. Unless we are in a very rarefied atmosphere, the soundscape is usually complicated. Even when we are sitting in the sun out in the country, we have multiple components to the sound scene we are listening to at any given moment. We hear the rustling of leaves in the trees and birds singing or quarreling in their branches, but the moving around of little rodents in the nearby bushes adds to the complexity.

With music on the menu, we listen to the rise and fall of volume and changes in complexity as instruments and voices move in and out of the composition of the soundscape. Sometimes it’s pleasing and sometimes it’s not.

Picking up rapidly on soundscape changes is a survival instinct that we are still fairly good with. Not so good as our dog perhaps, or that deer out in the woods.

Sudden changes in volume are important, of course, but something with large teeth creeping up on you won’t be adding much to volume. Rather it will be bringing in new sounds as it tries to approach stealthily. You turn your head, it stops moving and that sound is gone. You wait a little, shrug and continue and then you hear the sound appear again. The cat and mouse game continues until – well, that depends.

In this week’s PLoS ONE, Constantino et al have their paper in which they describe a series of experiments to see how easily people can spot changes to a sound scene as a new sound come is or an old one disappears. The scenes are non-musical and consist of groups of frequencies played together in groups of 4, 8 or 14. Experiments were carried out to eliminate problems such as changes in loudness as one sound appeared or disappeared from the mix.

The results were quite clear that sounds disappearing weren’t noticed as successfully as sounds appearing in the mix. The bigger the mix, the less the loss of one component was noticed, but even in the largest mix, the appearance of an additional sound was spotted rapidly and successfully.

Clearly our survival mechanism is dominant and our auditory senses work similarly to our visual ones where we pick up on a change as a head pops up. Just like the other animals out there, our first reaction is to get ready to run or take the safety off our gun.

  1. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0046167

Driving Tired Or Just Tired Of Driving


Driving tired is something that we all do from time to time. Driving around in most urban areas has become rather a pain in the rear, especially when going to and from our place of work. Commuting is always slowest when we have an early morning meeting and our nervous tension rises.

But that is not the only problem with those early meetings. We have in all probability put our alarm clock on earlier than usual, which wakes our grumpy partner, maybe the kids and certainly the dog and cat. ­ The latter demands food and the former demands walks.

The result is that you end up driving tired. Mistakes are, of course, due to those other dorks on the road, but when you’re driving tired, there are always many more of them travelling in the space that you have bought and paid for with you damn taxes!

 In a recent study published in PLoS ONE, Di Milia et al set about quantifying the effect of driver sleepiness during commuting (1). I should state at the outset that they did not look at the way a tired driver attracts dorks so that is an area crying out for grant applications. The study looked at sleepiness and the outcomes for night shift workers and those of us who purport to work during the day, but must commute.

 The study took place in Queensland, OZ, where they inveigled the local police to stop people for random breath tests and invited them after their blow job to go down the road and sign up for an “are you dozy?” survey. Not a great idea when you’re hurrying, bleary eyed, with your mouth tasting worse than the bottom of your parrot’ s cage, to that strategy meeting critical to your career prospects.

About 60% of the invited participants participated. This amounted to almost 650 drivers. A significant number worked the night shift. They indicated their tiredness level, how much sleep they’d had and how many driving booboos that they had made. No one totaled, killed or otherwise blotted their driver’s license, but there was far too much wandering across lanes accidentally for it to be a good thing.

Workers on the night shift were making more errors and were sleepier than non-night workers, but sleepiness was clearly bad. The authors suggest roadside tiredness tests rather like the random breath tests as a solution. Sounds like a very bad idea to me. Much better to rush forward conversion kits to make all our cars Google cars which will drive about with only the occasional word of advice and ecouragement from a hardworking Joe or Jill.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0045856