Quiet-List 1997

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New Scientist Article on Car Stereos

Below is the text of an article in New Scientist 
concerning the hazards of loud auto stereos.

  -- Michael Wright

by Laura Spinney
New Scientist    19 July 1997
Vol. 155 No. 2091

Listening to music while you drive can improve your 
reaction time and ability to avoid hazards, according
to Australian psychologists.  But turning your car
stereo up to full volume could turn you into a liability
on the roads.

The performance of complex tasks can be impaired
if people are subjected to high-intensity noise.  The
experience of pulling up at traffic lights alongside cars
throbbing with heavy bass prompted Helen Beh and
Richard Hirst of the University of Sydney to investigate
whether loud music interferes with driving.

The researchers recruited 60 men and women aged
between 20 and 28 and tested them on simulated
driving tasks under three noise conditions:  silence,
rock music played at 55 decibels, and the same music
blaring out at 85 decibels.

For 10 minutes the recruits sat in front of a monitor
operating a steering wheel and foot pedals representing
brake and accelerator.  They had to track a moving disk
on screen, respond to traffic signals changing colour,
and brake in response to arrows that appeared without

On the tracking task, there was no difference in perfor-
mance under the three noise conditions.  But under
both the loud and quiet music conditions, the volunteers
"braked" at a red light about 50 milliseconds sooner 
than they did when there was no music at all.  That could
mean a reduction in braking distance of a couple of
metres -- potentially, the difference between life and death
for a pedestrian.

When it came to the arrows that appeared across the
visual field, Beh and Hirst found that when the music was
quiet, people responded faster to objects in their central
field of vision by about 50 milliseconds.  For the people
listening at 85 decibels, response times dropped by a 
further 50 milliseconds -- a whole tenth of a second faster
than those "driving" with no music.

"But there's a trade-off," Beh told the European Congress
of Psychology.  "They lose the ability to scan the environ-
ment effectively."  In responding to objects intruding on 
their periperal vision, people subjected to 85-decibel rock
music were around 100 milliseconds slower than both 
the other groups.  Since some hazards -- such as children
running into the road -- emerge from the periphery, drivers
listening to loud music must be less safe as a result.

The beneficial effect of quiet music on attentiveness while
driving is probably related to the boost in arousal induced
by the "muzak" played at conversational level in many 
shops -- and which is thought to make customers pull more
products off the shelves.


The experimental methodology could stand some
refinement.  I think that research subjects for
this type of work always should be classified
according to whether they are noise-addicted
or not.   The faster response times alleged for 
the low-volume listeners might be true only for
the noise-addicted, who experience discomfort
in the absence of some sort of audio stimulus.

Additionally, the question of drowsiness versus
alertness needs to be addressed and controlled

It might be the case that the alleged faster response
times with music only works for people who are drowsy.  
In that event, should we be encouraging them to drive 
in the first place -- with or without music?

   -- Michael Wright
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