There have been any number of studies — the work of Warren Brodsky, for example — investigating the potentially harmful effects of driving while listening to loud music (particularly of a certain tempo).

But a new paper by Mark Horswill and Annaliese M Plooy, at the University of Queensland, “Auditory feedback influences driving speeds,” published in the latest edition of Perception, talks about the risk of a car being too quiet.

As any reader of car reviews will note, reduced “cabin noise” is always seen as a positive feature. Reduced noise is thought to mean more “comfort” for the driver, though there are more spurious reasons being put forth; Horswill quotes one automotive engineer who notes that “automobiles will have to become significantly quieter, keeping the noise out so passengers inside can enjoy the latest advances in communications and entertainment technologies.” (that’s right, cars are now intended to be rolling phone booths!)

The problem is that noise — road noise, engine noise, etc. — acts as a form of feedback, helping to increase the driver’s situational awareness (described by Neville Moray as “shorthand for keeping track of what’s going on around you in a complex, dynamic environment”).

In his study, Horswill had drivers look at a variety of filmed driving scenes, which were played at a variety of different speeds and under different levels of audio “stimulus.” He found that ” reducing noise made vehicle speeds appear slower than they were.” When the decibel level was reduced by 5, the drivers thought they were moving 5 kph slower than they really were. You may be thinking that people can simply use the speedometer as the more accurate form of feedback, but previous studies have found people consult their speedometers rather rarely (”approximately 12 times over the course of a 6.4 mile, or 10.2 km, route” — this during a trial whose very task was to keep a set speed). The difference in speed may also seem minor, but given that small increases in speed at higher speed led to much higher increases in crash risk and damage, this may not be as minor as it seems.

An observation once made in another paper (”The ironies of vehicle feedback in car design,” in Ergonomics by Guy Walker, et al.), that “drivers’ self-awareness of the state of their own situational awareness appears to be very poor,” also seems to apply in this case: Drivers did not realize how the lack of auditory cues was influencing their own perception. To be cue-less is to be clue-less.

This entry was posted on Wednesday, November 19th, 2008 at 10:45 am and is filed under Cars, Drivers, Traffic Psychology, Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.