Tuesday, June 2, 2009

Loud Pipes Risk Lives

Loud Pipes Risk Lives

By Scott Jarrett



            In all societies and cultures throughout history, the sounds and noises around us fall into two basic categories: background or ambient sounds, and signal sounds. Some cases in point might be that the sounds of the machinery in a factory become background to the laborers. The 5 o’clock siren is a signal. Workers largely come to ignore the din of noise from the machinery, but their attention is drawn instantly to the siren. Of course, if some machinery starts to make unusual noises, this could be an indication (signal) that some repair is needed, but generally the background doesn’t rise up into the realm of signal unless there is a reason.


            Many other examples of background and signal can be easily found. In each case, in order for a signal sound to be heard, the signal’s decibel level (it’s loudness) has to rise significantly above the background noise. The sirens of a modern police or fire vehicle are significantly louder than they were in early days of their implementation. This increase in loudness has been required so that these important signal sounds can be heard above an increasingly loud background.


            In our modernized mobile society, the most pervasive background sound around us is the sound of traffic. This is practically the only background sound when we are driving. The signal sounds we are trained to expect are those that signal some sort of emergency, like the siren of an ambulance, or a car horn warning of an impending mishap.


            So how do we characterize the loud pipes of a motorcycle? Is it background, or is it signal?


            To the rider, it is clearly background, unless there is a problem with the engine suddenly. The decibel levels of the background provided by these loud pipes sets a very high requirement for the levels of signal sounds needed to rise above the background and get the attention of the motorcyclist. Basically this means that the loud pipes will mask (sonically obfuscate) some pretty loud sounds from the outside world (such as a car horn or siren), some of which might be intended to alert the rider to dangers.


            Should the noise of a motorcycle’s loud pipes be considered as background or as signal to other drivers? If it is to be considered as signal, what response should be expected? Does it mean, “move out of the way?” If I am driving a small, quiet car and I want to be sure that you are aware of my existence, does that warrant my constant use of the horn? The point here is that if loud pipes are a signal sound, what precise, correct response can we agree upon as a society? If a person is suddenly surprised by an unexpected and unexplained signal sound, the usual reaction is one of surprise or fear, and when we react to sudden surprises we rarely react with a sensible driving technique. An air horn under your seat isn’t going to make you a better driver for the next few minutes.


            If loud pipes are to be thought of as background to all of us, then the expectation would be that things would just flow along as usual when they were present in our soundscape.  The problem here is that they are too loud to mix into the fabric of the background, so the only people who can put them into the background are the motorcyclists themselves.


            This combination of loud pipes representing a masking background sound to motorcyclists, and a signal sound to everybody else,  presents a huge safety hazard for both cyclists - because they can’t hear other signal sounds well - and to other motorists, because there is no prescribed response to the signal sound that these loud pipes represent.

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