- Forward-pointing pipes, even if angled slightly away from the machine, create the liability of putting stinky and harmful exhaust gasses all over the bike® when it is stopped in traffic with air moving toward the rider or not moving at all. Granted, this might not be a whole lot worse than the cigarette smoke some riders are getting (in open-faced, half-dome, or nonexistent helmets) but, as of yet, it’s becoming decreasingly acceptable to smell like tobacco smoke and it’s never been fashionable to reek of petroleum exhaust fumes.
But the excuse the bikers swear by is that loud pipes alert drivers to the presence of the bike (and rider) so the driver knows not to change lanes into the biker’s machine. The problem with that argument is that there’s a funny little physics phenomenon which is amazingly similar between sound and exhaust gasses. Back in the Mid-1990’s a Jr. High School science teacher explained the details in a motorcycle magazine article that I happened to read. I’ll paraphrase from (admittedly vague after all these years) memory:
- Sound is a wave of excited particles that kind of radiates out in all directions from the point-of-production. Hypothetically, if you drop a firecracker out of a small airplane the sound of the explosion will reach a point ten yards away up, down, left, right, north/south/east/west and combinations thereof at the same time. The radiation of sound to anyone listening is, of course, mitigated by things like wind direction and objects that may block (reflect or absorb) the sound waves. There’s a whole science and engineering industry (Acoustics) built up around controlling the extent to which sound waves are absorbed or reflected by different materials and combinations thereof.
To simplify tremendously, though, think back to when you were about 4 years old and talking through a cardboard tube or rolled-up newspaper. Neat effect, huh? Because the cardboard is more rigid than air the sound waves bounced off the interior sides and went more forward than sideways. And then, by using a cone instead of a straight tube, you could amplify your voice in one direction and sound loud to others while not deafening yourself. This, after all, is why many band instruments (particularly woodwinds and brass) are flared out at the ends. It makes the sound project more toward the wider portion of the cone, which a musician will point forward, toward the audience or microphone.
As you’ve noticed, though, automotive pipes tend to point backward from the vehicle, probably mostly for the sake of pushing the exhaust gases behind the driver (see #1 above). Remember that, before the mid-1970’s, a lot of cars generated a lot of thick ugly smoke. That stuff could impede a driver’s vision (and breathing:eek:) at a traffic light if he was blowing it all forward instead of to the rear. Plus, y’know, iron horse engineers emulated real horses by having the stinky exhaust gases go out the back.:dubious: [FONT=Arial][If anyone hasn’t guessed by now, I’m being facetious with this paragraph, so don’t bother to reply with corrections.][/FONT]
But pushing the stinky exhaust backward through a metal pipe also not-coincidentally pushes most of the combustion noise backward. If a motorcycle is moving forward, the gasses and sound being emitted are essentially being left in place while the vehicle moves away from the point of emission. Move the motorcycle forward at highway speed and you’re essentially leaving a “chunk” of sound behind you that the driver behind you has already passed through and left behind before his (her) brain has had a chance to recognize what it is and which vehicle it’s coming from. And even if the traveler(s) behind your loud motorcycle come to realize it’s you making the noise, the information is worthless. First off, they’ve already seen you (light travels faster than sound, blind people are not allowed to control a vehicle on our roads, and he’s looking forward). Secondly, if the guy behind you swerves he’s not going to hit you anyway; any mayhem he creates from such idiocy is going to be well behind you. Thirdly, the driver who needs to know you’re coming so he won’t swerve into your lane and splatter you isn’t going to hear your pipes – not just because he’s ahead of you already but because your pipes are pointed backward and, even if they were pointed forward you’re both moving past the emitted sound well before he could recognize your presence.
So that leaves one* last possible concern: The driver to the left or right of the loud motorcycle. Loud pipes don’t help in this scenario either, because…
[li]A motorcyclist, like any other vehicle operater, should not be sitting in someone else’s blind spot (if you can’t see his face in his side mirror, he can’t see you, either)[/li][li]A motorcyclist, like any other vehicle operator, should not let someone else sit in his blind spot. A driver approaching from behind has already seen the motorcyclist and a rider approaching a car from behind should use speed control to adjust the spacing ahead and behind the bike so the driver in the next lane can’t sit in that blind spot. [/li][li]Vehicles in especially slow (rush hour) traffic aren’t going to be swerving a full lane over very quickly regardless of the noise you’re making and if you’re paying attention at all you’ve got between 3 and 5 times more lane-width to use if you need to avoid a swerving car. Take responsibility and stay alert rather than passively relying on obnoxious noise and other drivers’ lack of tinnitus.[/li][/ol]
“Ah!” our physics-foolish friend would argue, “But in rush hour traffic a car could swerve just enough to hit me when I’m lane-splitting next to him – unless he hears my loud pipes next to him first.”
Well, first off, running loud pipes just for that rare possibility is pretty assinine. And those pipes are probably rendered useless by the fact that the driver who is reckless enough to swerve radically in snails-pace traffic probably won’t hear your loud pipes over the simultaneous noise of his radio, gps, and cell-phone conversation. Secondly, splitting lanes may be legal (depending on where you are) but it’s unnecessarily dangerous because…
[li]while street motorcycles in the 1970’s were air-cooled, the majority of bikes on the road today are water-cooled so they don’t require air-moving-across-cooling-fins in order to keep the engine from overheating [/li][li]if traffic is moving at less than 30 miles per hour, there’s a good reason for it and zooming forward between cars is basically rushing headlong and blindly into a pile-up[/li][li]if traffic is moving at more than 30 miles per hour, there’s no reason to be zooming between cars faster than that. There’s no way to have enough reaction time to stop if you suddenly encounter the cause of the congestion and everybody is moving at a decent pace --twice the speed of a jogger, if someone was foolish enough to jog down the highway at rush hour.[/li][/ol]
…so just get back in the queue and quit being a show-off.
So, yes, there are bikers who use loud pipes to be noticed. But the people who are noticing aren’t fellow travelers on the road; they’re people in the homes along the road who have to hear the noise after the biker has passed. Not only are those residents and their homes unlikely to swerve into the biker’s lane, but when they hear that biker’s loud pipes, they’re thinking “Damn! That’s obnoxious, narcisistic, and childish all at the same time!”
But maybe that kind of biker doesn’t understand a sixth-grader’s level of physics and/or lives by “Negative attention is better than being ignored.”
And that would mean those poor residents are right.
- Well, two, actually. But if the other driver is above or below the motorcycle, the issue of exhaust noise is not one of the biker’s primary concerns. :eek: