Adding the loudness on to of alertness and safe driving practices can only make you safer.
I thought this was already widely known as a myth, especially among bikers...
At speed, a car driver _generally_ cannot hear a motorcycle until it's already beside or in front of them. Regardless of the how loud the exhaust has been modified to be. The only time you can hear a motorcycle coming up from behind is at low speeds or a dead stop and not always then.
It's all thanks to physics. Sound travels through air, right? More specifically, air acts as a medium through which vibrations (sound waves) propagate. You also should already know that it travels pretty fast though air. Faster than any street-legal vehicle, but much slower than light.
So if sound travels faster than two hypothetical vehicles in question, why can't cagers hear approaching motorcycles? Three factors:
1. Movement. Picture this: Object A is stationary. Object B is stationary as well, but situated about 25 yards/meters away. Object B makes a noise at some arbitrary volume. Air is not a perfect conductor of sound, so the noise is attenuated to about 75% of its original volume by the time it reaches object A. Now, put the objects in motion at 60mph. Even though the distance between the objects is the same, the noise has to travel though significantly more air to reach object B, thus even more attenuation (loss of volume). If you've ever watched a fish try to swim upstream against a strong current, it's the same concept.
2. Direction. Sound from a vehicle exhaust is highly directional. The exhaust sound coming out of the pipe is going almost entirely in one direction: to the rear. The car in front of you is in the exact opposite direction. When you're cruising down the road on your modded-out hog and you think the exhaust sounds pretty good and throaty, it's probably deafening to anyone less than 1/2 mile behind you. But the car 20 feet in front of you hasn't even noticed you yet. The only time they're likely to hear anything at all is if your exhaust sound happens to bounce off another object like a bridge or billboard, but that's before factor 3 comes into play...
3. Ambient noise. Modern cars can be pretty quiet machines when equipped with proper tires, driving at moderate speed, and when few interior distractions are present. That is unfortunately not the case in the vast majority of vehicles I've been in. Bad tires, poor road conditions, excessive engine noise, a blaring radio, children, cell phones, air vent noise, wind noise (especially with the windows down) all greatly raise the noise floor in your typical automobile and positively demolish any chance you ever had of getting the driver's attention with your loud exhaust.
Now, I'm not saying that nobody ever hears a motorcycle before they see it. I'm saying that it's the exception rather than the rule, especially in common everyday driving situations. If you like having a loud exhaust, that's fine. Just don't think it adds any significant amount of safety to your riding. You get far better safety value by making yourself *visually* noticeable via a white helmet, high-viz garments, reflective surfaces, etc.
Also, I agree with the articles that loud bikes give two-wheeled enthusiasts in general a bad name. Nobody likes to be cruising down the road on a hot day and have to cover their ears or put up their windows while a biker passes by at 190 decibels.
