Are loud cans a good warning?

[northwind]

I used to have a twin system that was ridiculously loud... A couple of times on my commute, I'd come up behind a car and they'd hear me, panic, start looking around in a flap, and end up weaving all over the road. Hasn't happened since I went back to my WRP, which is loud but not that loud.

I have nothing else to add to this thread... It's already been said, if you depend on other people being aware you're there, you're doomed

Originally Posted by lynw

It was so noticeable I cant put it entirely down to simply getting 150 drivers who were more observant than the 100 odd drivers we past with him leading... but it DOES make a difference..this is hardly scientific. 2 bikers 2 sets of lights road positioning. Sorry but that's a bit flimsy.
but people DO hear approaching sounds from behind - no they don't they hear reflected sounds from the buildings in front and to the sides. You cant hear a sound if its travelling in the opposite direction

Originally Posted by Peter Henry

Your approaching from behind, human ears are best designed for hearing sounds coming to them from front or side but not at their best at all in picking up sounds from behind.

Correct!

Sound is pushed away from the exhaust behind you. In the absence of any reflection from buildings car windscreens etc then you wont hear it in your car. Certain objects reflect sounds others absorb sounds - its all relative.

Police/ambulance/fireengine sirens are specially designed so that traffic in front can hear them from a considerable distance. They push sound out 360 degrees at specific wavelengths and frequencies the human ear is extremely susceptble to - I find it difficult to believe that someone could travel for 2 miles without hearing an ambulance - unless they were deaf! Even today in our rideout we heard an ambulance from 2-300 yards away with helmets and in my case ear plugs in.

Anyway - Northy was right..."if you depend on other people being aware you're there, you're doomed"

[Biker Biggles]

Common sense says they must be useful in town or stationary/slow traffic,especially for pedestrians,but less so in fast moving stuff.The paradox here though is that most aftermarket cans are not that loud at low revs which is probably how you would be riding in slow conditions.The real noise comes on the open road when you wind it on.
The exception of course would be PH with his dry clutch,which will tell all and sundry that he is slowly coasting past that line of cars.