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Old 08-28-2013, 05:11 AM   #16
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Mat, you are confusing the speed of sound with its effective range of volume. It is very possible to outrun the sounds of sirens and loud pipes. It is why those loud pipes and sirens are annoying AFTER it has passed. It doesn't get your attention until it is right on top of you. It is too late then. Think about the last time a cop or fire truck was right behind you before you noticed them. Their siren was on since they left the station.
Keep the rubber side down. It works better that way!
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Old 08-28-2013, 03:25 PM   #17
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Ok, I think you need to rephrase "outrunning the sound" a bit. Sound travels at around 760mph.
I think what you mean is you might be outrunning the reaction time of the brain. The more distracted you are, the longer it takes you to realize that that sound is actually a siren behind you. You did hear it from a long distance, but you might not be reacting it, and not realizing what it is.

So no, its not physics but rather biology/neurology/psychology.
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Old 08-28-2013, 03:28 PM   #18
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Originally Posted by Typhon View Post
Let's not over think this. Put a baseball card in the spokes. Problem solved in 10 seconds for 10 cents.
Knobby tires will make almost as much noise, and are arguably more cool.
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Old 08-28-2013, 03:45 PM   #19
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Originally Posted by gmk999 View Post
Would you whiz along silently at 75 mph on the highway comfortably knowing that you cannot be heard by nearby motorists and pedestrians?
Or scarier yet, at 25 mph through a school zone?
When I ride or drive at highway speeds I don’t "hear" any other vehicles and if I do its only because they are obnoxious.
IMO My bike could be absolutely silent it would not make a real difference.

In town, congested area, lots of parked cars, lots of pedestrian traffic.
Maybe I would be extra cautious knowing I could not be heard, but honestly not any more than I allready do in that sitiuation on an ICE bike.
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Old 08-28-2013, 07:49 PM   #20
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No, I do mean "outrunning the sound". It is the common phrase used when discussing this phenomenon. A jet engine and a whisper both produce sound that travels at the same speed. Temperature, humidity, and atmospheric pressure all affect the speed of sound, however, it is around the number you quoted. The difference is in the frequency and decibels produced. As for frequency, the Doppler Effect plays a role in what we are discussing. As a sound producing object moves at greater speed it compresses the sound waves raising the frequency. Higher frequency sounds do not have the ability to travel the same distance as lower frequency ones. It is why you hear a loud motorcycle for a longer period of time as it roars away than when it was coming towards you. The second issue is decibels or volume. While both sirens and loud exhaust pipes have higher decibels, it must be taken into account that there is a limited range that those sounds can be heard as decibels decrease with distance. The sounds in question are further diminished with modern sound deadening materials used in today's vehicles. Those sounds produced must compete for the listener's attention with other sounds as well. As speed is increased, the time for a listener to hear the sound, register what that sound is, and then react appropriately to it is shortened the faster the object is moving. That is what is meant by "outrunning the sound". Studies have shown for emergency vehicle sirens, the speed an emergency vehicle can travel where another driver has the ability to hear, distinguish, and react is limited to the emergency vehicle driving at 45 to 60 mph. Emergency workers are trained to respond to calls with an awareness of the limitations of the siren to get the attention of other drivers. Loud pipes are subject to the same issues. The original poster posed a question about electric motorcycles and sounds produced in reference to safety. Increasing your decibels will have minimal effect on the reaction time of other drivers. Defensive riding and safety gear are much better areas to place one's concerns and energies to remain safer. In the few instances where a loud noise will make a difference, simply install a louder aftermarket horn. Loud pipes have the effect of giving the average citizen a bad opinion of motorcyclists, but that is the point for some riders.
Keep the rubber side down. It works better that way!

DirtMedic screwed with this post 08-28-2013 at 07:56 PM
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Old 08-29-2013, 06:35 PM   #21
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Originally Posted by OrangeYZ View Post
Somewhere between a freight train and an F-15 Eagle
Is that with or without Afterburner?
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Old 08-29-2013, 06:54 PM   #22
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I love the F-15 to death, and this won't be a popular answer, but electric bikes should be at least as loud as one of these.

For reference:
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Old 08-29-2013, 07:12 PM   #23
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Awesome photos
Keep the rubber side down. It works better that way!
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Old 08-31-2013, 06:02 PM   #24
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Sounds like an opportunity for custom sounds, much like ringtones on cell phones. Just direct the sound in front of the car so the driver does not have to listen to it. I am thinking of maybe a tune - how about wipeout:

Alternately, record the sound of an engine - even a gas turbine and use that. Or, once people start getting hit by cars that don't make much noise then they will look both ways before crossing the street. Of course, it's tougher for electric motorcycles who must avoid the zombies. Good thing flying cars aren't available!
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Old 08-31-2013, 08:28 PM   #25
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Originally Posted by Chip Seal View Post
On my morning walk, I hear the Priuses [Pious] coming down the road. Their tires make noise just like other cars.
Yep, even electric bikes will make tire and drive chain noise. Watch a vid of one of those electric trials bikes, they're definitely not silent.

But if there's a dipshit or dumbitch driving with their stereo at full volume and texting away while they're it, they won't notice you no matter how loud our bike is.
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