Just how reliable could something like this be? Seems pretty far fetched but you never know.

New speed traps could measure speed based on sound

A new type of speed trap developed by the University of Tennessee could detect the speed of a car based on the sound of its exhaust as it passes. According to a report in the 2548 issue of New Scientist, the system uses microphones to record the sound of passing cars, and then a computer program isolates the various vehicles. The program then calculates the vehicle’s speed by measuring the exhaust sound’s Doppler shift. According to patent filings, development was funded by the US Department of Energy. Unlike radar systems that can be detected by dashboard-mounted devices, this sound-based system would be undetectable.

 

Doppler radar gives them great results for tracking weather.

 

I think it could work. Like it says it singles out the cars. So at so many feet away your cars exhaust initiates the machine.

. . . I can't explain it but I understand it. I believe its just a calculation judging by when the sound of the exhaust initiates the machine to the loudness of your exhaust when it finally passes the machine. If your going over the speed limit your car will pass the machine quicker and the exhaust will get louder, to the machines ears, quicker.

Thats the best I can explain it. I'm just not nerdy enough to describe the math. [img]style_emoticons/<#EMO_DIR#>/22.gif[/img]

 

Calculating speed by measuring the Doppler Shift makes sense.

 

I knew I didn't like those UT guys!
[img]style_emoticons/<#EMO_DIR#>/smilies23.gif[/img]

 

What if you were driving a hybred and it was in electric only mode?

 

<div class='quotetop'>QUOTE(MY05GT @ April 28, 2006, 2:18 PM) Quoted post</div><div class='quotemain'>
Doppler radar gives them great results for tracking weather.
[/b][/quote]

ya it was supposed to rain today...and it was sunny.

 

what if you had extremely quiet exaust?

 

What if the machine got ran over! [img]style_emoticons/<#EMO_DIR#>/04.gif[/img]

 

<div class='quotetop'>QUOTE(OKCMustangGT @ April 28, 2006, 5:21 PM) Quoted post</div><div class='quotemain'>
Calculating speed by measuring the Doppler Shift makes sense.
[/b][/quote]
It should work. To counteract it you need speakers outside the car which plaback exhaust note in reverse doppler emulation. [img]style_emoticons/<#EMO_DIR#>/04.gif[/img] That is, the sound a car would make passing by at a much slower speed corrected for the actual speed of the vehicle.
The real problem of the detector is matching the exact car and picture with the exhaust. It won't work properly in traffic. [img]style_emoticons/<#EMO_DIR#>/headscratch.gif[/img]

 

I think people are getting enough tickets as it is. [img]style_emoticons/<#EMO_DIR#>/banghead.gif[/img]

On a side note, when i started up my car at the mall the other day my exhaust set off the alarm on a Honda Civic. It made my day. [img]style_emoticons/<#EMO_DIR#>/icon_mrgreen.gif[/img]

 

what if you down shifted while it was "listening" (or depressed the clutch)? That'd confuse it...

 

<div class='quotetop'>QUOTE(RottenRonny @ April 28, 2006, 11:54 AM) Quoted post</div><div class='quotemain'>
What if you were driving a hybred and it was in electric only mode?
[/b][/quote]

I doubt electric-only mode is used when at higher speeds. The hybrid setups I'm more familiar with use the electric motor (torquey) to assist acceleration from a stop or at low vehicle speeds (such as congested traffic). Maybe if the speed trap were calibrated for tire noise? electric motor whine? Where's the EMP gun when you need one?

 

i think its BS i doubt it will ever work, what about the civics with the fart cans,, etc... it can't be acurate, and some one will prove that hopefully
there gonna end up like the lie detectors they will be inadmissible

basiclly it won't be 100% acurate

quotes from a website

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"Everyone admits that polygraphs are unreliable."

Polygraph evidence is generally inadmissible in court because, ... "there is simply no consensus that polygraph evidence is reliable." Indeed, the lie detector is so untrustworthy that Congress passed the Employee Polygraph Protection Act in 1988, making it illegal for private-sector employers to compel workers to take polygraph exams. Prior to the law's passage, according to Senate testimony, an estimated 400,000 workers suffered adverse consequences each year after they were wrongly flunked on polygraphs.

"They're not even admissible in court." Senator Richard Shelby (R-Ala.). i left his name since he last name is shelby ahahhahah
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<span style="font-size:8pt;line-height:100%">http://www.motherjones.com/news/feature/2002/11/ma_148_01.html</span>

 

Don't think so, too many variables in sound based on aftermarket pipes. A decent radar operator will tag you and your radar detector will let you know you are about to be pulled over.