My car was beeping when a state trooper wanted to pass me. How come?

September 28, 2006 7:23 AM

My car was beeping when a state trooper wanted to pass me. How come?

I was driving on the Mass Pike last night, going 75-80 mph with traffic. I was in the far left lane when I heard beeping in my car, but figured it was the radio. The car behind me moved over to let the car behind him pass, and this second car moved right up to my bumper, indicating that he wanted to pass. I heard the beeping again as I moved over to let the car pass. Turns out it was a statie. Oops. He passed me and the rest of the ride was uneventful.

The beeping sounded as if it could have been the radio, but I'm pretty sure it wasn't. It was a series of single beeps, and I only heard them twice. I don't have a radar detector or anything like that, and it definitely wasn't my cell phone. I think it was more on the driver's side, but I could be wrong. It's an '89 Volvo 240.

Was it my car? Was it the trooper? Help, it's driving me nuts!

posted by good for you! to Travel & Transportation (26 answers total)

It's a high-speed indicator built into your car, probably. My BMW does the same thing if I hit 80 mph or so, and it never fails to momentarily freak me out.
posted by orthogonality at 7:31 AM on September 28, 2006

I had to turn that off in my Audi because it scared the crap out of me. I could set it to whatever speed I wanted it to go off on and thought 82mph was a good amount. It makes the same beep when it is low on gas and it scares me too. The beep sounds like how my old radar detector sounded when it detected a supermarket nearby.

I don' t know if they had that back in the 80s though. If it is a speed indicator, you'll need to get back on the highway and see if it goes off again. If you've had the car a while you would have probably noticed it by now.

I do know cops in Texas have weird horns and squawkers they employ to get people out of the way, but none which appear to come from inside the car.
posted by birdherder at 7:40 AM on September 28, 2006

Did you have the radio turned on? If he had moving radar running, it could've been the radar doing something to your radio amplifier or speaker electronics. (I.e. when you get a cell phone call and your phone is near your radio.)
posted by SpecialK at 7:40 AM on September 28, 2006

Maybe the cop had a Blackberry.
posted by sohcahtoa at 7:43 AM on September 28, 2006

Response by poster: ortho/birdherder: I don't think it's a speed indicator. I've had the car for a year-ish and never noticed it before. About a half hour before I saw the trooper I was going 85+ mph.

I've heard those squawker things before, and it wasn't that. But those always freak me out.

SpecialK: The radio was on, but this was definitely a beep, not a static-y speaker interference.

The first thing that actually went through my head was that something had "locked onto" my car, like in Top Gun, where they have to fly against each other to get the missile locks. (Oh God, it's Iceman!)
posted by good for you! at 8:16 AM on September 28, 2006

My best guess is that emergency vehicles are able to trasmit this sound across various radio frequencies as a way to make people realize there is something going on.

A couple years ago while watching the discovery channel I saw something like this was being implemented in Australia.
posted by Sonic_Molson at 9:00 AM on September 28, 2006

Were his lights and siren on? Or was he just driving on your tail?

(I'm guessing the lights weren't on?)
posted by Alt F4 at 9:16 AM on September 28, 2006

Response by poster: No lights or siren. I noticed the shape of the headlights, but didn't see anything to ID it as a cop til he passed. There weren't any incidents on the highway, it looked like he was just patrolling.
posted by good for you! at 9:20 AM on September 28, 2006

Sonic, check that tin-foil hat.
posted by dmd at 9:21 AM on September 28, 2006

Really. If "emergency vehicles are able to trasmit this sound across various radio frequencies" this fact would be well-known.
posted by Rash at 9:44 AM on September 28, 2006

It's very hard to localize a noise that comes from directly behind you, especially when you're in a car. The guy behind you honking because HEY, COP BEHIND ME, or the cop tapping his siren to get you both out of the way, might sound like it comes from anywhere.
posted by mendel at 9:44 AM on September 28, 2006

Some emergency vehicles transmit in a range that some radar detectors can detect. Perhaps this transmission was partially picked up by your radio, or, perhaps the police radio was bleeding into your radio?
posted by edgeways at 9:49 AM on September 28, 2006

I've been driving before and picked up the localized radio frequencies transmitted by in-car DVD players (at least, that's what I think it was). I was driving down 95, and as I passed an SUV, I noticed that my low-end radio frequency (some university station) was replaced by a sitcom / dialogue / tv-show-sounding bit of audio. I passed out of the "stream" of audio, and my radio station came back in. Curious, I slowed down again, so I'd be in the same position (relative to the SUV). Sure enough, the sound came back in.

Perhaps cops have a low-end frequency signal that they use in case your radio picks it up? It doesn't seem like a good use of funds, since it's only going to notify people on NPR and college radio stations, but, hey. Maybe.

Was your radio station on a low-end frequency?
posted by Alt F4 at 10:40 AM on September 28, 2006

The radar and police radio are on completely different bands from AM/FM radio. I don't buy that they would interfere at all.
posted by knave at 10:43 AM on September 28, 2006

Its an acoustic illusion. Happened to me. I swore it came from the car but it really was just sounds the cop car makes. I believe there's something funky about sound being point at the rear of your car. The rear doesnt really have much insulation, usually a trunk and some seats to block the wind.
posted by damn dirty ape at 11:04 AM on September 28, 2006

Response by poster: I've picked up FM-transmitter signals before. I don't know if it was DVD or MP3 or what, but that was weird until I figured it out. I was listening to 98.5 last night, so it wasn't very low, and usually those transmitters use more "outer" frequencies.

It sounded like a radar detector, but like I said, I don't have one. I've never heard a cop car make a noise like that.

Thanks for the answers so far. I'm starting to think I should line my car in tin foil, would store brand work or should I spring for the name brand? :)
posted by good for you! at 11:27 AM on September 28, 2006

good for you! writes "I'm starting to think I should line my car in tin foil, would store brand work or should I spring for the name brand? :)"

Reynolds makes a heavy duty foil that is twice the thickness of regular foil for BBQs and that kind of thing. It's much better for anything that'll be exposed to the wind. Also you can buy a self adhesive aluminum tape in 2" wide rolls. It's great for joining edges and is available from the home improvement big box borg near you in the heating section.
posted by Mitheral at 12:43 PM on September 28, 2006 [1 favorite]

Response by poster: Excellent, thanks Mitheral!
posted by good for you! at 2:56 PM on September 28, 2006

Somewhat unrelated - has anyone picked up an itrip or other fm transmitter broadcast from an ipod in another car? jukeboxing on the highway?
posted by chupwalla at 7:43 PM on September 28, 2006

I saw something like this was being implemented in Australia

I'm almost certain you're thinking of Emergalert, although this system broadcasts a beeping tone on AM and FM channels followed by an announcement about approaching emergency vehicles (which makes sense because otherwise motorists wouldn't have a clue what was going on), so I doubt this is the answer to the OP's question.
posted by harmless at 2:25 AM on September 29, 2006

Best answer: I have an '89 240 also, and frequently drive 80+ - I have never heard any beeps when speeding or when being passed by Johnny Law. I have heard the radar detector noises when driving this and other cars, though - maybe you just picked it up from another nearby car that was detecting the cop? Or maybe your radio/speaker cables have bad shielding...

Also, I found this article from 2004 - apparently, they were already getting excited about the idea doing emergency vehicle fm transmitting then, and the inventor is from MA and a former state trooper, so who knows?
posted by sluggo at 3:42 AM on September 29, 2006

Response by poster: sluggo I think you're probably right. My car has the original radio & speakers (afaik), so any shielding has probably deteriorated in the past 17 years.

The car behind me was a newish SUV, and I just remembered that there was a newish car next to me as the cop pulled up behind me, so there's a decent chance that I picked up something from one of them.

Those emergency vehicle alert systems are really interesting. Any houses in high traffic areas, or near police/fire stations may get tired of it pretty fast though.
posted by good for you! at 10:09 AM on September 29, 2006

Response by poster: I meant to ask, is Emergalert widely used in Australia?
posted by good for you! at 10:12 AM on September 29, 2006

chupwalla, happens all the time when I pass trucks on the expressway if my radio is set to 87.9 (a common preset on some fm transmitters). I usually can hear Howard Stern but sometimes get Country or Rock music.
posted by damn dirty ape at 10:26 AM on September 29, 2006

Might that result from some wireless rig for the stereo in those trucks' cabs?
posted by Rash at 4:29 PM on September 29, 2006

is Emergalert widely used in Australia?
Not widely, in fact from my brief googling just now I haven't found any info to indicate that it's even being trialled anywhere yet (not sure if I should be surprised about that).

Any houses in high traffic areas, or near police/fire stations may get tired of it pretty fast though.
Probably no more than they would get tired of the sound of sirens or the chorus of dogs howling with the sirens, but I guess it depends on how much sound-proofing they're used to having in their homes.
posted by harmless at 7:49 PM on September 29, 2006