Can I be an audio voyeur?

February 27, 2006 1:58 PM

In the movie The Conversation, Gene Hackman has a sonic surveillance device (a directional microphone?) which, when pointed at distant people, enabled him to tune in to their conversation. This made me think how interesting it could be to own such a device and use it to tune in to conversations other people are having in their car as you pass them on the freeway. Is this possible?
posted by forallmankind to Technology (20 answers total)

We had one as a toy when we were kids, and listened to the neighbours fighting.
posted by bonaldi at 2:00 PM on February 27, 2006

In theory. One type of listening device is called a "laser mic" basically, you point it at a window, and as the window vibrates, the light reflected off of it can be used to measure the change in the position of the glass. Since light is much faster then sound, you can take measurements at a high enough sample rate to reconstruct the sound.

That would probably be the best way to listen into a conversation in a car.

On the other hand, there is going to be a TON of noise outside of the car, rattling the windows, so I'm not sure if this would work to well, especially on the highway modern cars are also kind of soundproofed also.

Maybe you could bounce it off their rearview mirror?

The also sell really big directional mics which look like satellite dishes and are fairly obvious, and they don't go through glass or whatever.
posted by delmoi at 2:03 PM on February 27, 2006

I imagine the wind noise would make it quite difficult to hear anything clearly.
posted by borkencode at 2:04 PM on February 27, 2006

here are some cheap directional mics.
posted by delmoi at 2:04 PM on February 27, 2006

binoculars for your ears
posted by the cuban at 2:06 PM on February 27, 2006

Ever watch an NFL game and see the guys on the sidelines with what looks like big-ass glass dishes? These are handheld directional microphones, capturing audio for NFL Films.

This kind of thing won't be useful for cars. Too much background noise and worse -- the air all around you is moving really fast. Not good for capturing audio.

The laser mic thing is interesting, but I've never seen one outside of science fiction movies.
posted by frogan at 2:07 PM on February 27, 2006

Wouldn't a laser mic be rather dangerous to be pointing at people driving on the freeway?
Dear god, my eyes!
[cue CHiPs sequence with overturned watermelon/chicken truck and car jumping through the air]
posted by blueberry at 2:12 PM on February 27, 2006

Laser audio surveillance is pretty mature technology. Even Jay Leno and David Letterman have used it as a gimmick on their shows -- hardly science fiction. But yes, using it on moving vehicles is rather implausible.
posted by randomstriker at 2:12 PM on February 27, 2006

Seeing how The Conversation is from 1974, I would imagine it was a standard directional microphone (like a "shotgun mic") and not anything involving lasers.

Thanks for the reminder, I've been planning on adding that film to my rental queue...
posted by mikeh at 2:20 PM on February 27, 2006

Voyeurism, man.

*glances at nearby apartment complices, pats binocs*

And yeah, that's one of Hackman's best pictures. Rent it.
posted by cortex at 3:18 PM on February 27, 2006

Response by poster: Yeah - I rather thought that external noise would be a dealbreaker. Oh well, maybe I'll just get a laser mic (thanks, delmoi) and, as cortex suggests, listen to my neighbors instead.

A189Nut - it's just simple curiosity.
posted by forallmankind at 3:29 PM on February 27, 2006

Driving through the US-Canadian border, there was an array of sensors that I vaguely think for designed to hear conversations inside the car when you're waiting at the dotted line at the head of the queue while the car ahead is being interviewed.
If it was audio, it was pretty bulky gear.
posted by -harlequin- at 3:38 PM on February 27, 2006

If the car/driver is equipped with a bluetooth audio device, then The Car Whisperer might do what you want.
posted by Laen at 3:58 PM on February 27, 2006

conversations other people are having in their car as you pass them on the freeway

Are you from some place where people normally drive convertibles with the top down? Or were you really thinking you'd eavesdrop through the windows?
posted by AmbroseChapel at 4:18 PM on February 27, 2006

Parabolic Microphones: for example.

Make sure you get one with an automatic cutoff unless you want to permanently blow out your ears.
posted by alms at 6:33 PM on February 27, 2006

Never underestimate the power of modern signal-processing technology. The random wind noise against the window would be essentially continuous, unlike the conversation which would happen in fits and starts: this would make the conversation stand out in the data. The wind would also occupy a different spectrum than the conversation, making voices distinguishable from the data. With the right filtering (and I don't know if it can be done in real time), a laser mic should be able to record the conversations inside the car.

You probably don't have the skills to do that processing yourself though. You'd be better off recording the conversations on video and getting a lip-reader.

Harlequin: are you sure it wasn't the cameras used to photograph license plates?
posted by cardboard at 9:16 PM on February 27, 2006

Weird. I just watched that flick last night.
posted by keswick at 9:20 PM on February 27, 2006

He'd kill us if he had the chance (Emb.)....
posted by growabrain at 9:24 PM on February 27, 2006

Here's a site I found that has a design for a laser microphone.
posted by landtuna at 9:12 AM on February 28, 2006

cardboard:

Pretty sure - there was certainly no shortage of cameras aimed at the car - both at the plates and at us inside the car, but there were big arrays of other sensors as well.
posted by -harlequin- at 12:20 PM on February 28, 2006