Do parabolic mics work through thin walls?

[trecker4]

Hi,

hard to find a right internet forum for my problem, I try it here.

My neighbour is able to to hear very quiet sounds (like breathing) through a drywall between us. I know because he does not keep it secret and makes a "counter noise" each time, some kind of stalking.
So I'm very interested in what he uses. I've tried an el. stethoscope once on a drywall and realized that's not possible with it, you would hear clear spoken conversations but not more, instead loud noise from the whole house eg water pipes.

So the drywall is thin, even without auxiliary means I can hear single loud spoken words on the phone when I'm 3 metres away from the wall and my neighbour uses the phone near the wall, maybe 2 metres away. I can also roughly locate him left and right when he makes louder noises eg. when he tidies up.
The sound might also travel partly through or underneath the two doors which are not on that wall.


So my question is: Apart from bugs in the same room, can a parabolic mic achieve that (ie hearing you breathing or very quietly moving on a sofa)? Usually you are told that you need a sight line for parabolic mics to work but how is that with the mentioned thin wall?
If one can listen up to 100 metres outside with a parabolic mic, I imagine it's possible for a few metres inside, with a wall, but also without any wind noise, I have no idea.

Any help of anyone who has used a parabolic mic would be greatly appreciated.
(if you don't have a drywall, can you hear through doors?)

[bob91343]

This would be more interesting if something exciting was going on over there.

[cuibono]

A parabolic mic won't do it (thank goodness).

[Ron E]

laser listening devices can be quite effective on membranes, like panes of glass, or perhaps a wall. I would think that any listening device would have to deal with a lot of low frequency noise. Hold an spl meter up to your chest once and see how loud your heartbeat is with a mic in contact....

[star882]

Couple a white noise generator to the wall.

[amc184]

This is the creepiest thread I've seen on DIYAudio for a while. A laser mike would be my bet, I don't think a parabolic mike would work in this situation.

[pheonix358]

I have a cure for your problem but it is country dependent. Ring up your homeland security people and ask them how he manages to do it. They would likely be very interested. Don't do it anonymously and try to sound more concerned for your country than for yourself.

[Rodeodave]

Yep, that's a creepy thread, especially the title on it's own.
I don't think a parabolic mic works that way. From further away someone's mouth talking appears as a point source, the parabolic thing around the mic itself collects a larger volume of pressure-modulated air and focuses it on the membrane. Sound through a wall is not coming from a point source anymore, it's a plane. Pointing a parabolic mic at a wall would just collect the sound emitted from a small section of said wall.

The question is if this is enough, but I'd suspect that a stethoscope would work just a well in this situation. A laser mic would certainly do the job, but afaik it's not too easy to setup, not too cheap and in order to work needs readjusting and maintenance.

[Pano]

Actually a parabolic mic could work, just not as well as in open air. Since it is very directional, it will tend to exclude the noises in his room while picking up sounds coming thru the wall it's pointed at.
Add some amplification and he may be able to hear thru your wall just fine.

Or he is simply pressing his ear against the wall. Try banging on the wall while he's listening.

[Speedskater]

The parabolic mic will also pick up every noise reflecting off that wall.