Attempting to Record LFN.. Help!

[kozikowski]

What's on the other side of the neighbor?

They're both stand-alone houses, right? They're not, as in the US, Semi-Detached -- one common wall?

I was about to say that I find it hard to believe an effect that appears in your house wouldn't also be audible while standing between the two houses. Even if your house happens to resonate at that pulse rate, it has to be "excited" by something, and it's not easy to move a brick house. See: Three little pigs.

It's also rough to believe that a server computer could make enough noise to transition between two walls and a property space -- if there is one. If you have one common wall, then yes, certainly. We had one computer install that was clearly audible on the other side of the wall and we had to take steps to isolate it, particularly since the other room had to record audio.

You may be stuck with specialists. I don't know of a USB microphone amplifier with specifications down that low. The desperation method would be to contact Behringer. They might have application notes. Their web site pushes the idea of how well it records music, but nobody who has been in audio for longer than a week would use it for that. Maybe a cathedral microphone. Any time you want to record Bach in The Cathedral of Peter and Paul, you trot out this microphone. That would work, but it's unlikely. It's a specialist microphone and somebody must have had design notes or other information.

They may have an on-line forum.

Google.

Koz

[reubenstapes]

Hello

Yep, they are semi-detached; the hedge running on the right hand side of the photo of my property denotes the boundary.

“If you have one common wall, then yes, certainly. We had one computer install that was clearly audible on the other side of the wall and we had to take steps to isolate it, particularly since the other room had to record audio.”

Cheers.

[steve]

A slightly off-the wall solution: Get some tropical fish. The constant sound of the air pump will probably mask the LFN, but you will "like" the sound of the air pump because its restful humming reminds you that your beautiful fish are alive and well. (does your adjoining neighbour keep tropical fish?)

[kozikowski]

Yep, they are semi-detached

Oh, then it's easy. Tape the microphone to the common wall. Pick a spot roughly in the middle between the sides, top and bottom of the room. The effect should be magnified several-fold with that trick. As usual, two recordings, one with and one without.

I'm going with a refrigerator or freezer compressor. My sister has an older fridge that you can clearly hear rumbling in the basement under the kitchen when it's cooling. If you know which wall the kitchen is on, use that one.


I wonder about that aquarium thing. Have you ever seen an aquarium that didn't have a noisy pump? They exist, you just have to clean them more often. They feature fish that are not constantly racing two and fro to get away from the pump noise. They're a lot less entertaining. Much less action. Much more like nature.

So in order to avoid torturing the fish, you could just buy the pump and put it in a pail of water.

Koz

[reubenstapes]

Just waiting on a longer cable to get the microphone up to the wall itself, then hopefully, if you are right Koz, this will capture the sound. I’ll post up the results as and when I can get them.

Cheers.

[kozikowski]

It may capture more than that. You are experiencing the sound waves after the wall has had a chance to move the air in your house. Putting the microphone on the wall should record not only that sound, but also the overtones that normally wouldn't transmit to the air.

I still bet you find compressor or cooler noises.

Koz

[reubenstapes]

Well, this is it: a recording with the microphone firmly up against the dividing wall (I've been waiting to get the loudest night of LFN for weeks now and tonight was the night, the sound has been carrying through the house unabated); I have to say that I can detect no difference when using the Amplify then the Low Pass Filter with this recording compared to those recordings I have made when the microphone was sitting in the middle of the room, but maybe something was captured.

Steve: I did try an iPhone app that played soothing sounds to try and cover this f&*ck!n6 LFN, but when it came down to it, it was just noise on top of noise, but I appreciate the suggestion.

Anyway, I have certainly run out of ideas (looking at the Spectrogram (if I'm reading it correctly) there is plenty of LFN between the 300 and 0 mark but this could be the case with every recording when trying to capture ambient noise, I simply do not have the experience to do something constructive with this data if it does mean something.

Active LFN Mic Touching Wall.wav

(687.04 KiB) Downloaded 92 times

[kozikowski]

I did a simple amplify and analyze and there is a very significant bump at 19Hz -- just below where most people's hearing stops. It's the majority contribution in that sound clip. Nothing else comes close. You do have a lesser 49Hz bump which I attribute to the 50Hz power in your country.

If I listen on my killer sound system cranked to high volume I can hear a pulsing throbbing sound, but it's still not anything we can send to the housing authorities, for one thing, it's not very loud and for another, you need a killer sound system to hear it.

[time passes]

I pulled some magic. I filtered out everything above 30Hz and then jumped the pitch of the sound up 300%. Then Amplified again. That's the attached clip. Most houses do not rumble at 19Hz.

Koz

[kozikowski]

Now we need the control clip on a night without the rumble. Same settings so we do a direct comparison. Koz

[kozikowski]

Maybe someone was murdered and they hid the heart under your floorboards. Koz