Locate low frequency sound source

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fizzychicken

290 posts

Ultimate Geek

#194923 30-Mar-2016 10:33

For the past month the inside of my house has been plagued with a low frequency hum/vibration. If you imagine living next to a mains power station, its that kind of power hum. It can be heard in the garden and areas surrounding the house. I can say that I experience it louder in a specific area outside...however there is nothing there, no power lines or pipes etc. I have tried cutting the power and water to the building and it still occurs which makes me think that it is coming from one of my neighbours. Only think is that at enough distance from the house it gets hard to distinguish due to external noise. I am looking to try and find a way to record and locate the source of the sound. Doe anyone have any experience in attempting to record low frequency noise or know where such equipment could be obtained?

https://keybase.io/fizzychicken

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1024 posts

Uber Geek

#1522685 30-Mar-2016 10:43

Get youself a parabolic microphone, there used to be lots of them as kids toys for about $10, seem they have gone up in price.

http://www.jaycar.co.nz/Outdoors-%26-Auto-Products/Camping-%26-4WD-Accessories/General-Camping/%22Spy%22-Parabolic-Microphone-with-Recorder-and-8x-Magnifier/p/AM4040

This will give you an indication of what direction the noise is coming from ( assuming it is not too low for the amplifier circuit ) and hopefully it makes it easier to narrow down.

Regards

John

I know enough to be dangerous

MadEngineer

2168 posts

Uber Geek

Trusted

#1522688 30-Mar-2016 10:48

Contact your council as this kind of query isn't uncommon

Journeyman

726 posts

Ultimate Geek

#1522693 30-Mar-2016 10:57

Your brain is overheating.

Seriously though, you may be one of those people who swear they can hear The Hum:

https://en.wikipedia.org/wiki/The_Hum

http://www.livescience.com/38427-the-hum-mystery-taos-hum.html

http://www.dailymail.co.uk/sciencetech/article-2380368/Can-hear-The-Hum-How-1-50-world-affected-low-droning-noise-scientists-explain.html

There's a bunch of big generators near my house at the moment while Vector does some work. Maybe there are some in your suburb too?

gzt

11539 posts

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Lifetime subscriber

#1522710 30-Mar-2016 11:46

24 hours / 7 days ?

Batman

Mad Scientist
22549 posts

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#1522713 30-Mar-2016 11:52

Maybe there's fluid on your ear?

Involuntary autocorrect in operation on mobile device. Apologies in advance.

fizzychicken

290 posts

Ultimate Geek

#1522752 30-Mar-2016 12:52

yup 24/7

I've ruled out most local things, tried a bunch of apps on my phone but while that can prove the sound exists, as it peaks on the history chart in the trouble areas, it doesn't help me pin point a source.

Went to local jaycar just now but they didnt have much that would help, they did have a fluorescent light that was emitting a very similar sound which was handy when explaining what the sound was (no lights at home that could be causing the issue)

https://keybase.io/fizzychicken

gzt

11539 posts

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#1522775 30-Mar-2016 13:21

Any neigbours affected?

jmh

458 posts

Ultimate Geek

#1522777 30-Mar-2016 13:29

Probably a good idea to get the council out. While detection meters are quite cheap, the directional ones that pinpoint the source are quite pricey. They probably have them as standard. Also, although you have no powerlines there might be underground wiring. - contact the energy company to see if they'll come out and measure.

You could also try this guy if you are in Auckland: http://www.safespace.net.nz/ I had him round and he was able to pinpoint a number of sources of transmitting frequencies.

Batman

Mad Scientist
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#1522802 30-Mar-2016 14:18

gzt: Any neigbours affected?

Is the noise present in other suburbs?

Involuntary autocorrect in operation on mobile device. Apologies in advance.

gzt

11539 posts

Uber Geek

Lifetime subscriber

#1522815 30-Mar-2016 14:42

jmh:
Probably a good idea to get the council out. While detection meters are quite cheap, the directional ones that pinpoint the source are quite pricey. They probably have them as standard. Also, although you have no powerlines there might be underground wiring. - contact the energy company to see if they'll come out and measure.

You could also try this guy if you are in Auckland: http://www.safespace.net.nz/ I had him round and he was able to pinpoint a number of sources of transmitting frequencies.

OP issue is audio rather than some other disturbance.

lapimate

322 posts

Ultimate Geek

Trusted

#1522847 30-Mar-2016 15:55

SATTV: ... http://www.jaycar.co.nz/Outdoors-%26-Auto-Products/Camping-%26-4WD-Accessories/General-Camping/%22Spy%22-Parabolic-Microphone-with-Recorder-and-8x-Magnifier/p/AM4040 ...

Low frequency sound with its long wavelength is difficult to direction-find (think floor subwoofer); even if that mic is reasonably sensitive down to 50Hz unfortunately the tiny parabolic reflector on that mic would probably be next to useless in terms of direction-finding for 50Hz which has a wavelength a bit less than 7metre.You would also probably need a (band) filter to select around the approximate frequency you are detecting. You might have more success mapping the sound field around the house to see if you can discover which side it is loudest and go from there.

I have observed a low frequency noise/hum from an (tyre) air-compressor about 500metre away in suburbia.

Aredwood

3885 posts

Uber Geek

#1522874 30-Mar-2016 16:35

Ripple controller, pilot relay, or electricity meter if it is not a smart meter. Often these things remain switched on even when the power is off.

jmh

458 posts

Ultimate Geek

#1522876 30-Mar-2016 16:45

gzt:
jmh:

Probably a good idea to get the council out. While detection meters are quite cheap, the directional ones that pinpoint the source are quite pricey. They probably have them as standard. Also, although you have no powerlines there might be underground wiring. - contact the energy company to see if they'll come out and measure.

You could also try this guy if you are in Auckland: http://www.safespace.net.nz/ I had him round and he was able to pinpoint a number of sources of transmitting frequencies.

OP issue is audio rather than some other disturbance.

Other disturbances can cause audio, e.g. through vibration

SATTV

1024 posts

Uber Geek

#1522931 30-Mar-2016 20:01

lapimate:

SATTV: ... http://www.jaycar.co.nz/Outdoors-%26-Auto-Products/Camping-%26-4WD-Accessories/General-Camping/%22Spy%22-Parabolic-Microphone-with-Recorder-and-8x-Magnifier/p/AM4040 ...

Low frequency sound with its long wavelength is difficult to direction-find (think floor subwoofer); even if that mic is reasonably sensitive down to 50Hz unfortunately the tiny parabolic reflector on that mic would probably be next to useless in terms of direction-finding for 50Hz which has a wavelength a bit less than 7metre.You would also probably need a (band) filter to select around the approximate frequency you are detecting. You might have more success mapping the sound field around the house to see if you can discover which side it is loudest and go from there.

I am fully aware of wavelengths etc however even a cheap parabolic microphone has an amazing front to back ratio.

I did not want to get too technical as while this is a forum for geeks we all have our own strengths and weaknesses.

If you have a larger parabola you will get better results, if you had a prime focus satellite dish that could also work but might be too good as it may hear something too far away.

You could also add a variable frequency oscillator to adjust the the frequency to make it easier to hear, i.e. make 50Hz 250Hz

BTW the wavelink of 50Hz is 6000000 meters not allowing for any velocity factor in free air.

John

I know enough to be dangerous

RunningMan

5997 posts

Uber Geek

#1522939 30-Mar-2016 20:35

SATTV:

[snip]

BTW the wavelink of 50Hz is 6000000 meters not allowing for any velocity factor in free air.

Only if that sound is travelling at the speed of light ;-)

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