How to recorder a low noise, for someone with no knowledge

marcooo

New member
Hi everybody!
I need an advice on how to recorder a really low frequency noise that I have in my bedroom and I didn´t understand where it comes from.
Giving that I am the only one that hears that I would like to record it so I´ll have the evidence and maybe I can ask for an “inquiry”.

I´m not an expert and I don´t have any equipment, I would like to buy (or rent) a ZOOM H4n, stand alone machine that is easy to use (for someone like me).

But my question is:

Can it be so sensible to record a low frequency noise?

Thanks in advance
 

keith.rogers

Bobby'); DROP TABLE USER
Most good condenser mics should pick up a sound down to about 20Hz (a frequency most folks could only feel). Oddly, the few "handheld" digital recorder manuals I just searched and scanned do not specify the frequency response of the built-in microphones! The Zoom H4n Pro specs the mic input preamps at 20Hz-20kHz, though, so I expect the built-in mics have the range, but they may not be flatteringly flat, is all I can surmise for the lack of information.

If it's subsonic noise, you'd need something external spec'd to pick up that lower level frequency if it's audible, or if it's not, you're talking about something like a seismograph!
 

TalismanRich

Well-known member
You might check out this recent thread. This person was trying to record very low frequency noise. Depending on the frequency, many mics may not pick the noise well due to low freq roll off. He ended up using a speaker to pick up the noise. It worked, we were able to see the low frequency in a spectrum plot.

Mic for low vibration/bass-y noise
 

marcooo

New member
TalismanRich

thanks, is precious resource of information

keith.rogers
thanks.
maybe I'm wrong but I suppose that if I can easly hear it (in the night for example) the fq is at least 40-50hz
 

marcooo

New member
Hi everybody!
I tried to record the sound with a friend but no way. The only thing I understood is that is about 50hz.
No way to stop it, i tried also with some bass traps beside the bed and into the wardrobe but nothing changed.

Now i was wondering: is possible to create a "counter sound" with the same frequency that sends the sound to a couple of speakers behind the bed ?
In theory it kills the vibration and at least in the night i can sleep

Is it possible? Or better: is it possible to do by me?
Maybe with a frequency generator and a subwoofer?

Sorry I hope that i didn't say too many silly things.

Thanks in advance
 

TalismanRich

Well-known member
The problem with trying to generate a counter sound is that these things operate by trying to reverse the phase of a signal so that the sum is close to 0. This works with headphones, since the signal is at a constant set distance from your eardrum, hence it is very controlled. Trying to do that in a room can cause both cancellation and reinforcement since it will be bouncing around the room. Read up on Room Modes. Depending on the source and the room size, you could be situated in a reinforcing area.

Have you tried ear plugs? A good pair of NRR33 ear plugs can really knock down sound levels like that. They aren't that expensive, certainly worth a try.
 

rob aylestone

Well-known member
The first thing is to determine how loud it is above the noise floor in the room - have you got a phone that records? iPhones have pretty decent audio response - so if you put the phone in the room and then do a recording, you could bring that recording into some software - audacity is free, try that. You can use it to boost the levels - which will of course generate hiss - but your interest is in the bass end - so you might see something. Before you spend any money, try this. Realistically, low end noises can be transmitted through the building structure. I have a low rumble in my office which comes from the chip making machine in the pizza shop next door - it's bolted to their wall, and the rumble get's across a corridor = via the concrete floor, and comes up in my office. Yours could be this kind of thing - any HVAC units on the wall near you?
 

keith.rogers

Bobby'); DROP TABLE USER
If it’s a sound in the recording, then noise reduction software, if not something more basic like a high-pass-filter, may be the best solution after it’s been recorded. Post a recording so we can hear it and see what might work.
 

TalismanRich

Well-known member
From what I gathered in the OP's posts, he's not trying to record anything, he's trying to eliminate environmental noise that is interfering with his everyday life. The recording was to try to gather evidenced, so he might be able to get the problem resolved.
 
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keith.rogers

Bobby'); DROP TABLE USER
From what I gathered in the OP's posts, he's not trying to record anything, he's trying to eliminate environmental noise that is interfering with his everyday life. The recording was to try to gather evidenced, so he might be able to get the problem resolved.
I probably forgot what this was about....

Still, a recording would be interesting. You could try some manual noise reductions after isolating the noise, both in a DAW and then playing it in a room to see if it worked.

I do think the at it would be difficult to do in real-time unless the sound is extremely uniform.
 

spantini

COO of me, inc.
My top floor apartment has a low frequency vibration from the roof-mounted HVAC units. It's barely audible and I don't feel it at all unless I place a hand or other body part against a wall. There are, however, several ceiling fixtures (lighting and fans) which emit louder buzzing sounds due to the HVAC units and they are quite annoying. I have placed wooden shims between these fixtures and the ceiling to eliminate their buzzing. None of this is felt or heard in my bedroom studio 15-ft. away.
 

marcooo

New member
thanks everybody for the answers
thanks @spantini but my situation is different. First floor.
@TalismanRich yes is what I want to do. TO recorder to have an eveidence. I understood your answer and actully I what I thought, too complicated to do, basically impossible. And I just ordered better ear plugs (I have foam ones 32db but they are unstable)
@rob aylestone thanks, I know that can be a vibration that runs up on the building structure. And a HVAC unit can be the reason of that... the problem is that I didn´t find it.

Now I have a sound level meter that gives me 31,5 db on average in the night. Trying to understand the frequnecy I can say that is around 60 hz.
Looking at the Human Hearing Threshold:

nc-curves.png

Around 60 hz and 30 db is actually is the beginning of the hearing range.

But having no specific studies, just acustic basics.
So what do you think about that?

With those "evidences" I´ll ask the specific council's office to do something, but I have no idea if my request can be accepted (I already talked with them but is a long story).

Thanks again
 
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