Infrasound source

[LRJohnston]

What could be producing this infrasound in my home? (see image - 2 & 4 Hz around 75dB, 7 & 9 Hz about 60dB)

It's a residential neighborhood and there are no industrial or commercial buildings for miles. Location is KC suburbs - no windmills nearby. HVAC was not running when this was recorded.

 

[GregLocock]

Given the likely frequency response of your phone, I am rather dubious of the accuracy of that recording. There is no need for a mic to be sensitive below 20 hz, if it is sensitive to that it will waste an enormous amount of dynamic range on signals of little interest. However, you may have a pressure sensor as well.

Did you make recording while holding the phone, or with it laying on a solid structure, preferably lying on a piece of foam?



Cheers

Greg Locock


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[LRJohnston]

The mic allegedly can be accurate down to 10 hz - but only guaranteed to 20 hz. The mic was in a stand on a solid structure but not on foam.

There could certainly be some error in the exact frequencies and dB levels, especially below 10 hz. However, I can tell you there are physical sensations that come along with this infrasound that is presenting itself and it is a problem that I need to figure out. So, suggestions for identifying and pinpointing a possible source are what I'm hoping for here.

 

[GregLocock]

So you are several octaves below what any of the spec mentions. Most likely sources if it is not industrial are some form of road noise. But it could be vortices off a tall building, a tree, etc etc. If you had three mics that actually worked down to 1 Hz you could use them to triangulate the noise.

Cheers

Greg Locock


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[LRJohnston]

The mic I have was recommended by a sound engineer. Do you have recommendations for some that work down to 1 Hz?

 

[GregLocock]

Well, I've never done infrasound, 20 Hz is my lower cutoff for sound. You need both a mic cartridge, a conditioning amp, and a measuring system that are all capable down to 0.5Hz say. that is your entire measurement chain has to be capable.

Here's an example of an integrated SLM which claims to go to 1 Hz... claims Type 1, ie lab grade, but no specs.

https://www.sagetechnologies.com/pr...rs/42-rion-nl-62-infrasound-sound-level-meter

Cheers

Greg Locock


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