Annoying Hum

mheslep

Could be but I'd guess the variation is due to changes in the resonance frequency of one or both structures (HVAC on building, Russ's house-window) from temperature changes causing expansion-contraction.

BenG549

That's an interesting thought, what makes you think this would have large effect in this context? When studying environmental acoustics, we obviously spoke a lot about noise problems at dwellings and the effect of meteorological conditions on outdoor propagation, but we didn't talk, in this context, specifically about temperature changes really being that influential when changing the resonance of windows etc. (I accept that changing temperature will affect resonance, but not sure how much of an effect it would have on the interior noise level). Any knowledge or examples appreciated.

BobG

That is a cool app! I had to get it for my phone, too. I was measuring the frequency of the sound of my furnace and I can "see" my dog chewing on her rawhide bone.

mheslep

My relevant experience extends only to vibration tests on various mechanical enclosures for electronic equipment and the like. A temperature change of ~ 10C by itself is typically responsible for expansion of less than one part in a thousand or less, so no much effect should be seen there. But what did seem to happen is that some separate, but adjacent, rigid components in the structure, with their own resonances, would apparently via expansion compress each other and act as one rigid structure, and thus have a quite different resonance, up to an amplitude that re-disconnected the components. At least we would see different resonances exposed, and that was a hypothesis.

That hypothesis tends to match my observation of varying house resonances over temperature/humidity from aircraft going overhead, etc, and I've tended to chalk it up to wood frames, glass, drywall closing up, or opening, gaps. So for the house: all hypothesis, no test data.