Okay, for about the last three months my Honey has maintained that she can hear sounds in the bedroom that sound like a snapping noise, but I cannot hear it. We are both 62 years and I am aware that our hearing capabilities may change with age. I have asked her to try and locate the source of the sound and it appears to be coming from the ceiling of our bedroom. It is a one story house with just the attic and roof above it. I might add that we have "smart meters" for both gas and electric that were installed last year. Is there a portable device of some sort that I can use to detect or record these sounds to prove or disprove her concern and mitigate the issue? I do not know if these sounds are high or low frequency but I sure cannot hear them!
In theory any microphone that responds to those frequencies you can't hear ought to be able to be used to record them, so long as the recording media can store them as well. For standard CD-quality digital recordings the highest frequency you can store with any kind of fidelity is around 22KHz (the Nyquiist frequency for 44.1KHz, the CD standard), which should be well above your hearing range but is possible for people to hear.
A "snapping" noise tends not to be very low frequency so I think it's safe to assume that any sounds are in the higer range.
The trick, of course, is going to be detecting that those sounds were recorded if you can't hear them. One way is to use a frequency spectrum analysis tool (there's a spectrum view in the free software Audacity that should be helpful here) to visually look at what is happening across the audio spectrum. Another way, far more low-tech, is to ask someone who can hear them what they hear.
There are portable recorders available, both with built-in microphones and which accept external ones, but I don't know which ones if any have the frequency response you're looking for.
Going by its description, a "snapping noise" is almost certainly easily within range of human hearing. It can't be a bass noise because that would be described as a thump. It can't be too high frequency because it'd be described as some piercing shrill sound. Anything above 18 KHz will definitely not sound like a "snap". I would therefore guess that this sound is in fact within frequency range of microphones; the only concern I'd have is whether the microphone is sensitive enough to pick it up if it's very quiet.