The sounds houses make

Houses make some strange sounds. When you're a kid they're the sinister sounds from a horror movie; when you're an adult they're the even-more-sinister sounds of a potentially failing boiler (or are they?). Perhaps it's just curiosity, but I'd quite like to know what's causing the noises and why.

How? Sensitive microphones spread around the house, potentially coupled with infrasound and ultrasound sensors. Multiple microphones allows for triangulation and pinpointing of the source. Recordings could be uploaded and matched against an online library, for interpretation.

I suspect a lot of useful diagnostic information could be gleaned from some good sound analysis software and database, identifying when mechanical devices need maintenance. The concept could be applied to cars, household appliances, etc.