Sounds like someone drowning or something, at some points...
Hard to explain if she's already moved all around the house...
-Does your wife carry a water bottle around? (maybe the sloshing could explain it)
-Is the laptop liquid cooled?
-Is your in-laws house near water? (maybe the laptop microphone is sensitive to the frequency of the noises produced by/near the water, while the telephone receiver/human ear isn't)
-Is your in-laws house made of water beds?








