I lie in bed drifting of to sleep but I hear random clicking and creaking noises coming from somewhere in the house.
What is actually producing those noises? I’m aware with heat and cooling, joins expand and retract but to produce a quick clicking noise, I would expect it would require some velocity between two objects colliding. How are these noises made when nothing of significant scale is moving?
In: Physics
Put your hand on a flat, smooth surface, applying a light pressure. Then, very slowly, try to drag your had across the surface.
For a split moment, your hand will have moved, but the skin contacting the surface will not have moved. You should feel this as a light tugging feeling on the skin of your palm. Your skin is building up potential energy like a tiny spring.
Then, all at once, the friction between your skin and the surface gives way and your skin snaps back to meet your hand. The energy of the “spring” has been released all at once. If done correctly this might make a very quiet sound.
Basically, all of the rigid components of your house are doing this constantly. The expanding and contracting cause them to slide past one another at joints, but just like your hand, the initial friction prevents them from moving right away. Instead, they build up energy like tiny springs, until they’ve built up enough to overcome the friction. The sudden “snap” is audible as a cracking noise.
The actual amount of movement is tiny. Imperceptibly tiny. But it’s definitely happening.
Part of why they seem so loud is that the big, flat walls of your home act like the body of a guitar or the shell of a drum, carrying the vibrations from the source and helping them get transmitted to the air, making them far more audible. If your house was just framework with no finished walls you probably wouldn’t hear much anything.
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