I'm on the 1st floor and I occasionally hear a loud popping sound coming from the
Second floor. On the 2nd floor I removed existing hardwood and screwed on the
3/4" plywood to the joists, to eliminate a previous squeaky floor. The screwing was done
Months ago.


So what would cause the plywood to make popping sounds ?
And what can be done to fix it?

All wood shrinks and swells from a loss or gain of moisture. Humidity is moisture in vapor form.

Consistent humidity levels keeps wood from shrinking or swelling.