The sanding process is underway.
An aggressive sandpaper was used to “hog” through the old brittle, but rubbery carpet pad. I call this kind of sandpaper “shards of rock, bonded to paper” as the grit size is about 1/8″ and very sharp and angular.
Remember, always wear hearing protection and a breathing mask. I do not recommend those paper throw away dust masks. Spend $20 for a good fitting mask with HEPA filters-HEPA filters are generally pink color coded.