What's the plural form of soundproofing? Here's the word you're looking for.
Answer
The noun soundproofing can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be soundproofing.
However, in more specific contexts, the plural form can also be soundproofings e.g. in reference to various types of soundproofings
or a collection of soundproofings.