Can't find this info anywhere

So, the interent is being unhelpful. Figured someone on here might know.

I'm looking for foam for a fursuit, but not upholstry foam or anything similar. Due to heating issues, I was hoping to find some of the foam that is used in speakers and headphones. You know, the type that lets air through very easily (aka, let's you hear the sound, but protects the speaker from dust or cushions your ears).

I can't find what it's called, though. All my searches yield dampening materials (used in sound-blocking), which is very much what I don't want.

Any clue what the speaker foam is called? Or maybe where to buy it from in bulk/sheets? Thanks in advance!