Sound is usually found as a transitive verb "sound the alarm" or immediately followed by an adjective or adjective phrase "it sounds like it's coming from the attic".

It's almost never seen naked except when talking about "how something sounds" which follows from the latter usage above.

We're beyond grammar and in the weeds of idiomatic usage, but hopefully it's clear to English speakers that "it sounds" full stop is so eyebrow-raising that it should normally be avoided.

Unless you're being clever or meta, as the title here is, so it gets a pass in my opinion.

If it were written idiomatically, though, it'd be "images that make sounds".

I agree with you. I guess "sound on its own" was not the best explanation either, compared to the transitive one you provided.