The natural understanding is that "little silvery laugh" is "little, silvery laugh": little is interpreted as an adjective on "laugh", rather than as an adverb modifying "silvery".
If a native speaker wants to invoke the adverb meaning, the most natural way is to transform the sentence:
I heard a laugh that was a little silvery.
There is no way to pronounce "a little silvery laugh" which will convey the above alternative meaning unambiguously.
Even if you say "little silvery" without any pause in between, and then insert a pause before laugh, it does not reliably convey this meaning: some listeners will continue to interpret it as "a little, silvery", whereas some will accept that "a little silvery" is a unit. And pretty much all listeners will find the speech unnatural.