Learn Swedish: Han kastade sleven på disken med ett tyst muttrande. - He threw the ladle on the counter with a quiet grumbling.

In Swedish, you can turn a present participle into a noun to describe a continuous or repetitive action. When you do this, it always becomes an uncountable neuter noun, which is why it takes the article ett. Here, ett muttrande refers to the ongoing act of grumbling.

Since muttrande describes an action, why do we use the adjective tyst instead of an adverb?

Because muttrande has been turned into a noun in this sentence, and nouns are modified by adjectives, not adverbs. Since all nominalized present participles are neuter words, the adjective gets the neuter -t ending to match, resulting in ett tyst muttrande.

I thought disken meant the dirty dishes. How does it mean the counter here?

The noun en disk has two distinct meanings. It refers to the dishes waiting to be washed, but it also means a physical counter, like a kitchen counter, a shop counter, or a bar. The context of throwing a ladle onto a surface tells us it is a kitchen counter here.

Is ett muttrande uncountable, even though it uses the article ett?

Yes! These nominalized verbs describe an ongoing activity rather than countable objects, so they are generally uncountable. The word ett here functions as the indefinite article 'a' (a quiet grumbling), pointing to a general instance of the activity rather than the number one.