Crec que avui hi ha menys soroll a l'edifici.

Catalan often leaves out subject pronouns when they are already clear from the verb ending. Crec already means I think or I believe, so jo is not necessary.

You could say Jo crec que... for emphasis, but the neutral, natural version is just Crec que...

Crec is the 1st person singular form of creure, which means to believe or to think.

So Crec que... means I think that... or I believe that...

In this sentence, it sounds like the speaker is giving their impression or opinion.

Here que introduces a subordinate clause, just like that in English:

• Crec que avui hi ha menys soroll... = I think that today there is less noise...

In English, that is often omitted: I think today there is less noise... In Catalan, que is normally kept after verbs like crec, penso, sé, diu, and so on.

Avui means today.

It is placed near the beginning of the clause because it sets the time frame for the whole statement:

• Crec que avui hi ha menys soroll... = I think that today there is less noise...

Catalan word order is fairly flexible with adverbs, but this position sounds very natural.

Hi ha is the standard Catalan way to say there is or there are.

Examples:

• Hi ha un llibre = There is a book
• Hi ha llibres = There are books
• Hi ha menys soroll = There is less noise

So in your sentence, hi ha menys soroll means there is less noise.

In hi ha, hi is part of the fixed existential expression meaning there is / there are.

Historically and grammatically, hi is a locative pronoun, something like there. But for a learner, the most useful thing is to treat hi ha as a whole chunk meaning there is / there are.

So it is best to learn:

• hi ha = there is / there are

rather than trying to translate hi separately every time.

Because soroll means noise, which is usually treated as an uncountable noun, like noise in English.

So:

• menys soroll = less noise

If you used sorolls, that would mean noises, which is possible in some contexts, but it is less natural here. The sentence is talking about the general amount of noise, not separate individual noises.

Because soroll is being used in a general, uncountable sense.

Compare:

• Hi ha soroll = There is noise
• Hi ha menys soroll = There is less noise

This is similar to English, where you also usually say there is noise, not there is the noise, unless you mean some specific noise already known to both speaker and listener.

A l'edifici means in the building or at the building, depending on context.

It is made of:

• a = a preposition that can mean to, at, or in
• l' = the form of the definite article before a vowel
• edifici = building

So:

• el edifici is not correct
• l'edifici is the correct form before a vowel

After a, you get:

• a l'edifici

Catalan shortens the definite article before words beginning with a vowel.

So:

• el llibre = the book
• l'edifici = the building

The apostrophe shows that the article has been reduced from el to l' before the vowel sound.

Not completely. Catalan allows some flexibility, especially with adverbs like avui and place phrases like a l'edifici.

The given order is very natural:

• Crec que avui hi ha menys soroll a l'edifici.

But other orders can also work, depending on emphasis, for example:

• Crec que hi ha menys soroll avui a l'edifici.
• Crec que a l'edifici avui hi ha menys soroll.

The original sentence sounds neutral and idiomatic. It first gives the opinion, then the time, then the existence of less noise, and finally the location.