Learn Hardcore Norwegian: Jeg synes det er vanskelig å sove når det er støy i nabolaget. - I think it is difficult to sleep when there is noise in the neighborhood.

Synes is used for personal opinions based on experience or feelings. In this sentence it’s like saying “I find / I think (based on my experience) it is difficult to sleep …”.

synes = “think” as in “in my opinion, from my experience”
tror = “believe / think” about something you don’t know for sure (a guess or belief)
tenker = “am thinking” (the mental process; planning, reflecting)

So you say:

Jeg synes det er vanskelig å sove. – I find it difficult to sleep.
but
Jeg tror han kommer. – I think / I believe he is coming.

Why do we say Jeg synes det er vanskelig å sove and not Jeg synes å sove er vanskelig?

The most natural pattern in Norwegian is:

Jeg synes det er + adjective + å + infinitive
→ Jeg synes det er vanskelig å sove.

This uses det as a placeholder (“I think it is difficult to sleep”), which sounds very natural.
Jeg synes å sove er vanskelig is not wrong grammatically, but it sounds unusual and a bit heavy in everyday speech. Norwegians almost always choose the det er … å … pattern in this kind of sentence.

What is the function of det in Jeg synes det er vanskelig å sove?

Here det is a dummy / anticipatory subject (a “placeholder” pronoun).

Literally: Jeg synes det er vanskelig å sove = I think it is difficult to sleep.
The real “thing” that is difficult is å sove (to sleep), but Norwegian prefers to put det in subject position and move å sove to the end.

This is very similar to English:

It is hard to sleep (not To sleep is hard in ordinary speech).

What is the function of det in når det er støy i nabolaget?

Again, det is a dummy subject, but now in the meaning “there is”.

Det er støy = There is noise (literally “it is noise”).
Norwegian normally needs some kind of subject even when English uses “there” as a fake subject.

So:

når det er støy i nabolaget ≈ when there is noise in the neighborhood.
You cannot say *når er støy i nabolaget; the det is required.

Why is it når and not da in this sentence?

Both når and da can mean “when”, but they are used differently:

når:
- for repeated / general situations (whenever)
- for present and future time
da:
- for a single event in the past

In this sentence, we are talking about a general situation (any time there is noise), so når is correct:

Jeg synes det er vanskelig å sove når det er støy i nabolaget.

If you describe one specific night in the past, you would use da:

I går syntes jeg det var vanskelig å sove da det var støy i nabolaget. – last night, when there was noise…

Why do we use å sove here, and not another form of the verb?

Å sove is the infinitive form of the verb sove (“to sleep”). After adjectives like vanskelig, lett, morsomt, kjedelig etc., Norwegian uses å + infinitive:

det er vanskelig å sove – it is difficult to sleep
det er lett å lære norsk – it is easy to learn Norwegian
det er gøy å reise – it is fun to travel

You cannot say *det er vanskelig sove – the å is required in this structure.

Why is it å sove and not og sove?

Å and og are two different words:

å = to (used before a verb in the infinitive)
- å sove, å spise, å snakke
og = and (joins words or phrases)
- jeg liker kaffe og te, å lese og å skrive

In this sentence we need “to sleep”, so we must use å:

vanskelig å sove = difficult to sleep

*vanskelig og sove is a very common learner mistake and is incorrect.

What is the difference between støy, bråk, and lyd?

All three relate to sound, but with different nuances:

støy – noise (often neutral or technical; any disturbing sound, eg. traffic noise, construction noise). Common in phrases like støy i nabolaget, støyforurensing (noise pollution).
bråk – louder, more chaotic, often human-made noise; can also mean trouble or fuss.
- Det er mye bråk i gata. – There’s a lot of racket in the street.
lyd – sound in general, not necessarily negative.
- Jeg hørte en lyd. – I heard a sound.

In this sentence, støy fits well because it’s about disturbing background noise in the neighborhood. Bråk would also be possible, but it can sound like more rowdy, chaotic noise (parties, shouting, kids, etc.).

What exactly does nabolaget mean, and why does it end in -et?

Nabolag means “neighborhood”. The form nabolaget is the definite singular: “the neighborhood”.

et nabolag – a neighborhood
nabolaget – the neighborhood

In the sentence you are talking about your (or some specific) neighborhood, not neighborhoods in general, so Norwegian uses the definite form:

støy i nabolaget ≈ noise in the neighborhood (around where I live).

Is the word order når det er støy i nabolaget fixed, or can I change it?

Inside this subordinate clause introduced by når, the normal order is:

[når] + subject + verb + (rest)
→ når det er støy i nabolaget

You generally do not invert the verb and subject in subordinate clauses, so forms like *når er det støy i nabolaget are wrong.

You can, however, move the whole clause:

Når det er støy i nabolaget, synes jeg det er vanskelig å sove.

In the main clause after that, you must follow the V2 rule (the verb synes comes in second position).

Should there be a comma before når in this sentence?

In modern Norwegian, when a short når-clause comes at the end of the sentence, it’s common (and correct) not to use a comma:

Jeg synes det er vanskelig å sove når det er støy i nabolaget.

If you put the når-clause at the beginning, you must use a comma:

Når det er støy i nabolaget, synes jeg det er vanskelig å sove.

So in the original word order, leaving out the comma is standard.

How would this sentence look in the past tense?

You need to change both the verb synes and er to the past:

Jeg syntes det var vanskelig å sove når det var støy i nabolaget.

If it’s about one specific time, you might also switch når to da:

I går syntes jeg det var vanskelig å sove da det var støy i nabolaget. – Yesterday I found it difficult to sleep when there was noise in the neighborhood.

Are there other natural ways to say “I find it difficult to sleep when there is noise in the neighborhood”?

Yes, some common alternatives are:

Jeg har problemer med å sove når det er støy i nabolaget. – I have problems sleeping when there is noise…
Jeg har vanskelig for å sove når det er støy i nabolaget. – I have difficulty sleeping when there is noise…
Det er vanskelig for meg å sove når det er støy i nabolaget. – It is difficult for me to sleep when there is noise…

Your original sentence with jeg synes det er vanskelig å sove is very natural and common, especially for expressing a personal opinion or experience.

How do you pronounce støy and nabolaget?

Approximate pronunciations (Bokmål, standard eastern accent):

støy:
- øy is like the vowel in British English “boy”, but with your lips rounded more.
- IPA: /stœʏ/ – one syllable.
nabolaget:
- na like “naa” in “naah”,
- bo like “bo” in “boat” (but shorter),
- la like “la” in “lava”,
- get is roughly “yet” but with a hard g at the start.
- IPA (roughly): /ˈnɑːbulɑːɡə/ or /ˈnɑːbulɑːɡet/ depending on dialect.

Main stress is on the first syllable: NA-bo-la-get.