Learn Hardcore Norwegian: Hun sier at hun ikke tåler mer støy i huset i kveld. - She says that she cannot tolerate more noise in the house tonight.

In a main clause, the verb goes in second position (V2), so you say:
- Hun tåler ikke mer støy.
In a subordinate clause (after at, fordi, som, etc.), the pattern is:
subject + adverb (like ikke) + verb

So you get:

at hun ikke tåler mer støy …
(subject hun → adverb ikke → verb tåler)

at hun tåler ikke … is ungrammatical.

If I drop at, does the word order change, or do I still say hun ikke tåler?

You keep the subordinate-clause word order, even if you drop at:

Natural speech: Hun sier (at) hun ikke tåler mer støy …

Saying Hun sier hun tåler ikke mer støy … is heard in some dialects, but standard Norwegian teaching and writing keep:

hun ikke tåler (subordinate order), not hun tåler ikke.

Why do we repeat hun in Hun sier at hun ikke tåler …? Can we say Hun sier at ikke tåler …?

You must repeat hun. Norwegian is not a “drop-subject” language like Spanish or Italian. Every finite clause normally needs an explicit subject.

So:

Correct: Hun sier at hun ikke tåler mer støy …
Incorrect: Hun sier at ikke tåler mer støy …

Each clause needs its own subject:

Main clause: Hun sier …
Subordinate clause: (at) hun ikke tåler …

What exactly does tåler mean here? Is it physical tolerance or more like “can’t stand”?

tåle means to tolerate / to endure / to stand.

It can be:

Physical: Jeg tåler ikke melk. (I’m lactose intolerant.)
Mental/emotional: Jeg tåler ikke mer støy. (I can’t stand any more noise.)

In this sentence it’s emotional/mental tolerance, close to English “can’t stand” or “can’t take any more”.

Could we say Hun sier at hun ikke orker mer støy instead of tåler? What’s the difference?

Yes, you can:

Hun sier at hun ikke orker mer støy …

orke focuses more on having the energy / strength / patience:

ikke tåler = she cannot tolerate more noise (it’s too much for her in general).
ikke orker = she doesn’t have the energy / strength to deal with more noise.

In many situations they overlap and both sound natural. tåler is slightly more neutral; orker can feel a bit more emotional/exhausted.

Why is it mer støy and not flere støy?

Because støy (noise) is treated as an uncountable (mass) noun in Norwegian.

For uncountable nouns (water, noise, money) you use mer:
- mer støy (more noise)
- mer vann (more water)
For countable plural nouns you use flere:
- flere biler (more cars)
- flere lyder (more sounds)

So flere støy is wrong; you would need a countable noun:
flere lyder, flere lyder av musikk, etc.

Why is støy indefinite here and not støyen?

Indefinite støy means noise in general / any noise.

Hun tåler ikke mer støy = she can’t stand any more noise.

Definite støyen refers to some specific, identifiable noise:

Hun tåler ikke mer av støyen.
= She can’t stand any more of the noise (that we both know about).

In your sentence, the focus is general noise level in the house tonight, so the indefinite form støy is natural.

Why is it i huset and not på huset or hjemme?

i huset literally means in the house, i.e. inside the building.

i is the normal preposition for being inside something:
- i huset, i bilen, i butikken

på huset would mean on the house (on the roof, on the outer surface) or idiomatically free of charge in some contexts (e.g. a drink på huset).

You could also say:

Hun sier at hun ikke tåler mer støy hjemme i kveld.

That is more like at home rather than literally in the house. All are possible; i huset is just the most literal.

What does i kveld literally mean, and can I move it earlier in the sentence?

i kveld literally means in the evening, but idiomatically this evening / tonight.

You can move it, but some positions sound more natural than others:

Original: Hun sier at hun ikke tåler mer støy i huset i kveld.
Also natural: Hun sier at hun ikke tåler mer støy i kveld i huset. (a bit marked)
Or: Hun sier at hun i kveld ikke tåler mer støy i huset. (emphasizing tonight)

The most neutral is usually to keep i kveld near the end, after i huset, as in the original sentence. Time and place adverbials are quite flexible, but changing the order can change what you emphasize.

The verbs are in the present tense (sier, tåler), but the situation is about tonight. Why don’t we use a future form?

Norwegian often uses present tense with future meaning, especially when the future time is clear from context:

i kveld (tonight) tells us it’s about the future.

So:

Hun sier at hun ikke tåler mer støy i huset i kveld.
= She says she can’t stand more noise in the house tonight.

You could say:

Hun sier at hun ikke kommer til å tåle mer støy i huset i kveld.

This is a bit heavier and emphasizes the prediction; the simple present is more natural and common here.

Why do we use hun and not henne in this sentence?

hun is the subject form (nominative), and henne is the object form.

Subject: Hun sier … (She says …)
Object: Jeg ser henne. (I see her.)

In your sentence, both instances of hun are subjects of their clauses:

Main clause subject: Hun sier …
Subordinate clause subject: at hun ikke tåler …

So hun is correct; henne would be wrong here.