Lyden er skarp, så jeg lukker vinduet.

-en is the definite suffix for many common-gender nouns in Danish.

• en lyd = a sound
• lyden = the sound

So Lyden er skarp is literally The sound is sharp.

skarp literally means sharp and is commonly used metaphorically for sounds, just like in English:

• en skarp lyd = a sharp/piercing sound
  You might also hear related adjectives depending on nuance: høj (loud), skinger (shrill), gennemtrængende (penetrating).

Because skarp is an adjective describing the noun lyden (a common-gender noun). In Danish, predicate adjectives agree with gender/number:

• common gender singular: skarp
• neuter singular: skarpt (e.g., Et signal er skarpt)
• plural: skarpe (e.g., Lyde er skarpe)

Both can be correct, but they emphasize slightly different structures:

1) ..., så jeg lukker vinduet.

• så behaves like a conjunction meaning so, and the clause often keeps normal main-clause order (subject before verb): jeg lukker.

2) ..., så lukker jeg vinduet.

• Here så is often felt more like an adverb meaning then/so, and Danish main clauses typically use V2 word order (finite verb in position 2), giving lukker jeg.

In practice, both occur; many learners find så lukker jeg ... especially common in spoken Danish.

Because the sentence consists of two clauses:

• Lyden er skarp (clause 1)
• så jeg lukker vinduet (clause 2)

Danish commonly uses a comma to separate clauses, especially when one clause follows another as a consequence.

lukker is present tense of at lukke (to close/shut). It can mean:

• I close / I’m closing (context decides)

Past tense:

• jeg lukkede vinduet = I closed the window

Perfect:

• jeg har lukket vinduet = I have closed the window

vindue is a neuter noun: et vindue = a window.
The definite form takes -et:

• et vindue = a window
• vinduet = the window

So jeg lukker vinduet means I close the window (a specific one).

They overlap, but usage differs:

• at lukke = to close/shut (very general: doors, windows, boxes, apps, eyes, etc.)
• at stænge = to shut/close (often sounds a bit stronger or more formal; also used in fixed expressions like butikken er stængt = the shop is closed)

For a window, lukke is the most neutral, common choice.

Yes, but it changes nuance:

• lyden = the sound (neutral; could be pleasant or unpleasant)
• støjen = the noise (typically unpleasant/annoying)

So Støjen er skarp, så jeg lukker vinduet suggests it’s specifically noise rather than just a sound.

A rough guide (varies by accent):

• lyden: the y is a front rounded vowel (not English oo or ee), and d here is often a soft Danish d (very light).
• skarp: sk is like sk in English sky; the a is fairly open.
• vinduet: stress on vin-; the ending -uet is reduced in fast speech, often sounding like a quick, softened ending rather than clearly separated syllables.