bakkati neomu sikkeureowoseo changmuneul dadasseoyo.

이 is the subject particle. In this sentence, 바깥이 means outside or the outside and is treated as the thing that has the property 시끄럽다 (to be noisy).

So the first part is literally:

• 바깥이 너무 시끄러워서 = because outside was so noisy

Korean often marks the thing being described by an adjective with 이/가.

Because 창문 is the object of the verb 닫았어요 (closed).

• 을/를 marks the direct object
• 이/가 marks the subject

So:

• 창문을 닫았어요 = (I) closed the window

The window is the thing being acted on, so 을 is correct.

시끄럽다 is the dictionary form meaning to be noisy.

To connect it to a following clause with the meaning because or so, it changes to 시끄러워서.

The steps are:

• dictionary form: 시끄럽다
• informal stem change: 시끄러워
• connective ending: -서
• result: 시끄러워서

This is a very common pattern with ㅂ-irregular adjectives:

• 덥다 → 더워서
• 어렵다 → 어려워서
• 시끄럽다 → 시끄러워서

Here, -아서/어서 means because or so. It connects a reason to a result.

So the structure is:

• 바깥이 너무 시끄러워서 = because it was so noisy outside
• 창문을 닫았어요 = I closed the window

Together: Because it was so noisy outside, I closed the window.

This pattern is very common in Korean for natural cause-and-effect statements.

Both can express cause/result, but they work differently.

• -아서/어서 attaches directly to the first verb or adjective
• 그래서 is a separate word meaning so / therefore

Compare:

• 바깥이 너무 시끄러워서 창문을 닫았어요.
• 바깥이 너무 시끄러웠어요. 그래서 창문을 닫았어요.

Both are natural. The first one is smoother and more connected as one sentence. The second one feels like two separate sentences.

Literally, 너무 often means too or excessively, as in too much.

So here, 너무 시끄러워서 is most naturally understood as:

• because it was too noisy
• or because it was so noisy

In everyday Korean, 너무 is also often used like very, especially in casual speech. But in a sentence with a result like closing the window, the stronger meaning too/so fits very well.

Korean often omits subjects when they are obvious from context.

So 창문을 닫았어요 literally just says closed the window, but in natural English we supply the subject:

• I closed the window

In Korean, if the speaker is clearly talking about their own action, saying 저는 or 내가 is often unnecessary.

닫았어요 is in the polite standard style, often called 해요체.

It is:

• polite
• common in everyday conversation
• appropriate in many normal situations

The verb comes from 닫다 (to close), and in past tense polite form it becomes 닫았어요.

Compare:

• 닫았어요 = polite
• 닫았어 = casual/informal
• 닫았습니다 = more formal

Because the speaker is describing something they already did.

• 닫았어요 = closed
• 닫아요 = close / am closing depending on context

So this sentence describes a completed action: it was noisy outside, and as a result, the speaker closed the window.

Sometimes, yes, but they are not always identical in tone or usage.

• 바깥 often feels like outside as a place or area
• 밖 often means outside, but also appears in other meanings like except or only

In this sentence, 바깥이 너무 시끄러워서 sounds natural.
밖이 너무 시끄러워서 may sound less natural to many learners’ ears in this exact sentence.

So for this example, 바깥 is a good word to remember.

The basic Korean order here is:

reason + result

• 바깥이 너무 시끄러워서 = reason
• 창문을 닫았어요 = result

That is the most natural order for this sentence.

You could also make two sentences:

• 바깥이 너무 시끄러웠어요. 그래서 창문을 닫았어요.

But within one sentence, the order usually stays as reason first, action second when using -아서/어서.

In casual speech, it becomes:

바깥이 너무 시끄러워서 창문을 닫았어.

The only change is the final verb ending:

• 닫았어요 = polite
• 닫았어 = casual

Everything else stays the same.

The structure is:

noun + subject particle + adverb + adjective + cause ending + noun + object particle + verb

Broken down:

• 바깥이 = outside + subject particle
• 너무 = too / so
• 시끄러워서 = because it is noisy
• 창문을 = window + object particle
• 닫았어요 = closed

So a learner can think of it as:

[Because outside was so noisy] + [I closed the window].