eojesbame gongsa so-eum ttaemune jami an wasseoyo.

에 marks the time when something happened.

So 어젯밤에 means last night or more literally at last night.
With time words in Korean, 에 is often used, though with some very common time expressions it can sometimes be omitted.

• 어젯밤에 = last night
• 오늘 아침에 = this morning
• 3시에 = at 3 o’clock

In this sentence, 어젯밤에 sounds completely natural.

공사 소음 is a noun phrase meaning construction noise.

It is made of:

• 공사 = construction, construction work
• 소음 = noise, unwanted noise

So this is a fairly direct compound noun: construction noise.

A learner might also hear:

• 공사 소리 = construction sound/noise

But 소음 specifically emphasizes that the sound is noisy, disturbing, or unpleasant.

때문에 means because of or due to.

In this sentence:

• 공사 소음 때문에 = because of the construction noise

It follows a noun or noun phrase:

• 비 때문에 = because of the rain
• 감기 때문에 = because of a cold
• 공사 소음 때문에 = because of construction noise

It often sounds a little more objective or explanatory than some other because forms, and it is very commonly used when talking about causes, especially of negative results.

Because in Korean, the expression is 잠이 오다, literally sleep comes.

In that expression:

• 잠이 오다 = to get sleepy / for sleep to come
• 잠이 안 오다 = sleep doesn’t come / can’t fall asleep

So 잠 takes the subject particle 이, not the object particle 을.

That is why:

• 잠이 안 왔어요 = sleep didn’t come

This is a very natural Korean way to express I couldn’t sleep or I couldn’t fall asleep.

It is just a different natural expression in Korean.

English often says:

• I couldn’t sleep
• I couldn’t fall asleep

Korean often says:

• 잠이 안 오다 = sleep doesn’t come
• 잠이 오다 = sleep comes

So the Korean sentence is not unnatural at all. It is a common everyday way to talk about being unable to sleep.

It is similar to how different languages often describe bodily states differently. Korean is focusing on sleep arriving, not on you performing the action of sleeping.

Because the speaker is talking about a completed time in the past: last night.

So:

• 잠이 안 와요 = I can’t sleep / sleep doesn’t come
• 잠이 안 왔어요 = I couldn’t sleep / sleep didn’t come

Even though English often uses couldn’t sleep, Korean naturally uses the past form of 오다 in this expression.

Both can be translated as I couldn’t sleep, but the nuance is a little different.

• 잠이 안 왔어요
  = sleep didn’t come
  = I couldn’t fall asleep / I just couldn’t get sleepy

• 못 잤어요
  = I wasn’t able to sleep / I didn’t sleep well or at all

So 잠이 안 왔어요 focuses more on sleep not coming, while 못 잤어요 focuses more on the result of not sleeping.

In this sentence, 잠이 안 왔어요 fits very well because the noise prevented the speaker from falling asleep.

Yes, absolutely.

• 공사 때문에 잠이 안 왔어요 = I couldn’t sleep because of the construction.
• 공사 소음 때문에 잠이 안 왔어요 = I couldn’t sleep because of the construction noise.

The version with 소음 is more precise. It makes clear that the problem was not just the construction itself, but specifically the noise from it.

Yes, the subject or topic is omitted because it is understood from context.

A full version could be:

• 저는 어젯밤에 공사 소음 때문에 잠이 안 왔어요.

But Korean very often leaves out subjects like I, you, or we when they are obvious.

That is why the shorter sentence sounds natural and normal.

왔어요 is in the polite -어요/-아요 style, which is very common in everyday conversation.

It is polite and natural in many situations:

• talking to someone you do not know well
• talking to coworkers
• talking to a teacher
• general daily conversation

Other possible styles would be:

• 잠이 안 왔다 = plain style
• 잠이 안 왔습니다 = formal polite style

So 잠이 안 왔어요 is polite but not stiff.

In the exact form seen here, yes: 때문에 follows a noun phrase.

Examples:

• 소음 때문에
• 비 때문에
• 스트레스 때문에

But Korean also has a clause form:

• -기 때문에 = because

Example:

• 공사 소음이 너무 심했기 때문에 잠이 안 왔어요.
  = I couldn’t sleep because the construction noise was too loud.

So:

• noun + 때문에
• verb/adjective stem + 기 때문에

That is a very typical Korean sentence order.

Korean often places background information first, then the main point at the end.

So here:

• 어젯밤에 = time
• 공사 소음 때문에 = cause
• 잠이 안 왔어요 = result/main statement

This ordering feels natural in Korean because the verb usually comes last, and earlier parts set up the situation before the final statement.

Yes. Grammatically, both are possible:

• 잠이 안 왔어요
• 잠이 오지 않았어요

They mean basically the same thing.

But in everyday speech, 안 왔어요 usually sounds more natural and conversational.
오지 않았어요 can sound a bit more formal, careful, or emphatic.

So for normal conversation, 잠이 안 왔어요 is the more common choice.