i kibodeuneun soriga jagaseo bame sseodo gwaenchanhayo.

는 is the topic marker. In 이 키보드는, the speaker is introducing this keyboard as the topic and then saying something about it.

So the structure is basically:

• 이 키보드는 = as for this keyboard
• 소리가 작아서 밤에 써도 괜찮아요 = its sound is quiet/small, so it’s okay to use at night

Using 는 often gives a feeling like:

• Speaking of this keyboard...
• This keyboard, on the other hand...
• As for this keyboard...

It is very natural here because the sentence is describing a characteristic of the keyboard.

This is a very common Korean pattern.

• 이 키보드는 sets the overall topic: this keyboard
• 소리가 marks the specific thing being described about that topic: its sound

So the sentence works like this:

• As for this keyboard, its sound is quiet, so...

Korean often does this:

• Topic: the larger thing being talked about
• Subject: the part or feature being described

Some similar patterns:

• 이 집은 방이 커요. = As for this house, the room(s) are big.
• 그 사람은 눈이 예뻐요. = As for that person, the eyes are pretty.

So 소리가 작다 is describing one property of the keyboard: its sound.

Yes. 작다 literally means to be small, but when talking about sound, it means to be low/quiet.

So:

• 소리가 크다 = the sound is loud
• 소리가 작다 = the sound is quiet / low

This is very natural in Korean. Korean often uses big/small language for volume:

• 크다 for loud
• 작다 for quiet

So 소리가 작아서 means:

• because the sound is quiet
• since it doesn’t make much noise

Both can relate to being quiet, but they are not exactly the same.

• 소리가 작다 = the sound volume is low
• 조용하다 = to be quiet, calm, silent, not noisy overall

In this sentence, 소리가 작다 is very precise: it focuses on the keyboard’s actual sound level when used.

Compare:

• 이 키보드는 소리가 작아요. = This keyboard makes little noise / has a low sound.
• 이 방은 조용해요. = This room is quiet.

You could say 조용한 키보드 in some contexts, but 소리가 작다 sounds more concrete and direct for a keyboard.

Here, -아서 / -어서 connects two ideas and often means because, so, or and so.

So:

• 작아서 = because it is quiet / since it is quiet

The full logic is:

• The keyboard’s sound is quiet, so it’s okay to use at night.

A simple breakdown:

• 작다 = to be small/quiet
• 작아서 = because it is quiet

In this sentence, -아서 gives a natural cause-and-result connection.

Yes, 작으니까 would also be possible:

• 이 키보드는 소리가 작으니까 밤에 써도 괜찮아요.

This also means:

• Because the keyboard is quiet, it’s okay to use at night.

The difference is mostly in tone:

• -아서 / -어서 often sounds a bit smoother and more neutral
• -(으)니까 can sound a bit more explicit or reasoning-based, as if giving a justification

In everyday speech, 작아서 sounds very natural here.

This comes from the verb 쓰다 = to use.

When 쓰다 combines with -어도, it contracts:

• 쓰다 → stem 쓰-
• 쓰 + 어도
• 쓰어도 contracts to 써도

This is a very common contraction in Korean.

More examples:

• 쓰다 → 써요
• 쓰다 → 썼어요
• 쓰다 → 써도

So 밤에 써도 괜찮아요 means:

• It’s okay to use it at night
• literally, Even if you use it at night, it’s okay

This pattern means it’s okay to..., it’s fine if..., or literally even if..., it’s okay.

So:

• 써도 괜찮아요
  • literal: Even if you use it, it’s okay
  • natural English: It’s okay to use it

This is a very useful grammar pattern:

• 가도 괜찮아요 = It’s okay to go
• 먹어도 괜찮아요 = It’s okay to eat
• 앉아도 괜찮아요 = It’s okay to sit

In this sentence:

• 밤에 써도 괜찮아요 = It’s okay to use it at night

Here, 에 marks the time when something happens.

So:

• 밤에 = at night

In the sentence:

• 밤에 써도 괜찮아요 = It’s okay to use it at night

This use of 에 is very common with time expressions such as:

• 아침에 = in the morning
• 저녁에 = in the evening
• 주말에 = on the weekend

So 밤에 simply tells you the time context.

Korean often leaves subjects unstated when they are clear from context.

So 밤에 써도 괜찮아요 does not explicitly say who uses it. Depending on context, it could mean:

• I can use it at night
• You can use it at night
• It’s okay to use it at night in general

In English, we often choose one subject, but Korean frequently omits it. Here, the most natural translation is the general one:

• It’s okay to use it at night.

It can imply both acceptable condition and permission, depending on context.

Here, 써도 괜찮아요 means something like:

• It’s okay to use
• It’s fine to use
• You can use it

So yes, it can feel a little like permission, but in this sentence it mainly means:

• using it at night is not a problem

Because the keyboard is quiet, nighttime use is acceptable.

Yes, that is the literal structure, and it is perfectly normal in Korean.

A very literal breakdown is:

• 이 키보드는 = As for this keyboard,
• 소리가 작아서 = because its sound is small,
• 밤에 써도 괜찮아요 = it’s okay to use at night.

But in natural English, we would usually say:

• This keyboard is quiet, so it’s okay to use at night.
• This keyboard doesn’t make much noise, so it’s fine to use at night.

So the Korean wording is normal; it just maps into English a little differently.