Learn Hardcore Indonesian: Kami menutup jendela untuk mengurangi kebisingan luar, supaya ketenangan rapat tidak terganggu. - We close the window to reduce outside noise, so that the calmness of the meeting is not disturbed.

untuk is followed by a verb (or verb phrase) and functions like “to / in order to”:
- untuk mengurangi kebisingan luar = to reduce the outside noise
supaya is followed by a clause (a full mini-sentence) and functions like “so that”:
- supaya ketenangan rapat tidak terganggu = so that the quietness of the meeting would not be disturbed

So the structure is:

Kami menutup jendela (main clause)
untuk mengurangi kebisingan luar (purpose → verb phrase)
supaya ketenangan rapat tidak terganggu (further purpose/result → full clause)

You could rewrite it with just one purpose connector, but you’d have to change the structure, e.g.:

Kami menutup jendela supaya kebisingan luar berkurang.
Kami menutup jendela untuk menjaga ketenangan rapat.

Both are fine, just slightly different focus.

Why is it kebisingan luar and not kebisingan dari luar? Which is more natural?

Both are possible, but they feel slightly different:

kebisingan luar literally: outside noise / external noise
- Feels a bit more compact and formal/literary.
kebisingan dari luar literally: noise from outside
- Very natural in everyday speech, a bit more explicit.

In many everyday contexts, people would probably say:

Kami menutup jendela untuk mengurangi kebisingan dari luar.

The version with luar directly after kebisingan is still correct and natural, just slightly more concise and formal.

What does ketenangan rapat literally mean, and how is this noun formed from tenang?

tenang = calm, quiet (adjective)
ketenangan = calmness, tranquility, quietness (noun)

The pattern is:

ke- + ADJECTIVE + -an → abstract noun
- tenang → ketenangan (calm → calmness)
- ramai → keramaian (crowded/noisy → crowd/bustle)
- penting → kepentingan (important → interest/importance)

rapat here means meeting (a formal meeting), not tight/close.

So ketenangan rapat literally means:

the calm/quietness of the meeting
i.e. the peaceful/undisturbed atmosphere during the meeting

You could also say:

ketenangan dalam rapat = calmness in the meeting
suasana rapat yang tenang = a calm meeting atmosphere

All are grammatically fine; the original is just a bit more condensed.

Why do we say tidak terganggu instead of tidak diganggu? What’s the nuance between terganggu and diganggu?

Both come from the verb mengganggu (to disturb).

terganggu (with ter-)
- often describes a state or condition: to be disturbed, to be affected
- doesn’t emphasize who did the disturbing
- more neutral, often used for “unintentionally disturbed” or just “not in its ideal state”
Examples:
- Tidur saya terganggu. = My sleep is disturbed.
- Konsentrasinya terganggu. = His/Her concentration is disturbed.
diganggu (with di-)
- more clearly a passive voice of an action someone does
- you can more easily add an agent: diganggu oleh …
- can sound a bit more like someone actively bothered/interfered with something
Examples:
- Dia sering diganggu temannya. = He is often bothered by his friend.
- Rapat itu diganggu oleh suara musik keras. = The meeting was disturbed by loud music.

In this sentence:

supaya ketenangan rapat tidak terganggu
Focus is on the condition of the meeting’s calmness staying undisturbed, not on the agent causing disturbance. So terganggu is the more natural choice.

Could we just say supaya rapat tidak terganggu instead of supaya ketenangan rapat tidak terganggu?

Yes, and that would be very natural:

Kami menutup jendela untuk mengurangi kebisingan luar, supaya rapat tidak terganggu.
= We closed the window to reduce the outside noise so that the meeting would not be disturbed.

Differences:

supaya ketenangan rapat tidak terganggu
- focuses on the quiet/calm atmosphere of the meeting
- slightly more formal and abstract
supaya rapat tidak terganggu
- focuses on the meeting itself not being interrupted
- simpler and more common in daily speech

Both are correct; it’s just a matter of nuance and style.

Why is kami used instead of kita? What is the difference?

Both mean “we”, but:

kami = we (excluding the listener)
kita = we (including the listener)

In this sentence, kami implies:

The speaker and their group closed the window, but the person being spoken to was not part of that group.

If the speaker wants to include the listener in the group that closed the window, they would say:

Kita menutup jendela untuk mengurangi kebisingan luar, supaya ketenangan rapat tidak terganggu.

So the choice between kami and kita depends on whether the listener is included.

How is menutup formed from tutup, and why don’t we say menutupkan here?

Root: tutup = cover / lid / to close
menutup = to close (something), to cover (something)

Formation:

meN- + tutup → menutup
- The meN- prefix forms an active transitive verb:
  - menulis (meN- + tulis) = to write
  - membuka (mem- + buka) = to open
  - menutup (meN- + tutup) = to close

In this sentence:

Kami menutup jendela …
- menutup = active verb
- jendela = direct object

What about menutupkan?

menutupkan can mean to close something for someone / on behalf of someone, or can sound more causative.
- Dia menutupkan pintu untuk saya. = He closed the door for me.

Using menutupkan jendela here would sound odd or overly specific, as if stressing doing it for someone else. The neutral, standard form is just menutup jendela.

Could we say untuk kebisingan luar berkurang instead of untuk mengurangi kebisingan luar?

No, not with untuk in that way. Untuk normally needs to be followed by:

a noun, or
a verb phrase (bare verb), not a full clause with its own subject.

Compare:

✔ untuk mengurangi kebisingan luar
- mengurangi = verb
- whole thing is a verb phrase
✖ untuk kebisingan luar berkurang
- kebisingan luar berkurang is a clause (subject + verb), which doesn’t fit well after untuk.

If you want a clause of purpose like “so that the outside noise is reduced,” you would use supaya or agar:

supaya kebisingan luar berkurang
agar kebisingan luar berkurang

So:

Kami menutup jendela untuk mengurangi kebisingan luar. ✔
Kami menutup jendela supaya kebisingan luar berkurang. ✔
Kami menutup jendela untuk kebisingan luar berkurang. ✖ (unnatural)

What is the difference between supaya, agar, and biar? Could I replace supaya here?

All three can express purpose/result, similar to “so that / in order that”, but they differ in register:

supaya
- neutral, widely used in both spoken and written Indonesian
- fits well in semi-formal situations
agar
- a bit more formal and often found in writing, announcements, official documents
- can sound slightly more “official” than supaya
biar
- informal/colloquial, common in casual speech
- can sound too casual for formal writing

In your sentence, you can say:

… supaya ketenangan rapat tidak terganggu. (neutral)
… agar ketenangan rapat tidak terganggu. (a bit more formal)
… biar ketenangan rapat tidak terganggu. (more casual, spoken style)

All are grammatically correct; you just adjust based on how formal you want to sound.

How formal or informal does this whole sentence sound? How might it be said more casually?

The original:

Kami menutup jendela untuk mengurangi kebisingan luar, supaya ketenangan rapat tidak terganggu.

Sounds:

relatively formal / careful, suitable for written text, meetings, reports, or polite explanation.

More casual spoken versions might be:

Kita tutup jendelanya biar nggak terlalu bising dari luar, jadi rapatnya nggak keganggu.
Tadi jendelanya ditutup biar nggak berisik dari luar, supaya rapatnya tetap tenang.

Changes you see in casual speech:

kita instead of kami (if including the listener)
biar instead of supaya
nggak instead of tidak
bising/berisik instead of kebisingan
rapatnya nggak keganggu instead of ketenangan rapat tidak terganggu

The core meaning stays the same; only the register shifts.

How do you pronounce mengurangi and where is the stress?

mengurangi is syllabified as:

me-ngu-ra-ngi

Pronunciation tips:

me-: like “muh” (schwa sound)
ngu: like “ngoo” (as in “singer” + “oo”)
ra: “rah”
ngi: “ng-ee” (like “ng” in “sing” + “ee”)

Stress in Indonesian is generally even or slightly towards the last or second-to-last syllable, but it’s not as strong or contrastive as in English. You can put a slight stress on -ra- or -ngi, but you don’t need to worry much; as long as each syllable is clear, you’ll be understood:

me-ngu-RA-ngi
or me-ngu-ra-NGI

The more important thing is to pronounce the ng as a single sound (like in “sing”), not as “n” + “g” separately.