Küçük çocuklar aniden yüksek ses duyunca ürkebiliyor.

A helpful breakdown is:

• küçük çocuklar = small/little children

  • küçük = small, little
  • çocuklar = children

• aniden = suddenly

• yüksek ses = a loud sound / loud noise

  • literally high sound, but in Turkish this means loud sound

• duyunca = when (they) hear / upon hearing

• ürkebiliyor = can get startled / may get startled

So the structure is roughly:

• Subject: Küçük çocuklar
• Time/situation clause: aniden yüksek ses duyunca
• Main verb: ürkebiliyor

Turkish often puts the main verb at the end, so this word order is very normal.

Duyunca comes from duymak (to hear) plus the suffix -ınca / -ince / -unca / -ünce.

This suffix often means:

• when
• once
• upon
• sometimes if, depending on context

So:

• duymak = to hear
• duyunca = when hearing / when they hear / upon hearing

In this sentence, duyunca introduces the situation that causes the reaction:

• When they hear a loud sound suddenly, ...

It is a very common Turkish structure.

The form duyunca itself does not show a subject. Turkish often leaves that to context.

In this sentence, the natural reading is that the same people are doing both actions:

• small children hear the sound
• small children get startled

So English needs to make the subject explicit, but Turkish does not.

That said, -ınca/-ince clauses do not always have the same subject as the main clause. Context decides. For example, Turkish can also say things equivalent to:

• When Ahmet arrives, the children get happy.

So in this sentence, it is context—not the ending alone—that tells us the children are the ones hearing.

Both are possible, but they feel slightly different.

• yüksek ses = loud sound / loud noise, more general
• yüksek bir ses = a loud sound, a bit more explicitly one loud sound

In Turkish, bir often works like a/an, but it is not required as often as English articles are.

So:

• yüksek ses duyunca = when they hear loud noise / a loud sound
• yüksek bir ses duyunca = when they hear a loud sound

The version without bir sounds very natural and general.

Because ses here is an indefinite direct object.

In Turkish, direct objects are often:

• without accusative if they are indefinite or nonspecific
• with accusative if they are definite or specific

So:

• yüksek ses duymak = to hear a loud sound / loud noise
• yüksek sesi duymak = to hear the loud sound / that specific loud sound

In your sentence, the meaning is general, not about one particular known sound. That is why ses appears without the accusative ending.

Ürkebiliyor breaks down like this:

• ürk- = get startled / take fright
• -e bil- = can / may / be able to
• -iyor = present, ongoing, or habitual-type meaning depending on context

So ürkebiliyor literally means something like:

• can get startled
• may get startled
• is able to get startled

In this sentence, the best natural sense is not physical ability, but possibility/tendency:

• Small children can get startled when they suddenly hear a loud sound.

It suggests this is something that happens sometimes or can happen easily.

Because the nuance changes.

• ürküyor = gets startled / is getting startled
• ürkebiliyor = can get startled / may get startled

With -ebil-, the speaker is not saying this happens every single time. It sounds more like:

• this is possible
• this is a common tendency
• this can happen

So ürkebiliyor is softer and more general than a plain statement like ürküyor.

This is a very useful vocabulary question.

• ürkmek = to be startled, to jump in surprise, to take fright suddenly
• korkmak = to be afraid, to fear

A sudden loud sound usually causes a startle reaction, so ürkmek fits very well.

Compare:

• Yüksek ses duyunca ürktü. = He/She got startled when he/she heard a loud sound.
• Köpeklerden korkuyor. = He/She is afraid of dogs.

So in your sentence, ürkmek is better because the reaction is sudden and immediate.

Turkish often does not require a plural ending on the verb when the plural subject is already stated.

So both of these can be acceptable:

• Küçük çocuklar ... ürkebiliyor.
• Küçük çocuklar ... ürkebiliyorlar.

The version without -lar on the verb is very common and natural.

Since çocuklar already tells us the subject is plural, Turkish often leaves the verb in the singular-looking third-person form.

Aniden means suddenly, and here it most naturally modifies the hearing event:

• when they suddenly hear a loud sound

It does not really modify ses itself, because aniden is an adverb, not an adjective.

So the idea is not a sudden loud sound as a noun phrase. It is more:

• the children suddenly hear a loud sound

If you wanted to describe the sound itself as sudden, Turkish would normally use a different structure.

Turkish word order is flexible, but the given version is very natural.

The sentence:

• Küçük çocuklar aniden yüksek ses duyunca ürkebiliyor.

follows a common pattern:

• subject
• adverb
• object
• subordinate verb
• main verb at the end

You could move some parts for emphasis, but the emphasis would change. For example:

• Aniden yüksek ses duyunca küçük çocuklar ürkebiliyor.

This still works, but now the when they hear a loud sound suddenly part is more foregrounded.

So yes, Turkish can rearrange elements, but the original order is a normal, neutral choice.

Not necessarily. In this kind of sentence, küçük çocuklar usually means:

• young children
• little children

It can literally mean small children, but in context it usually refers to age more than physical size.

So English learners should understand küçük here as something like:

• little
• young

rather than focusing only on physical smallness.