Malakas ang tinig niya.

Because predicate-first word order is very common in Filipino.

In Malakas ang tinig niya, the sentence begins with the description/predicate malakas and then gives the topic ang tinig niya.

So the structure is roughly:

• Malakas = loud / strong
• ang tinig niya = his/her voice

This pattern is very normal in Filipino. English usually prefers subject + be + adjective, but Filipino often uses:

• Predicate + ang-marked topic

So this sentence is not unusual or poetic; it is standard.

Ang marks the topic of the sentence.

Here, ang tinig niya is the thing being talked about. The sentence is saying something about the voice.

So in:

• Malakas = the comment about it
• ang tinig niya = the topic

A helpful learner-friendly way to think of ang is that it often marks the noun phrase most central to the sentence, though it does not work exactly like English the.

Because niya is a genitive/possessive pronoun, and in this kind of phrase it normally comes after the noun it possesses.

So:

• tinig niya = his/her voice
• literally: voice his/hers

This is a very common pattern in Filipino:

• bahay niya = his/her house
• kotse niya = his/her car
• kaibigan niya = his/her friend

So tinig niya is the natural order.

It can mean either his or her.

Filipino third-person singular pronouns usually do not mark gender. So niya can refer to:

• his
• her

You figure out which one is meant from context.

Both can refer to voice, but they are not always identical in feel.

• boses is very common in everyday speech
• tinig can sound a bit more formal, literary, or expressive in some contexts

So:

• Malakas ang boses niya.
• Malakas ang tinig niya.

Both are understandable and natural, but boses is often the more conversational choice.

Yes, malakas often means strong, but it is also commonly used to mean loud depending on context.

Filipino uses malakas for things like:

• a loud voice
• a strong wind
• a strong force
• a loud sound

So with tinig or boses, malakas naturally means loud.

This is one of those cases where the best English translation depends on the noun being described.

Because malaki means big, not loud.

For sound or voice intensity, Filipino normally uses malakas, not malaki.

Compare:

• malaki = big / large
• malakas = strong / loud

So Malaki ang tinig niya would sound unnatural if you mean the voice is loud.

Yes. That is a very natural sentence.

In everyday conversation, many speakers would probably say:

• Malakas ang boses niya.

This has essentially the same meaning as Malakas ang tinig niya, but boses is more common in casual speech.

A few natural ways are:

• Napakalakas ng tinig niya.
• Napakalakas ng boses niya.
• Sobrang lakas ng tinig niya.
• Ang lakas ng tinig niya.

Notes:

• napakalakas = very/extremely loud
• sobrang lakas = very loud / too loud depending on context
• ang lakas ng ... is a very common exclamatory or emphatic pattern

You may notice that some of these use ng instead of ang because the structure changes slightly.

You can say:

• Hindi malakas ang tinig niya.

That means His/Her voice is not loud.

Here:

• hindi = not
• malakas = loud
• ang tinig niya = his/her voice

This is the normal way to negate an adjectival sentence like this.