El animal se asusta si oye demasiado ruido.

Asustarse is very commonly used to mean to get frightened / to become scared.

• El animal se asusta = The animal gets scared
• El animal asusta = The animal scares (someone else)

So the se changes the meaning. Here, the animal is the one experiencing the fear, not causing it.

Not exactly in the most literal sense.

With lavarse, the subject is clearly doing something to itself: He washes himself.

With asustarse, the reflexive form is often better understood as becoming frightened or getting scared, rather than literally frightening oneself. It is one of those verbs where the reflexive form is the normal way to express a change of state.

So in practice:

• asustar = to frighten
• asustarse = to get frightened

Oye comes from the verb oír, which means to hear.

This is the 3rd person singular present form:

• yo oigo
• tú oyes
• él/ella/usted oye

Since the subject is el animal, the verb form is oye.

Because Spanish usually does not need subject pronouns when the subject is already clear.

In English, you must say it hears.
In Spanish, the verb ending often tells you who the subject is, and here the subject has already been stated:

• El animal se asusta si oye demasiado ruido.

So oye already means it hears in context, with el animal as the subject.

Here, si means if.

• si oye demasiado ruido = if it hears too much noise

This is the normal word used for conditions.

Be careful not to confuse it with sí with an accent:

• si = if
• sí = yes

Because demasiado is acting as a determiner before the noun, like too much in English.

• demasiado ruido = too much noise

You do not use de in this structure.

Compare:

• mucho ruido = a lot of noise
• demasiado ruido = too much noise

Spanish treats ruido as an uncountable noun here, just like noise in English.

Because ruido here is being used as a mass noun, like noise in English.

You normally say:

• mucho ruido
• demasiado ruido

not usually demasiados ruidos, unless you mean separate individual noises or sounds in a more specific context.

So singular ruido is the natural choice in this sentence.

The present tense is often used in Spanish for general truths, habits, and typical reactions.

So:

• El animal se asusta si oye demasiado ruido.

means something like The animal gets scared if it hears too much noise as a general fact, not just one single event.

This is very similar to English, which also uses the present tense in this kind of conditional sentence.

Because it is a conditional clause explaining under what condition the animal gets scared.

The structure is:

• main clause: El animal se asusta
• conditional clause: si oye demasiado ruido

Spanish can also place the si clause first:

• Si oye demasiado ruido, el animal se asusta.

Both are correct. The meaning stays the same.

Sometimes, but the meaning changes slightly.

• oír = to hear
• escuchar = to listen to

Oír often refers more to perceiving sound.
Escuchar suggests more attention or active listening.

So in this sentence, oye demasiado ruido is natural because the idea is that the animal is exposed to too much noise. Using escucha could sound more like the animal is actively listening to it.

Spanish usually uses the definite article more often than English.

So El animal is the normal way to say the animal. If you just said Animal by itself, it would sound incomplete in a normal sentence.

Also, if the sentence is talking about an animal already known in context, the definite article is exactly what Spanish expects.

Yes. In this sentence, animal is treated as masculine singular:

• el animal
• demasiado ruido
• se asusta
• oye

The noun animal can refer to a male or female animal in real life, but grammatically the word itself is masculine unless you specify something else.

By default, Spanish assumes the same subject continues unless there is a clear change.

So in:

• El animal se asusta si oye demasiado ruido.

the understood subject of oye is also el animal.

If Spanish wanted to make it clear that someone else was hearing the noise, it would usually state that subject more explicitly.

In some contexts, yes, the idea can feel close to when in English, especially if it describes a regular reaction.

But grammatically, si means if. It presents the hearing of too much noise as the condition that causes the reaction.

So the most direct reading is still if.

In standard Spanish from Spain, oye is pronounced roughly like OH-yeh.

A few pronunciation notes:

• o is a pure vowel, like o in more, but shorter and cleaner.
• y in oye sounds like a consonant similar to the y in yes.
• e is like eh.

So: OH-yeh.