Mi perro se acerca a la puerta cuando oye el timbre.

In Spanish, acercarse (with se) means “to move/get closer (to something)”. It’s used reflexively, because the subject is moving itself.

• Mi perro se acerca a la puerta.
  My dog moves/comes closer to the door.

Without se, acercar is usually transitive: you move something else closer.

• Acerca la silla a la mesa.
  Move the chair closer to the table.

So in your sentence, the dog is moving itself closer, so you need se acerca.

With acercarse, Spanish uses the preposition a to mark the thing you approach:

• acercarse a algo / a alguien = to get close to something / someone

So you must say:

• Mi perro se acerca a la puerta. ✅
  not Mi perro se acerca la puerta. ❌

Think of it like “gets close to the door” — the a is the “to”.

Grammatically, se is a reflexive pronoun that matches the subject mi perro.

Conceptually, yes, it’s like “my dog brings himself closer”, but in natural English we just say “comes/gets closer”.

So:

• Mi perro se acerca a la puerta.
  Literally: My dog brings himself closer to the door.
  Natural: My dog comes up to the door.

Both relate to sound, but they’re used differently:

• oír = to hear (perceive sounds, whether you want to or not)
• escuchar = to listen (pay attention to sounds intentionally)

A dog simply hears the bell:

• Mi perro oye el timbre. = My dog hears the doorbell.

Escuchar would sound more like the dog is consciously “listening” to the bell, which is less natural here:

• Mi perro escucha el timbre. = My dog listens to the doorbell. (odd in this context)

The form depends on the time meaning of cuando:

1. For habits / general truths in the present, use present indicative:

   • Cuando oye el timbre, mi perro se acerca a la puerta.
     Whenever he hears the doorbell, my dog comes to the door. ✅

2. For future events (especially in the main clause), Spanish often uses present subjunctive after cuando:

   • Cuando oiga el timbre, se va a acercar a la puerta.
     When he hears the doorbell, he’s going to go to the door. (talking about a future, specific time)

Your sentence describes a repeated, habitual action, so oye (indicative) is correct.

Spanish uses the definite article (el, la, los, las) much more than English does.

Here, el timbre means “the doorbell (sound)” in general — it’s a specific, known thing in the situation (the doorbell of the house).

Compare:

• Cuando oye el timbre, mi perro ladra.
  When he hears the doorbell, my dog barks.

Dropping the article (cuando oye timbre) sounds incorrect or very foreign in standard Spanish.

Al = a + el, so it always has a sense of “to the”.

• Se acerca al timbre. = He moves to the doorbell (physically toward where the button is).

In your sentence, el timbre is what he hears, not where he goes:

• oye el timbre = he hears the bell (sound)
• se acerca a la puerta = he moves to the door

So oye al timbre would be wrong here; oír doesn’t take a with inanimate direct objects in this way.

Yes, that’s perfectly correct and very natural:

• Cuando oye el timbre, mi perro se acerca a la puerta.
• Mi perro se acerca a la puerta cuando oye el timbre.

Both word orders are fine; starting with Cuando… slightly emphasizes the condition/time.

Timbre is masculine (el timbre) and can mean:

• doorbell – most common in this context
• bell / buzzer – e.g. at a school, on a bike, etc.

In many Latin American countries, el timbre by default suggests a doorbell if the context is a house or door.

Other regional words:

• el portero / el intercomunicador – the intercom/entry system
• la campana – bell (more like a ringing bell, not usually a doorbell)

In Spanish:

• mi = my (possessive adjective)
• me = me (object pronoun: they see me, they call me)

You need the possessive before a noun:

• mi perro = my dog ✅
• me perro ❌ (ungrammatical)

Other forms:

• tu perro = your dog (informal singular)
• su perro = his/her/your (formal)/their dog

For a female dog, you normally say:

• Mi perra se acerca a la puerta cuando oye el timbre.

Perro is grammatically masculine and can sometimes be used generically (“dog” without specifying sex), but if you know it’s female and want to show that, use perra.

Yes, but the nuance changes:

• va a la puerta = goes to the door (focus on destination)
• se acerca a la puerta = comes up / gets close to the door (focus on the act of approaching, being near)

Both are natural. Se acerca paints the image of the dog moving close up to the door itself, maybe right next to it.

Yes, oír is irregular. Present indicative:

• yo oigo
• tú oyes
• él / ella / usted oye
• nosotros / nosotras oímos
• vosotros / vosotras oís (mainly Spain)
• ellos / ellas / ustedes oyen

In your sentence, mi perro = él, so you use oye.