Learn Hardcore Spanish (Latin America): Ya no me importa el ruido en la calle. - I don’t care about the noise in the street anymore.

No me importa el ruido en la calle = I don’t care about / The noise in the street doesn’t matter to me (a neutral statement; maybe you never cared, or we don’t know).
Ya no me importa el ruido en la calle = I no longer care about / The noise in the street doesn’t matter to me anymore (it used to matter, but now it doesn’t).

So ya no almost always implies a change compared to the past.

Why is it me importa and not yo importo or yo no me importo el ruido?

In Spanish, importar (in the sense used here) works like gustar:

The thing that matters is the grammatical subject.
The person it matters to is an indirect object, shown with a pronoun (me, te, le, nos, les).

So:

El ruido en la calle = subject (the noise)
me = to me (indirect object)
importa = matters / is important (3rd person singular, agreeing with el ruido)

The structure is:

[A mí] me importa el ruido en la calle.
= The noise in the street matters to me.

That is why it is me importa and not yo importo.
Yo importo would mean I am important (to someone), which is different.

What exactly is the role of me here? Is it reflexive?

Me here is not reflexive; it is an indirect object pronoun meaning to me / for me.

Reflexive: me lavo = I wash myself.
Indirect object: me importa = it matters to me.

In Ya no me importa el ruido en la calle, me tells you who is affected by the importance of the noise: to me.

You could also say the full form A mí ya no me importa el ruido en la calle for emphasis, but you still keep the pronoun me.

Why is it importa and not importan?

Importa agrees with the subject, which is el ruido (singular):

El ruido en la calle ya no me importa. → importa (singular)
Los ruidos en la calle ya no me importan. → importan (plural, agreeing with los ruidos)

Even though in English we say I don’t care (where I is the subject), in Spanish el ruido is the subject of importar in this construction, so the verb agrees with el ruido.

Can the word order change? Could I say El ruido en la calle ya no me importa?

Yes, the word order is flexible. These are all grammatically correct:

Ya no me importa el ruido en la calle.
El ruido en la calle ya no me importa.
A mí ya no me importa el ruido en la calle.
El ruido en la calle a mí ya no me importa.

The usual, neutral order is often Ya no me importa X, but:

Starting with el ruido en la calle puts more emphasis on the noise itself.
Starting with A mí emphasizes to me (specifically).

All of them essentially mean the same thing: The street noise doesn’t matter to me anymore.

What’s the difference between el ruido en la calle and el ruido de la calle?

Both can be translated as the noise in/on the street or street noise, and in many contexts they are interchangeable.

Subtle nuance:

el ruido en la calle
- Focuses a bit more on the location: the noise that is in the street.
- Often used when you imagine being inside and hearing noise outside on the street.
el ruido de la calle
- Focuses slightly more on the origin/source: the noise from the street.
- Common way to say street noise in general.

In everyday speech, both sound natural in Latin America; context usually matters more than the small nuance.

Why is it el ruido and not just ruido without the article?

Using el here makes ruido more specific and concrete:

Ya no me importa el ruido en la calle.
= The street noise (that we’re talking about, the usual noise) doesn’t matter to me anymore.

If you dropped the article and said:

Ya no me importa ruido en la calle.

it would sound off or incomplete in standard Spanish.

In Spanish, countable or concrete things usually take an article, especially when you mean the general, typical, known noise in a situation. So el ruido feels natural and idiomatic here.

Could I say no me importa ya el ruido en la calle or no me importa el ruido en la calle ya? Do they mean the same?

They are understandable, but less common and a bit marked in tone.

Natural options:

Ya no me importa el ruido en la calle. (most common)
El ruido en la calle ya no me importa.

Other possibilities:

No me importa ya el ruido en la calle. → more literary / formal / emphatic.
No me importa el ruido en la calle ya. → possible, but the ya sounds somewhat tacked on in many accents.

In real-life speech, ya no me importa X is the most typical and neutral way to say I don’t care about X anymore.

How is ya no me importa different from ya no me molesta?

Both are common, but they focus on different ideas:

Ya no me importa el ruido en la calle.
= The noise doesn’t matter to me anymore; I don’t care about it.
(It might still be loud, but emotionally or mentally you don’t care.)
Ya no me molesta el ruido en la calle.
= The noise doesn’t bother / annoy me anymore.
(It used to disturb or irritate you; now it doesn’t.)

Often they overlap; if something doesn’t bother you, you may also not care about it. But:

importar points to importance / concern.
molestar points to annoyance / discomfort.

Does ya no me importa imply something about the past, even though the verb is in the present?

Yes. Grammatically it is present:

me importa = it matters to me (now)

But adding ya no embeds a comparison with the past:

Ya no me importa...
= It no longer matters to me.
→ Implicit: Before, it did matter.

So Spanish uses present tense + ya no to express this idea of a change from past to present, where English often needs anymore / no longer.

Is ya no always used before the pronoun like in ya no me importa, or can it go after?

In this kind of sentence, ya no normally comes before the pronoun and verb:

Ya no me importa el ruido en la calle.

You can move ya no around a bit for emphasis, but you cannot break it with the pronoun in a strange way. For example:

✅ Ya no me importa el ruido.
✅ El ruido ya no me importa.
❌ No ya me importa el ruido. (not idiomatic)

So, keep ya no together, and usually put it right before the verb phrase:

Ya no + [pronoun] + verb
Ya no me importa, ya no le interesa, ya no nos gusta, etc.