Es difícil dormir bien cuando hace tanto ruido.

Because ser is normally used to describe something as generally or inherently difficult, while estar usually points to a temporary state or situation.

So Es difícil dormir bien... means Sleeping well is difficult... in a general sense.

You might hear está difícil in some contexts, but here es difícil is the most natural standard choice.

After expressions like es difícil, Spanish often uses an infinitive to talk about an action in a general way.

So:

• Es difícil dormir bien = It is difficult to sleep well

The infinitive dormir works like to sleep in English. It is not conjugated because no specific person is being named.

Spanish has two common patterns:

• Es difícil + infinitive
• Es difícil que + subjunctive

In this sentence, the speaker is talking about the action in general, so the infinitive is simpler and more natural:

• Es difícil dormir bien

If you wanted to mention a specific person, you could say:

• Es difícil que duerma bien = It’s difficult for him/her/me to sleep well

So the infinitive version is broader and more neutral.

Bien is an adverb, and it modifies dormir.

• dormir = to sleep
• dormir bien = to sleep well

Just like in English, the adverb tells you how someone sleeps.

Cuando means when. It introduces the situation in which sleeping well becomes difficult:

• cuando hace tanto ruido = when there is so much noise

It works just like English when in this kind of sentence.

This is a very common Spanish expression.

• hacer ruido literally looks like to make noise
• But in many contexts it is best understood as there is noise or it is noisy

So:

• hace tanto ruido = there is so much noise / it’s making so much noise

The verb hacer is used idiomatically here. Spanish often uses it in ways that do not translate word-for-word.

In this sentence, the subject is not stated. Spanish often leaves it out when it is unknown, unimportant, or obvious from context.

So hace tanto ruido can mean:

• there is so much noise
• it/that/he/she is making so much noise

Without more context, the sentence stays general. Spanish is very comfortable with this kind of omitted subject.

Because muy and tanto do different jobs.

• muy means very
• tanto means so much / so much of

Since ruido is a noun, Spanish uses tanto:

• tanto ruido = so much noise

You would not say muy ruido.

Compare:

• muy ruidoso = very noisy
• tanto ruido = so much noise

Because ruido is usually treated as an uncountable noun, like noise in English.

So Spanish normally says:

• mucho ruido
• tanto ruido

not usually muchos ruidos unless you mean different separate noises or sounds in a more specific sense.

Because in Spanish, uncountable nouns often appear without an article when speaking generally.

So:

• hace tanto ruido = there is so much noise

Adding an article would change the feel or make it more specific. The version without an article is the natural general expression here.

Yes. Hay tanto ruido is also very natural.

There is a slight difference in feel:

• hay tanto ruido focuses on the existence of noise
• hace tanto ruido often suggests that someone or something is producing the noise

In many everyday situations, both can work:

• Es difícil dormir bien cuando hay tanto ruido
• Es difícil dormir bien cuando hace tanto ruido

The original sentence is perfectly natural.

Yes. Spanish is flexible here.

You can also say:

• Cuando hace tanto ruido, es difícil dormir bien.

This means the same thing. The difference is mainly emphasis:

• Es difícil dormir bien... starts with the main idea
• Cuando hace tanto ruido... starts with the condition or situation

The present tense here expresses a general truth or a repeated situation.

• Es difícil dormir bien cuando hace tanto ruido means this is generally true whenever that situation happens.

It does not have to mean only right now. In Spanish, the present tense is often used for habits, general facts, and normal experiences.

A few useful points:

• Es is short: es
• difícil has the stress on -fí-, which is why it has an accent mark
• dormir is stressed on the last syllable: dor-MIR
• cuando is usually pronounced smoothly as two syllables
• ruido is usually pronounced RWI-do

The written accent in difícil is important because it shows where the stress goes.

It is standard and natural in Spain, and it is also understandable and normal across the Spanish-speaking world.

Nothing in the sentence is strongly regional. A speaker from Spain would use it naturally, but so would many speakers elsewhere.