Je me concentre mieux quand il y a moins de bruit.

Because se concentrer is usually used as a pronominal/reflexive verb in French when it means to concentrate.

• Je me concentre = I concentrate / I am concentrating
• The me is the reflexive pronoun matching je

If you say je concentre by itself, it sounds incomplete and usually means I concentrate something in a more literal or technical sense, as in I concentrate the solution. For mental focus, French normally uses se concentrer.

Me is the reflexive pronoun for je.

In dictionary form, the verb is se concentrer:

• je me concentre
• tu te concentres
• il/elle se concentre
• nous nous concentrons
• vous vous concentrez
• ils/elles se concentrent

In this sentence, me does not really mean myself in a strongly emphatic way. It is just part of how the verb is normally built.

Because mieux is the comparative form of bien and is used with verbs.

Here, mieux modifies me concentre:

• Je me concentre mieux = I concentrate better

Use meilleur with nouns:

• un meilleur livre = a better book
• une meilleure idée = a better idea

So:

• verb → mieux
• noun → meilleur / meilleure / meilleurs / meilleures

French normally does not use plus bien for better. The correct comparative form is mieux.

• bien = well
• mieux = better

So:

• Je travaille bien = I work well
• Je travaille mieux = I work better

Because the present tense in French is often used for general truths, habits, and things that are usually true, just like in English.

So Je me concentre mieux quand il y a moins de bruit means something like:

• I concentrate better when there is less noise
• I focus better when there is less noise

It is not limited to what is happening right now. It can describe a general fact about you.

Quand means when.

It introduces the condition or situation in which the first part is true:

• Je me concentre mieux = I concentrate better
• quand il y a moins de bruit = when there is less noise

So quand links the two ideas together.

You could also sometimes use lorsqu’, but quand is the most common and natural choice here.

Il y a is the standard French expression for there is / there are.

Literally, it comes from something like it has there, but you should learn it as a fixed expression:

• il y a du bruit = there is noise
• il y a moins de bruit = there is less noise

So in this sentence:

• quand il y a moins de bruit = when there is less noise

After expressions of quantity like moins de, French uses de, not the usual article.

Examples:

• moins de temps = less time
• moins d’eau = less water
• moins de bruit = less noise

Even though you would normally say:

• du bruit = some noise

after moins de, it changes to:

• moins de bruit

This is a very common French pattern.

Because bruit is being used as an uncountable idea, like noise in English.

• moins de bruit = less noise

French can use bruits when talking about separate noises/sounds:

• J’entends des bruits = I hear noises

But here the sentence is talking about noise in general, so singular bruit is the natural choice.

Yes, you could say avec moins de bruit, and it would be understandable:

• Je me concentre mieux avec moins de bruit

But quand il y a moins de bruit sounds a bit more natural if you want to express when there is less noise around.

The two versions are close, but they are not exactly identical:

• quand il y a moins de bruit focuses on the situation
• avec moins de bruit focuses more directly on the surrounding condition

Yes. French allows both orders.

• Je me concentre mieux quand il y a moins de bruit.
• Quand il y a moins de bruit, je me concentre mieux.

Both are correct. The second version puts more emphasis on the condition first.

A careful approximate pronunciation is:

zhuh muh kon-sontr myuh kan ee-lya mwan duh brwee

A few useful points:

• Je sounds like zhuh
• me sounds like muh
• concentre has a nasal sound in con-
• mieux sounds roughly like myuh
• quand sounds like kan
• il y a is often said smoothly together: ee-lya
• moins sounds roughly like mwan
• the final t in bruit is usually silent

In natural speech, the sentence flows quite smoothly without strong pauses.

Both relate to sound, but they are not the same.

• bruit = noise, often unwanted or distracting sound
• son = sound in a more neutral sense

In this sentence, bruit is the right word because the idea is that noise makes concentration harder.

Compare:

• Il y a du bruit dans la rue. = There is noise in the street.
• Le son est trop fort. = The sound is too loud.

So moins de bruit fits the meaning much better than moins de son here.