La contrôleuse vérifie les billets sans que personne ne parle trop fort.

Contrôleuse is the feminine form of contrôleur. French nouns for jobs or roles usually match the gender of the person being described.

• la contrôleuse = the female inspector/checker
• le contrôleur = the male inspector/checker

In this sentence, the person is female, so French uses la contrôleuse.

Vérifie is the third-person singular present indicative of vérifier.

It agrees with the subject la contrôleuse, which is singular.

So:

• la contrôleuse vérifie = the inspector checks / is checking

In French, the present tense can often translate into English as either checks or is checking, depending on context.

Les billets means the tickets. It refers to the specific tickets being checked in that situation.

French often uses the definite article when the objects are understood from context. Here, the inspector is checking the tickets that the passengers have, so les billets is natural.

If you said des billets, it would sound more like some tickets, which is less specific.

Sans que means without followed by a clause with its own subject and verb.

Compare:

• sans billet = without a ticket
• sans parler = without speaking
• sans que personne ne parle = without anyone speaking / without anyone talking

So sans is used before a noun or an infinitive, but sans que is used when you need a full clause.

Because sans que normally requires the subjunctive in French.

So after sans que, you say:

• sans qu’il parte
• sans que nous sachions
• sans que personne ne parle

Here, parle is the present subjunctive of parler.

A useful thing to know: for many -er verbs, the singular subjunctive forms look exactly like the present indicative forms. So il parle can be either indicative or subjunctive depending on the grammar around it. In this sentence, it is subjunctive because of sans que.

Because personne is grammatically singular.

Even though it refers to people in general, French treats personne meaning no one / anyone as a singular subject, so the verb is singular too:

• personne ne parle
• not personne ne parlent

This is similar to English no one speaks, not no one speak.

In standard French, personne meaning no one / nobody normally goes with ne before the verb:

• Personne ne parle. = Nobody is speaking.

So personne ne parle is the normal French structure.

In this sentence, English often translates it more naturally as without anyone speaking too loudly, even though the French structure uses personne ne. That is just how the idiom works across the two languages. It is not an incorrect double negative in French.

Also note that this personne is a pronoun meaning no one / anyone, not the noun une personne meaning a person.

In very informal spoken French, many speakers drop ne, so you may hear:

• sans que personne parle trop fort

But in standard written French, and in careful speech, ne is normally kept:

• sans que personne ne parle trop fort

So for learners, the safest form to use is the full standard one with ne.

With verbs like parler, crier, chanter, or frapper, French often uses fort as an adverb meaning loudly or hard.

So:

• parler fort = to speak loudly
• parler trop fort = to speak too loudly

That is the normal, natural expression. Fortement exists, but it would sound less natural here.

Only if the person doing the speaking is the same as the main subject.

• La contrôleuse vérifie les billets sans parler trop fort.
  = The inspector checks the tickets without speaking too loudly.

In that version, the inspector is the one not speaking too loudly.

But your sentence says:

• sans que personne ne parle trop fort

That means the second action has its own subject: personne. In other words, it is about no one / anyone speaking too loudly, not specifically the inspector.

Yes. A very literal breakdown is:

• La contrôleuse = the female inspector
• vérifie = checks
• les billets = the tickets
• sans que = without that / without
• personne ne parle = no one speaks
• trop fort = too loudly

A very literal English version would sound awkward:
The inspector checks the tickets without no one speaking too loudly or without that anyone speak too loudly.

That is not good English, but it helps show the French structure. The natural English translation is something like The inspector checks the tickets without anyone speaking too loudly.

A rough English approximation is kon-troh-luhz.

A few tips:

• con- sounds like kon
• trô has a long o sound
• leuse ends with a sound like luhz
• the final -e is not pronounced separately

The ô with the circumflex does not change the grammar; it is just part of the spelling and pronunciation of the word.