בדרך כלל הרחוב פחות רועש כשהחלון סגור והחדר מואר.

Yes. בדרך כלל is a very common fixed expression meaning usually, generally, or as a rule.

Literally, the words are:

• דרך = way
• כלל = rule / general principle

But as a phrase, you should learn בדרך כלל as a single chunk meaning usually.

Hebrew often puts time or frequency expressions near the beginning of the sentence, just like English can do:

• Usually, the street is less noisy...
• בדרך כלל הרחוב פחות רועש...

So starting with בדרך כלל is completely natural. It sets the general situation first.

הרחוב means the street. The prefix ה־ is the Hebrew definite article, equivalent to English the.

So:

• רחוב = a street / street
• הרחוב = the street

In this sentence, Hebrew uses the definite form because it is talking about the street in a general or contextually known sense.

פחות means less, and רועש means noisy.

So:

• רועש = noisy
• פחות רועש = less noisy

This is the normal Hebrew way to make a less + adjective comparison.

Examples:

• פחות יקר = less expensive
• פחות גדול = less big / smaller in comparison
• פחות רועש = less noisy

Because רועש agrees with הרחוב.

In Hebrew, adjectives must agree with the noun in gender and number.

• רחוב is masculine singular
• so the adjective is רועש = masculine singular

Compare:

• רחוב רועש = a noisy street
• עיר רועשת = a noisy city

Here are the relevant nouns in the sentence:

• רחוב = masculine
• חלון = masculine
• חדר = masculine

That is why you get:

• רועש
• סגור
• מואר

all in masculine singular form.

In the present tense, Hebrew usually does not use a separate word for is / are in sentences like this.

So:

• החלון סגור = the window is closed
• החדר מואר = the room is lit

This is very normal Hebrew grammar.

Compare:

• הוא עייף = he is tired
• הדלת פתוחה = the door is open
• הילדים בבית = the children are at home

There is no separate present-tense is/are word in these kinds of sentences.

In this sentence, סגור functions like an adjective meaning closed.

So:

• החלון סגור = the window is closed

It describes the state of the window, not an action happening right now.

This is similar to English closed in the window is closed.

מואר means lit, illuminated, or well-lit.

It comes from the verb להאיר = to light / to illuminate.

So:

• החדר מואר = the room is lit / illuminated

Here מואר describes the condition of the room.

Good question. The difference is roughly this:

• מאיר = lighting / shining / illuminating
• מואר = lit / illuminated

So:

• החדר מואר = the room is lit
  The room is receiving light.
• החדר מאיר would suggest the room itself is shining or giving light, which is usually not what you mean.

That is why מואר is the natural choice here.

Yes, in writing it appears as one unit here: כשהחלון.

It is made of:

• כש־ = when
• החלון = the window

So:

• כשהחלון סגור = when the window is closed

This כש־ is a very common way to say when before a clause.

Examples:

• כשאני בבית = when I am at home
• כשיורד גשם = when it rains
• כשהדלת פתוחה = when the door is open

Yes. The sentence means that both conditions are part of the same situation:

• כשהחלון סגור
• והחדר מואר

Together, that means: when the window is closed and the room is lit

So the street is less noisy under those conditions.

Because Hebrew, like English, often lets one when cover two coordinated parts.

So this:

• כשהחלון סגור והחדר מואר

means:

• when the window is closed and the room is lit

You could think of the when as applying to both parts. Repeating it is usually unnecessary.

Yes, but more specifically it expresses a general present or habitual/general truth idea.

Because of בדרך כלל (usually), the sentence means something like:

• this is generally the case
• this is what typically happens

So it is not just about one single moment, but about a usual situation.

Because Hebrew often uses a simple descriptive structure where English might also just say is less noisy.

• הרחוב פחות רועש = the street is less noisy

This describes a state, not necessarily a change happening step by step. If you wanted to emphasize becoming less noisy, Hebrew could use a different verb, but here the sentence is simply describing the usual condition.

The structure is:

• בדרך כלל = usually
• הרחוב = the street
• פחות רועש = less noisy
• כשהחלון סגור והחדר מואר = when the window is closed and the room is lit

So the pattern is basically:

Usually + subject + description + when-clause

That word order is natural in Hebrew.

Exactly.

• חלון is masculine singular, so: סגור
• חדר is masculine singular, so: מואר

If the nouns were feminine, the forms would change. For example:

• הדלת סגורה = the door is closed
• הכיתה מוארת = the classroom is lit

This agreement is an important part of Hebrew grammar.

Yes, depending on context, רועש can be translated as noisy or sometimes loud.

In this sentence, noisy is the most natural translation because it describes the street environment rather than, for example, the volume of a single sound.

So:

• הרחוב פחות רועש = the street is less noisy

is the most idiomatic understanding here.