बाहर बारिश हो रही है, इसलिए मैं आपकी आवाज़ नहीं सुन सकता।

Hindi does not need a dummy subject like English it in weather expressions.

So English it is raining becomes simply:

बारिश हो रही है
literally, rain is happening

That is completely normal Hindi. There is no need to add a word meaning it.

बाहर means outside or outdoors.

At the beginning of the sentence, it sets the scene:

बाहर बारिश हो रही है = It’s raining outside

Hindi often puts time/place words early in the sentence, though word order can be somewhat flexible. Here, starting with बाहर sounds very natural.

Hindi commonly expresses weather events like this with होना plus the progressive form:

बारिश हो रही है
literally: rain is happening

This is the usual way to say it is raining.

So:

• बारिश = rain
• हो रही है = is happening / is going on

Even though it sounds different from English, this is one of the standard Hindi patterns for weather.

Because बारिश is a feminine noun in Hindi.

In हो रही है, the progressive participle agrees with the noun:

• masculine singular: रहा
• feminine singular: रही
• plural: रहे

Since बारिश is feminine singular, Hindi uses रही:

बारिश हो रही है

इसलिए means therefore, so, or that’s why.

It introduces the result:

बाहर बारिश हो रही है, इसलिए मैं आपकी आवाज़ नहीं सुन सकता।
= It’s raining outside, so I can’t hear your voice.

By contrast, क्योंकि means because and introduces the reason.

Compare:

• मैं आपकी आवाज़ नहीं सुन सकता, क्योंकि बाहर बारिश हो रही है।
  = I can’t hear your voice because it’s raining outside.

• बाहर बारिश हो रही है, इसलिए मैं आपकी आवाज़ नहीं सुन सकता।
  = It’s raining outside, so I can’t hear your voice.

Because आवाज़ is a feminine noun, and the possessive must agree with the noun being possessed.

So:

• आपका = your (with masculine singular nouns)
• आपकी = your (with feminine singular nouns)
• आपके = your (with plural or some oblique forms)

Since आवाज़ is feminine singular:

आपकी आवाज़ = your voice

आप is the polite/formal word for you in Hindi.

So:

• आपकी आवाज़ = your voice (polite/formal)
• तुम्हारी आवाज़ = your voice (informal/familiar)
• तेरी आवाज़ = your voice (very informal/intimate, or rude in the wrong context)

Using आपकी shows politeness or respect toward the listener.

Because सुनना usually takes a direct object without को.

So the normal phrasing is:

मैं आपकी आवाज़ नहीं सुन सकता
= I cannot hear your voice

Hindi often leaves out को with inanimate or general direct objects. With सुनना, that is very common.

Adding को here would usually sound marked or unnecessary:

• normal: आपकी आवाज़ सुन सकता
• less neutral/emphatic: आपकी आवाज़ को सुन सकता

So the version without को is the standard choice.

With सकना (to be able / can), Hindi uses the verb stem, not the infinitive.

So:

• dictionary form: सुनना = to hear
• stem used before सकना: सुन

That gives:

• सुन सकता = can hear
• सुन सकती = can hear (female speaker)
• सुन सकते = can hear (plural/respectful)

This is the normal pattern in Hindi:

• कर सकता = can do
• जा सकता = can go
• समझ सकता = can understand

सकता agrees with the speaker, because the subject is मैं.

Since मैं itself does not show gender, the form of the verb tells us about the speaker:

• मैं ... सुन सकता = I can hear (speaker is male)
• मैं ... सुन सकती = I can hear (speaker is female)

So if a woman were saying this sentence, it would be:

बाहर बारिश हो रही है, इसलिए मैं आपकी आवाज़ नहीं सुन सकती।

A learner will often expect:

मैं आपकी आवाज़ नहीं सुन सकता हूँ।

That version is also correct and more explicit.

In everyday Hindi, especially in speech, the present-tense हूँ / है / हैं is often omitted when the meaning is already clear from context. So:

• मैं आपकी आवाज़ नहीं सुन सकता हूँ = fully explicit
• मैं आपकी आवाज़ नहीं सुन सकता = very common in natural speech

So the sentence you have is natural, especially conversationally.

Here नहीं negates the ability to hear:

मैं आपकी आवाज़ नहीं सुन सकता
= I cannot hear your voice

In Hindi, नहीं usually comes before the part being negated, and with verb phrases it often appears before the main verb expression.

So this placement is very natural:

• नहीं सुन सकता = cannot hear

Learners should notice that Hindi does not build negation the way English does with do not or cannot; instead, it usually places नहीं before the verb phrase.