Learn Hardcore Russian: Перед входом в зоопарк собралась большая толпа, и слышен радостный звук детских голосов. - In front of the entrance to the zoo a big crowd has gathered, and the joyful sound of children’s voices can be heard.

перед зоопарком – in front of the zoo as a whole (somewhere outside, near the zoo territory)
перед входом в зоопарк – specifically in front of the entrance to the zoo

The author wants to emphasize the exact location where people gather: at the entrance gate, not just somewhere near the zoo building or territory. That’s why вход is used.

Why is it в зоопарк (accusative) and not в зоопарке (prepositional)?

The difference is movement vs location:

в + accusative = movement into something
- идти в зоопарк – to go to the zoo
в + prepositional = location inside something
- быть в зоопарке – to be in the zoo

In перед входом в зоопарк, the phrase в зоопарк is tied to the idea of an entrance leading into the zoo. Grammatically, native speakers conceptualize that as “entrance to the zoo” → вход в зоопарк with the accusative.

Why is the verb собралась in the feminine form? Isn’t толпа a group of people?

Yes, толпа means “crowd” (a group of people), but grammatically in Russian it is a singular feminine noun:

толпа – feminine, singular

Verbs in the past tense agree with the grammatical gender of the subject, not with the natural gender or the “collective” idea:

толпа собралась (fem. sg.) – the crowd gathered
группа пришла (fem. sg.) – the group came
армия наступала (fem. sg.) – the army advanced

So собралась (feminine past) is correct because of толпа.

What does the -сь in собралась do? Why not just собрала?

The -сь (or -ся) is the reflexive/postfix form. It changes the meaning of the verb:

собрать – to collect/gather something
- Она собрала вещи. – She packed (gathered) her things.
собраться – to gather oneself / to come together, assemble
- Люди собрались. – People gathered (came together).

Here собралась большая толпа means “a large crowd formed/gathered there.” It’s not that someone “gathered” the crowd; the crowd itself formed. That’s why the reflexive form собралась is used.

Why is the word order собралась большая толпа, not большая толпа собралась?

Both are grammatically correct. The difference is nuance and focus:

БОЛЬШАЯ ТОЛПА собралась.
Neutral, subject-first word order: “A big crowd gathered.”
СОБРАЛАСЬ большая толпа.
Verb-first puts a bit more emphasis on the result/event (the fact that it gathered), and большая толпа comes as new information.

This verb-first pattern is also very natural in descriptions of scenes, like in narratives:

На площади стояла высокая церковь.
Возле дома росло большое дерево.

So собралась большая толпа sounds descriptive and slightly more “literary” or narrative in style.

Why is there a comma before и слышен радостный звук детских голосов?

The sentence has two main clauses joined by и:

Перед входом в зоопарк собралась большая толпа
(там) слышен радостный звук детских голосов

Each clause has its own predicate:

собралась (gathered)
слышен (is heard / can be heard)

In Russian, when two independent clauses share the same subject/situation but each has its own predicate, they are usually separated by a comma before и:

Солнце село, и наступила ночь.
Дети играли, и звучал смех.

So the comma marks two coordinated clauses.

What exactly is слышен? Is it a verb? Why not слышно?

Слышен here is a short-form adjective from the full adjective слышный (“audible”). Short-form adjectives are often used as predicates and can be translated like “is …”:

звук слышен – the sound is audible / can be heard

The structure is:

слышен (short adj. masc. sg.) + радостный звук (masc. sg.)
- They agree in gender and number.

If you say слышно, that’s an impersonal adverb-like form (often from neuter short forms) and doesn’t agree with any noun:

Слышно детские голоса. – One can hear children’s voices. (literally, “It is hearable children’s voices.”)

So:

слышен радостный звук – more literally “a joyful sound is audible” (emphasizes the existence/quality of a specific sound)
слышно детские голоса – “children’s voices can be heard” (emphasizes the fact that they are heard, no specific noun as subject)

The sentence chooses слышен to make радостный звук the grammatical subject.

Could we also say слышатся детские голоса here? How would that change the meaning?

Yes, you could say:

… и слышатся детские голоса.

Differences:

слышен радостный звук детских голосов
Focus on one joyful sound; slightly more descriptive/poetic; the subject is звук.
слышатся детские голоса
Focus on the voices themselves being heard as separate sources; the subject is голоса.

Stylistically:

слышен радостный звук детских голосов – more literary, paints a “soundscape”
слышатся детские голоса – neutral descriptive phrase

Both are correct; it’s mostly a matter of style and what exactly you want to highlight.

Why is it звук детских голосов (singular звук) instead of plural звуки детских голосов?

Both are possible, but they have slightly different nuances:

звук детских голосов – the sound of children’s voices (as one combined background sound)
звуки детских голосов – the sounds of children’s voices (more like multiple distinct sounds)

The singular звук here emphasizes the idea of one general, joyful “noise” or “hum” coming from children. It’s more natural when you’re talking about an overall soundscape rather than individual sounds.

Why is детских голосов in the genitive plural?

The phrase звук детских голосов is a classic “X of Y” structure, like in English “sound of children’s voices”. In Russian, this is usually expressed with genitive:

звук чего? – детских голосов (genitive plural)

Formation:

детский (children’s, adj.) → детских in genitive plural
голос (voice) → голосов in genitive plural

Other similar examples:

шум машин – the noise of cars
смех детей – children’s laughter
запах цветов – the smell of flowers

Why is детских before голосов, not after it?

In Russian, attributive adjectives almost always come before the noun they modify:

детские голоса – children’s voices
большая толпа – a big crowd
радостный звук – a joyful sound

When you put the phrase into genitive plural:

детские голоса → детских голосов

The word order doesn’t change; the case ending changes, but the position of the adjective relative to the noun stays the same.

Could we say перед входом в зоопарк была большая толпа instead of собралась большая толпа? What’s the difference?

Yes, you can say:

Перед входом в зоопарк была большая толпа.

Difference in meaning:

была большая толпа – simply states that a big crowd was there (a static situation).
собралась большая толпа – emphasizes that a big crowd has formed/gathered there (a dynamic result).

So:

собралась adds the idea of coming together, not just existing. It’s more vivid and event-focused.

Why is собралась in the past tense while слышен seems to be present? Is there a tense mismatch?

This combination is natural in Russian because they describe different aspects of time:

собралась – past tense, perfective: the crowd has already gathered (completed action).
слышен – present-like state: the sound is now audible as a result.

So the idea is:

First, a big crowd formed (completed event in the past relative to “now” in the scene).
As a result, now the joyful sound of children’s voices is heard.

Russian often uses a past perfective verb to show a completed action and then a present/state predicate to show the current result of that action in the same sentence. This does not feel like a tense mistake to native speakers.