Mi amigo soltó una carcajada al escuchar el chiste.

It’s a very natural Spanish expression meaning he burst out laughing or he let out a loud laugh.

Literally, soltar means to release, to let go, or to let out, and una carcajada means a loud laugh / a guffaw / a burst of laughter.

So word-for-word, it is something like:

• soltó = he let out
• una carcajada = a loud laugh

In English, we usually would not say he released a laugh, but in Spanish this is a normal and idiomatic way to express sudden laughter.

Because the sentence describes a completed action at a specific moment in the past.

• Mi amigo soltó una carcajada = My friend burst out laughing
• It happened once, at a particular moment, after hearing the joke.

The preterite (soltó) is used for that kind of event: a single, finished action.

If you used the imperfect, soltaba, it would sound unusual here unless you were describing a repeated or ongoing action in some special context.

So:

• soltó = one completed burst of laughter
• soltaba = he used to let out laughs / he was bursting out laughing repeatedly or as background

The accent mark shows both pronunciation and which tense/person it is.

• solto is not a correct standard form here
• soltó means he/she/it let out in the preterite

The accent tells you the stress falls on the last syllable:

• sol-TÓ

It also helps distinguish it from other forms of the verb.

Carcajada is a big, loud, sudden laugh. It is stronger and more vivid than risa.

Compare:

• risa = laughter / laugh
• carcajada = hearty laugh, guffaw, burst of loud laughter

So if someone smiles or laughs lightly, you would not usually use carcajada. This word suggests something more forceful and audible.

That makes the sentence sound expressive: the joke really made him laugh.

Because Spanish often uses the singular to describe one burst or one instance of something.

• soltar una carcajada = to let out a laugh / burst out laughing

This does not mean the person laughed only once in a mechanical sense. It means there was one sudden episode of loud laughter.

You could use the plural in other contexts, but the singular is the normal expression here.

Al + infinitive is a very common Spanish structure meaning:

• when
• upon
• on
• while

depending on context.

So:

• al escuchar el chiste = when he heard the joke / upon hearing the joke

It connects the laugh to the moment of hearing the joke.

This structure is extremely common in Spanish:

• Al entrar, saludó a todos. = When he came in, he greeted everyone.
• Al verlo, me sorprendí. = When I saw him, I was surprised.

Yes. Both are correct, but they feel slightly different.

• al escuchar el chiste = upon hearing the joke / when hearing the joke
• cuando escuchó el chiste = when he heard the joke

The version with al + infinitive is compact and elegant, and it strongly links the two actions. It often sounds a bit more fluid in narration.

The version with cuando escuchó is more explicit because it gives you a fully conjugated verb.

Both are natural:

• Mi amigo soltó una carcajada al escuchar el chiste.
• Mi amigo soltó una carcajada cuando escuchó el chiste.

Both verbs can relate to hearing, but they are not always identical.

• oír = to hear
• escuchar = to listen, or sometimes to hear in a slightly more attentive sense

In many contexts, Spanish speakers use escuchar naturally with things like stories, comments, or jokes. Here, al escuchar el chiste sounds completely normal.

You could also hear:

• al oír el chiste

That would also be correct. The difference is small in this sentence.

Because the sentence refers to a specific joke, presumably the one that was just told.

• el chiste = the joke
• un chiste = a joke

Using el suggests the speaker and listener both know which joke is meant, or that it has just been introduced by the context.

If you said un chiste, it would sound less specific:

• Mi amigo soltó una carcajada al escuchar un chiste. = My friend burst out laughing on hearing a joke.

That is grammatically fine, but it does not point to a particular joke in the same way.

In this sentence, yes, it is more vivid and expressive.

Compare:

• Mi amigo se rió al escuchar el chiste. = My friend laughed when he heard the joke.
• Mi amigo soltó una carcajada al escuchar el chiste. = My friend burst out laughing when he heard the joke.

Both are correct, but soltó una carcajada gives a stronger image. It suggests a sudden, noticeable laugh.

So this choice is more descriptive and colourful.

Spanish often leaves out subject pronouns because the verb ending already tells you who the subject is.

• soltó = he/she/it let out

So Mi amigo is enough to show who did the action. You do not need él.

You could say Él soltó una carcajada..., but that would usually add emphasis or contrast, for example:

• Yo no me reí, pero él soltó una carcajada. = I didn’t laugh, but he burst out laughing.

In the original sentence, él would be unnecessary.

Usually, yes.

• mi amigo = my male friend
• mi amiga = my female friend

In some contexts, amigo can be used in a general or mixed-gender sense, but in a simple sentence like this, most learners should understand mi amigo as my male friend.

Yes. Spanish allows some flexibility in word order, although the original version is the most neutral and natural.

For example:

• Al escuchar el chiste, mi amigo soltó una carcajada.

This means the same thing. It just puts the time/action trigger first: Upon hearing the joke, my friend burst out laughing.

The original order is more straightforward:

• Mi amigo soltó una carcajada al escuchar el chiste.

Both are correct.

Yes. It sounds natural and idiomatic in Spain.

A few notes:

• chiste is the normal word for joke
• soltar una carcajada is a normal, expressive phrase
• the whole sentence sounds like standard written or spoken Spanish

It is slightly more vivid than very basic everyday speech, but it is absolutely natural.