El somier vuelve a hacer ruido porque una tuerca se ha aflojado.

Yes. In Spain, somier commonly means the bed base or slatted frame under the mattress. It is a very normal everyday word there.

A native English speaker might first think it means the whole bed, but it usually refers specifically to the supporting structure underneath the mattress.

Spanish usually uses the definite article more often than English.

So el somier means the bed base. In English, you might sometimes say the bed frame or just the frame, but in Spanish the article is normally kept.

Volver a + infinitive means to do something again.

So:

• vuelve a hacer ruido = it makes noise again / it starts making noise again

This is a very common structure in Spanish:

• Volví a leer el mensaje = I read the message again
• Ha vuelto a llamar = He/She has called again

Both are possible, but they are not exactly identical in feel.

• vuelve a hacer ruido emphasizes that the action is happening again
• hace ruido otra vez also means it makes noise again, but it is a little more direct and less built around the idea of returning to a previous state

In many contexts, they are interchangeable. Volver a + infinitive is just a very common and natural way to express again in Spanish.

Because hacer ruido is the normal expression for to make noise.

Spanish often uses hacer + noun in places where English uses a different structure:

• hacer ruido = make noise
• hacer daño = cause harm / hurt
• hacer una pregunta = ask a question

So here, hacer ruido is simply the standard collocation.

Yes, volver is an irregular stem-changing verb.

Its infinitive is volver, but in the present tense the o changes to ue in stressed forms:

• yo vuelvo
• tú vuelves
• él/ella vuelve
• nosotros volvemos
• vosotros volvéis
• ellos vuelven

So el somier vuelve means the bed base goes back to / comes back to, and with a hacer ruido, it becomes starts making noise again or makes noise again.

Because porque is the conjunction meaning because.

Compare:

• porque = because
• por qué = why
• el porqué = the reason
• por que = a less common combination used in special structures

In this sentence, the speaker is giving a reason, so porque is correct.

Tuerca means nut in the mechanical sense, as in a nut and bolt.

It is feminine, so it takes una:

• una tuerca
• la tuerca

The sentence uses una tuerca because it is introducing it as a nut, not referring to one already specifically identified.

Here se shows that the nut has become loose.

Compare:

• aflojar algo = to loosen something
  
  • He aflojado la tuerca = I have loosened the nut
• aflojarse / se ha aflojado = to come loose / to become loose
  
  • La tuerca se ha aflojado = The nut has come loose

So this is not saying who loosened it. It presents the change of state as happening to the nut itself.

For learners, a good practical translation is:

• se ha aflojado = has come loose

Because in this sentence aflojado is part of the verb form, not an adjective.

The structure is:

• se ha aflojado

This is the present perfect of the verb aflojarse. In compound tenses with haber, the past participle does not agree with the subject in gender or number.

So you say:

• La tuerca se ha aflojado
• Los tornillos se han aflojado

But if you use it as an adjective, agreement appears:

• La tuerca está aflojada = The nut is loose

In Spain, the present perfect is very commonly used for recent past actions or situations that are still relevant now.

So:

• se ha aflojado = it has come loose

This suggests a past change with a present result: the nut became loose, and that explains the noise now.

In many parts of Latin America, speakers might more naturally say:

• se aflojó

Both can be correct, but se ha aflojado sounds especially natural in Spain.

Yes, but the meaning changes slightly.

• una tuerca se ha aflojado = a nut has come loose
  
  • focuses on the change or event
• una tuerca está floja = a nut is loose
  
  • focuses on the current state

The original sentence explains the cause by pointing to something that has happened, so se ha aflojado is a very natural choice.

Because hacer ruido is a fixed expression.

Spanish usually says:

• hacer ruido = make noise

Not normally:

• hacer un ruido unless you mean make a noise / a particular sound

So:

• El somier hace ruido = The bed base makes noise
• El somier hizo un ruido raro = The bed base made a strange noise

Yes, to some extent. The original order is very natural:

• El somier vuelve a hacer ruido porque una tuerca se ha aflojado.

You could also say:

• Porque una tuerca se ha aflojado, el somier vuelve a hacer ruido.

But that sounds more marked or more deliberately structured. The original sentence is the most neutral everyday order: statement first, reason after.

A rough pronunciation guide:

• somier ≈ soh-MYER
• tuerca ≈ TWER-kah

A few notes:

• In somier, the stress falls on the last syllable: -mier
• In tuerca, ue forms a diphthong, so it sounds like twer-

If you want to sound more like Spain Spanish, the c in tuerca before a is a normal k sound, so there is nothing unusual there.

Sometimes, yes, depending on what you mean exactly.

Possible related words:

• cama = bed
• estructura de la cama = bed frame structure
• base = base
• somier = bed base / slatted frame

But somier is the most precise word here if the noisy part is the base under the mattress, not the whole bed in general.