Su acento suena muy natural en español.

Su is a possessive adjective that can mean:

• his accent
• her accent
• their accent (singular they or plural they)
• your accent (formal usted)

Spanish su is ambiguous by itself; the context tells you whose accent it is.

If you specifically mean informal your (speaking to a friend, in Spain), you would more usually say:

• Tu acento suena muy natural en español. → informal you
• Su acento suena muy natural en español. → formal you or his/her/their

In careful speech or writing, Spanish sometimes avoids the ambiguity by using phrases like:

• El acento de él / de ella / de ellos / de usted…

You can say Su acento es muy natural en español, and it is correct.

However, sonar (here suena) literally means to sound, and it’s the most natural verb when talking about how something sounds to the ear:

• Su acento suena muy natural en español.
  → Focus on how it sounds when you hear it.

• Su acento es muy natural en español.
  → More neutral, a bit more like a general description.

In practice, both are fine, but native speakers very often use sonar for accents, voices, music, etc.

• Infinitive: sonar (to sound)
• suena = 3rd person singular, present indicative

So it means it sounds (here: his/her/your/their accent sounds).

Conjugation in the present (European Spanish pronunciation, but same forms everywhere):

• (yo) sueno – I sound
• (tú) suenas – you sound (informal singular)
• (él / ella / usted) suena – he/she/you (formal) sound
• (nosotros) sonamos – we sound
• (vosotros) sonáis – you all sound (informal plural, Spain)
• (ellos / ellas / ustedes) suenan – they / you all (formal) sound

Because:

• natural here is an adjective describing acento (accent).
• muy is an adverb meaning very that modifies adjectives and other adverbs.

You use:

• muy + adjective/adverb → muy natural, muy rápido, muy bien
• mucho/mucha/muchos/muchas + noun → mucho trabajo, mucha gente

So mucha natural would be wrong; the correct structure is muy natural.

In Spanish, every noun has grammatical gender, even if the concept doesn’t feel gendered in English.

• acento is a masculine noun.
• That’s why you’d say:
  
  • un acento (not una acento)
  • el acento (not la acento)
  • un acento muy natural

The possessive su doesn’t change for gender, so it stays su whether the noun is masculine (acento) or feminine (voz):

• su acento
• su voz

With languages, Spanish often omits the article in general statements, especially after certain verbs and prepositions:

• Habla español muy bien.
• En español es diferente.

After en, both are technically possible:

• en español – the standard, neutral way to say in Spanish
• en el español de Argentina / de México… – when you specify a variety or make it very specific

In your sentence, we’re talking about Spanish in general, so:

• Su acento suena muy natural en español. ✅
• Su acento suena muy natural en el español. ❌ (sounds odd unless followed by something like de México, de España, etc.)

In Spanish, names of languages and nationalities are written in lowercase, unless they start the sentence:

• Habla español y francés.
• Es español, pero vive en Alemania.

So:

• en español is correct.
• en Español would normally be a spelling mistake (except in titles, logos, etc.).

Yes, that’s completely correct:

• Su acento suena muy natural en español.
• Su acento en español suena muy natural.

Both are grammatical and natural. The difference is subtle:

• First version: slightly more focus at the end on en español.
• Second version: it highlights his/her/your accent in Spanish as a unit, then comments that it sounds very natural.

In everyday speech, both are used without any real difference in meaning.

Suena is pronounced roughly like SWAY-na in English.

Breakdown:

• sue- → sue is a diphthong [swe], like the swe in sweater.
• -na → nah, with a clear a as in father.

Phonetic approximation: [ˈswe.na].

Use:

• Tu acento suena muy natural en español.

  • speaking to someone informally, as tú (friends, similar age, casual situations, common in Spain).

• Su acento suena muy natural en español.

  • formal you (usted)
  • or his / her / their accent (3rd person)

So if you’re talking to a friend in Spain, Tu acento… is the usual choice.

Yes, this is also correct:

• Tiene un acento muy natural en español.
  → literally He/She/You has a very natural accent in Spanish.

The nuance:

• Su acento suena muy natural en español.
  → focuses more on how it sounds to you.

• Tiene un acento muy natural en español.
  → a bit more neutral, like a description of the property of the accent.

Both are common compliments about someone’s Spanish.

Yes. If the language is clear from context, you can simply say:

• Su acento suena muy natural.
• Tu acento suena muy natural.

Adding en español is useful when you want to be explicit or when multiple languages could be involved, but it’s not grammatically required.