El umbral auditivo se expresa en decibelios.

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Breakdown of El umbral auditivo se expresa en decibelios.

• expresar: to express
• el decibelio: the decibel
• el umbral auditivo: the hearing threshold

Questions & Answers about El umbral auditivo se expresa en decibelios.

Why does the sentence use se expresa instead of just expresa?

Because se expresa is a very common way in Spanish to express an idea like is expressed.

So:

• El umbral auditivo expresa... would mean the auditory threshold expresses..., which sounds wrong because the threshold is not doing the action itself.
• El umbral auditivo se expresa en decibelios means the auditory threshold is expressed in decibels.

This is sometimes called a passive se construction. Spanish often prefers this structure instead of the full passive with ser.

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Could you also say El umbral auditivo es expresado en decibelios?

Yes, grammatically you could, but it sounds much less natural in normal Spanish.

Spanish usually prefers:

• se expresa en decibelios

rather than:

• es expresado en decibelios

The version with se is shorter, smoother, and much more common in scientific, technical, and general writing.

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Why is it El umbral auditivo and not La umbral auditiva?