Learn Hardcore Korean: gwiro sorireul deutneun ge dangyeonhaeyo. - It’s natural to hear sounds with the ears.

귀 means “ear.” When you attach -로, it indicates the means or instrument (“through/by way of”). So 귀로 literally means “through the ears.” If you used -에 (귀에), you’d simply mark the location (“at the ear”), not the medium by which you hear.

Why is 소리를 marked with 를, and can we omit 소리 completely?

소리 means “sound.” -를 is the object particle, because sounds are what you hear. You can omit 소리 if it’s clear from context—귀로 듣는 게 당연해요 still means “It’s natural to hear with your ears.” Including 소리를 makes it explicit that you’re talking about hearing sounds.

What does 듣는 게 mean, and why is 게 used here instead of 것?

듣는 is the adjective form (present participle) of 듣다 (“to hear”). Adding -게 is a contraction of 것이, nominalizing the verb clause into “hearing.” The full, more formal version is 듣는 것이 당연해요, but in everyday speech 듣는 게 is shorter and more natural.

What does 당연해요 mean, and can we use other words like 물론이에요?

당연해요 is the polite present tense of 당연하다, meaning “it’s natural,” “it’s only logical,” or “of course.” You could use 물론이에요 (“of course”), but 당연해요 emphasizes that something logically follows from given facts, rather than just expressing agreement.

Can we change the word order or shorten the sentence, for example to 귀로 듣는 게 당연해요?

Yes. Korean word order is flexible. 귀로 듣는 게 당연해요 (“It’s natural to hear through your ears”) is perfectly acceptable. You could also say 소리를 귀로 듣는 게 당연해요, but dropping 소리를 or moving it around doesn’t change the core meaning.

What’s the difference between 듣다 and 들리다? Why use 듣다 here?

듣다 is an active verb: “to hear” or “to listen to something” (you do the hearing). 들리다 is the passive form: “to be heard” or “to be audible.” Since this sentence describes the active process of using your ears to hear sounds, 듣다 is the correct choice.