Why can't I hear the difference between Korean sounds like ㄱ, ㅋ and ㄲ, and what practice fixes it?
Synapse makes this guide, the free Sound Gym it links to, and the app at the end. What it says about Korean sounds comes from the phonetics research listed under Sources, checked on 5 November 2026.
Korean splits ㄱ ㅋ ㄲ, ㄷ ㅌ ㄸ, ㅂ ㅍ ㅃ and ㅈ ㅊ ㅉ three ways, and in Seoul Korean today much of the difference is in the vowel after the consonant: it starts low after a plain consonant and high after an aspirated or tense one, while an aspirated consonant carries a strong puff of breath that a tense one does not. English, like many languages, tells these consonants apart mainly by breath or voicing, so the ear merges them until you train it with short, daily listening drills on words that differ in just that one sound.
The sound chart
Korean has five of these series. Each row below is one series; each column is one way of releasing it. The letters are written in the official Revised Romanization, which spells the plain consonants g, d, b and j even though, at the start of a word, they are not voiced like English g, d, b or j.
| Series | Plain | Aspirated | Tense |
|---|---|---|---|
| k sounds | ㄱ g | ㅋ k | ㄲ kk |
| t sounds | ㄷ d | ㅌ t | ㄸ tt |
| p sounds | ㅂ b | ㅍ p | ㅃ pp |
| ch sounds | ㅈ j | ㅊ ch | ㅉ jj |
| s sounds | ㅅ s | none | ㅆ ss |
What you hear at the start of a word, for the k, t, p and ch sounds:
| Type | Breath after the consonant | The vowel after it |
|---|---|---|
| Plain | A light puff. Many younger Seoul speakers give it nearly as much breath as an aspirated consonant. | The pitch starts low, and the voice is a little breathy. |
| Aspirated | A strong puff, like English p, t or k at the start of a word. | The pitch starts high. |
| Tense | Almost no puff, and a tight start. | The pitch starts high, and the voice is clear and tight rather than breathy. |
The pitch difference is clearest at the start of a word said on its own or at the start of a phrase. In the middle of a phrase, a plain consonant between two vowels becomes voiced, so 아기 (baby) sounds close to "agi", and that voicing sets it apart from the other two.
What to listen for in each series
ㄱ, ㅋ and ㄲ (g, k, kk)
Try 기 (energy), 키 (height) and 끼 (flair). ㄱ sits between English g and k: no voicing before it, a light puff after it, and a low start to the vowel. ㅋ has the strong puff of the k in "kite". ㄲ is closest to the k in "sky": no puff, but pressed tighter.
Listen for: the low start of 기 against the high starts of 키 and 끼, then the burst of air in 키 that 끼 does not have.
ㄷ, ㅌ and ㄸ (d, t, tt)
Try 달 (moon), 탈 (mask) and 딸 (daughter). ㄷ sits between English d and t, ㅌ has the puff of the t in "top", and ㄸ is closest to the t in "stop", pressed tighter.
Listen for: the low start of 달 against the high starts of 탈 and 딸, then the burst of air in 탈 that 딸 does not have.
ㅂ, ㅍ and ㅃ (b, p, pp)
Try 불 (fire), 풀 (grass) and 뿔 (horn), the three words Synapse's first Korean lesson opens with, or 발 (foot) and 팔 (arm). At the start of a phrase, researchers describe 발 and 팔 as differing mainly in pitch: low for 발, high for 팔.
Listen for: a low start in 불 and 발 and a high start in 풀, 뿔 and 팔, then the puff in 풀 that 뿔 does not have.
ㅈ, ㅊ and ㅉ (j, ch, jj)
Try 자다 (to sleep), 차다 (to kick) and 짜다 (to be salty). These three are affricates, a stop released into a short hiss, and they split three ways just like the stops. ㅈ sits between English j and ch, ㅊ has the puff of the ch in "chair", and ㅉ has no puff and a tight start.
Listen for: the low start of 자 against the high starts of 차 and 짜, then the breath in 차 that 짜 does not have.
ㅅ and ㅆ (s, ss)
Try 사다 (to buy) and 싸다 (to be cheap). These two are a pair, not a triplet. ㅅ is a softer hiss followed by a short breath, and the vowel after it sounds breathy. ㅆ is a sharper, longer hiss with no breath after it. Unlike the stops, the two do not reliably differ in pitch. Before ㅣ the breath after ㅅ shrinks or disappears, so 시 and 씨 are harder to tell apart than 사 and 싸.
Listen for: the breath between the hiss and the vowel in 사다, which 싸다 does not have, and the sharper hiss of 싸다.
Why your ear merges them
If English is your first language, your ear sorts these consonants into two groups by the breath after them: p, t and k with a puff, and b, d and g with little or none. In a 2023 study, English speakers with little or no experience of Korean heard both plain and aspirated Korean stops as English p, t and k, and rated both as good examples. Tense stops landed in either group, most often with b, d and g.
Plain and aspirated run together because both carry breath. In Seoul Korean today the gap in breath between them has narrowed, especially among younger speakers, and pitch has taken over: the vowel after a plain consonant starts low. English listeners rely mainly on breath to tell these consonants apart, not on pitch, so an English ear is not yet listening where the difference is. The romanization adds to it, since g, d, b and j suggest voiced English sounds that the plain consonants are not.
Speakers of other languages draw these lines in other places, so which Korean letters run together for you depends on the language you grew up with.
How to train it
- Listen to the vowel first. Ask whether it starts low or high, then ask about the breath.
- Practise with pairs of words that differ only in this sound, such as 달 and 탈, and pick which word you heard before you see the answer.
- Check each answer right after you give it.
- Keep sessions to a few minutes and come back the next day.
- Then say the words yourself, copying the pitch as well as the breath.
You can start now, free and with no account, in the Korean Sound Gym: you hear one word of a pair and pick which one it was. The same gym is there with its page in Japanese and Persian.
In the Synapse app you learn Korean from your own language, which can be any of its other 25 languages. In ear training you compare Korean sounds with the nearest sounds in your language, and when the Korean sound is ㄱ, ㄷ, ㅂ or ㅈ, you see its tense, plain and aspirated letters side by side with a note on the pitch. The video lesson How can I read my first Korean words? starts with 불, 풀 and 뿔.
Sources
- Yoonjung Kang (2014). Voice Onset Time merger and development of tonal contrast in Seoul Korean stops: A corpus study. Journal of Phonetics 45, 76–90. Plain and aspirated stops merging in breath, and pitch separating them, across 117 Seoul speakers aged 19 to 71.
- Hye-Young Bang, Morgan Sonderegger, Yoonjung Kang, Meghan Clayards and Tae-Jin Yoon (2018). The emergence, progress, and impact of sound change in progress in Seoul Korean: Implications for mechanisms of tonogenesis. Journal of Phonetics 66, 120–144. The pitch of the following vowel as the main cue at the start of a phrase, and 발 and 팔 as an example.
- Eun Jong Kong, Mary E. Beckman and Jan Edwards (2011). Why are Korean tense stops acquired so early? The role of acoustic properties. Journal of Phonetics 39(2), 196–211. Short breath and a tight voice after tense stops, low pitch after plain stops, and plain stops voiced between vowels.
- Taehong Cho, Sun-Ah Jun and Peter Ladefoged (2002). Acoustic and aerodynamic correlates of Korean stops and fricatives. Journal of Phonetics 30(2), 193–228. The three types differing in the voice quality of the following vowel.
- Charles B. Chang (2013). The production and perception of coronal fricatives in Seoul Korean: The case for a fourth laryngeal category. Korean Linguistics 15(1), 7–49. How ㅅ and ㅆ differ, and why pitch does not separate them.
- Charlie Nagle, Shelby Bruun and Melissa Baese-Berk (2023). Perceptual assimilation of Spanish, Thai, and Korean stop consonants by native English speakers. Proceedings of the 20th International Congress of Phonetic Sciences. How English listeners hear the three Korean stops.