I know someone who did work with Korean and said he couldn't hear them unless he was specifically listening for them but that you could hear the brunt of it on the vowel. In either case they're not geminate.
This has been bothering me for some time too so I'll keep an eye out for this thread.
wiki wrote:The Korean consonants also have elements of stiff voice1, but it is not yet known how typical this is of faucalized2 consonants. They are produced with a partially constricted glottis and additional subglottal pressure in addition to tense vocal tract walls, laryngeal lowering, or other expansion of the larynx.
1The term stiff voice describes the pronunciation of consonants with a glottal opening narrower, and the vocal cords stiffer, than what occurs in modal voice.
2Faucalized voice, also called hollow or yawny voice, is the production of speech sounds with an expanded laryngeal cavity. It contrasts with harsh voice, in which the larynx is compressed.