In the Original game, You can hear two hidden sound effects while playing the game.
Whispering Sound when you suffered dizziness[]
You can hear a Some whispering sound if you make a dizziness yourself until your vision becomes blurred.
Overview[]
The sound you hear when Hui-min feels dizzy is the one woman's Desperate calls.
The woman says, "누가 좀 도와주세요. (Somebody help me.)" And her voices are heard overlapping some times.
In the game file, this sound file is named "패닉 (Panic)".
The Faint Sound in the Lost & Found Room[]
If you go the Lost & Found Room, You can hear the sounds like radio music faintly.
Overview[]
The sound is mixed with noise like radio music sound quality and the music is stopped as if you turn off the radio power.
And that sound is heard repeatedly.
In the game file, this sound file is named "라디오 (Radio)".
This sound is presumed to be the beginning part of Palobina [Ending theme]