Since I bought this phone, I can't turn off shutter sound.
It like LG not allow to do it.
but I found solution by accident.
this is the solution
1. go to mp3 player
2. make new playlist
3. add 2 music to playlist
IMPORTANT !
the length of each music should be very short like 20 seconds
4. set auto repeat to all
5. start playing music
6. press option, press minimized
now you are in normal screen, and music keep playing
7. turn volume lowest but still can hear music
8. after first music end the player will take about 2 seconds before play next music
this is important moment
turn on shutter of camera at this second
if this is success, the music will keep playing and your camera function will work at the same time
9. press shutter and you will see, no shutter sound annoy you.
Note :
in step 8 before turn on shutter, if you are quick enough , press volume to lowest until you can't hear, and turn on shutter, you will get perfect silent shutter sound of KC550