what is that sound?

[ero]

im sure u guys relised too, theres a sound that keeps repeating it self and i have no idea what it means. its not part of the music because i mute that anyway and it plays in all levels and towne.
but if anyone knows please lemme know xD
thanks.

the sound is like a 3 second piece which sounds like a guitair or a strum.

no no no its not an emoticion, i already got all of em, its some other random sound.