Shrieker and calibrated sensor

I am trying to build a door that uses the CSS with signal strenght 15 to detect when a chicken is killed in the room. I saw that the CSS can indeed trigger the shrieker but only on a few frequences, I found 1,2,7,11 and 12. Is it a known bug or an intended feature? In any case, if it is possible, can someone help me with it?