How old is the 19 inch lcd? Have you used it much? Do you mean your LCD has built in speakers? Or is the crackling actually coming from the LCD itself (with no speakers)?
Crackling can be caused by many things.
Is your LCD old? That can cause crackling. Worn out speakers...etc.
Static. If it's really dry in your room, and or dusty this can cause that.
Your power cable for your LCD. Are there many wires near it?
Just to be safe I wouldn't connect it just yet....