According to Knox County's emergency management, the ridges around Knoxville limit the range tornado sirens have in the area.
Due to the limited range, the cost would be to high to make the project feasible in this area.
The city of Greenback does have tornado sirens, but the areas hit hardest by Wednesday night's storms were too far away to hear them.
This is a another reason why Tennessee officials strongly recommend families have weather radios.