I don't know about STL-10s, but I'd heard that about Toshiba sirens and Japan's mountainous terrain. Makes sense, though. One important detail often forgotten about penetration is that an "attack" signal cuts through ambient noise better because it covers a range of frequencies. I have heard distant sirens where all I could hear was part of the wind up and wind down. The steady pitch was too high to carry.pyramid head wrote:I do not know where I read this, but I think somebody said that STL-10's were made for mountainous area's, and the low tone is for penetration. Is this correct?