It could also be taken into account that the 612s rotate so the sound will sound different when the siren head is on axis with the camera microphone. Don't know how true this is but it's a possibility The Effect is called Doppler Shift... An Example is of a Big Rig Truck Honks his horn from behind ...

I forgot about that 2T22 in Crystal City. I saw it on TV back in 1993, if I remember correctly, during coverage of the big flood. Isn't it across the street from a water tower? I didn't know about the sirens in Hillsboro and Festus that you mentioned. I thought that Hillsboro had a yellow Model 5 o...