A quick search shows 120dB at 1m isn't abnormal for a truck air horn. A line of them from far enough away will decrease in level by 3dB per doubling of distanc

A quick search shows 120dB at 1m isn't abnormal for a truck air horn. A line of them from far enough away will decrease in level by 3dB per doubling of distance. 8 doublings would make it ~96dB at 256m.