[CaptSkip]

Like I said I don't know the physics, but if the first blast was lower in intensity, the first blast wave might also move slower and fall of more quickly as distance increases.

The only "Law" I can speak to is the "Inverse Square Law".

"...the inverse square law applies to diverse phenomena. Point sources of gravitational force, electric field, light, sound or radiation obey the inverse square law. It is a subject of continuing debate with a source such as a skunk on top of a flag pole; will it's smell drop off according to the inverse square law?"

http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html

[coloradan]

Nope, loud sounds travel as fast as quiet ones, unless there's a shock wave, which can exceed the speed of sound. But once it's no longer a shock wave, it's just ordinary sound and travels at sound speed. True, HE bombs make shock waves, but they dissipate in tiny fractions of a second and can't be used to explain an 8 sec. delay. It takes a large nuclear weapon to support a shock wave that continues to exist 8 seconds after detonation.