How Far Can you Hear Class B Fireworks

From 1m to 10 miles, the dBA volume drops by about 85 dBA.

A soft whisper is about 30dBA. So a firework would have to be about 115 dbA at 1m for you to hear it as a soft whisper 10 miles away.

Display class Fireworks in the UK are limited to 120 dBA, the guideline doesn't make it very clear at what distance this is, it could be at the normal viewing distance - a few tens of meters. So it is plausible that you could hear the fireworks from 10 miles away if it were suitably quiet.

About one day a year we hear the sharp, metallic click of iron shots from a sunken driving range several blocks away. The rest of the time, totally undetectable in our quiet neighborhood. IOW, if stratified air reflects or channels the sound in an unusual way, the standard numbers can evidently be greatly exceeded.

Last night (New Year's Eve) we were astonished to hear very low frequency mortar reports that we think came from barges on San Francisco Bay at SF. I mean VERY LOW frequency. The sound would have to have traveled 32 miles south over the water then ashore for another 3 miles. Later in the evening, we watched a replay on TV and believe we recognized the pattern of the heavier explosions. Have never heard it on the Fourth of July ( summer versus winter). We found the sound very enjoyable...like listening to a very expensive woofer.