[Barrie Yates]

Originally Posted by MargaretR

You may have 'industrial deafness'.

"The distance of travel of any sound depends on several factors. Some of these are:

1. Wind direction [sound waves are enhanced downwind of the source.
2..Temperature of the air [the cooler/denser the air is, the greater the travel distance].
3. Within some limitations, higher humidity will enhance the travel distance of sound."

"The distance that sound wave can travel and be heard is also a property of the air's temperature gradient. When the air near the ground is warmer than the air at higher elevations, then sound refracts (or bends) upward. Similarly, when the air is cooler near the ground (or water surface) than at higher elevations, the sound refracts (or bends) downward."

Distance travelled can vary according to environmental factors

BBC NEWS | Magazine | Can sound really travel 200 miles?

You forgot to mention the effect of frequency in your dissertation.