Atmospheric focusing

Atmospheric focusing is a phenomenon that happens when sound waves travel through the atmosphere. When sound waves travel through the air, they have to pass through different layers of air that can have different temperatures, pressures and other stuff.
When the sound waves move from one layer of air to another layer with a different temperature and pressure, it can cause the sound waves to speed up or slow down and this is called atmospheric focusing. This means that if you make a noise, the sound can travel a lot further than it normally would.