When Denver experiences pleasant and temperate springs and autumns, and neither air conditioners nor heaters are being operated, many citizens opt to leave windows and doors ajar. These actions, allow aircraft, vehicle traffic, and other exterior noise to permeate deeper into the home, hence increasing awareness of noise and its associated annoyance.
A greater number of noise complaints are received in the spring and autumn when people are outside and windows are open.
In addition, during warm temperatures, the air density (air molecules per cubic foot) decreases significantly, thereby reducing aircraft performance and lift. (Aircraft performance is dependent upon the number of molecules in the atmosphere. The fewer number of air molecules, the lesser the engine and airframe performance.) Consequently air density decreases as airport altitude increases.
Aircraft noise is also more noticeable on cloudy days. Low ceiling cloud cover tends to reflect or reverberate aircraft noise downward off the clouds, thus confining it.