Noise Basics

 

Airport noise abatement offices around the country receive many phone calls from residents. They often want to know why aircraft noise varies so much from day to day. Varying weather conditions are one of the major causes of noise variation.

Wind direction and speed have a direct impact on the direction that aircraft can take off and land. Aircraft almost always take-off and land INTO the wind. This increases the speed of the air flowing over an aircraft's wings as it takes off and lands, which helps to increase the margin of safety in case of an engine failure or other such problems.

Airports have multiple runways that point in different directions so that, as wind direction and speed change, aircraft will still be able to operate in and out of the airport safely. Consequently, residents who live and work around airports find that aircraft fly over their homes or workplaces on some days while not on others.

Airplane

Another impact that wind direction and speed can have on aircraft noise is caused by the nature of noise itself. Noise (sound) travels through the air in a wave form much like ripples in a pond. With each sound event, circular waves move out from the source (center) in all directions. Just how much sound reaches a particular place on the ground depends on the speed and direction of the wind. It can also depend on local variations in temperature such as relative humidity and barometric pressure. Because the weather changes during the day, day-to-day, and season-to-season, the level of sound that residents experience also changes. Unfortunately, weather is one of the greatest factors that affect aviation noise but it is also the factor over which we have the least control.

Glossary Words:

noise abatement, noise, runway

For definitions of words used in this section go to the NoiseQuest Glossary of Terms.

 

Photo Credit: Penn State University PARTNER Low Frequency Noise Team