Sound is Down in April

The Metropolitan Airports Commission (MAC) owns and operates a permanent system of 39 sound monitoring sites around Minneapolis-Saint Paul International Airport (MSP). Aircraft and community sounds are collected, with a goal to capture as much aircraft sound as possible from airplanes flying to and from MSP.

With fewer airplanes flying in and out of MSP in April, there was a notable decrease in the number of aircraft sound events compared to previous years (monthly reports are available at https://customers.macnoms.com/reports/).  The MSP monthly operations reports provide only aircraft sound information; however, other sound data are also collected and evaluated by MAC staff.

The chart below shows a daily system-average sound level in a metric called the Equivalent Level (LAeq ). The LAeq is the continuous A-weighted sound level equivalent to the average sound energy for a period of time. The LAeq takes into account all sounds regardless of the source, including sounds from aircraft, wind, and community noises (dogs barking, road traffic, sirens, construction activity, trains, etc.).

April2020Sound
The chart above compares April 2020 sound data to the four-year average for April in 2016 through 2019. The comparison reveals a reduction of about 4 decibels (dB) LAeq in April 2020 from the April-average. For perspective, a sound increasing or decreasing by 3 to 5 dB is a change that would be perceptible to most people. Higher LAeq on April 1, 2020 and April 16, 2020 are likely due to tornado siren drills those days.

The reduction makes sense when considering the abrupt decrease in the number of aircraft flying into and out of MSP in April, but there are other factors that may also contribute to the reduction in the average LAeq, such as fewer vehicles traveling and less community activity near sound monitoring sites. These quieter conditions are not typical and communities should be aware that airplane activity is expected to slowly rebound as airlines continue to adjust their operations based on passenger demand.

More information about sound monitoring is available at: https://macnoise.com/faq/what-sound-monitoring.