Sound is still Down in 2021Posted on May 26, 2021
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 aircraft flying to and from MSP.
In May of last year, we provided information on the sound data collected by this system of sound monitoring sites and discussed how changes in aircraft and community activity resulted in about a 4 decibel (dB) reduction in the daily system average LAeq in April of 2020 compared to the previous four-year average (article available here). The LAeq, or Equivalent Level, represents the continuous sound level equivalent of the average sound energy for a period of time. The LAeq takes into account all sounds regardless of the source, including sounds from aircraft, environment (i.e. wind, thunder, wildlife), and community noises (i.e. road traffic, sirens, construction activity, trains).
The chart below compares April 2021 LAeq sound data to April 2020 LAeq as well as to the four-year average LAeq for April in 2016 through 2019. The comparison reveals that sound around MSP is still below pre-pandemic levels, with a reduction of over 1 dB LAeq in April 2021 from the 2016-2019 April-average. Higher LAeq on April 1, 2020, April 16, 2020, April 7, 2021, and April 15, 2021 are likely due to tornado siren drills those days.
The continued decrease in sound energy is most likely attributed to the reduced aircraft activity levels as well as community noises such as vehicle traffic and other community activity near sound monitoring sites. These quieter conditions are not typical and are expected to return to previous levels as aircraft and community activity continues to return to normal.
More information about sound monitoring is available at: https://macnoise.com/faq/what-sound-monitoring.