Photo credit: Robert Sullivan has dedicated this photo to the public domain

by Daniel Fink, MD, Chair, The Quiet Coalition

At the recent Acoustical Society of America meeting in Nashville, Tennessee, I attended a session on measuring aircraft noise. Several of the papers presented discussed the acoustic characteristics of NASA’s X-59 experimental supersonic plane, which is being developed under NASA’s QUESST program. Lockheed Martin, which is collaborating with NASA, states:

The X-59 is an experimental supersonic aircraft shaped to reduce the loudness of a sonic boom reaching the ground to that of a gentle thump. The X-plane accomplishes this by tailoring the volume and lift distribution to separate the shocks and expansions associated with supersonic flight.

On a personal note, I once heard the sonic boom of the Concorde, the only supersonic plane ever in commercial use. My sons and I were visiting my parents in New Jersey in the early 2000s, and we drove to Ft. Hancock, where my father had been stationed during World War II. We then drove to the nearby community of Highland Park to get a better view of the decommissioned fort. All of a sudden we heard a boom, and looked to the northeast to see the Concorde preparing to land at JFK. Highland Park is about 20 miles from JFK.

The experimental plane is being developed as a prelude to a reintroduction of supersonic commercial aviation. One of the problems of supersonic planes, at least for those living under flight paths, is the sonic boom created when the plane breaks the sound barrier, i.e., goes faster than the speed of sound. The mathematics of the sonic boom are complex, but the X-59 is specifically designed to minimize its noise impact. I was surprised to learn that its sonic boom is supposed to be no louder than 75 decibels, about as loud as a car door closing. This is important because the carpet width of the sonic boom–how wide an area it can be heard over–can be as wide as 40 miles.

NASA will be testing the X-59’s sonic boom across the United States, at locations in various regions yet to be determined.

Whether supersonic commercial aviation will return to the skies remains to be seen, but I am gratified that researchers at the FAA or funded by the FAA are concerned about aviation noise for at least one class of aircraft.

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