Residents of Galveston, Texas will serve as “sonic thump” guinea pigs.

Some background: Supersonic travel over land has been banned in the US since 1973, owing to the huge noise produced when a plane breaks the sound barrier. In 2016, NASA announced that Lockheed Martin had won the contract to design the X-59, a plane that uses “boom reduction” technology to let planes fly faster than Mach 1 without making such a racket.

The quiet boom: Starting in November, F/A-18 Hornets will create regular sonic booms over the water near Galveston and quieter sonic “thumps” directly over the town. F/A-18s can only “simulate” the quieter sonic thump over a very limited area—the real deal will have to wait for a plane designed from the ground up—but they will allow for testing of the concept. Noise level readings will be taken, and at least 500 town residents have been asked to record their experiences.

Why it matters: The results will help verify whether these thumps are quiet enough to avoid disturbing residential areas, and establish a testing process for the X-59. The information will then be fed to engineers working on the new supersonic jet.

Hear the difference between the booms and thumps in the video above. You can hear a double boom at 43 seconds and a thump at 2:34.