New research suggests that sound impacts can be particularly annoying in cities, where tall buildings and narrow streets increase noise levels and delay noise.
Aircraft that move faster than the speed of sound create a shock wave in the form of a short-lived impact. These intense sound impacts damaged people’s hearing, shattered windows and caused others physical damage to houses and buildings (CH: 19.12.64). NASA is developing aircraft with more muffled shots, but the sound will not disappear completely. Even modest booms can become a problem in cities.
“It is expected that the noise level caused by these lower-level bonds will be significant,” said study co-author Didier Dragna of the Lyon School in France.
Dragna and his colleagues simulated the strikes of supersonic planes flying over buildings. In a building that stood out in the open, the noise lasted about a tenth of a second. The sound reflected from the building slightly increases the noise level on the side facing the approaching plane and reduces it on the side facing away.
However, for saturated urban landscapes, the noise reflected from buildings after a sound shock fills the areas between buildings and resonates like an echo of a clap in the palm of an empty hallreports the team in June Journal of the Acoustic Society of America. Their simulations showed that even after the initial boom passed, the noise persisted for a few seconds, creating what Dragna describes as the thunderous roar of windows and doors.
Civilian aircraft in the United States are generally prohibited from flying over land at supersonic speeds. But NASA will begin test flights of its “quiet” The X-59 is a supersonic aircraft over cities in 2024. “It’s important to predict what the noise and annoyance levels will be because of these supersonic planes,” Dragna says.