"Urban canyons" prolong the sound boom in cities

“Urban canyons” prolong the sound boom in cities

Spread of an N-wave sound boom above (a) an insulated building and (b) several buildings. Credit: Didier Dragna

Twenty years after Concorde’s retirement, several industrial and research projects want to make supersonic aviation a reality again. However, supersonic planes produce sound barriers that are high enough to justify noise problems and regulations, which limits their use over land.

IN Journal of the Acoustical Society of AmericaUniversity of Lyon researchers conducted simulations that compared how loud barriers reflect differently on a single building, two adjacent buildings and several buildings at regular intervals.

“This article is the first study that addresses the spread of the boom in one Urban environment“, said co-author Didier Dragna.” The resonance phenomenon in an urban canyon has been thrown into the light of the sound boom, and its significance has been quantified. “

The Federal Aviation Administration is currently banning it commercial aircraft from traveling faster than Mach 1 over land and from a certain distance offshore where a boom can reach the shores of the United States. Recent attempts have made low-noise supersonic aircraft, but noise problems due to the noise boom may be more pronounced in cities, where buildings form canyons that distort the barriers.

The group performed numerical simulations to use equations from the field of fluid dynamics to predict the boom in different urban configurations.

“This approach allows us to accurately account for the reflection of the boom on the streets and facades of the buildings,” said Dragna. “With these simulations we were able to determine the ground pressure signals due to sonic boom spread and reflection over the buildings and derive sound levels. We can therefore predict the noise disturbance that the population feels due to sound barriers. “

The researchers found that the wider the streets are compared to the height of buildings, the fewer barriers are affected by the presence of several buildings.

Narrow streets introduce a more complex boom spread through several reflections on building facades. Although they do not affect the volume of the barrier, they tend to prolong the ground level pressure signals in urban canyons through increased resonance between buildings.

Dragna said that their research underlines the importance of the shape of cities for the properties of sound barriers at ground level. The group aims to investigate the phenomenon further by looking at typical city configurations.

The article is entitled “Sonic boom reflection on an isolated building and multiple buildings.”


Image: Seeing an X-plane sound boom


More information:
Sonic boom reflection on an isolated building and several buildings, Journal of the Acoustical Society of America (2022). DOI: 10.1121 / 10.0010452

Quote: ‘Urban canyons’ extends sonic booms in city (2022, June 7) retrieved June 7, 2022 from https://phys.org/news/2022-06-urban-canyons-prolong-sonic-booms.html

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