Right temperature and wind conditions can bend sound like a prism bends light, found study conducted by researchers. They took measurements of sound levels, wind speed and direction up to about 1000 feet and used it in models of noise that included the prism-like effects of wind and temperature on sound waves.
"What we managed to show is the combination of the crosswind and the temperature gradient can cause sound that's going to go vertically (to) get refracted back down," Discovery News quoted Nick Ovenden of University College, London as saying.
"The sound was literally bent back downwards," he added.
This effect usually happens at dawn and dusk because sound bends from hotter air into cooler air. During the day, the ground is hotter than the air above it so sound bends vertically upwards.
Similarly, sound bends towards slower wind speeds, so the right crosswinds can bend sound around barriers.
The sound levels measured a third of a mile from the highway, which normally has little highway noise were at times above 67 decibels.
"You can argue that those sorts of things a noise barrier can't do much about," said Ovenden.
He explained that the expensive walls lining the sides of highways to protect the immediate neighbors from the roar of traffic are rendered ineffective. This is because "that sound has gone maybe 50 or 100 feet up and then it has come back down," he added.
The study has been presented at a meeting of the Acoustical Society of America.