Professor Vincent Olivieri explains how sound travels for the Los Angeles Times

What caused the thumping of Inglewood music festival to disrupt so many? Blame the weather?

Los Angeles Times
By Karen Garcia | Aug. 10, 2024

Living in Westchester, Chris Bankoff said, he’s used to two types of noise: the occasional house party by Loyola Marymount University students, and the engine roar of planes taking off from LAX.

What he didn’t expect to hear Aug. 2 was the low-frequency thumping of music coming from HARD Summer, a house- and techno-music festival held at Hollywood Park in Inglewood, about 5 miles from Bankoff’s home.

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So, what happened?

El Segundo City Manager Darrell George said in a statement that he reached out to Inglewood City Manager Mark Weinberg, who said the event’s organizers made mistakes when they set up the performance spaces that exacerbated the “bass reverberation.”

Inglewood Mayor James T. Butts Jr. issued a statement nearly a week after the first complaints, saying the sound and vibration issues experienced were “related to certain bass frequencies” that can be affected by “stage position, reflection off of buildings, and atmospheric conditions including wind.” Butts added that putting a stage on the elevated American Airlines Plaza “was a major contributor to the issue,” and said the area will be off-limits to concerts in the future.

Judging from the anecdotes shared by residents, increased bass reverberation isn’t what people in the South Bay were hearing, said Vincent Olivieri, professor of sound and design at U.C. Irvine.

“‘Reverberation’ refers to the millions of reflections off of different surfaces that give spaces their particular sound,” Olivieri explained. It’s the reason a cave, with hard stone walls that cause lots of acoustic reflections, sounds like a cave and not a living room, he said.

“The reverberation explanation also doesn’t account for why it appears that only folks to the southwest of the venue heard it,” he said.

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Temperature comes into play especially on a warm to hot day, Hoover said.

After the sun sets, the air at the ground level will cool, but the air at higher elevations will usually remain much warmer (a “temperature inversion”). These different temperature bands can cause sound waves to bend or refract downwards toward the ground because of the difference in the speed that sound waves travel in warm and cool air, said Jason Corey, associate professor of music for the University of Michigan.

Furthering the temperature-inversion explanation, Olivieri said sound waves or sonic energy can be influenced by microclimates.

Think of a heat dome but on a smaller scale. Under the right conditions, a collection of warm air can sometimes serve as a overhead mirror bounding sonic energy down. This is particularly likely to happen during summer festivals.

As the sonic energy leaves an outdoor concert venue, a portion travels up toward the atmosphere. Here, sonic energy leaving HARD Summer toward the southwest could have hit a pocket of warm air that was halfway between the venue and the affected neighborhoods, Olivieri said.

“That pocket of warm air can serve as a kind of acoustic mirror and refract [the sonic energy] right back down” into the affected neighborhoods] he said.

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