Chris Bankoff lives in Westchester and is accustomed to two kinds of noise: the occasional house party hosted by Loyola Marymount University students and the roar of planes taking off from LAX.
What he didn’t expect to hear on August 2 was the low, thumping music of HARD Summer, a house and techno festival held at Hollywood Park in Inglewood, about five miles from Bankoff’s home.
When he first heard the beats that Friday, he thought it was a neighborhood party and dismissed it. But the next afternoon, Bankoff said, the noise resumed and was even louder than the day before.
“I could hear the change in rhythm,” he said. “It was like someone pulled up in front of the house and played loud music in their car.”
In North Redondo Beach, about 9 miles from the entertainment venue, Sondra Segall thought she heard construction. The noise didn’t bother her, but she wondered how she could hear it.
Residents of Manhattan Beach, El Segundo and Hermosa Beach also took to the Nextdoor app and Reddit to ask questions or complain about the noise. El Segundo police received more than 100 calls on Friday and 200 on Saturday; the number dropped to 50 calls on Sunday, possibly in response to community warnings and social media posts.
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Neither the festival organizer, Insomniac Events, nor Hollywood Park responded to requests for comment before publication.
While Inglewood’s noise ordinance limits concert volumes, it says those limits don’t apply to events at Hollywood Park that end at midnight. So the HARD Summer performers, who ended their sets around 11 p.m., likely performed at or above airport runway volume.
HARD Summer organizers told KABC-TV in a statement: “While we always operate within legally allowable decibel levels, we have sound monitors on site to monitor and respond to any noise complaints.”
The energy in sound waves decreases as they travel farther from their source. So even if the music was amplified to the pain threshold, the volume should have dropped below that of a muffled conversation within a few miles of the concert.
What happened?
El Segundo City Manager Darrell George said in a statement that he had contacted Inglewood City Manager Mark Weinberg, who said event organizers made mistakes in setting up the stages that exacerbated the “bass reverberation.”
Inglewood Mayor James T. Butts Jr. issued a statement nearly a week after the initial complaints, saying the noise and vibration issues being experienced were “related to certain bass frequencies” that can be affected by “the position of the stage, reflection from buildings and atmospheric conditions, including wind.” Butts added that placing a stage on the elevated American Airlines Plaza was “a significant contributor to the problem,” and said the area will be off-limits to concerts in the future.
Judging from residents’ accounts, it wasn’t the increased bass reverb that people in the South Bay heard, said Vincent Olivieri, a professor of sound and design at UC Irvine.
“‘Reverberation’ refers to the millions of reflections from different surfaces that give spaces their specific sound,” Olivieri explained. It’s why a cave, with hard stone walls that create lots of acoustic reflections, sounds like a cave and not a living room, he said.
“The reverberation explanation also doesn’t explain why it seems like only people southwest of the site heard the sound,” he said.
If Inglewood’s explanation is incorrect, how could residents up to nine miles southwest of the site hear the low-frequency vibrations from HARD Summer? Experts in audio engineering and acoustics speculate about how the sound could have traveled so far.
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How the sound might have traveled
The festival’s musical acts played on five stages set up in the parking lots surrounding SoFi Stadium. With these types of outdoor shows, there are no walls to interrupt the flow of sound outside, said Tony Hoover, principal for McKay Conant Hoover, acoustic and audiovisual consultants.
And unlike indoor entertainment venues, there is no roof to block out the sound, he said.
Deep bass is a big part of hip-hop, techno and electronic music, said Barry Rudolph, president of the Los Angeles chapter of the Audio Engineering Society. He said he’s confident the festival used powerful amplifiers and huge speakers to reproduce the sound fully and at high volume.
“Loud and long sound waves can vibrate the surrounding buildings, causing them to resonate with this extra sound energy,” the spokesperson said, adding to the problem of sound leaking from the stages into the community.
It’s like hearing a car coming down the street with a stereo that’s shaking the windows: You can hear the music before the car comes into view, Rudolph said.
Still, Rudolph doubted that HARD Summer’s low frequencies would travel 9 miles. More plausibly, he said, the thumping bass traveled about a mile from Hollywood Park in all directions (unlike higher frequencies, he said, low frequencies are omnidirectional).
And yet, there are plenty of people who live far from Hollywood Park who say they heard the rhythmic rumble of the festival on Friday and Saturday.
Hoover said it was not unusual for the sound to travel for miles, but he was shocked to learn that people nine miles away could hear the thumping.
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He described the sound coming from Hollywood Park as “kind of a big bubble of sound that keeps getting bigger.” But as the bubble gets bigger, it gets weaker. That’s why the volume decreases the further you get from the source of the sound.
However, the bubble can change shape due to wind and temperature, both on the ground and in the air layers above.
Temperature plays a major role on a warm to hot day, Hoover said.
After the sun goes down, the air at ground level cools, but the air at higher altitudes tends to stay much warmer (a “temperature inversion”). These different temperature bands can cause sound waves to bend, or refract, downward toward the ground because of the difference in the speed at which sound waves travel in warm and cool air, says Jason Corey, an associate professor of music at the University of Michigan.
To further elaborate on the explanation for the temperature inversion, Olivieri said that sound waves, or sonic energy, can be affected by microclimates.
Think of a heat dome on a smaller scale. Under the right conditions, a collection of warm air can sometimes act as a mirror above your head, reflecting sonic energy downward. This is especially common during summer festivals.
As sonic energy leaves an outdoor concert venue, some of it travels upward into the atmosphere. Here, sonic energy leaving HARD Summer toward the southwest could have struck a pocket of warm air halfway between the venue and the affected neighborhoods, Olivieri said.
“That pocket of warm air can act as a kind of acoustic mirror and refract the radiation [the sonic energy] “back to the affected neighborhoods,” he said.
Corey agreed, saying that during a temperature inversion, “sound travels upward from a concert hall into the warmer air layer and bends downward after passing over buildings and other obstacles, reaching the ground miles away from the concert.”
Hoover was skeptical, saying that the wind and some other factors had to be just right to create the temperature inversion effect, especially at such great distances. But Olivieri said that if the bass signal was louder than it should have been, and if the sound was bouncing off a high-temperature microclimate system back into neighborhoods to the southwest, that might help explain why those neighborhoods heard the pulsating bass and others didn’t.
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The long-range sound of a concert is not a new phenomenon. It’s becoming more common thanks to improvements in concert sound technology, says Dave Revel, president of Technical Multimedia Design, a consulting firm that often helps venues mitigate noise.
He added: “It’s a logical technological development, but it also brings challenges in terms of ambient noise. Today we have very large, powerful sound systems that can reproduce a wide frequency range.”
When it worked at events at the Rose Bowl and the Fairplex, Revel said, Technical Multimedia Design found that people 4 miles away could still hear the music, particularly the bass.
The role of noise regulations
Another possible factor in this incident is Inglewood’s noise ordinance.
Volume is measured in decibels, or units of sound pressure. But there are different standards for measuring decibels when regulating noise — one focuses on the frequency range of human speech, and another is more attuned to a full range of frequencies, including bass frequencies.
Generations of community noise ordinances have been based on the old standard, which focuses on frequencies common to human speech, Revel said. “They never expected that music [would have] bass in it.”
The city of Inglewood’s ordinance falls into that category. The challenge, Revel said, is that it relies on a standard that “doesn’t take into account all frequencies and certainly not the low frequencies that go further.”
Concerts and festivals can easily remain within the law, because ‘the law essentially ignores the bass’.
In 2015, Revel’s company was hired by the Fairplex in Pomona to help mitigate noise during the HARD Summer Festival in July, after complaints about “unbearable noise levels” had been heard months earlier, the Daily Bulletin reported.
Revel said he remembers measuring the sound during the event.
“We were actually within the community noise limit for the entire concert, but people’s windows were rattling,” he said. “People who lived right next door to the concert, their windows were rattling because the bass was insane.”
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This story originally appeared in the Los Angeles Times.