Travis Scott's recent Auckland concert. Photo: Tiana Haxton/RNZ
Travis Scott's first performance in New Zealand on Wednesday night to a sold-out crowd of 50,000 at Auckland's Eden Park was the loudest in decades, according to some of the stadium's surrounding residents.
Scott is one of rap's superstars whose productions set benchmarks for audio-visual possibilities.
However, seismometer data from Wednesday night's concert show that other gigs technically caused more vibrations than Scott's, but much of that has to do with crowd movement rather than what's coming from the sound system.
The apparent loudness of his concert could also be a matter of taste - sound frequencies that we don't like might seem more annoying than sounds we do like.
Seismometer data for the Foo Fighters and Travis Scott concert. Photo: GNS Science
Data recorded by GNS Science, a crown entity tasked with monitoring for earthquakes and volcanic eruptions, show that ground vibrations at Scott's concert were about half of those recorded during a 2011 concert by rock group the Foo Fighters.
"The cause of the shaking is most likely the weight of the 50,000 fans dancing, as 50,000 fans is equal to around 5,000 tonnes of mass moving (or moshing) on the ground for the duration of the concert," says Elisabetta D'Anastasio, GNS Science's seismic duty officer. "The sound system probably contributed as well, especially the bass frequencies coupling into the earth."
The two seismic sensors that picked up the concert's vibrations were close to Eden Park and in Herne Bay. Wednesday's vibrations peaked at 8:30 pm and from 9 pm until 10 pm. Scott's set started at 9 pm.
Travis Scott. Photo: AFP
That's about the time that Mount Eden resident Melissa, 26, thought someone was revving a car right outside her home, about one and a half kilometres from Eden Park.
"I was hoping they were driving away but it turned out it was the Travis Scott concert.
"It just felt like the house was shaking like when a big truck goes by."
For other concerts such as Ed Sheeran, the crowd cheering and a tiny bit of music was all Melissa said she could hear from her house.
Melissa wasn't alone in her unwanted Scott concert experience. Others took to social media to share their distress with some longtime residents claiming it was the loudest concert they had heard in decades.
Seismometer readings from Mount Eden and Herne Bay during the Travis Scott concert. Photo: GNS Science
Eden Park declined to release the sound levels a consultancy firm recorded in and outside the stadium during Scott's concert, but a spokesperson said sound levels were within the allowable sound limits.
Professor Yusuke Hioka from the Acoustics and Vibration Research Centre at the University of Auckland said the volume levels heard by some residents surrounding the stadium could be to do with psychoacoustics and how our brains interpret sound.
Some frequencies "may have caused more annoyance than others, resulting in the claim feeling one [is] louder than another," he wrote in an email to RNZ.
"Naturally, [the] subjective aspect also includes personal preference, so if the claimant prefers rock music than classical music, they may not have felt it was noisy, but it could have been the other way round."
In other words, if you don't like Scott's music or some of the sounds he uses, it could seem more distracting and potentially louder.
About 50,000 people attended Travis Scott's Auckland concert. Photo: Tiana Haxton/RNZ
But then again, bass, which is increasingly dialled up in modern music, travels easier through structures like stadium walls, according to Hioka.
"... then it's likely the amount of sound energy reaching the resident areas would have been higher than those sounds mainly with high-frequency sound."
Furthermore, DJ and rap music lean more on pre-recorded tracks so volume limits can be pushed higher than music that relies on live instruments, like the Foo Fighters, according to Dr Andrew Hall, also from the University of Auckland.
"... there may be limits on how loud you can go with live instruments before you end up with issues such as feedback."
So, was Scott's concert really that loud? From a science and data perspective, we don't know, but the RNZ reporter Tiana Haxton who reviewed the concert certainly thought so.
"I was comfortably in the stands somewhere smack bang in the middle and I could literally feel the bass vibrating in my bones.
"I went with my partner and we pretty much had to yell directly in each other's ears to hear each other."
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