I got super excited about the Queen Nefertiti / King Tut secret chamber theory a year or two back (which used similar methods, it seemed), and was really disappointed when it turned out to be all wrong...
This is not the same method at all and this is much more reliable. For King Tut, they used ground penetration radar, which is very hard to interpret. Here: (1) this is confirmed by 3 independent teams using 3 different detection technologies, (2) we used the same statistical criteria as for discoveries in particle physics (deviation 5 sigma from the model).
In addition, we clearly see the new void on Nagoya's data (Fig.2).
Unfortunately, cosmic-ray muons cannot be used in King Tut tomb because we can only see "above us" (the muons come from the sky).
However, we can acquire data for more time (depending on the detector technology), which will give us more statistics.
The ScanPyramids team is being very careful not to describe the cavity as a "chamber".
He says the muon science is sound but he is not yet convinced the discovery has significance.
"It could be a kind of space that the builders left to protect the very narrow roof of the grand gallery from the weight of the pyramid," he told the BBC's Science In Action programme.
"Right now it's just a big difference; it's an anomaly. But we need more of a focus on it especially in a day and age when we can no longer go blasting our way through the pyramid with gunpowder as [British] Egyptologist Howard Vyse did in the early 1800s."
One of the team leaders, Hany Helal from Cairo University, believes the void is too big to have a pressure-relieving purpose, but concedes the experts will debate this.
I've posted this video elsewhere in the this thread but putting here for completeness. It's a better overview compared to the bbc article.
Voids have had precedents in Egyptology. My favourite being the mess the Mormons got into with the Book of Abraham. Their visionary founder guy buys some Egyptian 'scrolls' from someone who was doing the rounds taking some mummies on tour. So this was magically interpreted as the Bible Part 3, the New, new testament, a.k.a. The Book of Abraham. There were those that had seen the scrolls so they were known to actually exist however there was some big fire in Chicago and the scrolls were apparently lost.
Many decades later someone finds the scrolls in New York, they checked out to be the real deal as the illustrations were the same, including the missing bits. By now people knew a thing about how to read these things properly and the 'scrolls' that had inspired the Book of Abraham turned out to be standard funeral documents, a death certificate of sorts.
The bits that were missing from the 'scrolls' included the heads of Horus et al, therefore our Mormon friends were drawing in the heads of 'Abraham' et al. It was beyond their imagination that Egyptian figures on papyrus documents would have heads of other animals, dogs etc. So the Mormons got it completely wrong, they filled the void in with expected content - human heads - but that was an assumption too far.
So yes, this is just science, nobody is trying to found a new religion here.