On July 31st 1999 Japanese band “Glay” put on the show “Glay Expo” attracting a record 200,000 attendees. According to Wikipedia “The Glay Expo ’99 Survival at Makuhari Messe gathered a total audience of 200,000 people, making it the largest-ticketed concert ever held by a single act, certified by Guinness World Records“
Amazingly, when the crowd is simultaneously waving their arms in time with the music, you can see the sound waves as they flow through the audience. See the Gif below, or see the full video further down. It is most evident in the section beginning at 1min 8 seconds.
Read more in the book “The Theory of Sound (Cambridge Library Collection – Physical Sciences)“
Enjoying a 30 year career, Glay released 15 Studio albums, and sold an estimated 51 million records; 28 million singles and 23 million albums. Hear more: “Glay – Glay 20Th Anniversary Live Box Vol.2“
See how different piano notes reverberate through a bowl of water
Another good example at the Obama inauguration