The current Guinness record for “loudest crowd roar at a sport stadium” is 131.76 decibels, set during a soccer match at the Ali Sami Yen Sport Complex Turk Telekom Arena on March 18, 2011, in Istanbul, Turkey, by fans of Turkey’s Galatasaray S.K. club. Here’s more about the record-setting attempt from Guinness:
The sound level was measured from the side line of the stadium. Distance to the crowd was 2 meters. They were given 3 attempts. The first attempt was at 20:50 pm, it measured 112.08 dbA. The second attempt was at 21:03 pm and measured 130.55 dbA. The third attempt took place at 21:15 pm and produced a reading of 131.76 dbA. A notary and one witness (sound engineer) were present. The precision measuring noise level meter (certified and calibrated) was a Bruel & Kjaer 2250 RAM DT-8850. This was the first derby game which took place at the brand new home (stadium) for Galatasaray SC and its fans. 49,488 fans of Galatasaray SC and 2,500 fans of Fenerbahce SC were counted that day. The game was finally won by Fenerbahce SC, 2-1.
On their website, the Seahawks say Seattle’s 12th Man has been measured at 112 decibels — louder than a power saw or a rock concert, and not much quieter than a Boeing 747.