Football governing body FIFA has okayed the plastic trumpet for the tournament, which starts on Friday, after organisers did tests at a match at Johannesburg's 95,000-seater Soccer City due to worries the din could drown out emergency announcements.
While normally reserved for local games, the vuvuzela can now also be heard at warm-up matches and practice sessions ahead of the tournament, even those not involving South Africa's Bafana Bafana.
The tests, conducted late last month in a sound-proof studio, found the vuvuzela emitted 127 decibels, more than the air horn - 123.5 decibels - and the Brazil's samba drums.
A referee's whistle was fourth while the cowbell, a favourite in Switzerland and Austria, trailed at 114.9 decibels.
"To put it in perspective, when a sound is increased by ten decibels our ears perceive it as being twice as loud, so we would consider the vuvuzela to be more than double the volume of the cowbell," audiologist Robert Beiny said in a statement.
Some foreign players complained at last year's Confederation Cup about the din, and Thailand manager Bryan Robson that he was unable to communicate with his players during a friendly against South Africa.
South Africa coach Carlos Alberto Parriera wants even more noise to help inspire the world's lowly 83rd-ranked Bafana Bafana through its tough Group A matches against Mexico (June 11), and former champions Uruguay (June 16) and France (June 22).
