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 Hear the World Foundation - an initiative formed by Swiss hearing products group Phonak to raise awareness about hearing loss - said tests showed it produced a dangerously loud sound, far out-blasting a chainsaw.
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.
Hear the World said extended exposure to 85 decibels risked permanent hearing loss and urged fans to use protection, such as ear plugs and ear muffs.
The vuvuzela can be heard across South Africa as football fever grows ahead of the June 11-July 11 tournament, from airports to shopping centres, but at stadiums tens of thousands of people will blow the trumpet, such like constant car hooters in a traffic jam.
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.
FIFA President Sepp Blatter has defended it, though, saying it as as much a part of local football as bongo drums and chanting in other countries.
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).
The study found that it was not only trumpets, drums and horns that can hurt your ears, two excited supporters cheering a goal on either side of you can produce 121.6 decibels, also drowning out a chainsaw at just 100 decibels.
