By Robert-Jan Bartunek
BRUSSELS, May 16 (Reuters) - Ear-splitting vuvuzelas were an ever-present backdrop to the 2010 World Cup finals in South Africa. Four years on, two Belgian entrepreneurs hope to fill stadiums in Brazil with the high-pitched noise from plastic trumpets dubbed "diabolica".
Fabio Lavalle, 26, and David dos Santos, 31, from the southern Belgian town of Mons, have invented a collapsible, pocket size trumpet, which, not unlike an air horn, produces a sound at around 98 decibels - equivalent to a hand drill.
"After the Belgian national team qualified in October, we said to each other, we have to make something," Lavalle told Reuters in his office surrounded by cardboard boxes filled with the plastic trumpets painted in various national colours.
Lavalle and Dos Santos chose the name diabolica after getting suggestions on social media site Facebook, linking it closely to the "Red Devils", the Belgian national team.
"But I guess the name now has become synonymous with the infernal sound it makes," Dos Santos said with a smile.
After an initial batch of 10,000 pieces sold within weeks, the pair stepped up marketing and distribution efforts, selling 400,000 pieces which retail at nine euros ($12.34) each.
With little under one month to go until the start of the World Cup, the pair hope to sell one million by the end of the tournament.
"It's ambitious but I think we can make it," Lavalle said.
The constant droning of the vuvuzela disturbed broadcasters and players at the 2010 finals.
Lavalle said, however, that he did not want to compete with the African trumpets.
"Everybody hated the vuvuzela. What we are trying to do is to replace the gas canister horns because gas canisters are no longer allowed," Lavalle said, adding that fans would use the diabolica mostly to celebrate goals rather than play it uninteruptedly.
The diabolica will have to compete for fans' attention with a Brazilian percussion instrument called the "caxirola". ($1 = 0.7291 Euros) (Reporting by Robert-Jan Bartunek; editing by Justin Palmer)