By Diana Neille
JOHANNESBURG (Reuters) - World Cup authorities are doing tests Thursday to check whether the ear-splitting din from South Africa's vuvuzela fan trumpets could pose a security risk during the tournament.
Foreign fans and players complained about the noise of the plastic trumpets, which sound like a herd of charging elephants, during last year's Confederations Cup -- a dress rehearsal for the soccer spectacular which starts on June 11.
Asked about the vuvuzelas again Thursday, chief local organizer Danny Jordaan said the noise levels would be checked when South Africa play Colombia in a friendly World Cup warm up Thursday night at the 90,000-capacity Soccer City stadium in Johannesburg, when noise levels are likely to reach their peak.
"I think the stadium operations require sometimes the attention of the people in the stadium... for example, if there is an order to evacuate that stadium and an announcement is made, you have to ask yourself, will everyone in that stadium hear that evacuation order?" he said.
Jordaan said the playing of national anthems would also require respect to be shown.
"We will look tonight where, for the first time we'll have a full stadium at Soccer City, and then we'll see whether or not levels of noise impact on the efficiency of the operation," Jordaan added at Johannesburg's Ellis Park stadium, one of the tournament's 10 venues.
He said stadium security and management would assess the impact of vuvuzelas after the match and indicated fans may be asked to pipe down for emergency announcements, without giving details.
"Can we have a conversation, can there be instructions, is there difficulty because of these noise levels? Then we will talk to the people," Jordaan said.
Thailand manager Bryan Robson complained earlier this month that he could not communicate with his players during a 4-0 friendly drubbing by South Africa at the new Nelspruit stadium, when around 40,000 fans were present to blow the horns.
The former England captain suggested the trumpets could give South Africa an advantage in the World Cup, both by lifting their morale and deafening the opposition, and said managers would have to find new ways to give instructions to players.
But South Africa's Brazilian coach Carlos Alberto Parreira said they should take advantage of the din. "We want it louder and louder," he said.
South African scientists have warned fans to take ear plugs to World Cup matches to avoid damaging their hearing.
(Writing by Barry Moody; Editing by Alison Wildey)