JOHANNESBURG, (Reuters) – World Cup authorities are  doing tests 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.

But FIFA President Sepp Blatter said they were as  characteristic of South African football as bongo drums or  singing in other countries and would not be banned.

Asked about the vuvuzelas again on Thursday, chief local  organiser Danny Jordaan said the noise levels would be checked  when South Africa play Colombia in a friendly World Cup warm up  on 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.