According to Wikipedia:
The vuvuzela also known as lepatata is a typical 65 cm (2.13 ft) plastic blowing horn that produces a loud, distinctive monotone note....Many types of vuvuzela, made by several manufacturers, may produce varying intensity and frequency outputs. The intensity of these outputs depends on the blowing technique and pressure exerted.
The vuvuzela is most used at soccer matches in South Africa, and it has become a symbol of South African soccer as the stadiums are filled with its loud and raucous sound that reflects the exhilaration of supporters. The intensity of the sound caught the attention of the global soccer community during the 2009 FIFA Confederations Cup in anticipation of South Africa hosting the 2010 FIFA World Cup.