A wall of sound hit athletes as they stepped out for the first day of competition at London's Olympic Stadium.
Blasts of cheering came from the crowd at the packed 80,000-capacity venue, and spiked to a higher pitch whenever a British athlete stepped in to view.
The noise was so loud when heptathlete and Team GB poster girl Jessica Ennis, one of the first Britons to race on the track, appeared that you almost could not hear the announcement of the runners' names.
IAAF president Lamine Diack said: "It was wonderful to arrive at the Olympic Games this morning and see a totally packed stadium for the first session of athletics. I do not remember the last time this happened and it shows the great affection Britain has for our sport."
Meanwhile, a spectator has been arrested after the family of an Australian cyclist was apparently subjected to a torrent of abuse at the Velodrome, Locog said.