The Olympic track and field no longer uses the starting pistols anymore. And the reason for that is that the guns were posting demonstrably slower start times. Which kind of means we humans could actually be achieving faster run times. Usain Bolt could be finishing a 100m run in god knows how fast.
For a long time, the sound of the gun was pumped in from behind each runner at the same time it fired, but runners would still wait for the sound of the actual gun. Sounds like a lot of time loss. And it is:
[Michael] Johnson's reaction time, [Peter Hürzeler of OMEGA] said, "was 440 thousandths of a second. Normally athletes leave between 130 and 140 thousandths of a second. ... I asked him, why did you have such a bad starting time?" Turned out, Johnson was in the ninth position, and the sound of the gun was reaching him too slowly.
Four tenths of a second is a massive amount of time in a sprint. [The Atlantic]