Most tennis players will have encountered distractions from a noisy crowd as they were about to serve at some point in their career, but few will have had a distraction quite as imposing as the one Ana Konjuh received in her fourth round US Open match.
The Croatian was serving for the match when a security guard tested the air raid siren, just as Konjuh tossed the ball up ready to serve.
The sudden alarm shook Konjuh, who was clearly scared by the volume and sudden nature of the siren.
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Unseeded teenager Konjuh progressed into the quarter-finals of the US Open after a shocking fourth round victory over the Polish fourth seed Agnieszka Radwanska.
The 18-year-old Croatian progressed after a 6-4 6-4 victory over one of the top seeds and favourites for the tournament in Radwanksa, who would've been one of the players in prime position to win a Grand Slam should the odds-on favourite Serena Williams slip up at any stage.
This US Open represents Konjuh's best Grand Slam tournament of her career by a distance, with her furthest progression previously being the third round at Wimbledon in 2014.
Konjuh is only ranked 92nd in the world and needed a solid showing at a Slam to prove that the potential she has can be converted into ability and success in the future.
However, it doesn't get any easier for Konjuh as she will now face the tenth seed Karolina Pliskova of the Czech Republic for a place in the semi-finals of the US Open at Flushing Meadows.
You can see the moment Konjuh was alarmed in the video below.
The tenth seed has six singles titles to her name during her career, but has a shockingly poor record at Grand Slams, not befitting of a player seeded so highly.
Before this tournament, Pliskova was also yet to surpass the third round at a Grand Slam, reaching the third round on three separate occasions, at the 2014 US Open, and the Australian Open in 2015, and earlier in 2016.
The Czech does however have some experience at the deep end of major tournaments in the doubles, having reached the semi-finals of two of the previous three majors alongside doubles partner Julia Goerges.