Switzerland's Stan Wawrinka plays a shot against Germany's Dominik Koepfer in the second round match of the French Open tennis tournament at the Roland Garros stadium in Paris, France, Wednesday, Sept. 30, 2020. (AP Photo/Alessandra Tarantino)PARIS – A tennis player at the French Open was visibly startled by a sonic boom Wednesday just as he was about to serve a ball. But with no forewarning, residents around Paris — along with fans and players inside Roland Garros — expressed their fears of an explosion on social networks. On Court Suzanne Lenglen, the second-biggest stadium at the French Open, Dominik Koepfer was interrupted mid-serve by the bang's loud clap. Elina Svitolina was playing Renata Zarazua on Court Philippe Chatrier, the tournament's biggest stadium, when she heard the noise.