While It may be cultural because of her heritage, every tennis fan know the rules of tennis.. its not a football or other type of non golf event.
Gee apparently you havent been to a 'live' DC match, fans from both sides are rowdy, especially the Spanish and South American fans, even when I did media for Swiss v Aussie some years back, I couldnt hear well because of the cow bells the Swiss fans had everytime Roger won a point

same with Wawrinka, Aussie fans screaming out Oi Oi OI, Aussie lost of course, next time I will bring some ear plugs with me

Tennis players just have to 'deal;' with the noise, I mean if it gets over the top, the umpire can ask the crowd to be quiet and dont call out when a player is trying to serve