I just sent her an email:
"Serena, you are such a great tennis player, but it has become truly embarrassing to watch you play with all of the noises you make. Can't you please cool that down a little bit? It sounds like you are either having an orgasm or getting stabbed and it's just not pretty. Please, please stop. Thanks and keep up the (otherwise) good work.
"
http://www.serenawilliams.com/feedback/default.sps