The slashfilm.com website has posted up an article discussing some of the reasons why it has often become more difficult to understand the dialogue in films these days. There are a number of points that cover creative choices such as Christopher Nolan’s approach in various films and mixing with theatrical dynamics that doesn’t necessarily translate to all listening situations to not enough respect being given to sound on sets and actors mumbling and whispering styles. It’s a big frustrating topic, but the article gives a good summary in layman’s terms.