To put it simply, the audience doesn't laugh along with Sheldon, Leonard, Raj and Howard. The audience laughs at them. It becomes clearer if you watch the show focusing on Penny's role. Through synecdoche, Penny represents popular and socially functional people, and the four main protagonists are in a sense antagonized and positioned against Penny due to their differences. The worst part is that the comedy of the Big Bang Theory relies on positioning the audience as an outsider to "nerdy" society and being someone like Penny who doesn't understand all the geeky scientific references that are made. This is not the only unpleasant part. In one particular episode, there is a scene where the characters are playing Dungeons and Dragons and background laughter is used without a word being spoken. Isn't it relatively clear by now that Chuck Lorre wants us to laugh at the fact that the characters are playing a stupid board game? This example is just the beginning of an endless list, including scenes like laughing at the characters while they collect action figures, read comics, and dress up as superheroes at a Halloween party. Another annoying thing is the insistent laughter aspect behind it