whistles from the crowd

I was curious if anyone else, especially those that went to the game, noticed the numerous plays where there were whistles being blown from the crowd? I noticed it first on a the kickoff return following ND's FG, and there was the play where the penalty was waived.  WTF?!?

I am not making excuses for the loss, but it infuriated me to no end, and I felt like the refs had to have heard it, and should have started giving 15 yard penalties.

Thoughts?