Hissssssssss

I have started hisssssssing when I disapprove of something. This is new and somewhat disturbing. O'Tim and I were watching Oprah's Legends Ball and talking about how over the top and pretentious it was and I started the hissssssssing. When did this happen? I'll give some examples. My carpool and I were talking about a friend of hers whose husband is cheating on her a mere 2 months into their marriage. I hissssss. She tells me that he has been having the affair since before they were married. I hissssss. She questions why he even got married to her. I hisssss. One of my students talks during a test. I hissssss. I see way too much of one of my student's boobs. I hissssss. What has happened to me and how can I stop this!!! Hisssssssss.