The last few days I've noticed a problem while practicing - air is leaking out of my mouth somehow, it's like my embouchure isn't firm enough or something. The only variable is that I just purchased a new mouthpiece - a Selmer C* Soloist. I had previously been using a regular Selmer C*. I've never had this problem before, and it started happening when I began using this mouthpiece. Have any of you come across this before? Is it a matter of me merely needing to adjust to this mouthpiece? It's incredibly annoying, to hear this slight whoosh of air going out as I play.