My son is 10 (nearly 11). He has been playing for one year and has been doing very well. He has just encountered a problem that he has never had before. As he plays air escapes through his nose. He is not experiencing any sinus related problems and he seems to be doing everything normally. I've played for many years so I can affirm that he is not making any obvious mistakes. The problem is happening at the back of his throat. I am at a total loss as how to help him overcome this. He is very frustrated. Any suggestions would be greatly appreciated.