Wow you just totally described me I know how annoying those noises are, i have recently suffered a panic attack in school with all the adrenaline and horrible feelings that come with it because of that .It was soo bad i was so nervous and stiff my face felt icy cold as well as my whole body and i was hyperventilating SOOO horrible and it was weird considering that i have been dealing with this for three years now !So it was a very random situation! Its soo silly to get all worked up for a dumb little thing like that but it has been bugging me so much ever since that i have been trying everything to avoid that stupid growling bubbling noise. I have tried driking a glass of water with baking soda its suppose to help you but well it hasn't done much for me but who knows it might work for you and also i always have a bottle of water handy it has SAVED me a lot i don't eat much and i'm so clumsy and indiscreet that i can't get away with eating in class so water works great and besides no one will think its weird if you take some occasional sips during class. So far that's all the tips i have so i hope I've help you and if you have found any other helpful tips feel free to share them they'll be very appreciated!