That would be what i would be worried about, Richard, don't want to be up all night for falling leaves twigs etc, or wildlife, and i wouldn't want it to be 100db loud at any rate. Wouldn't be popular if it ever goes off at 100db either
Simple thing to prevent theft, put your bivvy next to your rods, put all of your bags and bait and everything inside your bivvy, leave the door open with the butts slightly inside, result no idiot will try to nick you rods, as you are right next to them.
Its ideal for me with my dillo, i put the butts inside (where possible) and leave the door so it just clears the rods, (sometimes i leave it so the door is resting on the handles)
Ryan