Most likely the first few deer through the fence area won't be what you are looking for. Practice on them to see their reaction. Yes, sometimes the condition prevent the deer from hearing you, so make sure whatever it is you do it loud enough for them to hear. The second to the last thing I would do is whistle to stop a deer. The first is to say something, like... HEY! Doing these two noises will put deer on high alert and will ready them to bolt at any moment. Grunting with a tube or your mouth are good choices as they are more natural. Since you will be using a muzzle loader, you will have an advantage over a bowhunter if the shot is rushed because they won't jump the string... nor your sabot. LOL! Good timing to make the sound is when they are in the air or just as they land.
iSnipe