The last buck I took off our place was an 8 point that was about 50 yards from the feeder. There was a doe there also. I dropped the buck with a 7mm Rem Mag - which, as most of you know makes a VERY loud bang. When I pulled the trigger on the buck the doe jumped, ran a few feet - stopped for a moment to look at the downed buck, and then slowly meandered off. The inital BANG caught her attention, but immediately there after she was clueless. As such, you'll never convince me that scare tactics would work in the long run. The deer will eventually just ignore the noise...
Since I have a similar issue with our 4 acres of vineyard, we're in the process of installing an 8' deer fence. We've also clear cut around the vineyard by at least 75 feet on all sides and a good 150 feet from the back of the property (which is the direction they come from).