Looking at the photo, you've created your own problem by putting the fence so close to the A/C unit. All the noise is not being disspated upwards, it's being bounced back off of the fencing materials. I'm afraid that in this situation the only recourse would be to get an estimate on moving this unit somewhere else. Around here the most popular "method" of hiding an A/C unit is a six foot chain link fence with barbed wire. Every day around here there is a report of someone's unit being stolen while they are asleep within the house. One of my neighbor's had this happen just last month. Just cut the freon lines, cut the electrical, have two men lift the unit up and into a waiting pick-up truck. They are even taking the package units and disconnecting the sheet metal ducting while people sleep right beside them in their bedrooms.