Altitude makes a tremendous difference in noise levels - a plane at 4000 ft makes half the noise than at 2000 ft, which is unfortunately for many of us, a common landing altitude even outside the 10 mile circle where the guidline asks pilots to be above 3000 ft. A slightly higher guidline combined with better compliance would make a tremendous impact by itself even inside the 10 mile line.

Figure 1 - End of 2005 compliance with guidelines