The previous comment by ron started off on the right track but he got derailed when he blames the equipment. Your problem is with improperly sized duct work and/or duct work design. if either(or both) the return duct or supply duct is too small, you will get noise along with poor air distribution(hot and cold rooms). Also if you have a high resistance filter installed, it will reduce air flow and increase the noise. If your system is more than 2 years old and you have not had the proper maintenance done, your cooling coil may be dirty, restricting the air flow and increasing the noise. The best thing to do is find a good HVAC contractor(ask for and check references, or ask your friends) and have them look at your system. They can help you the best.