Loud sucking noise from inside intake

[tysbol584]

Last night I cleaned my electronic air filter and replaced the regular filter. After that I noticed from the intake inside the house a louder sucking noise than usual. At first I thought i did something to the filters and it was the air passing through them however when the heat shuts off but the fan still blows the noise level is back to normal. Why is this? It is very cold (28 this morning) outside and there is some ice buildup on the heatpump outside. Also I do have a variable stage air handler is it blowing harder because of the cold air and I just noticed it after I cleaned the filters. Any help thanks.

[jadnashua]

If the filters were really dirty, and the combination with potentially needing to run faster (on the variable speed air handler), you may have uncovered an inadequately designed return duct system - i.e., it could be too small. You may have moved something in a room to block the return, or if they have a damper, closed one or more. Returns often do not have a damper on them, but could.