All air vents, meaning supply registers and return grilles make some noise when the system fan is running. This is normal. Some systems are louder than others. Some systems are much louder.
For example; a house with plenty of return air including return vents in every room will probably be quieter than a system with just one large return cut directly into the return side of the equipment. There is nothing really wrong with the latter, it is just a less expensive and very basic approach to ducting the equipment.
The most common complaint we get on this matter is usually from return vents making a high-pitched, tuning-fork type of sound. This usually, not always, but usually indicates a lack of return air. The system needs to pull more air so the pressure and velocity increases, thus increasing the sound level. By adding more return air, the pressure reduces, the system doesn't have to works as hard and it quiets down.
Now, why do we have a lack of return air? It could be as simple as a blocked air filter. Maybe someone shut off the supply vents- yes this could cause the problem as well. The system is designed to move a certain amount of air. By blocking either the return or supply vents it causes a pressure problem - increasing the sound level. We have seen furniture blocking return vents, restricting air flow.
After checking the obvious, the next step would be to have a technician inspect the system's performance. Hannabery's service technicians can not only check the equipment but can diagnose the ductwork for proper air-flow. Along with system pressures and temperature splits, we can check for proper CFM and static pressures.
Below is a list of possible causes and things to check. Items in blue usually require a service call. Items in red however can be addressed, even fixed by the homeowner.
