Reducing register noise

[Jim]

The ceiling hvac register in my bedroom is noisy. The noise is primarily broad band "whishing" from the air over the blades of the damper and diffuser. If I remove the register, the duct is very quiet.

Are there quiet diffuser/registers out there? I just replaced the register with one that has individual curved blades which helped a bit. The damper portion is wide open and only contributes to noise making. Are there diffusers withoug dampers? Would it be advisable to dampen the line closer to the attic AC unit? Or getting a professional to reduce the fan speed?

The room also has a return vent. Of course, it also is a noise maker. I was able to stop the high frequency singing by "tuning" the grill blades.

Thanks, Jim

[Jim]

Thanks for the reply, Edwin.

The register has two controls: an inside damper which I have wide open and outside diffuser blades which are adjusted to make the air flow parallel to the ceiling. I read that this was best for efficiency. Maybe I will try to remove the damper blades.

Regards, Jim

[Edwin Pawlowski]

Keep it off. If you normally have it wide open, they it is really not doing much aside from making noise. Probably looks better than an open hole too, but that's about all.

Yes. YOu can probably modify what you have also.

[PipeDown]

Air Noise comes from turbulance, it would stand to reason that the act of diffusing causes turbulance and therefore noise.

If you want a quieter register you want one that allows for smooth airflow. You still want a damper bacause a wide open vent means that vents elsewhere in the house will have reduced airflow. The damper allows you to balance the air to each room.

You could also add an air filter to the register which would slow and mix the air before the diffuser reducing noise in that stage, it may result in slightly reduced airflow but you said noise was a problem not trying to hog the A/C for your room. Check the other rooms as well. If a register is closed somewhere, you might be getting too much air at your location.

A larger register will also help by allowing the same volume of air to exit a larger area, the velosity of the air over the diffuser will be reduced which will reduce noise as well.

[Walter R.]

I have had this problems in several houses: An unbalanced airflow system. Too much air is coming from this outlet, leaving airflow in others too slow. In one house, where all registers whistled, I rewired the fan down to the low setting and that fixed it. In other houses I just stuck a towel or fiberglass insulation in the duct behind the register, reducing the airflow.

Probably have everyone jump on me for this, but it worked fine.