Thanks for the useful information. I didn't know about the KA forums...this is only my 2nd posting. I guess I'm still pretty new at this. I'll check it out. As for my KA DW it's old and has had parts break over the years and we've chosen not to fix them as they don't interfere with its cleaning ability. It does a fairly good job cleaning dishes but is somewhat loud...loud enough that you wouldn't want to run it when people are around. I just wanted to know the db level to compare with newer models on the market. Giving KA a call sounds like that will answer my question.

It's probably undersized and doing no good for the system. What is the size, and what is the tonnage of the system? Undersized ductwork systems are not good for the equipment.

It is a whistler - not terrible but slightly annoying. When we moved in, we never fired up the old furnace because of manifold cracks, so I don't know if it was also noisy. Before installing the new furnace, the HVAC guy said the ducting should be fine. A lower fan speed works, but it takes forever to heat the house. The duct opens from below into a larger box. For some reason, extra drywall was removed from the top of the hole, which is roughly 22-1/2" x 4-3/4", and an extra 4 or 5 inches from the sides of the hole exposing some 2x4s framing the box. The vent cover (31-1/4" x 7-1/4") is about 3/4" deep and mounted against the drywall. Because the vent is much larger than the hole, I suspect the whistling is caused by air coming through the louvers at the sides that are doing nothing more than covering exposed 2x4s. This air has to turn 90 degrees and travel 4 or 5 inches through a space only about 1-1/2" deep before entering the duct box. I can easily open the hole maybe another 3/4" at one side (probably not much help?), but more than this in either dimension would involve cutting into some 2x4s. Would it help to get a smaller vent, closer to the size of the hole - replacing some of the missing drywall? Would a wooden vent help the noise? Maybe an egg crate vent with bigger holes? Or all of these? Or none of these? Any and all suggestions are greatly appreciated.

Roger, What you are most likely hearing is the sound of an undersized pipe and excessive water velocity in the pipe. This is not normal, but way too common. I would assume that if you opened up your soffit, you would find a 1/2" pipe feeding two bathrooms. If you decide to open up the soffit, personally I would replace the pipe with a 3/4" to each bathroom, I believe that would solve your problem for good and may cost less than $40.00 (Piping only) as opposed to the cost of insulation and other symptom fixes. Opening up the soffit is the other cost. If you are going to address only the symptoms, 6" fiberglass batt insulation works well for deadening sound. You will also have to address each point where the pipe touches the structure, armaflex insulation is good for this purpose or special sound deadening inserts. Hope this helps, Dan Martyn