Well, I finally got the bathroom and range vent fans replaced with computer fans.
The bathroom vent was relatively easy. I drilled 2 holes in the old fan mount to accomodate the new fan. Using a Sound Pressure Meter on scale A, the original bathroom vent fan measured 74 DB at approx 1 meter. The new fan measured 53 DB at approx 1 meter.
I also replaced the original range vent fan (which so happens to be the same motor and blades used in the bathroom vent). This one was a bit trickier. I took down the range hood, there were 4 square head screws going into the bottom of the cabinet. Once I got the vent down, I removed the original fan and used the original fan bracket for one of the screw mounts for the computer fan.
The fit was not perfect for the 120 mm fan, but I could not figure out a way to mount two 80 mm computer fans to the exit vent in the rear of the range hood. The 80 mm fans were about 3-4 mm too large to fit. I improvised by using a wire tie on the opposite corner mount to secure the fan.
The result was a reduction of 22 DB. Original fan measured 74 DB and the replacement measured 52 DB. Now, we can watch TV in the Living room even when cookign with the range vent on.
The fan I used for both was an Antec Pro Series Double Ball-Bearing 120 mm Case Fan with these specs:
12 VDC .24 A
79 CFM
2000 RPM
29.8 DBA
I think the difference in measured noise versus rated noise is caused by echos in this application.
Also, a note on the range vent fan...the original did not have special marking for flammability safety, etc. I assume the metal grill in front of the fan reduces the chance of grease, etc getting to the fan. However, I am not sure if there are any safety issues in using a different fan.
I posted photos at:
http://fifthwheelliving.com/gallery/...umName=RV-Mods
Fred