Noise Level Results
Noise levels are very acceptable and may be one of two saving graces for the T40. While the resistor was in place, and the fan was spinning at 1358 RPM I took a sound measurement and got a reading of 32 dB.
Without the resistor inline, the fan was spinning at 1858 RPM and while audible, was still only 52 dB here. One thing I did notice at high speeds is that I was starting to get a vibration from the fan. Using just the fan from the T20 got rid of the issue, but the fan equipped on my T40 would cause one strong enough to feel through the desk.