A local installer has installed a Lennox HSX15048 4 ton AC, a C3350/60C Coil, and a Lennox G61MP60C110 Furnace. I requested a G61MPV60C110 furnace with a variable speed fan. The installer says that a variable speed fan furnace will be noisy due to the cavitation of the fan. I have a 20 by 20 inch drop to the furnace filter for plenty of return air. Is it true that a variable speed fan will be noisy due to cavitation?