I tried reducing the speeds with Speedfan but any changes I make don't seem to affect it. Speedfan recognizes it and calls it Fan1, but at the bottom it only lists Pwm1, Pwm2, Pwm3. Changing the percents on those doesn't do anything to the fan speed.
Disabling automatic/smartfan control has the opposite effect, in which it makes the fan run full blast all the time. But the point is moot as that fan uses a 3 wire header. (the 4th wire generally being the one that allows the motherboard or the user to altar the fan speed)