I use the magnetospeed barrel cooler. IMHO, the noise is obnoxious and really so if you wear electronic hearing protection that picks up ambient sound. I use it only when nobody else is around. I did add a couple small rubber pads to it to help with the vibration buzz that it sometimes produces against the action but you can't get away from the motor noise. (I can hear it 50 yds away)
I have a hard time believing it makes a significant difference. When I think about exposed external area of the barrel and even just a slight breeze, it is hard for me to believe the internal air push of the relatively small battery powered device through the bore is making a big difference. When I use it, it's mostly because there isn't anything else to do while the barrel cools and I figure it can't hurt.