Liquid cooling, especially when using an All-in-One (AIO), tends to be quieter than the fan on a CPU heatsink. Again, this can vary, in that there are air coolers with fans specifically designed to reduce noise, and fan settings or fan selection can impact the amount of noise generated. Overall, though, liquid cooling tends to generate less sound, as the small pump is usually well insulated, and radiator fans tend to run at lower RPM (revolutions per minute) than those on the CPU heatsink.