CPU can be downgraded to reduce fan noise

For this you have tools

Disable intel burst

echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo

Force the CPU to not upper a frequency:

echo 30 > /sys/devices/system/cpu/intel_pstate/max_perf_pct

you can check the all values with :

cat /sys/devices/system/cpu/intel_pstate/*

you can check you CPU frequency with:

cat /proc/cpuinfo | grep MHz

you can check :