If reducing power, and passive heat sinks do not bring the result a fan can be connected to the connector GPIO 5V power pin 2 (or pin 4) and Ground pin 6 to run permanently making noise and damaging the fan after a while.

Additionally when having a 3 wire fan, the fan can be PWM temperature controller via a GPIO14 (pin 8) that is configured using the performance entry in sudo Raspberry-config