Q: My MacBook Air is making a lot of noise all the time

Please read Apps can affect Mac performance, battery runtime, temperature, and fan activity - Apple Support.

Identify any processes that seem to be using an inordinate amount of CPU time.

If you can find no reason for the fan noise — in other words, if Activity Monitor fails to identify any particular burdensome processes — then an SMC Reset is justified: Reset the System Management Controller (SMC) on your Mac - Apple Support.

Excerpted from that document:

Indicators that your SMC might need to be reset

 

... The computer fans run at high speed, though the computer is not experiencing heavy usage and is properly ventilated.