Some inverters include a fan for cooling the inverter. You may hear it humming when the inverter is operating.
When the inverter converts electricity from the solar panels to usable electricity (DC to AC), your inverter may make a humming noise.
When the inverter starts up or goes into sleep mode, you may hear a few “clicks”. This is normal, inside the inverter is some kind of switch that opens or closes when the inverter connects to the grid.