Why Does my Electric Pump Change Sound?

Your GentleTent 12v electric SUP air pump uses an advanced 2-phase process.  First of all, always preset the target pressure on your pump before inflating.  (Note, you do not have to inflate all the way to the maximum pressure).  The first phase of the inflation process is the fill phase, and the pump will have a whirring sound.  Once the fill is complete, the pump will suddenly sound raspy as it automatically shifts to the pressurization phase.  This is normal.  The pump will shut off entirely once the GentleTent structure has reached the target pressure that you dialed into the pump.