He already told you. The noise is the pump priming up, it happens for 2-3 seconds every time you turn key on. Sounds like a whine or whir coming from gas tank area.
If noisy and you've never noticed it before then it COULD be going bad, getting noisier is a sign of one going bad. Normally the noise is so slight most people never notice it.
It can be erratic, car starts fine for a week and then out of the blue won't once.
Change filter for sure if it's never been done.