1996 Chevy Suburban buzzing noise?

We just purchased a 96 Chevy Suburban a week ago. We have noticed a high pitched buzzing sound coming from the way back drivers side, it isn’t always the same pitch, it does change is the gas pedal is pressed(which is faster buzzing and higher pitched). We are thinking it is the fuel pump. Would this be accurate? Any other tests we can do to narrow it down?

Thank you in advance!