pads aren't the concern - specifically check the pins, pad clips, and emergency brake mechanism. one of those is corrupting pad movement. they'll hang in a general "range" of movement sometimes making them hard to diagnose and having intermitten or condition/speed related symptoms, until the pad starts to wear at an angle and symptoms escalate.
clean each pin, regrease with high quality grease (not generic permatex).
pad clips can get bent, rusty, or corroded/built up and cause pad movement issues as well.
emergency brake can stick at the hub.
or it's suspension related - a ball joint/bushing is moving under load.
Can you tell which corner it's coming from - you should have a vague idea where it's coming from if it's an audible noise. if not - have someone stand outside the vehicle and listen or change seat positions to listen from inside.