98 Ford Ranger Wheels or axle whistle when rotating

My Ranger (65,000m) makes a whistle or high pitched squeel when in motion. When stationary and reving the engine, there is no noise. I aquired the truck recently, and only put down the windows for the first time during a warm spell so I’ve been unaware of the noise until now. I don’t know when the sound began. Any ideas?

Does the noise change in volume and/or pitch as you speed up and slow down? Is it related to engine RPM or road speed?

Brake pad wear indicator.