Wear and age on Engine Sensors

What is your question?

I am curious to know if age more than anything can cause Sensors not work correctly without any codes? One in particular being the crank sensor and if it cause a pitch noise sort of like a high pitch hum. I am getting a noise at 40 mph like pulsing high pitch hum. When I let off the accelerator it stops and starts when accelerating again. This is just a very light acceleration and above that speed it becomes less. The sound is the area of the power steering and engine main pulley. I guess this seems peculiar but so is this noise. Just to add it has about 101,000 miles now and has been doing this for maybe 2 or more years now. Also if I replace the crank sensor would any other might need replaced along with it?