Why can some people hear higher pitches than others?

What is this question doing under Electricity and Magnetisim? Sound is a mechanical phenomenon. It does not have to be produced by a speaker.

Perhaps you have in mind the 60Hz hum in consumer electronic equipment? It is caused by poor filtering of the power supply, or by coupling from the pre-filtered power supply to sensitive circuitry elsewhere in the device.

Sometimes, it is even caused by the motion of the power transformer windings. As they age, the glue holding them in place breaks down and they can actually make noise by their own mechanical vibrations, without relying on the speakers at all. The winding does undergo an actual mechanical force from the electromotive force (emf) of the current flowing in it.

But in a new, properly designed power transformer, that mechanical motion will be too small to make substantial noise.