Is it possible to hear electricity (or some byproduct)?

yes, if you drop a hit of acid, you can also hear colors and smell sounds.

I think you can hear it charging and discharging the surrounding air.

I think.

You did not mention whether you had anything plugged into the protector. Assuming that you do not, there are electronic components in the protector which may generate noise. However, to my knowledge, none should have the cycle that you describe. The only expected noise would be a constant 60 hertz hum, similar to the noise of a doorbell transformer or similar device.

Yes, all of my computer equipment is plugged in but not on.

It really sounds like a frequency only some ears would hear.

I’m thinking the surge protector is getting old. Can they get old?

Remember that the computer does draw power all the time that it is plugged in to the protector. Unplug the computer and the noise will change. It is possible for the protector to age but unlikely to be the source of the noise.

Thanks :)

Ever drive under high voltage power lines? It can actually be kind of loud. Also, try lowering the volume of an iPod (flash based) to the lowest it will go and flip through songs or videos. I swear it makes a sound if you listen real close. I could be wrong, but it sounds real enough to convince me.

You cannot hear electricity. You can only “hear” vibrations in the air. These vibrations can be caused by static discharge, etc. If what you speak of is truly a surge protector, then you may want to get a new one. When a surge protector is tripped a physical connection is broken (it’s why you have to push a button afterwards). It may be trying to break the circuit and failing due to a mechanical problem and thus may be faulty. If it is a UPS (uninterruptible power supply) then that may be normal.