My 2003 Honda Civic EX started making a fairly loud (not extreme) humming-type (not rattling, vibrating, or clicking) sound yesterday and is still making it. It is noticeable from inside and outside the vehicle. I'm not sure humming is the best word, it also kind of sounds like a belt is powering a turbine.

There is no check engine light. The vehicle performs normally outside of the sound. The sounds appears to be emanating from the area of the power steering pump, alternator, and belt. While it does appear to come from that area, I don't know that the issues are limited to those components.

The sound exists at idle, and worsens with acceleration. When acceleration is let off, the sound dampens in turn but is still there.

I can't find an exact solution from google/youtube. The closest sounds I hear on other examples are issues people have had with power steering, by replacing the O rings on the power steering lines. My power steering fluid is at max level and there do not appear to be air bubbles in the power steering reservoir when the engine is operating. I wonder if that could really be it then. No apparent power steering fluid leaks.

Any thoughts or suggestions would be much appreciated.