It definately happens, but only with the automatic volume control turned on. You can definately turn this feature off if you want. That would resolve it.

Why is it happening? I believe it is because wheel speed is actually determined by a number of pulses as the wheel rotates. As you go fast, you get a lot of pulses over a short period of time. As you are going very slowly, you get a small number of pulses.

In a typical system the speed would be determined by a number of pulses over some fixed time. Let's say that this time is 1 second (in practice it's probably more like 100 ms, or 1/10th of a second. So let's also say that we are getting one pulse every 0.9 seconds. Most of the time you would get one pulse per time period, but every 9th and 10th time you would get two pulses per time period. This can appear as doubling the speed.

The automatic volume control would see that the speed doubled, and crank the volume.

I don't know if this is the cause, but the symptoms would match the theory.

I don't think it is a cause for concern, and is definately quirky. I don't think it has anything to do with our hybrids, other than the radio is probably the same.

2005 Ford Escape Hybrid - Titanium Green, 4WD, Appearance Pkg, Leather, Nav System