Yes, I had a similar speaker problem (buzz) in my front and rear passenger speakers. The sound alternated between two different tones front to rear and sounded almost like crickets. Turning off the ignition always immediately stopped the sound. My dealer rewired the amp (something about a service bulletin), but it did not fix the problem. Then about two months later the sounds stopped completely, so I'm not exactly sure what it was -- just that it was very annoying there for a while... Good luck figuring it out!!