I bought my T-C used 6 months ago. I could barely hear a hum when it was next to my ear. Now I can hear it at 1 meter in a quiet room. I used PXA clocker settings memclock- 133M, CPU clk-266M Turbo-399. It changed the pitch so I can barely hear it now. I don't know about PalmOne's claim that it is internal electronics. It still hums when all sounds are off or headphone is plugged in. It sounds like the screen to me. When PocketTunes turns off the screen and continues to play music, the hum is gone completely.