Very strange sound???

[notheon]

Using HTC touch pro for 2 months. Everything's fine until yesterday.
I suddenly heard a strange sound (much like buzzing zzz... sound) from the earphone speaker, which lasted until now.
I tried the loudspeaker & by the usb earpiece but the sound is normal.
So, I reboot it, same thing happens.
I use diamond tweak and advanced config to adjust back the volume to normal, but it is same also.
Is it the earphone speaker problem? Anything that I can do? And if it is speaker problem, do you think it is under warranty?
Thanks for your expert opinion and help!