It's not easy to notice it, at 1st I thought mine was OK - but play any tune that has some lower volume parts and you can hear it.
Also, play any MP3, pause it - and you will hear the high pitched whine / hiss - it sort of sounds like electronic interference of some sort.
So the sound is always there just masked until quieter passages.
To test , use headphones, turn up the volume, play an mp3, use YouTube - anything with audio, then PAUSE the item and listen - you will hear a second or so of the noise, then it will stop.
Mfeaturefeeature phones never had this problem (VGA1000, FUSIC) and tried with my original Droid and Wife's Eris - no interference / hiss etc. and all sound better, pretty lame for a $299 , flagship / high end brand new smart phone!
This, horrible battery life every 3G everyt so often which may be the cause , but yet my Droid, Eris, BBerry for work do not) , and the lack of bright whitelooksow (loooks like mustard) - not looking like a keeper and with nothing else worthy on VZW (dual core, 1Gb ram) - looking like a Photon (if theissuesious isues aren't present) or an Epic Touch 4G - both $99 on Sprint.