For the cost of the iPod, one should be able to expect near perfection. Odd, then, that the distinctive white earbuds--which make one a target for envy (and in some precincts, much worse)--don't block out ambient sound. Not to worry; you can replace them for half the price with powerful little Philips HE 592 earbuds, which create a virtual surround-sound effect. And for good or ill, they come in white.