Why do I hear white noise when I listen to audio through earphones?

[Heinstar]

I recently bought a Base line Mac mini from Apple online and whenever I turn on an audio(even if it's on mute), I hear a hissing sound/white noise in the background along with the audio. Once I turn off the audio, it takes fifteen seconds for the hissing sound to go away. I tried plugging in different pairs of earphones but they all had the same result.

But when I plugged in a headphone, the hissing sound wasn't there anymore. I heard on some forum that this problem occurs in all Mac mini and that it's an engineering problem so there's nothing I can do about it. But when I asked the local Apple reseller, he told me that this is a uncommon problem and I should send it back to Apple.

So who is right? Will I be able to get a Mac mini without this audio problem if I send it back to Apple?

Thanks.

EDIT: I meant Earphones not earplugs! Sorry english isn't my first language...