2nd Gen Gameboy Color Annoying Noise?

[Eight.Bit]

I finally got my Pokemon Blue version in the mail, and I started playing it last week. It works perfectly, saves, it's like brand new except for the Gameboy Color has this annoying noise coming out of it. It works perfectly as well, except when I use headphones, there's a low-pitched, slightly distorted humming sound coming out of them in addition to the game sound, even when the volume is turned down to nothing (volume of the strange noise is constant, volume of the game sound adjusts correctly).
I tried a different pair of headphones, same problem. Occurs on both mono & stereo settings. No difference if I wiggle or rotate the headphone plug. The volume control works fine, as does the GBC's speaker.
Anybody know if this is normal? And if it's not normal, what should I do about it?
Any advice is welcome. :)

 

[Mega_Kris]

have u attempted other gameboy games?

 

[Eight.Bit]

have u attempted other gameboy games?

Nope, I don't own any other games. D: But when I turn it on without any games inside of it, it still makes the noise. Is it normal?

 

[Zehn]

You speaker might be bust or not making contact with the bord. The speak isn't soldered down on the GBC, just held there by the case