Noise in my speakers

[almabet]

Hi everybody!
I have a hack with follow specifications:

Core i7 3770 Ivy Bridge
Board Gigabyte Z68XP-UD4
32 GB RAM Corsair Vengeance
Video EVGA GT 640
3 H.D.D. Hitachi Sata III 1 TB (each one)
1 H.D.D. seagate barracuda 500 GB
1 H.D.D. Western Digital 500 GB
DVD Writer Sony Optiarc
ASUS Bluetooth Dongle
WiFi card TP-Link WDN4800 PCIe
PSU XFX Pro 850 Watts
Thermaltake Overseer RX-I Chassis

I´m musical producer. The hack is fully working and very powerful.
The problem is that i perceive a disturbing noise through the speakers, basically when the hard drive is operating.
This noise is very annoying to my work.
I changed the PSU (previously had a thermaltake 430 watts) and the problem persists.
Also noticed waves on a computer screen like electrical interference.
Someone told me that this noise could be caused by a component of the computer that was generating interference.
Anyone have an idea what could be wrong with my system?

Thanks for your time and help.

 

[almabet]

I forgot ... I'm using OS X 10.8.2 mountain lion, and recently updated the BIOS to UEFI BIOS.