There is a high-pitched digital noise that comes from the speakers of this iMac. I know it's the speakers because when I plug in headphones, the noise comes out of them as well.

The noise in headphones sounds like this: a short buzz of static and then a number of pitched beeps. It sounds like the noise that happens sometimes when you turn off a digital TV.

When I don't have headphones plugged in, sometimes a high-pitched sound comes from the iMac - I can turn it off by adjusting the speaker volume using the keyboard.

I'm afraid that this sound may signal the end of this iMac, and it's also very distracting/impossible to use headphones because the noise is so distracting. Please help!

Info about the computer:

Model Name: iMac
Model Identifier: iMac6,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.16 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 4 MB
Memory: 4 GB
Bus Speed: 667 MHz
Boot ROM Version: IM61.0093.B07
SMC Version (system): 1.10f3
Serial Number (system): W871412VVGN
Hardware UUID: 00000000-0000-1000-8000-0017F2D86CB2

Intel High Definition Audio:

Device ID: 0x10EC0885
Audio ID: 16
Available Devices:
Headphone:
Connection: Combo
Line In:
Connection: Combo
Speaker:
Connection: Internal
Internal Microphone:
Connection: Internal
S/P-DIF Out:
Connection: Combo
S/P-DIF In:
Connection: Combo