Why does my laptop make odd noises from the headphone port?

I have an Advent 7110 Laptop. Every since I have had it, it has made odd noises when I use the headphone slot. In terms of the Laptops own speakers they are fine and there is no audio trouble but when I decide to use the headphone output to listen using headphones or plug it into something such as an amplifier it gives off this strange noise. The noise is hard to describe, it's kind of a buzzing, wavy noise. I believe it is connected to how the Laptop is working, it is though I can hear the laptop processing things. It sounds like the headphone output is linked to the processor or something. I believe it is linked to how the laptop works because it seems to have a link to the processing light on the laptop and also before there was a beeping noise as well as the buzzing however when I disabled the laptops infra-red the beeping stopped. Can anyone explain what this noise might be and how I could possibly get rid of it! Thanks very much :)