AUDIO-Minimizing hiss during recording

I have an Audio-Technica ATR30 microphone plugged directly into my eMac audio input using a Mono Plug Adapter. During recording into a simple program SoundStudio 2.2. there is a constant hiss underlying the audio. This is not room noise. It sounds almost like an analog tape hiss.

I have cordless phone in the room and run an airport wireless network.
Would these have any "magnetic" effect on the microphone?
Possibly just the audio sound card built into the mac.

We also used an Griffon iMic USB input device. We got a hiss on that too.

Any strapping "older and experienced" pro audio men out there to help a newbie audio gal?


thanks!!!