Loud Crackling Noise On Internal Mic Input, Not present using new user acct? Options

[peterrosen]

I downloaded Audio Recorder. Upon playback of my first recording, a loud crackling noise was bubbling under my speach. I created a new user and made a recording and the input of my mac AL Book was CLEAN! Something in my administration user configuration is creating noise???? I used to make clean tracks with Digital Performer using the built in Mic. Now (I haven't tried it after many softwares have been installed) even in DP I am getting the same loud noise floor! Can anyone suggest why this is and how I can go about discovering the source of the noise in one user, and not the other?