This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
There are several ways to get "static" when recording sounds on your GS. One is to have incorrect settings for the sound recording program. If input level is set too low, you may be recording relatively more noise than sound. If input level is set too high, you may be getting "clipping"-- the signal gets chopped at the peaks-- which can sound like static. Also, check the Sampling Rate setting. A too-low sampling rate can result in glitchiness which sounds like static. If you have not already done so, try experimenting with your sound recording program's settings. If your sound input board has more than one input, then, one may be for "Line Input" for recording from a tuner, tape deck, etc. and another may be for "Mic". If there is a choice, be sure your sound source goes to the right input. For example, to record using a microphone, it should be plugged into "Mic". Hum usually indicates a different problem. Almost always it indicates a broken or very poor Ground/shield connection. Check your connector jacks and plugs. Sometimes just turning a cable plug in the socket/jack will establish a good contact and end hum. If you are using a microphone, it could be the source of problems. Static can come from a mic which is damaged, has some sand, etc. sitting on the diaphram, has an intermittant ON/OFF switch, has a damaged cord, or has a loose connection at the plug. Or; you may be using a perfectly good microphone which is badly mismatched to your sound input board. For example, a high quality mic may deliver a very low output. Your input circuit may auto-boost amplification to try to compensate; but, the result may be to obtain an audible recording with greatly increased noise. (Your signal-to-noise ratio at the input is too low.) By the way, the mic supplied with Hyperstudio (the Apple IIgs version) is not an especially high quality unit; but, it works fine with Hyperstudio's GS sound input board. If you are not sure that your mic is okay and is the right sort for your sound input board, try swapping in one from a tape recorder, etc.. ----------------------------