Hi,
I agree with Brian.
I even want to go a step further. Show us photos of your circuit and the wiring. Tell us what cables you use and their length.
Also I´m a friend of "not suppressing the symptom" but avoid the existance of the noise at all. Thus I recommend to find out what´s the source of the noise. It may be the power supply, some internal circuit problems, some internal oscillations, externally introduced noise... and so on.
Thus the noise frequencies (and their overtones) give a lot of informations. Show us the spectrum of the noise, using an scope, an FFT, maybe use your PC´s audio card to record and process the signal.
Klaus