You'll want to cut out a lot of the bass, so it sounds as if you are hearing the audio through small, cheap speakers. You can do this very simply with an EQ. Some distortion would also be good to get that radio interference effect.

I don't know what Goldwave can do (I use Sound Forge on PC and Soundtrack on Mac), but I imagine it will have these effects, at minimum.

What kind of Radio, AM or FM? AM is generally mono and FM is stereo. Use a parametric EQ and move the bell curve around till you get what you want. You might also want to look into bit decimators. They have various names but the basic principle is to not only reduce the frequency response, but to also reduce the bit depth of the wave form.

Say you have a 44.1Khz 24 bit full frequency wave. Apply an EQ filter and a bit reducer and you might end up with a 22Khz 12bit wave filtered by an 11K notch filter. If you can animate these parameter changes, like in Ableton live, you can simulate interference then have the wave restore back to normal.