Most symptoms of strange sounds using Variax Custom Tunings are the result of a simple inescapable fact: the string is still vibrating at its physically-tuned frequency. Your ears are relatively close to, and very sensitive to, the acoustic string vibration. You can hear it. Unless the volume of your Variax tuning is very loud, or the acoustic sound is blocked by closed earphones, your ear hears both the physical tuning and the altered tuning. Not usually a pleasing sound.