Why does my induction cooktop make humming, whistling, or crackling noises during operation?

These noises are normal and are a result of induction technology's use of electromagnetic fields to heat cookware. A low humming sound occurs at high heat levels and quiets when the heat is reduced; quiet whistling happens when the cooking vessel is empty and stops once food or water is added; crackling results from cookware made of multiple layered materials vibrating at their contact surfaces. Loud whistling can occur with multi-layered cookware used at maximum output on two cooking zones simultaneously and quiets when the heat level is reduced. (Page 22)