Zinc carbon batteries are more commonly used in low-drain devices, whereas the Panasonic alkaline range spans the entire appliance spectrum: from low- to high-drain.
This is a vibration noise which occurs when electric current flows through a transformer or a winding wire inside a component part. However, the charger may still be used without any concern as there is no need to worry from a safety point of view.
Never use Ni-MH rechargeable batteries for waterproof appliances, appliances specifically designed for alkaline batteries, or in appliances with battery indicators.