It’s all to do with the melon…
Beluga whales have a prominent, round-shaped bump on their heads just in front of their blowhole, which is called a melon. This fatty mass is sensitive to sound and movement and helps the whale with echolocation (producing sound waves that bounce off an object and vibrate back to the whale to help it locate where it is).
The melon is used for communicating (it enables the beluga to create different sounds and facial expressions), but it is also covered in a hard skin that provides protection for when the beluga hits its head against the ice to break it up.
The beluga whale is one of the only cetaceans whose neck vertebrae are not fused to its head, enabling it to be much more flexible in its movements.