What is the primary function ascribed to carbonic acid ($ ext{H}_2 ext{CO}_3$) regarding the drinking experience, distinct from the flavor roles of stronger acids?

To create the characteristic 'bite' or tingling sensation (fizz).

Carbonic acid's most crucial contribution to the beverage experience is sensory rather than strictly chemical acidity. It is directly responsible for the effervescence, which manifests as the characteristic 'bite' or tingling feeling perceived in the mouth. This sensation occurs because the carbonic acid irritates the specific sensory receptors in the oral cavity. Although it contributes a mild tartness, its primary role is linked to this tactile, prickly mouthfeel, contrasting with the aggressive sourness provided by stronger acids like citric or phosphoric acid, which are added primarily for flavor and preservation.