This study proposes a novel interface for sensing swallowing activities (based on the sound produced when swallowing) that is mounted on the back of the neck. Recently, owing to the aging of the population, the number of dysphagia patients has been increasing. Although various types of diacrisis and dysphagia testing methodologies already exist, several problems remain. For example, the videofluorography methodology requires extensive preparation; it presents risks of aspiration and demands knowledge about diacrisis, and it must be performed in a medical facility. This study introduces a wearable sensing system that can be used in daily life. As it gives direct, real-time information regarding swallowing movements, this device is also aimed at being used for rehabilitation purposes. The proposed system uses a new evaluation technique that is based on the duration of the swallowing action.