Swallowing sounds are transient signals generated by multiple events in the swallowing mechanism and can provide information about normal or abnormal functioning and coordination of swallowing structures. In recent years, there has been an increasing interest in digital signal processing of swallowing sounds in various food and liquid volumes and consistencies. Therefore, this systematic review focuses on the identification of discrete acoustic features associated with different bolus consistencies to provide a differential diagnosis of swallow sounds in healthy adults across food and liquid viscosities.