I scratch and tap my nails on a plastic chair! Also my left hand has longer nails than the other, so you can definitely hear the different as I tap. I scratch up and down chair before rhythmically tapping my nails. Then I just break into scratch and finger tapping patterns, some are soothing and calm, others get faster and chaotic. The climax is when I scratch nails in fast circles before calming you will finger tapping and tight scratching.