A hollow rattle

Clink. A high... sudden ring. Across the floor... near the white pipes. A plastic ruler lay in my path. I stepped straight... hard. Crackle... under my sole. Did not go around. Kept moving. Reached the tall iron pipe. A loose metal washer rested loose at the joint. I reached out. Pressed my finger against the rim. Tap... it rattled against the iron. A quick, hollow hum. It shivered under my touch. Again... tap. Slow... steady. The sound filled the corner.