The first tube considered consists of two open cylinders of different diameters joined end to end. The theoretical expression for the frequencies of standing waves in such tubes is not new, but it leads to a rather surprising result which is now tested experimentally. The second tube considered consists of two open cylinders of different diameters joined by a conical connecting tube. A theoretical expression for the frequencies of standing waves in such a tube is developed. For the one tube examined experimentally the agreement between theory and experiment is satisfactory.