Sound speed measurements have been made using a standing wave technique for possible inclusion in Project Listen Up! In a previous paper [S. A. Cheyne and W. C. McDermott, “Sound speed measurements in air using a variable sound source and tubes,” J. Acoust. Soc. Am. 125, 2625 (2009)], sound speed measurements in tubes were made using traditional standing wave techniques. A low-cost variable frequency sound source was constructed and used to produce the sound waves. Resonances in the source itself made it difficult to make reliable measurements. Also, it was difficult to detect the tube resonances by simply listening to the resonances with one’s ear. In this work, we have improved the quality of the apparatus to make it easier to generate and detect tube resonances.