I am a physics teacher and I my class is currently studying sound waves. I had my class make some noise makers with straws as shown here. http://www.physics.org/interact/physics-to-go/straw-oboes/ We measured the frequencies coming from the straws and they seem to act like a pipe open at both ends since all the harmonics are present. The frequencies seem to be much lower than we would expect though. I had students use the length of the straw and the fundamental frequency to find the speed of sound. Most of them were getting answers between 120 and 145 m/s. We considered the straw length to be half a wavelength and then multiplied the wavelength by the fundamental frequency to find the speed. Am I missing something here, or is there some reason that this behaves differently than a typical open ended air column? Thanks for any help!