1. The problem statement, all variables and given/known data You blow across the open mouth of an empty test tube and produce the fundamental standing wave of the air column inside the test tube. The speed of sound in air is 344 m/s and the test tube acts as a stopped pipe. If the length of the air column in the test tube is 14.0 cm, what is the frequency of this standing wave? L = 0.14m V = 344 m/s Closed Tube 2. Relevant equations Closed Tube Frequency = Fn = nVair / 4L 3. The attempt at a solution F1 = 1*344 / 4*0.14 = 614khz I thought this was the right answer, but the online program says it's incorrect.