Cross Fell: Singing gatepost at Kirklands

The wind was blowing across the hole in the gate post on the way up Cross Fell. It was oscillating between a low note that we thought was around middle C and a much higher note. So which type of stationary wave was being formed. Both ends of the top are closed so let's try the idea that there is a node at each end like on a guitar string. The wave is then a single loop and the wavelength is twice the length of the tube. The tube was about 1 metre long so wavelength = 2m. Speed of sound in air is approximately 340 metres per second. So frequency = wave speed/wavelength = 340/2 = 170Hz. The other alternative is a node at one end and an antinode at the hole which is a quarter of a wavelength and might be worth 70cm. So wavelength = 2.8 metres and frequency = 121 Hz. Middle C is 261 Hz. I'd say first mode is most likely. The higher note would be the second harmonic at 340Hz.