I found this instrument in Bitts Park Carlisle a while ago. You bang the xylophone but there are pipes behind.
The xylophone bars are fixed - this one is 10cm apart. If the fixture points act as nodes then the wavelength of the stationary wave is 20cm. Assuming speed of sound of 340m/s that gives frequency of 1700Hz. It was nowhere near as high as that!
The pipe behind was about 15cm long. Given an antinode at each end, the wavelength is 30cm and the frequency 1100Hz. I still don't think it was that high. I will have to wait until I'm allowed to go again to test my memory of the pitch.
