There is appearing a non-predictable frequency in a spectrogram that is measuring the vibration frequency of the Soundhauss tube experiment.

Question

My lab team is studying the behavior of sound frequency in a Soundhauss tube — a tube with one closed and one open extremity. We recorded the sound and used an app to see the frequency of the sound in a spectrogram. According to theory, there should be frequencies relative to 1/4, 3/4, 5/4 (etc.) of the wavelength, but the spectrogram is also showing a frequency (with low intensity) relative to the sound predicted in a fully opened tube.

Comments

Which literature do you suggest to get acqiuanted  with your problem?

I heard sometime ago in PF that an antenna of radio should built in length of 1/4 that of the wavelength of the signals which are supposed to be read by the antenna.

I never heard a theoretical explanation from first principles why is it quarter?