Acoustics of a pressurized air-filled pipe open at one-end at varying depths

A rigid pipe with a loudspeaker at one end and open at the other end, was submerged in a water tank at various depths. Microphones were placed along the length of the pipe to measure the acoustic response of the duct due to the acoustic excitation from an internal loudspeaker. Compressed air was injected into the pipe to equalise the internal pressure of the pipe caused by the water pressure acting on the open end of the pipe. The results were that the acoustic resonance frequencies of the duct did not alter with depth.