Abstract
An ensemble of monopoles can approximately describe the radiation field of underwater organ pipes in low frequencies. Two extreme monopoles represent the mouth and the end opening respectively. Each of middle ones represents a pipe segment of halfwavelength. Phase difference and strength ratio between a middle monopole and a extreme one are theoretically considered. Experiment on the radiation field pattern of first mode confirms theory on it based on the above monopole approximation. Radiation field largely epends on pipe material because its distensibility governs the radiative strength of pipe wall.
