ACOUSTIC FIELD AROUND AN EXIT OF FLANGED CYLINDRICAL DUCT WITH A COAXIAL CAVITY

In relation to reduction and passive control of noises emitted from du cts or openings of machineries, the acoustic field radiated from a fla nged cylindrical duct having a coaxial cavity at the exit of the duct was investigated for various depths and radii of the cavity. Structure s of the acoustic field generated by a sound source located at a dista nce from the exit were analyzed numerically using the finite differenc e method. Also, experiments were conducted to obtain the distribution of acoustic pressure levels and acoustic intensities around the exit u sing a three-dimensional intensity microphone system. It is shown that the cavity attached to the duct affects the acoustic field markedly a nd an appropriate configuration of the cavity reduces sound pressure l evel significantly. It is also shown that the acoustic field is well s imulated by the present numerical calculation method.