The partial coherence function technique has been applied to a room air conditioner of window type(RAC-Model GA-810 made by "Gold-Star") to identify the noise sources of it. To this end, the RAC with multiple noise sources has been modelled as a four-input/single output system. For this model, the sound pressures and the accelerations measured at different points have been taken as the inputs and the sound pressure measured at the point apart from the surface of the RAC by 1 m has been taken as the output. Then the model with arbitrary random inputs has been changed to the model with ordered conditioned inputs by using the optimum linear least-squares prediction technique.
From this model, the partial coherence functions between each input and the output of the system have been obtained by the digital iterative operations. The analysis of these functions shows the following results.
(1) Vibrations of the compressor are the major source of noise at low frequency region. And vibrations of the shroud, baseplate and cover of the RAC result from the vibration of compressor, rear fan, motor and the blower, and they increase the total front noise level of the RAC at low frequency region.
(2) The blower-scroll assembly is the major source of noise in the RAC at frequency region around 750Hz, and the intake port of the scroll affects the total front noise level of the RAC in broad frequency band up to 1500Hz.
