Measurement of the Acoustic Source Characteristics of the Intake Port in the Refrigerator Compressor

In the refrigerator compressors, the suction mufflers are commonly used to reduce the notse propagated through the intake valve system. In order to optimize the muffler design, it is necessary to characterize the source characteristics, i.e., the source impedance and the strength, of the intake system. In this paper, assuming the intake system as one-port, linear, time-invariant one, the acoustic source at the intake port of the actually operating compressor is estimated by using the multiple-microphone method. In the present method, an overdetermined linear system which contains two transfer functions between two pairs among three sensors is solved using the Moor-Penrose pseudo-inverse. The obtained source parameters are successfully used to predict the radiated source pressure at the intake system in the compressor. INTRODUCTION In the compressors of the refrigerators, the suction mufflers are used to reduce the noise propagated from the intake valve system and their performance is dependent on the acoustic source characteristics. Therefore, the characterization of the acoustic source modeling the sound emission from the intake port in operation is important in the proper design and the evaluation of the muffler system. Assuming oneport, linear, and time-invariant, the source can be characterized by the internal source impedance and the source strength. These source properties can be estimated by either the direct method (standing_ wave ratio method, two-microphone method and multiple-microphone method) or the indirect method (twoload method, four-load method). The comparisons of these methods can be found in many previous works [1-3]. In this paper, the source characteristics of the intake port in the compressor are measured by employing the multiple-microphone method [4] which complements the drawback of the frequency response of the conventional two-microphone method.