The technigue of changing frequency and reducing noise (CFRN) is used in noise reduction for the QD58 type reciprocating refrigerator compressor.On the basis of the orthogonal tests results,a kind of clapboard with suitable geometric dimensions is designed to modulate the acoustic natural frequencies of the cavity in compressor,bringing satisfactory results for noise reduction.Using the sensibility formulas of geometric parameter of the clapboard to the natural frequencies,its geometric dimensions are revised to reach the optimal acoustic working state of an actual compressor.