Just Noticeable Differences (JND) in sound quality metrics-Zwicker's loudness, sharpness, roughness and fluctuations strength, and Auto-Correlation Function (ACF) parameters-were investigated using refrigerator sounds. An original refrigerator sound was set as a reference stimulus and the reference signal manipulated in terms of sound quality for use as a comparison stimulus. Forty participants were asked to evaluate the differences in sound quality of sound pairs, and the value of JND was determined using the criteria of 75% correct answers. The results showed that JNDs of loudness, sharpness, roughness, and fluctuation strength were 0.5 sone, 0.08 acum, 0.04 asper, and 0.012 vacil, respectively. JNDs of ACF parameters such as Φ(0), τ1 and Φ1 were 2.0 dB, 0.4 ms, and 0.08 dB, respectively. The results of the present study provide criteria for sound quality enhancement of refrigerator sounds, especially the amount of value for perceptual improvements.