A perception experiment and analyses were conducted to clarify the acoustic features of pop-out voice. Speech items pronounced by 779 native Japanese speakers were prepared for stimuli by mixing them with a babble noise that consisted of overlapping short sentences spoken by 10 Japanese speakers. Using a 5-point scale, 12 Japanese participants rated the pop-out score of the speech items listened using headphones. The scores and acoustic features of the speech items were investigated using correlation analysis and principal coordinate analysis. It was revealed that the pop-out score relates to the acoustic features such as overall intensity, relative intensity in the high-frequency range, fundamental frequency, dynamic feature of the spectrum, and a spectrum shape in high frequency. The results suggest that these are crucial acoustic features for the pop-out voice.