Period doubling (PD) is a type of creaky voice that contains two alternating periods, which contribute to an indeterminate pitch with a low and rough quality. By presenting data from Mandarin Chinese read speech recordings, this study probes the articulatory properties of period-doubled voice and its tonal distribution based on time-domain measures using electroglottography (EGG). Besides the alternation of frequency and amplitude in two adjacent glottal cycles, alternation of contact quotient and symmetry quotient was also seen in a few samples, suggesting that PD is likely articulated through two alternating pulses with distinct voice qualities and pitches. Preliminary data also suggest H1*-H2* is the most salient cue differentiating PD, vocal fry, and modal voice.