Abstract: The biosonar system of Pratt's roundleaf bats is characterized by the peripheral dynamics including variable structural deformation caused by noseleaf and pinna motions as well as the dynamic adjustment of ultrasonic pulse sequence caused by variations of pulse number and emitting time. To investigate whether there is a relationship between the two sources of variability, the noseleaf and pinna motions with the records of biosonar pulses are synchronously collected in biological experiments. Two frequently occurred noseleaf/pinna motion patterns are chosen for analyses. A novel spike-train similarity space (SSIMS) method for analyzing neural spike sequences are used to classify the biosonar pulse sequences emitted exactly during the corresponding noseleaf/pinna motions. The results show that the variabilities in biosonar pulse sequence match the peripheral dynamics, i.e., different noseleaf/pinna motion patterns correspond to the biosonar pulse sequences with different pulse numbers and emitting times.