 The two species were first distinguished on the basis of their different-frequency echolocation calls.The common pipistrelle uses a call of 45 kHz, while the soprano pipistrelle echolocates at 55 kHz.The two species are sometimes called the 45 kHz pipistrelle and the 55 kHz pipistrelle, or the bandit pipistrelle (common) and the brown pipistrelle (soprano).