Echolocation calls are usually ultrasonic—ranging from 20 to 200 kilohertz (kHz) in frequency, while human hearing usually peaks at around 20 kHz. Even so, we can hear some bats’ echolocation clicks, such as the Spotted bat (Euderma maculatum). The sounds made by hitting two round pebbles together resemble these noises. Echolocation calls are generally characterized by their frequency range; their decibel intensity (dB); and their millisecond duration (ms).nnBats generate echolocation calls with both constant frequencies (CF) and varying frequencies that are often modulated in terms of pitch (FM). A complex sequence of calls is produced by most bats, combining CF and FM elements. Although low frequency sound travels beyond high frequency sound, higher frequency calls provide the bats with more detailed information, such as the size, range, position, speed and direction of the flight of a prey especially at night. These sounds are thus used more frequently.