The types of signals which are seen in echolocating calls in bats can be categorised into constant frequency (CF) and frequency modulated (FM) signals. In this study the CF and the FM signals are artificially generated and applied to a bat echolocating model to investigate the detection of targets of different dimensions and materials. The two different types of artificial signal are convolved with the measured backscattering impulse response of various types of target objects. As a result the emitted and reflected echolocating signals as an air transmission stage in the echo generation mechanism in bats are reconstructed. The spectrogram of the reconstructed echolocating signal from the object is calculated and the image subtraction between the spectrograms of two different objects is used to generate the pattern spectrogram which indicates difference in the properties between the two different targets. This is investigated to extract the values corresponding to both dimension and material properties. The results appear to show different peak and notch characteristics for the various target properties. The signal properties of objects produced by the different echolocating signals are then compared with each other and the effects on each pattern spectrogram are investigated. Although more results from various types of object and further development of the signal processing method are required to numerically validate the approach, this study is considered as an effective model-based approach to investigate echolocation in bats.