Abstract: This paper presents a practical model of echoes for sonar engineering. Based onthe fact that sonar systems usually use high frequency band-limited signals, the transferfunction is appropriate to characterize the target. At high frequencies, all the echocomponents such as the specular reflected waves, the corner waves and various elasticscattering waves can be thought of the echoes from some equivalent scattering centers orhighlights. The whole target is characterized by a highlight array in space. In this paper ageneral expression of the transfer function of the highlight,which includes the amplitude,time delay and phase factors,is derived. A determined parameter group provides a concretetarget model. The echo waveform simulaTion can also be performed by using the modelpresented in this paper.