1. A method to image a formation by automatically characterizing an echo contained in an ultrasonic signal, the ultrasonic signal being generated with an ultrasonic transducer, the method comprising: a. receiving data corresponding to the ultrasonic signal with the ultrasonic transducer of a downhole acoustic tool; b. calculating an energy ratio of the ultrasonic signal and localizing the echo contained in the ultrasonic signal using the energy ratio; comprising; b1. calculating an energy ratio function of the ultrasonic signal, wherein the energy ratio function is E x = a 1 ( ∑ i = x + 1 x + L ⁢ ⁢ E i ∑ i = x - L x - 1 ⁢ ⁢ E i ) / ( 1 + a 2 ⁢ E total ) , where Ex is energy at a given data point, a 1 and a 2 are energy adjustment factors, L is a window length, ∑ i = x + 1 x + L ⁢ ⁢ E i is signal energy, ∑ i = x - L x - 1 ⁢ ⁢ E i is noise energy and E total is total energy; and b2. identifying a maximum value of the energy ratio function of the ultrasonic signal, wherein the maximum value corresponds to an approximate location of the echo contained in the ultrasonic signal; c. windowing a portion of the ultrasonic signal around the localized echo; d. calculating a Fast Fourier Transform (FFT) and a Hilbert envelop of the windowed portion of the ultrasonic signal; e. estimating M echo parameter vectors from the FFT and the Hilbert envelope of the windowed portion of the ultrasonic signal, wherein each of the M echo parameter vectors comprises a plurality of echo parameters; f. calculating M parametric echo models based on each of the M echo parameter vectors; and g. iteratively minimizing a difference between the windowed portion of the ultrasonic signal and a sum of the M parametric echo models; transmitting parameters from the M parametric echo models for use in characterizing the formation.