During transmission, a speed of sound pulses gradually reduces due to acoustic impedance. Regulating a length or a density or a sound speed of the sound pulses affects their average speed in the transmitting medium, sound intensity and detecting depth. Time of flight (TOF) and TOF shift can be used to calculate the depth and moving speed of detecting objects. Calculating a speed of moving objects by simultaneously detecting TOF shift at same site from two separated piezoelectric (PZT) elements improves the testing results with accuracy, simplification and reproducibility. Coding sound pulses to obtained the TOF and the TOF shift will simultaneously calculate the depth and the moving speed of sampling points, which can be used to construct 2D and 3D images for these motionless and/or moving sampling points. Coded sound pulses also improves the quality of the imaging.