Pulse wave velocity (PWV) is widely used for estimating the stiffness of an artery. PWV is measured by the time of travel of the "foot" of the pressure wave over a known distance. This technique has a low time resolution and is an average measurement of artery stiffness between the two measuring sites. The elastic modulus of the artery can be estimated with PWV, but the surrounding tissue effects are not considered. In this paper an external short pulse wave is generated noninvasively in the arterial wall by the radiation force of ultrasound. The pulse wave velocity in the artery is measured by a scanning technique with high-time resolution. The effect of tissue-mimicking gelatin on the artery is analyzed by measuring the wave velocity of the artery without and embedded in gelatin. It is found that the tissue-mimicking gelatin significantly stiffens the rubber tube and the artery if they are embedded in gelatin.