Images obtained using synthetic aperture sonar systems are often degraded by the effects of multiplicative and additive noises resulting from turbulence of the medium, random vibrations of the transmitter and receiver system, and various noise sources. In this paper, first, a unified evaluation of the effects of multiplicative and additive noises on the reconstructed image is proposed. In this method, the coefficient of variation of the image is used as the measure. Then, the correlation technique, which has been proposed in a previous paper to reduce the effects of turbulence, is evaluated using this measure. To show the plausibility of the theoretical discussions, several experimental results, which were obtained using a specially arranged synthetic aperture sonar system to evaluate the effects, are presented. The relation between the number of sampling points and the quality of reconstructed images is shown, and the effect of the correlation technique is examined under the condition that large turbulences of the medium exist. These results show the effectiveness of the proposed method.