Modified Normalized Least Mean Square (MNLMS) Algorithm, which is a sign form of NLMS based on set-membership (SM) theory in the class of optimal bounding ellipsoid (OBE) Algorithms, requires a priori knowledge of error bounds that is unknown in most applications. In a special but popular case of measurement noise, a simple Algorithm has been proposed. With some simulation examples the performance of Algorithm is compared with MNLMS.