During the standardization process of the GSM half rate codec, extensive subjective listening tests were performed in November 1992 in order to select the final half rate codec candidate for the GSM system. In addition an unofficial objective analysis was performed by the authors using an objective measure for speech quality. This paper describes the fundamentals of this objective quality measure based on psychoacoustics, see also [1],[2]. A detailed comparison is given between the results of the subjective listening tests in terms of Mean Opinion Score (MOS) and the objective quality measure. A high correlation between both measures was observed for slightly distorted speech, a poorer correlation for larger distorted speech.