Speech understanding is a fundamental human ability that enable flexible communication among individuals. Understanding natural speech in normal conditions is a fast and automatic process. It is facilitated through integration between prior knowledge about a speech signal and multimodal speech inputs. In situations where listening conditions are adverse, for example due to hearing impairment or environmental noise, speech understanding is challenged and reliance on prior knowledge increases. Prior knowledge about phonology and semantics are involved in predictive mechanisms that generates more successful speech understanding. Working memory processing seems to be involved in influencing the quality of such predictions. To evaluate the role of working memory in the quality of linguistic predictions, a cortical comparison using MEG was used. MEG data from a previous experiment, where participants performed an auditory sentence completion task with background noise was analyzed. Results from statistical analysis, time-domain analysis and time frequency analysis suggests that differences in working memory processing does not influence the quality of linguistic predictions. Further research is required to assess what factors are involved in the quality of linguistic predictions which could lead to unsuccessful speech understanding, in order to improve communication in everyday situations.