Speech audiometric assessment of informational masking

In communication situations with multiple speakers, speech recognition is adversely affected by energetic masking (EM) and informational masking (IM). IM characterizes masking effects caused by irrelevant information from competing speakers. This work investigates an approach to assess IM based on the Oldenburg Sentence Test (OLSA). Furthermore, the influence of interaural time differences (ITD) and aging effects on IM are considered.

IM was measured by superimposing two sentences from the OLSA. The beginning of the target sentence was indicated by the keyword "Stefan". To segregate between target and masker sentences, ITDs from 50 to 400 μs were included. The participants were asked to selectively attend to the target sentence and repeat the spoken words. Potential factors associated with speech recognition results were assessed by an auditory measure of temporal fine structure and a neuropsychological profile. The study comprised 16 normal-hearing listeners between 18 and 77 years of age.

Despite the clinically normal hearing participants, the analysis showed a significant relationship between speech recognition outcome and pure tone thresholds. All participants benefited from small ITDs between the target and masker sentence with regard to the unmasking of IM. The magnitude of unmasking could not be explained by any of the factors assessed in this study. Error analysis and the comparison with the literature reveal that the OLSA could be a useful tool to assess IM. Also in line with the current literature is the relationship between speech recognition outcome and pure tone thresholds, as well as the strong effect of ITDs on the release from IM.

Speech audiometric assessment of IM is of high relevance with regard to everyday communication situations. Due to its structure, the OLSA seems to be a useful tool for determining IM.