Evaluation of an Audiovisual-FM System: Investigating the Interaction Between Illumination Level and a Talker’s Skin Color on Speech-Reading Performance

Abstract

A program designed to evaluate the benefits of an audiovisual–frequency modulated (FM) system led to some questions concerning the effects of illumination level and a talker’s skin color on speech-reading performance. To address those issues, the speech of a Caucasian female was videotaped under 2 conditions: a light skin color condition and a dark skin color condition. For the latter condition, makeup was applied to the talker’s face. For both skin color conditions, the talker was recorded while speaking sentences under 7 different levels of illumination: 2, 3, 4, 16, 60, 256, and 600 footcandles (fc). Fifteen participants completed the speech perception task in a visual-only modality. The results revealed a significant interaction of illumination level and skin color. For the light skin color condition, speech-reading performance improved systematically as the illumination level increased from 3 to 16 fc. For the dark skin color condition, no differences in speech-reading performance were observed between the 2-fc and the 3-fc conditions. However, a large improvement in speech-reading performance was observed as the illumination level increased from 4 fc to 16 fc. It is speculated that in addition to an overall effect of illumination level, the contrast in luminance at the level of the talker’s face has an effect on speech-reading performance.