Effects of acoustic environments on speech comprehension by native-English-speaking listeners

This study investigates the effects of acoustic conditions on speech comprehension, rather than speech intelligibility as often reported in existing literature. Sets of 15-minute-long listening comprehension tests were developed based on the format of the Test of English for International Communication (TOEIC). Each test set includes four types of tasks: matching aural phrases to photographs, selecting appropriate responses to aural questions, and answering questions after listening to conversations (between two talkers) and talks (single talker). Within the Nebraska acoustics test chamber, native-English-speaking participants were asked to perform these tests under 15 acoustic conditions, from combinations of three background noise levels (RC-30, 40 and 50) and five mid-frequency reverberation times (0.4 to 1.1 seconds). The background noise levels were varied via an Armstrong i-Ceiling system, while the reverberation times were simulated from convolving the anechoic test signals with binaural room impulse responses, gathered in situ from a variable classroom mockup space at Armstrong World Industries. A two-channel playback system was used to present the convolved audio signals, with an inverse room-response filter to correct for the test chamber's room effect. Statistical analyses of the results will be presented, demonstrating how background noise levels and reverberation times impact speech comprehension.