Perceptual effects of a flattened fundamental frequency at the sentence level under different listening conditions

The purpose of this series of experiments was to examine the effect of a flattened fundamental frequency (F0) contour on the intelligibility of sentence length material in different listening environments. Eight speakers of different genders and ages produced sentences from the Speech Perception in Noise Test (SPIN). Each utterance was subjected to a resynthesis technique that allowed flattening of the fundamental frequency while maintaining the timing and spectral characteristics of the utterances. To avoid learning effects two groups of listeners were chosen to complete word transcription and interval scaling tasks of the unmodified and flattened F0 utterances under different listening conditions (competing white noise or multi-speaker babble) to obtain measures of speech intelligibility. Results were that a flattened fundamental frequency contour negatively influences speech intelligibility regardless of the nature of the competing background noise. Learning outcomes (1) To appreciate the role fundamental frequency variation plays in speech intelligibility. (2) To understand the importance of considering environmental noise in clinical speech intelligibility testing.