Effect of articulatory and acoustic features on the intelligibility of speech in noise: An articulatory synthesis study

Abstract

In noisy conditions, speakers involuntarily change their manner of speaking to enhance the intelligibility of their voices. The increased intelligibility of this so-called Lombard speech is enabled by the change of multiple articulatory and acoustic features. While the major features of Lombard speech are well known from previous studies, little is known about their relative contributions to the intelligibility of speech in noise. This study used an analysis-by-synthesis strategy to explore the contributions of multiple of these features. To this end, an articulatory speech synthesizer was used to synthesize the ten German digit words “Null” to “Neun”, for all 16 combinations of four binary features, i.e., modal vs. pressed phonation, normal vs. increased F1 and F2 formant frequencies, normal vs. increased f0 mean and range, and normal vs. increased duration of vowels. Subjects were asked to try to recognize the synthesized words in the presence of strong pink noise and babble noise. Compared to “plain” speech, the word recognition rate was most improved by pressed phonation, followed by an increased f0 mean and f0 range, and increased formant frequencies. Increased duration of vowels slightly reduced the recognition rate for pink noise but had no effect for babble noise.