Intelligibility characteristics of superior esophageal speech presented under various levels of masking noise.

Broad-band masking of speech was used to assess the effects that broad-band masking noise had upon the recognition of consonants and vowels produced by esophageal speakers. Procedures were developed to compare the articulation functions of superior esophageal speech with those of normal speech under comparable levels of masking noise. Within the range of speech-to-noise ratios studied, articulation functions for vowels were essentially the same for esophageal and normal talkers (4% per dB). With respect to consonants, the intelligibility scores for esophageal speech were 12 to 14% lower than for normal speech under adverse noise conditions. Gains in the consonant articulation functions were 2.5%/dB and 4%/dB for normal and esophageal talkers, respectively. For adverse noise conditions, the lowered consonant scores for esophageal speakers were the result of poorer than normal intelligibility for liquid-glides and nasal and, secondarily, for stop consonants. Additional differences between the intelligibility characteristics of esophageal and normal speech were found in work-position and voicing features.