Natural-sounding speech can still be poorly intelligible

Evidence

Two parameters are found to be important by those who work on speech: the “intelligibility” and the “quality” or “naturalness” of the speech. Both reflect human perception of the speech itself, and while they are most directly measured subjectively with panels of human listeners, research is being carried out to make equivalent objective measurements of these because of the problems of setting up listening experiments and the inherent interand intralistener variability. The relationship between intelligibility and naturalness is not fully understood. Speech that is unintelligible would usually be judged as being unnatural. However, muffled, fast or mumbling speech is natural but less intelligible, and speech that is highly intelligible may or may not be unnatural. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2398 (#expands, via linked claim)

In terms of “overall sound quality,” there is some disagreement between the groups. Those with normal hearing preferred all of the channels running at or close to reference levels; anything else is a degradation. Note that the difference between all three channels running at reference level, and the L and R loudspeakers attenuated by 3 dB, is trivial (and statistically insignificant). In total contrast, listeners with hearing disabilities, having difficulty understanding speech, clearly voted for progressively more monophonic sound. They obviously associated speech intelligibility with sound quality. — , Toole, Floyd E - Sound reproduction-…, 1437 (#contradicts, via linked claim)

Categorization

• XREF: connects to: Prescriptive rule choice hardly affects speech intelligibility outcomes; Speech intelligibility and naturalness are distinct perceptual dimensions that do not track each other — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2398; Intelligibility is measured by proportion of words heard correctly, not by perceived quality (+3 more)

Broader Connections

• Speech intelligibility and naturalness are distinct perceptual dimensions that do not track each other #expands (0.92) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2398
• Intelligibility is measured by proportion of words heard correctly, not by perceived quality #corroborates (0.80)
• Hearing-impaired listeners equate speech intelligibility with overall sound quality. #contradicts (0.78) — , Toole, Floyd E - Sound reproduction-…, 1437
• Linguistic context lets listeners understand speech at lower acoustic intelligibility #qualifies (0.75)
• Priming from previously heard clear speech can boost intelligibility of degraded speech #expands (0.72)