Speech-intelligibility JNDs cannot be cleanly separated from SNR JNDs

Evidence

This raises the question as to whether the JNDs initially measured (in Sect. 2.1 above) were intelligibility rather than SNR JNDs (i.e., were the listeners basing their responses on changes in word intelligibility or in changes in signal-to-noise ratio?) We reasoned that by changing the stimuli to ones with a far steeper psychometric function (MacPherson and Akeroyd 2014 ), namely triple digits, the JND in the appropriate domain would be constant, but the JND in the other domain would change. On testing this hypothesis, we found that the mean SNR JND for digits was 2.5 dB (σ= 0.8 dB) and the mean Intelligibility JND estimate for digits was 17.5 % (σ= 7.2 %). SNR and Intelligibility JNDs were significantly less using digits in unfiltered random (white) noise than sentences in same-spectrum noise [t (23) = 2.98; p = 0.007 and t (23) = 5.00; p = 0.00005]. Across stimuli, both the SNR JND differences (mean 0.5 dB) and the Intelligibility JND differences (mean 8.92 dB) were significantly non-zero (z(23) = 2.98; p = 0.003, and z(23) = 5.00; p ≈ 0). That both differences were non-zero was unexpected; it indicates that one cannot be certain whether the 3 dB SNR JND is indeed the JND for SNR or instead the JND for Intelligibility. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5683

Categorization

Category: Causal Relationships

• XREF: Connects to the classic 3 dB SNR just-noticeable-difference literature on speech reception thresholds and psychometric function slope work.

Related

• Measured SNR JNDs may actually reflect intelligibility rather than SNR discrimination (similarity 0.96)
• Listeners may be judging speech intelligibility rather than raw signal-to-noise ratio (similarity 0.92)
• Detectable changes in speech SNR correspond to roughly 26 percent changes in word intelligibility (similarity 0.90)
• Listeners’ SNR JNDs may actually be intelligibility JNDs, not signal-level ones. (similarity 0.85)
• Listeners may judge SNR changes via perceived intelligibility rather than raw signal level (similarity 0.85)
• A 3-dB reduction in signal-to-noise ratio lowers intelligibility by 12% (similarity 0.84)
• The just noticeable difference in signal-to-noise ratio for speech is about 3 dB (similarity 0.84)
• Speech intelligibility saturates beyond certain signal-to-noise ratio bounds. (similarity 0.83)
• A psychophysical JND in signal-to-noise ratio does not guarantee subjectively meaningful benefit to patients (similarity 0.83)
• A 3 dB SNR just-noticeable difference corresponds to a 26% intelligibility change in listeners. (similarity 0.83)
• The range of SNRs contributing to speech intelligibility is wider than SII standards assume (similarity 0.82)
• Hearing thresholds correlate more strongly with speech intelligibility at low signal-to-noise ratios. (similarity 0.82)
• SNR just-noticeable difference grows from about 3 to 3.7 dB at positive reference SNRs (similarity 0.81)
• Normal-hearing listeners detect a 3 dB change in speech-to-noise ratio (similarity 0.81)
• A 1 dB SNR improvement raises speech intelligibility by 7 to 19 percent. (similarity 0.81)