The just noticeable difference in signal-to-noise ratio for speech is about 3 dB

Evidence

2.1 The JND for Changes in SNR The JND for SNR was measured for adults of varying hearing ability at different reference SNRs using adaptive and fixed-level procedures based on the classic level discrimination paradigm (cf. McShefferty et al. 2015 ). The stimuli were equalised IEEE sentences uttered by a native British English speaker (Smith and Faulkner 2006 ) in same-spectrum noise, presented over headphones in a sound-attenuated booth. Noises began and ended simultaneous with the speech signal, and there was a 500-ms gap between intervals. Both intervals contained the same randomly chosen sentence, and after both intervals, participants were prompted to respond to which one was clearer. In each interval the levels of both speech and noise were adjusted to maintain a presentation level of 75 dB A; to minimize other cues, the level of each interval was roved independently by a maximum of ±2 dB. In a two-interval/alternative forced-choice task, participants were presented, in randomized order, with a reference interval at a fixed reference SNR (either ‑6, 0, or + 6 dB), and a target interval at the reference SNR plus an increment (ΔSNR) that was either varied adaptively or presented at fixed, randomly interleaved ΔSNRs. The adaptive procedure estimated 79 % correct from the geometric means of the best two of three three-up/one-down tracks. The fixed-level procedure estimated 79 % correct from fitting a maximum-log-likelihood logistic function to the data. The procedures produced equivalent results to 0.1 dB, so results were combined across procedures for each reference SNR. The results are shown in Table 1 . The SNR JNDs at the three SNR references of ‑6, 0 and + 6 dB SNR were 2.8, 2.9, and 3.7 dB respectively; the first two were statistically no different and both less than the third [t (91.3) = 4.07; p = 0.0001 and t (121.4) = 4.11; p = 0.00007, respectively]. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5674

Categorization

• corroborated: 4 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 5674
• XREF: connects to: A 3 dB SNR just-noticeable difference corresponds to a 26% intelligibility change in listeners. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5669; SNR just-noticeable difference grows from about 3 to 3.7 dB at positive reference SNRs — Dijk, Pim van, Physiology, Psychoacoustics and…, 5676; A meaningful speech-in-noise benefit requires at least 6 dB of SNR improvement (+1 more)

Broader Connections

• A 3 dB SNR just-noticeable difference corresponds to a 26% intelligibility change in listeners. #expands (0.80) — Dijk, Pim van, Physiology, Psychoacoustics and…, 5669
• SNR just-noticeable difference grows from about 3 to 3.7 dB at positive reference SNRs #qualifies (0.78) — Dijk, Pim van, Physiology, Psychoacoustics and…, 5676
• Hearing-impaired level just-noticeable-differences are about 1 to 2 dB #contradicts (0.75)
• A meaningful speech-in-noise benefit requires at least 6 dB of SNR improvement #qualifies (0.72)