On Detectable and Meaningful Speech-Intelligibility Benefits.

Area of Science:

• Auditory perception
• Speech intelligibility
• Psychoacoustics

Background:

• Signal-to-noise ratio (SNR) is critical for hearing speech in noise.
• Current understanding of meaningful SNR benefit is limited.
• The just noticeable difference (JND) for SNR is proposed as a psychophysical basis for benefit.

Purpose of the Study:

• To measure the just noticeable difference (JND) for signal-to-noise ratio (SNR).
• To establish the just meaningful difference (JMD) for SNR.
• To investigate the relationship between JND, JMD, and speech intelligibility.

Main Methods:

• Adaptive and fixed-level procedures were used to measure SNR JND.
• Speech-intelligibility psychometric functions were analyzed.
• Subjective scaling and report tasks assessed JMD for SNR, measuring intervention-seeking behavior.

Main Results:

• The average SNR JND was approximately 3 dB for sentences in same-spectrum noise.
• A change of at least 6 dB in SNR was required to reliably motivate participants to seek intervention (JMD).
• A gap exists between achievable SNR improvements and those perceived as meaningful.

Conclusions:

• The JND for SNR in speech intelligibility tasks is approximately 3 dB.
• A 6 dB change in SNR is necessary to signify a meaningful benefit and prompt intervention.
• Findings suggest current audibility metrics may not fully capture the user experience of speech intelligibility benefits.