Subjective and Objective Speech Intelligibility During the Tracking of Noise Tolerance Test

Area of Science:

• Audiology
• Speech Perception
• Hearing Science

Background:

• The Tracking of Noise Tolerance (TNT) test guides users to set background noise levels for tolerable speech understanding (>90% intelligibility).
• Listener adherence to the 90% intelligibility criterion in the TNT test remains unverified.

Purpose of the Study:

• To objectively and subjectively measure speech intelligibility using TNT materials.
• To analyze speech intelligibility at various signal-to-noise ratios (SNRs) experienced during the TNT test.

Main Methods:

• Employed a single-blind, within-subjects design with 24 reference hearing (RH) and 17 hearing-impaired (HI) listeners.
• Utilized the objective-subjective intelligibility difference (OSID) test to generate performance intensity (P-I) functions.
• Estimated speech intelligibility at TNT noise valleys, peaks, and averages using individualized P-I functions.

Main Results:

• Subjective intelligibility was ~90% at TNT valleys, but significantly lower (<50%) at peaks and averaged 58-69%.
• Objective intelligibility closely matched subjective intelligibility in RH listeners.
• Unaided HI listeners showed a 12-18% poorer objective than subjective intelligibility; aided HI listeners had within 1-8% difference.

Conclusions:

• Listeners generally met the TNT's 90% intelligibility goal at noise valleys.
• Listeners may have used criteria other than intelligibility (e.g., loudness) for TNT peaks.
• The TNT test provides valuable information on SNRs required for varying subjective intelligibility levels.