Selection of test-setup parameters to target specific signal-to-noise regions in speech-on-speech intelligibility testing

Abstract

Objective: To investigate the magnitude of the change in speech-reception threshold (SRT) provided by altering four different test-setup parameters. Furthermore, to determine whether these changes in SRT are of a sufficient magnitude, such that they can be used to design a test-setup in future experiments that target a predefined signal-to-noise ratio (SNR) region. This could be particularly important if the test contrast investigated is confounded with test SNR. Design: The investigated test-setup parameters were: Spatial separation between target (0°) and maskers (±15°, ±30°, ±45°, or ±75°), number of maskers (two, four or six), scoring method (scoring percent-correct words or sentences) and masker gender (same or opposite to target). Twenty SRTs were measured per test subject. Study sample: Twenty hearing-impaired test subjects participated over two visits. Results: Alteration of masker gender, spatial separation between target and masker (±15°, ±30°, ± 45°), and scoring method was shown to offer SRT changes of a sufficient magnitude. The different test setups resulted in average SRTs ranging from −4.0 to 3.3 dB. Conclusion: Deliberately selecting test setup parameters can change the overall difficulty of the test by up to 7.3 dB SRT. Thus, a future experiment can, to this extent, be designed to target a specific SNR region.