Purpose: The purpose of this study was to evaluate the effect of low-pass filtering on the detection of word-final /s/ and /z/ for children and adults with normal hearing.
Method: Stimuli were nouns from the University of Western Ontario Plurals Test (Glista & Scollie, 2012), low-pass filtered with 5 different cutoff frequencies: 8000 Hz, 5000 Hz, 4000 Hz, 3000 Hz, and 2000 Hz. Listeners were children (age range = 7-13 years) and adults with normal hearing. The task was a 2-alternative forced-choice task with a picture-pointing response.
Results: Performance was worse for lower than for higher low-pass filter cutoff frequencies, but the effect of low-pass filtering was similar for children and adults. Nearly all listeners achieved 100% correct performance when stimuli were low-pass filtered with cutoff frequencies of 8000 Hz or 5000 Hz. Performance remained well above chance even for the most severe filtering condition (2000 Hz). Restricting high-frequency audibility influenced performance for plural items to a greater extent than for singular items.
Conclusion: The results indicate that children and adults with normal hearing can use acoustic information below the spectral range of frication noise typically associated with /s/ and /z/ to discriminate between singular and plural forms of nouns in the context of the University of Western Ontario Plurals Test.