Low-frequency signals support perceptual organization of implant-simulated speech for adults and children

Abstract

Objective Using signals processed to simulate speech received through cochlear implants and low-frequency extended hearing aids, this study examined the proposal that low-frequency signals facilitate the perceptual organization of broader, spectrally degraded signals. Design In two experiments, words and sentences were presented in diotic and dichotic configurations as four-channel noise-vocoded signals (VOC-only), and as those signals combined with the acoustic signal below 250 Hz (LOW-plus). Dependent measures were percent correct recognition scores, and the difference between scores for the two processing conditions given as proportions of recognition scores for VOC-only. The influence of linguistic context was also examined. Study Sample Participants had normal hearing. In all, 40 adults, 40 7-year-olds, and 20 5-year-olds participated. Results Participants of all ages showed benefits of adding the low-frequency signal. The effect was greater for sentences than words, but no effect of configuration was found. The influence of linguistic context was similar across age groups, and did not contribute to the low-frequency effect. Listeners who scored more poorly with VOC-only stimuli showed greater low-frequency effects. Conclusion The benefit of adding a very low-frequency signal to a broader, spectrally degraded signal seems to derive from its facilitative influence on perceptual organization of the sensory input.

Non‐auditory neurocognitive skills contribute to speech recognition in adults with cochlear implants

“…These sentences were four words in length, syntactically correct, but semantically anomalous (e.g., “Soft rocks taste red”), used by Nittrouer and colleagues …”

“…These sentences were four words in length, syntactically correct, but semantically anomalous (e.g., "Soft rocks taste red"), used by Nittrouer and colleagues. 32 Non-auditory Measures of Neurocognitive Functioning. Non-auditory tasks from the Leiter-3 International Performance Scale were used to assess global intelligence (" Figure Ground," "Form Completion," and "Visual Patterns"), controlled fluency ("Attention Sustained"), and working memory ("Forward/Reverse Memory").…”

All Cues Are Not Created Equal: The Case for Facilitating the Acquisition of Typical Weighting Strategies in Children With Hearing Loss

“…These stimuli from earlier experiments were vocoded using the same MATLAB routine as used in previous experiments (e.g., Nittrouer & Lowenstein, 2010; Nittrouer, Lowenstein, & Packer, 2009; Nittrouer et al, 2014). All stimuli were first band-pass filtered with a low-frequency cut-off of 250 Hz and a high-frequency cut-off of 8,000 Hz.…”

Benefits of preserving stationary and time-varying formant structure in alternative representations of speech: Implications for cochlear implants

“…They originally came from the Hearing in Noise Test (Nilsson et al, 1994). In addition, 54 of the 56 four-word sentences (4 for practice, 50 for testing) used in Nittrouer et al (2014) were presented in this study. These sentences are comprised entirely of monosyllabic content words and are syntactically correct but semantically anomalous (e.g., Ducks teach sore camps).…”

“…To create the vocoded stimuli, the same MATLAB routine was used as in previous experiments (e.g., Nittrouer and Lowenstein, 2010;Nittrouer et al, 2009;Nittrouer et al, 2014). All sentences were first band-pass filtered with a lowfrequency cut-off of 250 Hz and a high-frequency cut-off of 8000 Hz.…”