Sensitivity to isolated and concurrent intensity and fundamental frequency increments by cochlear implant users under natural listening conditions

Abstract

Sensitivity to acoustic cues in cochlear implant (CI) listening under natural conditions is a potentially complex interaction between a number of simultaneous factors, and may be difficult to predict. In the present study, sensitivity was measured under conditions that approximate those of natural listening. Synthesized words having increases in intensity or fundamental frequency (F0) in a middle stressed syllable were presented in soundfield to normal-hearing listeners and to CI listeners using their everyday speech processors and programming. In contrast to the extremely fine sensitivity to electrical current observed when direct stimulation of single electrodes is employed, difference limens (DLs) for intensity were larger for the CI listeners by a factor of 2.4. In accord with previous work, F0 DLs were larger by almost one order of magnitude. In a second experiment, it was found that the presence of concurrent intensity and F0 increments reduced the mean DL to half that of either cue alone for both groups of subjects, indicating that both groups combine concurrent cues with equal success. Although sensitivity to either cue in isolation was not related to word recognition in CI users, the listeners having lower combined-cue thresholds produced better word recognition scores.

Effect of spectral smearing on the perceptual segregation of vowel sequences

“…As these mechanisms are probably involved in speech-in-speech understanding, it can be argued that they could contribute to the difficulty displayed by HI listeners in multi-talker environments. Given the strength of the F 0 cue for segregation of voices in the current study, it may be assumed that CI users, who have F 0 difference limens roughly one order of magnitude poorer than their NH counterparts (Rogers et al, 2006), will also experience considerable difficulty segregating voices in multi-talker environments. This assumption is supported by studies indicating relatively poor segregation abilities in CI users (e.g.…”

The Perception of Sentence Stress in Cochlear Implant Recipients

“…The results described below revealed that changes in F 0 and intensity are important indicators for CI users. The procedure of Rogers et al (2006) used difference limens (DLs) determined for the modification of isolated cues to equate perceptual evidence of intensity and F 0 increments. Their approach is based on the assumption that psychometric functions relating detectability to increment size of the corresponding parameter can be approximated by a linear equation (Turner & Nelson 1982).…”

“…Because the acoustic properties of stressed syllables depend on each other, and a combination might yield a different perception than the presentation of individual cues (Rogers et al 2006), stimuli with concurrent cues were created. As a first attempt to examine stress perception in CI recipients with concurrently changing parameters, we decided to combine the two cues that proved to be the most important ones for stress perception in natural utterances for an additional discrimination experiment.…”

Evidence of across-channel processing for spectral-ripple discrimination in cochlear implant listeners

“…5(b)] thresholds with the overall intensity discrimination mechanism were lower than thresholds of CI users at roves of 0, 7, and 15 dB (p < 0.001 for all three comparisons). The conservative (small) estimate of detection noise used here was the mean of the intensity difference limens for words of the top two performers in the data reported by Rogers et al (2006). Even when no detection noise was modeled [open circles in Fig.…”