Speech perception for adult cochlear implant recipients in a realistic background noise: effectiveness of preprocessing strategies and external options for improving speech recognition in noise

Abstract

Background: Although cochlear implant patients are achieving increasingly higher levels of performance, speech perception in noise continues to be problematic. The newest generations of implant speech processors are equipped with preprocessing and/or external accessories that are purported to improve listening in noise. Most speech perception measures in the clinical setting, however, do not provide a close approximation to real-world listening environments.

Purpose: To assess speech perception for adult cochlear implant recipients in the presence of a realistic restaurant simulation generated by an eight-loudspeaker (R-SPACE) array in order to determine whether commercially available preprocessing strategies and/or external accessories yield improved sentence recognition in noise.

Research design: Single-subject, repeated-measures design with two groups of participants: Advanced Bionics and Cochlear Corporation recipients.

Study sample: Thirty-four subjects, ranging in age from 18 to 90 yr (mean 54.5 yr), participated in this prospective study. Fourteen subjects were Advanced Bionics recipients, and 20 subjects were Cochlear Corporation recipients.

Intervention: Speech reception thresholds (SRTs) in semidiffuse restaurant noise originating from an eight-loudspeaker array were assessed with the subjects' preferred listening programs as well as with the addition of either Beam preprocessing (Cochlear Corporation) or the T-Mic accessory option (Advanced Bionics).

Data collection and analysis: In Experiment 1, adaptive SRTs with the Hearing in Noise Test sentences were obtained for all 34 subjects. For Cochlear Corporation recipients, SRTs were obtained with their preferred everyday listening program as well as with the addition of Focus preprocessing. For Advanced Bionics recipients, SRTs were obtained with the integrated behind-the-ear (BTE) mic as well as with the T-Mic. Statistical analysis using a repeated-measures analysis of variance (ANOVA) evaluated the effects of the preprocessing strategy or external accessory in reducing the SRT in noise. In addition, a standard t-test was run to evaluate effectiveness across manufacturer for improving the SRT in noise. In Experiment 2, 16 of the 20 Cochlear Corporation subjects were reassessed obtaining an SRT in noise using the manufacturer-suggested "Everyday," "Noise," and "Focus" preprocessing strategies. A repeated-measures ANOVA was employed to assess the effects of preprocessing.

Results: The primary findings were (i) both Noise and Focus preprocessing strategies (Cochlear Corporation) significantly improved the SRT in noise as compared to Everyday preprocessing, (ii) the T-Mic accessory option (Advanced Bionics) significantly improved the SRT as compared to the BTE mic, and (iii) Focus preprocessing and the T-Mic resulted in similar degrees of improvement that were not found to be significantly different from one another.

Conclusion: Options available in current cochlear implant sound processors are able to significantly improve speech understanding in a realistic, semidiffuse noise with both Cochlear Corporation and Advanced Bionics systems. For Cochlear Corporation recipients, Focus preprocessing yields the best speech-recognition performance in a complex listening environment; however, it is recommended that Noise preprocessing be used as the new default for everyday listening environments to avoid the need for switching programs throughout the day. For Advanced Bionics recipients, the T-Mic offers significantly improved performance in noise and is recommended for everyday use in all listening environments.

Figure 1

R-SPACE eight-loudspeaker system.

Figure 2

Individual and mean R-SPACE speech reception thresholds (SRTs) for the 20 Cochlear Corporation recipients. The black and gray bars represent the SRTs obtained with the subjects’ preferred preprocessing strategy and Focus (Beam+ autosensitivity + adaptive dynamic range optimization), respectively. Subjects’ preferred listening strategies are listed in Table 1. Error bars represent ±2 SE measurements.

Figure 3

Individual and mean R-SPACE speech reception thresholds (SRTs) for the 14 Advanced Bionics recipients. The black and gray bars represent the SRTs obtained with the behind-the-ear mic and T-Mic, respectively. Error bars represent ±2 SE measurements.

Figure 4

Individual and mean R-SPACE speech reception thresholds (SRTs) for the 16 Cochlear Corporation recipients who participated in Experiment 2. The black, hatched, and gray bars represent the SRTs obtained with Everyday (adaptive dynamic range optimization [ADRO]), Noise (autosensitivity [ASC] + ADRO), and Focus (Beam + ASC + ADRO), respectively. Error bars represent ±2 SE measurements.