Evaluation of the NAL Dynamic Conversations Test in older listeners with hearing loss.

OBJECTIVE: The National Acoustic Laboratories Dynamic Conversations Test (NAL-DCT) is a new test of speech comprehension that incorporates a realistic environment and dynamic speech materials that capture certain features of everyday conversations. The goal of this study was to assess the suitability of the test for studying the consequences of hearing loss and amplification in older listeners. DESIGN: Unaided and aided comprehension scores were measured for single-, two- and three-talker passages, along with unaided and aided sentence recall. To characterise the relevant cognitive abilities of the group, measures of short-term working memory, verbal information-processing speed and reading comprehension speed were collected. STUDY SAMPLE: Participants were 41 older listeners with varying degrees of hearing loss. RESULTS: Performance on both the NAL-DCT and the sentence test was strongly driven by hearing loss, but performance on the NAL-DCT was additionally related to a composite cognitive deficit score. Benefits of amplification were measurable but influenced by individual test SNRs. CONCLUSIONS: The NAL-DCT is sensitive to the same factors as a traditional sentence recall test, but in addition is sensitive to the cognitive factors required for speech processing. The test shows promise as a tool for research concerned with real-world listening.

Development and preliminary evaluation of a new test of ongoing speech comprehension.

OBJECTIVE: The overall goal of this work is to create new speech perception tests that more closely resemble real world communication and offer an alternative or complement to the commonly used sentence recall test. DESIGN: We describe the development of a new ongoing speech comprehension test based on short everyday passages and on-the-go questions. We also describe the results of an experiment conducted to compare the psychometric properties of this test to those of a sentence test. STUDY SAMPLE: Both tests were completed by a group of listeners that included normal hearers as well as hearing-impaired listeners who participated with and without their hearing aids. RESULTS: Overall, the psychometric properties of the two tests were similar, and thresholds were significantly correlated. However, there was some evidence of age/cognitive effects in the comprehension test that were not revealed by the sentence test. CONCLUSIONS: This new comprehension test promises to be useful for the larger goal of creating laboratory tests that combine realistic acoustic environments with realistic communication tasks. Further efforts will be required to assess whether the test can ultimately improve predictions of real-world outcomes.

An evaluation of the performance of two binaural beamformers in complex and dynamic multitalker environments.

OBJECTIVE: Binaural beamformers are super-directional hearing aids created by combining microphone outputs from each side of the head. While they offer substantial improvements in SNR over conventional directional hearing aids, the benefits (and possible limitations) of these devices in realistic, complex listening situations have not yet been fully explored. In this study we evaluated the performance of two experimental binaural beamformers. DESIGN: Testing was carried out using a horizontal loudspeaker array. Background noise was created using recorded conversations. Performance measures included speech intelligibility, localization in noise, acceptable noise level, subjective ratings, and a novel dynamic speech intelligibility measure. STUDY SAMPLE: Participants were 27 listeners with bilateral hearing loss, fitted with BTE prototypes that could be switched between conventional directional or binaural beamformer microphone modes. RESULTS: Relative to the conventional directional microphones, both binaural beamformer modes were generally superior for tasks involving fixed frontal targets, but not always for situations involving dynamic target locations. CONCLUSIONS: Binaural beamformers show promise for enhancing listening in complex situations when the location of the source of interest is predictable.

An examination of speech reception thresholds measured in a simulated reverberant cafeteria environment.

OBJECTIVE: There is increasing demand in the hearing research community for the creation of laboratory environments that better simulate challenging real-world listening environments. The hope is that the use of such environments for testing will lead to more meaningful assessments of listening ability, and better predictions about the performance of hearing devices. Here we present one approach for simulating a complex acoustic environment in the laboratory, and investigate the effect of transplanting a speech test into such an environment. DESIGN: Speech reception thresholds were measured in a simulated reverberant cafeteria, and in a more typical anechoic laboratory environment containing background speech babble. STUDY SAMPLE: The participants were 46 listeners varying in age and hearing levels, including 25 hearing-aid wearers who were tested with and without their hearing aids. RESULTS: Reliable SRTs were obtained in the complex environment, but led to different estimates of performance and hearing-aid benefit from those measured in the standard environment. CONCLUSIONS: The findings provide a starting point for future efforts to increase the real-world relevance of laboratory-based speech tests.