Katrina Freeston

Cognitive spare capacity: evaluation data and its association with comprehension of dynamic conversations

It is well-established that communication involves the working memory system, which becomes increasingly engaged in understanding speech as the input signal degrades. The more resources allocated to recovering a degraded input signal, the fewer resources, referred to as cognitive spare capacity (CSC), remain for higher-level processing of speech. Using simulated natural listening environments, the aims of this paper were to (1) evaluate an English version of a recently introduced auditory test to measure CSC that targets the updating process of the executive function, (2) investigate if the test predicts speech comprehension better than the reading span test (RST) commonly used to measure working memory capacity, and (3) determine if the test is sensitive to increasing the number of attended locations during listening. In Experiment I, the CSC test was presented using a male and a female talker, in quiet and in spatially separated babble- and cafeteria-noises, in an audio-only and in an audio-visual mode. Data collected on 21 listeners with normal and impaired hearing confirmed that the English version of the CSC test is sensitive to population group, noise condition, and clarity of speech, but not presentation modality. In Experiment II, performance by 27 normal-hearing listeners on a novel speech comprehension test presented in noise was significantly associated with working memory capacity, but not with CSC. Moreover, this group showed no significant difference in CSC as the number of talker locations in the test increased. There was no consistent association between the CSC test and the RST. It is recommended that future studies investigate the psychometric properties of the CSC test, and examine its sensitivity to the complexity of the listening environment in participants with both normal and impaired hearing.

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.

A dynamic speech comprehension test for assessing real-world listening ability

BACKGROUND Many listeners with hearing loss report particular difficulties with multitalker communication situations, but these difficulties are not well predicted using current clinical and laboratory assessment tools. PURPOSE The overall aim of this work is to create new speech tests that capture key aspects of multitalker communication situations and ultimately provide better predictions of real-world communication abilities and the effect of hearing aids. RESEARCH DESIGN A test of ongoing speech comprehension introduced previously was extended to include naturalistic conversations between multiple talkers as targets, and a reverberant background environment containing competing conversations. In this article, we describe the development of this test and present a validation study. STUDY SAMPLE Thirty listeners with normal hearing participated in this study. DATA COLLECTION AND ANALYSIS Speech comprehension was measured for one-, two-, and three-talker passages at three different signal-to-noise ratios (SNRs), and working memory ability was measured using the reading span test. Analyses were conducted to examine passage equivalence, learning effects, and test-retest reliability, and to characterize the effects of number of talkers and SNR. RESULTS Although we observed differences in difficulty across passages, it was possible to group the passages into four equivalent sets. Using this grouping, we achieved good test-retest reliability and observed no significant learning effects. Comprehension performance was sensitive to the SNR but did not decrease as the number of talkers increased. Individual performance showed associations with age and reading span score. CONCLUSIONS This new dynamic speech comprehension test appears to be valid and suitable for experimental purposes. Further work will explore its utility as a tool for predicting real-world communication ability and hearing aid benefit.

Factors affecting reliability and validity of self-directed automatic in situ audiometry: implications for self-fitting hearing AIDS

BACKGROUND A reliable and valid method for the automatic in situ measurement of hearing thresholds is a prerequisite for the feasibility of a self-fitting hearing aid, whether such a device becomes an automated component of an audiological management program or is fitted by the user independently of a clinician. Issues that must be addressed before implementation of the procedure into a self-fitting hearing aid include the role of real-ear-to-dial difference correction factors in ensuring accurate results and the ability of potential users to successfully self-direct the procedure. PURPOSE The purpose of this study was to evaluate the reliability and validity of an automatic audiometry algorithm that is fully implemented in a wearable hearing aid, to determine to what extent reliability and validity are affected when the procedure is self-directed by the user, and to investigate contributors to a successful outcome. RESEARCH DESIGN Design was a two-phase correlational study. STUDY SAMPLE A total of 60 adults with mild to moderately severe hearing loss participated in both studies: 20 in Study 1 and 40 in Study 2. Twenty-seven participants in Study 2 attended with a partner. Participants in both phases were selected for inclusion if their thresholds were within the output limitations of the test device. DATA COLLECTION AND ANALYSIS In both phases, participants performed automatic audiometry through a receiver-in-canal, behind-the-ear hearing aid coupled to an open dome. In Study 1, the experimenter directed the task. In Study 2, participants followed a set of written, illustrated instructions to perform automatic audiometry independently of the experimenter, with optional assistance from a lay partner. Standardized measures of hearing aid self-efficacy, locus of control, cognitive function, health literacy, and manual dexterity were administered. Statistical analysis examined the repeatability of automatic audiometry; the match between automatically and manually measured thresholds; and contributors to successful, independent completion of the automatic audiometry procedure. RESULTS When the procedure was directed by an audiologist, automatic audiometry yielded reliable and valid thresholds. Reliability and validity were negatively affected when the procedure was self-directed by the user, but the results were still clinically acceptable: test-retest correspondence was 10 dB or lower in 97% of cases, and 91% of automatic thresholds were within 10 dB of their manual counterparts. However, only 58% of participants were able to achieve a complete audiogram in both ears. Cognitive function significantly influenced accurate and independent performance of the automatic audiometry procedure; accuracy was further affected by locus of control and level of education. Several characteristics of the automatic audiometry algorithm played an additional role in the outcome. CONCLUSIONS Average transducer- and coupling-specific correction factors are sufficient for a self-directed in situ audiometry procedure to yield clinically reliable and valid hearing thresholds. Before implementation in a self-fitting hearing aid, however, the algorithm and test instructions should be refined in an effort to increase the proportion of users who are able to achieve complete audiometric results. Further evaluation of the procedure, particularly among populations likely to form the primary audience of a self-fitting hearing aid, should be undertaken.

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

Abstract 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.

Identification of conductive hearing loss using air conduction tests alone: reliability and validity of an automatic test battery.

Objectives: The primary objective of this study was to determine whether a combination of automatically administered pure-tone audiometry and a tone-in-noise detection task, both delivered via an air conduction (AC) pathway, could reliably and validly predict the presence of a conductive component to the hearing loss. The authors hypothesized that performance on the battery of tests would vary according to hearing loss type. A secondary objective was to evaluate the reliability and validity of a novel automatic audiometry algorithm to assess its suitability for inclusion in the test battery. Design: Participants underwent a series of hearing assessments that were conducted in a randomized order: manual pure-tone air conduction audiometry and bone conduction audiometry; automatic pure-tone air conduction audiometry; and an automatic tone-in-noise detection task. The automatic tests were each administered twice. The ability of the automatic test battery to: (a) predict the presence of an air–bone gap (ABG); and (b) accurately measure AC hearing thresholds was assessed against the results of manual audiometry. Test–retest conditions were compared to determine the reliability of each component of the automatic test battery. Data were collected on 120 ears from normal-hearing and conductive, sensorineural, and mixed hearing-loss subgroups. Results: Performance differences between different types of hearing loss were observed. Ears with a conductive component (conductive and mixed ears) tended to have normal signal to noise ratios (SNR) despite impaired thresholds in quiet, while ears without a conductive component (normal and sensorineural ears) demonstrated, on average, an increasing relationship between their thresholds in quiet and their achieved SNR. Using the relationship between these two measures among ears with no conductive component as a benchmark, the likelihood that an ear has a conductive component can be estimated based on the deviation from this benchmark. The sensitivity and specificity of the test battery vary depending on the size of this deviation, but increase with increasing ABG size, with decreasing test frequency, and when results from multiple test frequencies are taken into account. The individual automatic tests comprising the battery were found to be reliable and valid, with strong, significant correlations between the test and retest results (r = 0.81 to 0.99; p < 0.0001) and between automatic and manual audiometry procedures (r = 0.98 to 0.99; p < 0.0001). Conclusions: The presence of an ABG can be predicted with a reasonably high degree of accuracy using AC tests alone. Applications of such a test battery include any clinical context in which bone conduction audiometry or specialized diagnostic equipment is unavailable or impractical. Examples of these include self-fitting hearing aids, whose efficacy relies on the ability of the device to automatically administer an in situ hearing test; self-administered adult hearing screenings in both clinical and home environments; large-scale industrial hearing conservation programs; and test environments in which ambient noise levels exceed the maximum permissible levels for unoccluded ears.

Psychometric effects of adding realism to a speech-in-noise test

The speech reception threshold (SRT) is routinely measured in the laboratory to assess speech understanding in noise, but is often reported to be a poor predictor of performance in real world listening situations. The overall goal of this work is to determine whether introducing realistic aspects to speech tests can better capture individual differences and ultimately produce more relevant performance measures. We examined the psychometric effects of (a) transplanting a standard sentence-in-noise test into a simulated reverberant cafeteria environment, and (b) moving from sentence recall to a new ongoing speech comprehension task. Participants included normal hearers and hearing-impaired listeners (who were tested with and without their hearing aids). SRTs in the cafeteria environment were significantly correlated with standard SRTs, but were poorer overall and more sensitive to hearing loss. The comprehension task, despite having very different demands to sentence recall, produced similar SRTs under these conditions. The benefit of hearing aids was weakly correlated across the two listening environments and the two listening tasks. These manipulations promise to be useful for the creation of realistic laboratory tests that are engaging and challenging, yet controlled enough to be useful for psychophysical experiments.

Evaluation of the NAL dynamic conversations test in older listeners with hearing loss

Abstract 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.

Estimating realistic speech levels for virtual acoustic environments

Speech intelligibility is commonly assessed in rather unrealistic acoustic environments at negative signal-to-noise ratios (SNRs). As a consequence, the results seem unlikely to reflect the subjects’ experience in the real world. To improve the ecological validity of speech tests, different sound reproduction techniques have been used by researchers to recreate field-recorded acoustic environments in the laboratory. Whereas the real-world sound pressure levels of these environments are usually known, this is not necessarily the case for the level of the target speech (and therefore the SNR). In this study, a two-talker conversation task is used to derive realistic target speech levels for given virtual acoustic environments. The talkers communicate with each other while listening to binaural recordings of the environments using highly open headphones. During the conversation their speech is recorded using close-talk microphones. Conversations between ten pairs of young normal-hearing talkers were recorded...