Equivalent threshold sound pressure levels for click and CE-Chirp® stimuli delivered by the SnapPROBE™.

OBJECTIVE: To estimate the equivalent threshold sound pressure levels (ETSPLs) for nine stimuli used today and in the future for universal newborn hearing screening and diagnostics delivered by the Interacoustics SnapPROBE™. DESIGN: The Click and eight variants of the CE-Chirp® were included to establish ETSPLs when delivered by the SnapPROBE™. The short duration stimuli were presented at a 20/s repetition rate for about 1-2 s following the international standards for establishing ETSPLs. STUDY SAMPLE: 50 ears from a total of 27 normal hearing young adult subjects (female/male = 16/11; age = 21-25 years, mean age = 23.1 years). RESULTS: Peak-to-peak equivalent signal levels and root mean square signal levels (at 20/s repetition rate) for the nine stimuli are stated. CONCLUSIONS: The ETSPLs are in alignment overall with those found in previous studies, while some levels are about 2-6 dB higher for this study compared to the Interacoustics Titan IOW probe and the ER-3A insert earphone. The results are relevant for present and future universal newborn hearing screening and diagnostics carried out with the SnapPROBE™ to ensure that correct stimulation levels are applied.

Efficient Detection of Cortical Auditory Evoked Potentials in Adults Using Bootstrapped Methods.

BACKGROUND: Statistical detection methods are useful tools for assisting clinicians with cortical auditory evoked potential (CAEP) detection, and can help improve the overall efficiency and reliability of the test. However, many of these detection methods rely on parametric distributions when evaluating test significance, and thus make various assumptions regarding the electroencephalogram (EEG) data. When these assumptions are violated, reduced test sensitivities and/or increased or decreased false-positive rates can be expected. As an alternative to the parametric approach, test significance can be evaluated using a bootstrap, which does not require some of the aforementioned assumptions. Bootstrapping also permits a large amount of freedom when choosing or designing the statistical test for response detection, as the distributions underlying the test statistic no longer need to be known prior to the test. OBJECTIVES: To improve the reliability and efficiency of CAEP-related applications by improving the specificity and sensitivity of objective CAEP detection methods. DESIGN: The methods included in the assessment were Hotelling's T2 test, the Fmp, four modified q-sample statistics, and various template-based detection methods (calculated between the ensemble coherent average and some predefined template), including the correlation coefficient, covariance, and dynamic time-warping (DTW). The assessment was carried out using both simulations and a CAEP threshold series collected from 23 adults with normal hearing. RESULTS: The most sensitive method was DTW, evaluated using the bootstrap, with maximum increases in test sensitivity (relative to the conventional Hotelling's T2 test) of up to 30%. An important factor underlying the performance of DTW is that the template adopted for the analysis correlates well with the subjects' CAEP. CONCLUSION: When subjects' CAEP morphology is approximately known before the test, then the DTW algorithm provides a highly sensitive method for CAEP detection.

A spectro-temporal modulation test for predicting speech reception in hearing-impaired listeners with hearing aids.

Spectro-temporal modulation (STM) detection sensitivity has been shown to be associated with speech-in-noise reception in hearing-impaired (HI) individuals. Based on previous research, a recent study [Zaar, Simonsen, Dau, and Laugesen (2023). Hear Res 427:108650] introduced an STM test paradigm with audibility compensation, employing STM stimulus variants using noise and complex tones as carrier signals. The study demonstrated that the test was suitable for the target population of elderly individuals with moderate-to-severe hearing loss and showed promising predictions of speech-reception thresholds (SRTs) measured in a realistic set up with spatially distributed speech and noise maskers and linear audibility compensation. The present study further investigated the suggested STM test with respect to (i) test-retest variability for the most promising STM stimulus variants, (ii) its predictive power with respect to realistic speech-in-noise reception with non-linear hearing-aid amplification, (iii) its connection to effects of directionality and noise reduction (DIR+NR) hearing-aid processing, and (iv) its relation to DIR+NR preference. Thirty elderly HI participants were tested in a combined laboratory and field study, collecting STM thresholds with a complex-tone based and a noise-based STM stimulus design, SRTs with spatially distributed speech and noise maskers using hearing aids with non-linear amplification and two different levels of DIR+NR, as well as subjective reports and preference ratings obtained in two field periods with the two DIR+NR hearing-aid settings. The results indicate that the noise-carrier based STM test variant (i) showed optimal test-retest properties, (ii) yielded a highly significant correlation with SRTs (R2=0.61) exceeding and complementing the predictive power of the audiogram, (iii) yielded significant correlation (R2=0.51) with the DIR+NR-induced SRT benefit, and (iv) did not provide significant correlation with subjective preference for DIR+NR settings in the field. Overall, the suggested STM test represents a valuable tool for diagnosing speech-reception problems that remain when hearing-aid amplification has been provided and the resulting need for and benefit from DIR+NR hearing-aid processing.

The Audible Contrast Threshold (ACT) test: A clinical spectro-temporal modulation detection test.

Over the last decade, multiple studies have shown that hearing-impaired listeners' speech-in-noise reception ability, measured with audibility compensation, is closely associated with performance in spectro-temporal modulation (STM) detection tests. STM tests thus have the potential to provide highly relevant beyond-the-audiogram information in the clinic, but the available STM tests have not been optimized for clinical use in terms of test duration, required equipment, and procedural standardization. The present study introduces a quick-and-simple clinically viable STM test, named the Audible Contrast Threshold (ACT™) test. First, an experimenter-controlled STM measurement paradigm was developed, in which the patient is presented bilaterally with a continuous audibility-corrected noise via headphones and asked to press a pushbutton whenever they hear an STM target sound in the noise. The patient's threshold is established using a Hughson-Westlake tracking procedure with a three-out-of-five criterion and then refined by post-processing the collected data using a logistic function. Different stimulation paradigms were tested in 28 hearing-impaired participants and compared to data previously measured in the same participants with an established STM test paradigm. The best stimulation paradigm showed excellent test-retest reliability and good agreement with the established laboratory version. Second, the best stimulation paradigm with 1-second noise "waves" (windowed noise) was chosen, further optimized with respect to step size and logistic-function fitting, and tested in a population of 25 young normal-hearing participants using various types of transducers to obtain normative data. Based on these normative data, the "normalized Contrast Level" (in dB nCL) scale was defined, where 0 ± 4 dB nCL corresponds to normal performance and elevated dB nCL values indicate the degree of audible contrast loss. Overall, the results of the present study suggest that the ACT test may be considered a reliable, quick-and-simple (and thus clinically viable) test of STM sensitivity. The ACT can be measured directly after the audiogram using the same set up, adding only a few minutes to the process.

Toward a clinically viable spectro-temporal modulation test for predicting supra-threshold speech reception in hearing-impaired listeners.

The ability of hearing-impaired listeners to detect spectro-temporal modulation (STM) has been shown to correlate with individual listeners' speech reception performance. However, the STM detection tests used in previous studies were overly challenging especially for elderly listeners with moderate-to-severe hearing loss. Furthermore, the speech tests considered as a reference were not optimized to yield ecologically valid outcomes that represent real-life speech reception deficits. The present study investigated an STM detection measurement paradigm with individualized audibility compensation, focusing on its clinical viability and relevance as a real-life supra-threshold speech intelligibility predictor. STM thresholds were measured in 13 elderly hearing-impaired native Danish listeners using four previously established (noise-carrier based) and two novel complex-tone carrier based STM stimulus variants. Speech reception thresholds (SRTs) were measured (i) in a realistic spatial speech-on-speech set up and (ii) using co-located stationary noise, both with individualized amplification. In contrast with previous related studies, the proposed measurement paradigm yielded robust STM thresholds for all listeners and conditions. The STM thresholds were positively correlated with the SRTs, whereby significant correlations were found for the realistic speech-test condition but not for the stationary-noise condition. Three STM stimulus variants (one noise-carrier based and two complex-tone based) yielded significant predictions of SRTs, accounting for up to 53% of the SRT variance. The results of the study could form the basis for a clinically viable STM test for quantifying supra-threshold speech reception deficits in aided hearing-impaired listeners.

Modified T2 Statistics for Improved Detection of Aided Cortical Auditory Evoked Potentials in Hearing-Impaired Infants.

The cortical auditory evoked potential (CAEP) is a change in neural activity in response to sound, and is of interest for audiological assessment of infants, especially those who use hearing aids. Within this population, CAEP waveforms are known to vary substantially across individuals, which makes detecting the CAEP through visual inspection a challenging task. It also means that some of the best automated CAEP detection methods used in adults are probably not suitable for this population. This study therefore evaluates and optimizes the performance of new and existing methods for aided (i.e., the stimuli are presented through subjects' hearing aid(s)) CAEP detection in infants with hearing loss. Methods include the conventional Hotellings T2 test, various modified q-sample statistics, and two novel variants of T2 statistics, which were designed to exploit the correlation structure underlying the data. Various additional methods from the literature were also evaluated, including the previously best-performing methods for adult CAEP detection. Data for the assessment consisted of aided CAEPs recorded from 59 infant hearing aid users with mild to profound bilateral hearing loss, and simulated signals. The highest test sensitivities were observed for the modified T2 statistics, followed by the modified q-sample statistics, and lastly by the conventional Hotelling's T2 test, which showed low detection rates for ensemble sizes <80 epochs. The high test sensitivities at small ensemble sizes observed for the modified T2 and q-sample statistics are especially relevant for infant testing, as the time available for data collection tends to be limited in this population.