Asymmetry measures for quantification of mechanisms contributing to dynamic stability during stepping-in-place gait.

The goal of this study is to introduce and to motivate the use of new quantitative methods to improve our understanding of mechanisms that contribute to the control of dynamic balance during gait. Dynamic balance refers to the ability to maintain a continuous, oscillating center-of-mass (CoM) motion of the body during gait even though the CoM frequently moves outside of the base of support. We focus on dynamic balance control in the frontal plane or medial-lateral (ML) direction because it is known that active, neurally-mediated control mechanisms are necessary to maintain ML stability. Mechanisms that regulate foot placement on each step and that generate corrective ankle torque during the stance phase of gait are both known to contribute to the generation of corrective actions that contribute to ML stability. Less appreciated is the potential role played by adjustments in step timing when the duration of the stance and/or swing phases of gait can be shortened or lengthened to allow torque due to gravity to act on the body CoM over a shorter or longer time to generate corrective actions. We introduce and define four asymmetry measures that provide normalized indications of the contribution of these different mechanisms to gait stability. These measures are 'step width asymmetry', 'ankle torque asymmetry', 'stance duration asymmetry', and 'swing duration asymmetry'. Asymmetry values are calculated by comparing corresponding biomechanical or temporal gait parameters from adjacent steps. A time of occurrence is assigned to each asymmetry value. An indication that a mechanism is contributing to ML control is obtained by comparing asymmetry values to the ML body motion (CoM angular position and velocity) at the time points associated with the asymmetry measures. Example results are demonstrated with measures obtained during a stepping-in-place (SiP) gait performed on a stance surface that either remained fixed and level or was pseudorandomly tilted to disturb balance in the ML direction. We also demonstrate that the variability of asymmetry measures obtained from 40 individuals during unperturbed, self-paced SiP were highly correlated with corresponding coefficient of variation measures that have previously been shown to be associated with poor balance and fall risk.

A convergent validity study: Listening in Spatialized Noise-Sentences (LiSN-S) test and the Hearing in Noise Test (HINT).

OBJECTIVES: The primary purpose of this study was to compare Listening in Spatialized Noise - Sentence (LiSN-S) test and the Hearing in Noise Test (HINT) thresholds in order to determine if the two tests measure the same construct (convergent validity). The secondary purpose was to determine performance differences between the two test protocols. The third purpose was to determine the relationships between quiet measures (pure-tone average [PTA] and HINT Quiet thresholds) vs. speech-in-noise performances. DESIGN: Statistical analyses included descriptive statistics, Spearman rho statistic, repeated measures analysis of variance (ANOVA) and linear mixed model analyses. Study sample: Fifty-six young adults with normal PTAs (≤15 dB HL for 0.5-4.0 kHz) participated in this study. RESULTS: No statistically significant relationships were found between LiSN-S and HINT measures (poor convergent validity). However, statistically significant relationships were found between the quiet measures (HINT Quiet thresholds and average PTA(0.5-4.0 kHz)) vs. the LiSN-S (same and different voices) ±90° performances. CONCLUSION: LiSN-S performances in two-talker babble cannot be generalized to the ability to recognise HINT sentences in steady-state speech-shaped noise, and vice versa. The results imply that LiSN-S ± 90° thresholds were influenced by hearing sensitivity or by supra-threshold distortions that co-vary with hearing sensitivity.

Sentence Recognition in Steady-State Speech-Shaped Noise versus Four-Talker Babble.

BACKGROUND: Speech recognition in noise (SRN) evaluations reveal information about listening ability that is unavailable from pure-tone thresholds. Unfortunately, SRN evaluations are not commonly used in the clinic. A lack of standardization may be an explanation for the lack of widespread acceptance of SRN testing. Arguments have been made for the utilization of steady-state speech-shaped noise vs. multi-talker babble. Previous investigations into the effect of masker type have used a monaural presentation of the stimuli. However, results of monaural SRN tests cannot be generalized to binaural listening conditions. PURPOSE: The purpose of this study was to investigate the effect of masker type on SRN thresholds under binaural listening conditions. RESEARCH DESIGN: The Hearing in Noise Test (HINT) protocol was selected in order to measure SRN thresholds in steady-state speech-shaped noise (HINT noise) and four-talker babble with and without the spatial separation of the target speech and masker stimuli. STUDY SAMPLE: Fifty native speakers of English with normal pure-tone thresholds (≤ 25 dB HL, 250-4000 Hz) participated in the study. The mean age was 20.5 years (SD 1.01). DATA COLLECTION AND ANALYSIS: All participants were tested using the standard protocol for the HINT in a simulated soundfield environment under TDH-50P headphones. Thresholds were measured for the Noise Front, Noise Left, and Noise Right listening conditions with HINT noise and four-talker babble. The HINT composite score was determined for each noise condition. The spatial advantage was calculated from the HINT thresholds. Pure-tone threshold data were collected using the modified Hughson-Westlake procedure. Statistical analyses include descriptive statistics, effect size, correlations, and repeated measures ANOVA followed by matched-pairs t-tests. RESULTS: Repeated measures ANOVA was conducted to investigate the effects of masker type and noise location on HINT thresholds. Both main effects and their interaction were statistically significant (p < 0.01). No significant differences were found between masker conditions for the Noise Front thresholds. However, for the Noise Side conditions the four-talker babble thresholds were significantly better than the HINT noise thresholds. Overall, greater spatial advantage was found for the four-talker babble as opposed to the HINT noise conditions (p < 0.01). Pearson correlation analysis revealed no significant relationships between four-talker babble and HINT noise speech recognition performances for the Noise Front, Noise Right conditions, and the spatial advantage measures. Significant relationships (p < 0.05) were found between masking noise performances for the Noise Left condition and the Noise Composite scores. CONCLUSIONS: One cannot assume that a patient who performs within normal limits on a speech in four-talker babble test will also perform within normal limits on a speech in steady-state speech-shaped noise test, and vice-versa. Additionally, performances for the Noise Front condition cannot be used to predict performances for the Noise Side conditions. The utilization of both HINT noise and four-talker babble maskers, with and without the spatial separation of the stimuli, may be useful when determining the range of speech recognition in noise abilities found in everyday listening conditions.

The relationship between speech recognition in noise and non-speech recognition in noise test performances: Implications for central auditory processing disorders testing.

BACKGROUND: According to the American Academy of Audiology, a recommendation for frequency-modulation systems may be based upon performances on speech perception tests that do not include background noise. PURPOSE: The primary purpose of this study was to evaluate the presumption that non-speech recognition in noise test results are related to speech recognition in noise ability for a group of young adults. RESEARCH DESIGN: Performances on the non-speech recognition in noise tests included in the SCAN-3:A test battery were compared to speech recognition in noise performances as measured with the auditory figure ground subtest of the SCAN-3:A and the Hearing in Noise Test. STUDY SAMPLE: Fifty-four young, native speakers of American English with normal pure-tone thresholds participated in the study. DATA COLLECTION AND ANALYSIS: For the purposes of this study, the SCAN-3:A raw scores were used. The Hearing in Noise Test was administered in a simulated soundfield environment under headphones. The Spearman rho statistic was used to determine the relationships between non-speech recognition in noise vs. speech recognition in noise test results. RESULTS: No significant relationships were found between the auditory figure-ground results and any of the non-speech recognition in noise subtest performances. Modest but statistically significant relationships were found between the Hearing in Noise Test Composite scores vs. the competing words-directed ear and the time compressed sentences subtests of the SCAN-3:A. CONCLUSION: Of the four non-speech recognition in noise subtests that were evaluated, only the competing words-directed ear and the time-compressed sentences performances were significantly correlated to the Composite scores of the Hearing in Noise Test. The results demonstrated a limited external validity for two of the four non-SRN tests for the determination of SRN ability.

The Relationship between Random Gap Detection and Hearing in Noise Test Performances.

BACKGROUND: Temporal acoustic cues are particularly important for speech understanding, and past research has inferred a relationship between temporal resolution and speech recognition in noise ability. A temporal resolution disorder is thought to affect speech understanding abilities because persons would not be able to accurately encode these frequency transitions, creating speech discrimination errors even in the presence of normal pure-tone hearing. PURPOSE: The primary purpose was to investigate the relationship between temporal resolution as measured by the Random Gap Detection Test (RGDT) and speech recognition in noise performance as measured by the Hearing in Noise Test (HINT) in adults with normal audiometric thresholds. The second purpose was to examine the relationship between temporal resolution and spatial release from masking. RESEARCH DESIGN: The HINT and RGDT protocols were administered under headphones according to the guidelines specified by the developers. The HINT uses an adaptive protocol to determine the signal-to-noise ratio where the participant recognizes 50% of the sentences. For HINT conditions, the target sentences were presented at 0° and the steady-state speech-shaped noise and a four-talker babble (4TB) was presented at 0°, +90°, or -90° for noise front, noise right, and noise left conditions, respectively. The RGDT is used to evaluate temporal resolution by determining the smallest time interval between two matching stimuli that can be detected by the participant. The RGDT threshold is the shortest time interval where the participant detects a gap. Tonal (0.5, 1, 2, and 4 kHz) and click stimuli random gap subtests were presented at 60 dB HL. Tonal subtests were presented in a random order to minimize presentation order effects. STUDY SAMPLE: Twenty-one young, native English-speaking participants with normal pure-tone thresholds (≤25 dB HL for 500-4000 Hz) participated in this study. The average age of the participants was 20.2 years (SD = 0.66). DATA COLLECTION AND ANALYSIS: Spearman rho correlation coefficients were conducted using SPSS 22 (IBM Corp., Armonk, NY) to determine the relationships between HINT and RGDT thresholds and derived measures (spatial advantage and composite scores). Nonparametric testing was used because of the ordinal nature of RGDT data. RESULTS: Moderate negative correlations (p < 0.05) were found between eight RGDT and HINT threshold measures and a moderate positive correlation (p < 0.05) was found between RGDT click thresholds and HINT 4TB spatial advantage. This suggests that as temporal resolution abilities worsened, speech recognition in noise performance improved. These correlations were not statistically significant after the p value reflected the Bonferroni correction for multiple comparisons. CONCLUSION: The results of the present study imply that the RGDT and HINT use different temporal processes. Performance on the RGDT cannot be predicted from HINT thresholds or vice versa.