1,721,004 research outputs found
Effects of eye position on the vestibular evoked myogenic potential
No full textConclusion: The position of a subject's eyes during vestibular evoked myogenic potential (VEMP) recording significantly alters the magnitude of the response. This change is largely due to an alteration in the tonicity of the sternocleidomastoid muscle (SCM) caused by variations in the position of the eye. However, even if electromyographic (EMG) normalization is conducted effects of eye position remain.Objective: To determine if eye position has a significant effect on the magnitude of the VEMP.Subjects and methods: VEMPs were collected from 32 ears measured on 16 healthy subjects. The recordings were made unilaterally using the head turn method. The acoustic stimuli were 500 Hz air-conduction short tone bursts. VEMPs were measured in three recording conditions: (i) eyes in the same direction as head turn, (ii) eyes straight ahead, (iii) eyes in the opposite direction to head turn.Results: All 32 ears tested showed a VEMP response with eyes in all three positions. Repeated measures analysis of variance (RM-ANOVA) verified an overall significant effect of eye position (p<0.001). Post hoc paired t tests revealed statistically significant differences between the eyes opposite and the other two conditions (p<0.001). Normalization of the VEMP magnitude using pre-stimulus EMG reduced the effect; however, some variability remained
An investigation of the use of band-limited chirp stimuli to obtain the auditory brainstem response
No full textAuditory brainstem responses (ABRs) using clicks enable global objective estimation of hearing threshold. Recently, it has been suggested that a chirp stimulus may produce a synchronous response from a larger portion of the basilar membrane than a click, and that a chirp will produce a greater amplitude response than a click at the same sensation level. Various workers have modified the stimulus to achieve frequency specificity (e.g. using tone-bursts). The present investigation used band-limited chirp stimuli having the same frequency-delay characteristics as the chirp mentioned above that compensate for frequency-dependent cochlear delays. The intention was to generate highly synchronized neural responses across parts of the nerve fibre array. Stimuli were presented at sensation levels between 10 and 50 dB to 10 adult subjects. Wave V was consistently identifiable even for low-frequency stimuli. Wave V amplitude increased and latency decreased as stimulus frequency increased. The latency decrease is consistent with high-frequency responses arising from basal regions of the cochlea. ABR thresholds were defined by objective estimation and visual inspection. Average ABR thresholds were 16 dB higher than behavioural thresholds for high-frequency chirps (3000-6000 Hz), increasing to 25 dB for low-frequency chirps (375-750 Hz). These ABR thresholds are closer to behavioural thresholds and have a smaller variance than reported for tone-burst stimuli without masking. However, they are not as close as those reported for tone-bursts in notched noise. The disadvantage of the band-limited chirps is that they have a wider spectral spread than tone-bursts and hence may elicit a response from unwanted frequency regions of the basilar membrane
A statistical approach to measuring hearing thresholds from auditory brainstem responses
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Objective prediction of the sound quality of music processed by an adaptive feedback canceller
No full textAdaptive feedback cancellers in hearing aids can produce unpleasant sounding distortion artefacts (entrainment) in response to periodic inputs, including music. Reliable objective metrics that predict user-perceived distortion could significantly reduce development costs for new hearing aids. The aim of this study was to gain insight into the ability of different objective metrics to predict subjective ratings of the sound quality of music processed by adaptive feedback cancellation. The metrics tested consisted of perceptual measures from established audio quality models (including PEAQ, PEMO-Q and Rnonlin). Neural networks were used to map between the values of the perceptual measures and a subjective scale of perceived quality. Training data consisted of values of perceptual measures obtained from ten different excerpts of orchestral music processed by a simplified model of a hearing aid with an adaptive feedback canceller, and corresponding subjective ratings obtained from 27 normal hearing subjects. An optimal combination of perceptual measures to use as inputs to a network input was found using an extended Fourier amplitude sensitivity test (EFAST). Our results suggest that the most salient inputs to a multivariate model of measured quality ratings consist of perceptual measures related to spectral noise loudness, modulation differences between clean and processed signals, and correlation-based measurement of nonlinear distortion. The intraclass correlation between mean subjective ratings and the output of a network combining these perceptual measures was high (r=0.95), which compares favourably to results from previous studies of perceptual quality metric
Visual reinforcement audiometry with cross-talk cancellation. A feasibility study (Poster)
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