Biomedical subjects

Wouter A Dreschler

Publications and source records attributed to Wouter A Dreschler.

8 recordsLinked to original sources

PubMed2006

Dexamethasone and long-term outcome in adults with bacterial meningitis.

OBJECTIVE: This follow-up study of the European Dexamethasone Study was designed to examine the potential harmful effect of adjunctive dexamethasone treatment on long-term neuropsychological outcome in adults with bacterial meningitis. METHODS: Neurological, audiological, and neuropsychological examinations were performed in adults who survived pneumococcal or meningococcal meningitis. RESULTS: Eighty-seven of 99 (88%) eligible patients were included in the follow-up study; 46 (53%) were treated with dexamethasone and 41 (47%) with placebo. Median time between meningitis and testing was 99 months. Neuropsychological evaluation showed no significant differences between patients treated with dexamethasone and placebo. The proportions of patients with persisting neurological sequelae or hearing loss were similar in the dexamethasone and placebo groups. The overall rate of cognitive dysfunction did not differ significantly between patients and control subjects; however, patients after pneumococcal meningitis had a higher rate of cognitive dysfunction (21 vs 6%; p = 0.05) and experienced more impairment of everyday functioning due to physical problems (p = 0.05) than those after meningococcal meningitis. INTERPRETATION: Treatment with adjunctive dexamethasone is not associated with an increased risk for long-term cognitive impairment. Adults who survive pneumococcal meningitis are at significant risk for long-term neuropsychological abnormalities.

Adult↗

PubMed2006

Extended speech intelligibility index for the prediction of the speech reception threshold in fluctuating noise.

The extension to the speech intelligibility index (SII; ANSI S3.5-1997 (1997)) proposed by Rhebergen and Versfeld [Rhebergen, K.S., and Versfeld, N.J. (2005). J. Acoust. Soc. Am. 117(4), 2181-2192] is able to predict for normal-hearing listeners the speech intelligibility in both stationary and fluctuating noise maskers with reasonable accuracy. The extended SII model was validated with speech reception threshold (SRT) data from the literature. However, further validation is required and the present paper describes SRT experiments with nonstationary noise conditions that are critical to the extended model. From these data, it can be concluded that the extended SII model is able to predict the SRTs for the majority of conditions, but that predictions are better when the extended SII model includes a function to account for forward masking.

Adolescent↗

PubMed2005

Release from informational masking by time reversal of native and non-native interfering speech.

In many studies, the influence of intelligibility of the interfering speech is avoided by reversing it in time. Usually, intelligibility with time-reversed interfering speech indeed is higher compared to that with normal interfering speech. However, due to the nature of speech, reversed speech also gives rise to increased forward masking. The latter will result in a decrease in intelligibility. Thus, differences in intelligibility as a consequence of reversing speech in time are due to two opposite effects. This paper describes a speech reception threshold (SRT) test with intelligible and unintelligible interfering speech played normally and time-reversed. With Dutch listeners, Swedish reversed interfering speech gave a rise in SRT of 2.3 dB compared with the Swedish interfering speech (played normally). The difference can be attributed to differences in forward masking. Dutch time-reversed interfering speech gave a decrease in SRT of 4.3 dB compared to (intelligible) Dutch interfering speech. The latter is the result of both a release from informational masking and an increase in forward masking. Therefore, the amount of informational masking is larger than 4.3 dB and, if one assumes similar differences in forward masking for Dutch and Swedish speech, may amount to 6.6 dB.

Acoustic Stimulation↗

PubMed2004

Gold and titanium in the oval window: a comparison of two metal stapes prostheses.

OBJECTIVE: The objective of this study was to evaluate the hearing results of stapes surgery with 2 different full metal stapes prostheses. STUDY DESIGN: Retrospective analyses were carried out on the pre- and postoperative hearing results obtained after primary stapedotomy with 2 different prostheses. PATIENTS: We studied 106 patients with otosclerosis treated by stapes surgery. INTERVENTION: Fifty-three patients had a stapedotomy with a gold piston and 53 patients received a titanium piston after stapedotomy. MAIN OUTCOME MEASURES: The results were compared according to mean audiometric parameters. Furthermore, the individual audiologic results were demonstrated with the Amsterdam Hearing Evaluations Plot (AHEP). This method is a visual presentation of the hearing result for each operated ear. RESULTS: These AHEPs showed that the heavier gold piston (shaft Ø 0.4 mm and weight 10192.0 microg) gives more overclosure gain (28.3%) than the lightweight (shaft Ø 0.4 mm and weight 2541.0 microg) titanium piston (9.4% cases of overclosure). CONCLUSIONS: Because of the different properties of the 2 pistons (gold very malleable, titanium rather stiff), a choice can be made for different anatomic or pathologic situations in the operated middle ear. The "overclosure effect" of the gold piston is higher compared with the titanium piston.

Adult↗

PubMed2004

Methodological aspects of an adaptive multidirectional pattern search to optimize speech perception using three hearing-aid algorithms.

In this study we investigated the reliability and convergence characteristics of an adaptive multidirectional pattern search procedure, relative to a nonadaptive multidirectional pattern search procedure. The procedure was designed to optimize three speech-processing strategies. These comprise noise reduction, spectral enhancement, and spectral lift. The search is based on a paired-comparison paradigm, in which subjects evaluated the listening comfort of speech-in-noise fragments. The procedural and nonprocedural factors that influence the reliability and convergence of the procedure are studied using various test conditions. The test conditions combine different tests, initial settings, background noise types, and step size configurations. Seven normal hearing subjects participated in this study. The results indicate that the reliability of the optimization strategy may benefit from the use of an adaptive step size. Decreasing the step size increases accuracy, while increasing the step size can be beneficial to create clear perceptual differences in the comparisons. The reliability also depends on starting point, stop criterion, step size constraints, background noise, algorithms used, as well as the presence of drifting cues and suboptimal settings. There appears to be a trade-off between reliability and convergence, i.e., when the step size is enlarged the reliability improves, but the convergence deteriorates.

Algorithms↗

PubMed2002

The relationship between the intelligibility of time-compressed speech and speech in noise in young and elderly listeners.

A conventional measure to determine the ability to understand speech in noisy backgrounds is the so-called speech reception threshold (SRT) for sentences. It yields the signal-to-noise ratio (in dB) for which half of the sentences are correctly perceived. The SRT defines to what degree speech must be audible to a listener in order to become just intelligible. There are indications that elderly listeners have greater difficulty in understanding speech in adverse listening conditions than young listeners. This may be partly due to the differences in hearing sensitivity (presbycusis), hence audibility, but other factors, such as temporal acuity, may also play a significant role. A potential measure for the temporal acuity may be the threshold to which speech can be accelerated, or compressed in time. A new test is introduced where the speech rate is varied adaptively. In analogy to the SRT, the time-compression threshold (or TCT) then is defined as the speech rate (expressed in syllables per second) for which half of the sentences are correctly perceived. In experiment I, the TCT test is introduced and normative data are provided. In experiment II, four groups of subjects (young and elderly normal-hearing and hearing-impaired subjects) participated, and the SRT's in stationary and fluctuating speech-shaped noise were determined, as well as the TCT. The results show that the SRT in fluctuating noise and the TCT are highly correlated. All tests indicate that, even after correction for the hearing loss, elderly normal-hearing subjects perform worse than young normal-hearing subjects. The results indicate that the use of the TCT test or the SRT test in fluctuating noise is preferred over the SRT test in stationary noise.

Adult↗

PubMed2002

The effects of phonemic compression and anti-upward-spread-of-masking (anti-USOM) on the perception of articulatory features in hearing-impaired listeners.

The effect of speech processing on articulatory-feature recognition was studied in a group of hearing-impaired listeners with high-frequency sensorineural losses. Individual difference scaling (INDSCAL) and sequential information analysis (SINFA) were applied to a set of consonant-vowel-consonant responses measured under various conditions of speech processing. The processing consisted of high-frequency phonemic compression combined with compensation for anti-upward-spread-of-masking (i.e. anti-USOM). In quiet, we found an improved recognition of frication with compression, whereas additional anti-USOM improved the recognition of the second and third vowel-formants. In background noise, we found remarkably negative effects of anti-USOM on the recognition of features containing low-frequency cues, such as voicing and nasality. We conclude that the combined results of SINFA and INDSCAL provide important insights into the possibilities and limitations of phonemic compression and anti-USOM.

Analysis of Variance↗

PubMed2002

International Outcome Inventory for Hearing Aids (IOI-HA): results from The Netherlands.

This paper presents data on the Dutch translation of the International Outcome Inventory for Hearing Aids (IOI-HA). The inventory was used as an additional postal tool in a nationwide study on the benefits of bilateral hearing aid fitting. Responses of 505 hearing aid users were analysed. Descriptive statistics and inter-item correlations are reported. Factor analysis resulted in the extraction of two factors. Cronbach's alpha coefficients and corrected item total correlations showed high internal consistency of the scales. Significant correlations were found between IOI Factor 2 and the Hearing Handicap and Disability Inventory and subscales of the Amsterdam Inventory for Hearing Disability and Handicap.

Adolescent↗