[Cockayne syndrome with marked cerebral symptoms]. / Cockayne-Syndrom mit betonter zerebraler Symptomatik.

The course of Cockayne syndrome is reported in two sisters over a period of 14 years. Both girls developed characteristic clinical signs early. Reaching the second decade progeria and psychomotor deficits progressed quickly with a marked mental decline brought about by the cerebral destruction which is demonstrated by successive CT und MRI scan. The effects of defective DNA repair mechanisms on progeria and mental deterioration are discussed and differential diagnoses are shown.

Direct comparison of the impact of head tracking, reverberation, and individualized head-related transfer functions on the spatial perception of a virtual speech source.

A study of sound localization performance was conducted using headphone-delivered virtual speech stimuli, rendered via HRTF-based acoustic auralization software and hardware, and blocked-meatus HRTF measurements. The independent variables were chosen to evaluate commonly held assumptions in the literature regarding improved localization: inclusion of head tracking, individualized HRTFs, and early and diffuse reflections. Significant effects were found for azimuth and elevation error, reversal rates, and externalization.

Survey of commercial airline pilots' hearing loss.

64 commercial airline pilots (ages 35-64 yr, Mdn: 53) were surveyed regarding hearing loss and tinnitus. Within specific age groups, the proportions responding positively exceed the corresponding proportions in the general population reported by the National Center for Health Statistics.

[Progressive facial hemiatrophy (Parry-Romberg syndrome]. / Hemiatrophia faciei progressiva (Parry-Romberg-Syndrom).

Two children with progressive facial atrophia are described. In both asymmetria of the face was the reason for neuropediatric examination. Discrete neurological symptoms of this neurocutaneous syndrome were found. In patient 1 atrophia of one side of the face had developed shortly after surgical treatment of a mandibular exostose on the other side of the face. In patient 2 first signs of hemifacial atrophia were found in the newborn. Both children showed only discrete neurological symptoms. Etiology of this rare disease is still unknown, causal treatment is not possible.

Localization using nonindividualized head-related transfer functions.

A recent development in human-computer interfaces is the virtual acoustic display, a device that synthesizes three-dimensional, spatial auditory information over headphones using digital filters constructed from head-related transfer functions (HRTFs). The utility of such a display depends on the accuracy with which listeners can localize virtual sound sources. A previous study [F. L. Wightman and D. J. Kistler, J. Acoust. Soc. Am. 85, 868-878 (1989)] observed accurate localization by listeners for free-field sources and for virtual sources generated from the subjects' own HRTFs. In practice, measurement of the HRTFs of each potential user of a spatial auditory display may not be feasible. Thus, a critical research question is whether listeners can obtain adequate localization cues from stimuli based on nonindividualized transforms. Here, inexperienced listeners judged the apparent direction (azimuth and elevation) of wideband noisebursts presented in the free-field or over headphones; headphone stimuli were synthesized using HRTFs from a representative subject of Wightman and Kistler. When confusions were resolved, localization of virtual sources was quite accurate and comparable to the free-field sources for 12 of the 16 subjects. Of the remaining subjects, 2 showed poor elevation accuracy in both stimulus conditions, and 2 showed degraded elevation accuracy with virtual sources. Many of the listeners also showed high rates of front-back and up-down confusions that increased significantly for virtual sources compared to the free-field stimuli. These data suggest that while the interaural cues to horizontal location are robust, the spectral cues considered important for resolving location along a particular cone-of-confusion are distorted by a synthesis process that uses nonindividualized HRTFs.

Headphone localization of speech.

Three-dimensional acoustic display systems have recently been developed that synthesize virtual sound sources over headphones based on filtering by head-related transfer functions (HRTFs), the direction-dependent spectral changes caused primarily by the pinnae. In this study 11 inexperienced subjects judged the apparent spatial location of headphone-presented speech stimuli filtered with non-individualized HRTFs. About half of the subjects "pulled" their judgments toward either the median or the lateral-vertical planes, and estimates were almost always elevated. Individual differences were pronounced for the distance judgments; 15% to 46% of stimuli were heard inside the head, with the shortest estimates near the median plane. The results suggest that most listeners can obtain useful azimuth information from speech stimuli filtered by nonindividualized HRTFs. Measurements of localization error and reversal rates are comparable with a previous study that used broadband noise stimuli.

The combination of interaural time and intensity in the lateralization of high-frequency complex signals.

In an effort to examine the rules by which information arising from interaural differences of time (IDT) and interaural differences of intensity (IDI) is combined, d"s were measured for trains of high-frequency clicks (4000 Hz, bandpass) possessing various combinations of IDT and IDI. The number of clicks was either 1 or 8, with the interclick interval either 2 or 10 ms. A 2-IFC task was employed in which the paired values of IDT and IDI favored one side during one interval and the other side during the other interval. Data obtained with the combined cues are compared to those obtained with IDTs or IDIs alone in order to determine the degree to which processing of the two cues is done independently. Results suggest that lateralization with such stimuli is based on the sum of the temporal and intensive differences and not on independent evaluations of their separate presences.