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Results for “Perceptual Distortion”

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PubMed1982

Evaluation of high-fidelity hearing aids.

An essential building block for any high-fidelity hearing aid is an amplifier-transducer-coupling combination that does not audibly degrade the sound, that is, provides high-fidelity sound reproduction as judged by someone with normal hearing. To demonstrate that such a combination is possible, two binaural pairs of hearing aids were assembled using available hearing aid transducers and electronic components, one pair of Over-The-Ear hearing aids with 8-kHz bandwidth and one pair of In-The-Ear hearing aids with 16-kHz bandwidth. Objective insertion-gain measurements on these aids, obtained with a KEMAR manikin in a diffuse sound field, revealed a frequency-response accuracy comparable to that available in expensive high-fidelity loudspeakers. Subjective fidelity ratings obtained from three groups of listeners judging prerecorded A-B-A comparisons (made from equalized eardrum-position microphones in a KEMAR manikin) produced a similar conclusion. We conclude that the important question for hearing aid research is no longer "What can a hearing aid be designed to do?" but "What should a hearing aid be designed to do for the hearing impaired?"

Acoustics↗
PubMed1992

Articulatory function after resection of the tongue and floor of the mouth: palatometric and perceptual evaluation.

Linguapalatal contact patterns and the time course of changes in contacts during utterances of/asa, ata, a sa, aca/ were measured using electropalatography (EPG). The relations between these data and perceptual scores in 17 glossectomized patients after various surgical methods were examined. The linguapalatal contact patterns produced during perceptually less distorted sounds varied with the place and manner of articulation. Patterns having very few contacts or a posterior groove produced more distorted /s/ sounds; however, types of EPG patterns producing less distorted /s/ sounds were relatively frequent. Distortion of the and /c/ sounds was less often produced by variation of the EPG patterns, whereas /t/ sounds were most frequently judged to be highly distorted. Patterns that showed complete constriction along the dental arch or constriction on the anterior portion of the hard palate, as well as rapid release for plosion by the tongue tip, produced less distorted /t/ sounds. The results revealed that glossectomized patients often evidenced defective stop sounds. It was concluded that mobility rather than volume of the residual tongue is required to produce less distorted stops.

Adult↗
PubMed1996

A preliminary investigation into the aetiology of Meares-Irlen syndrome.

A recent double-masked placebo-controlled trial has confirmed that some children experience a reduction in symptoms of eyestrain and headache when they read through individually prescribed coloured filters and has shown that this benefit cannot be solely attributed to a placebo effect. People who are helped by coloured filters in this way have been described as having "Meares-Irlen syndrome'. We investigated the mechanism of this benefit by studying the optometric and visual perceptual characteristics of the children in the double-masked study. This population had normal refractive errors and heterophorias (none of the subjects had strabismus). They demonstrated slightly, but significantly, reduced amplitudes of accommodation and vergence and poor stereo-acuity. However, these factors seemed to be correlates of Meares-Irlen syndrome rather than the underlying cause. Pattern glare, a sensitivity to striped patterns (e.g. lines of text), was prevalent in our sample and was significantly associated with the subjects' symptoms. The spatial contrast sensitivity function was normal.

Adolescent↗
PubMed2001

The effect of perceived length on visuomotor localization.

PURPOSE: The purpose of this experiment was to study visuomotor localization in the presence of either a horizontal array of equally spaced dots or a thin horizontal line. METHODS: Pointing behavior was used to assess directional localization. In experiment 1, subjects were made myopic using a contact lens and then corrected with a spectacle lens. Subjects were tested in the presence and absence of a regularly spaced, horizontal array of dots with and without the contact lens/spectacle combination. In experiment 2, subjects wore the contact lens/spectacle in all cases. Some subjects were tested in the presence and then in the absence of a regularly spaced, horizontal array of dots while the order of conditions was reversed for other subjects. In experiments 3 and 4, subjects were tested without the contact lens/spectacle combination. In experiment 3, subjects were tested in the absence and then in the presence of a regularly spaced, horizontal arrays of dots. In experiment 4, subjects were tested in the absence and then in the presence of a thin horizontal line. RESULTS: In experiment 1, in the absence of the array of dots, subjects undershot targets with the contact lens/spectacle combination. When the array was present, pointing with the contact lens/spectacle combination was accurate. In experiment 2, subjects undershot targets in the absence of the array of dots if this condition was performed first. If the array was present in the initial condition, the pointing undershoot in the second condition (array absent) was reduced. In all cases, the pointing undershoot was reduced in the presence of the array. In experiments 3 and 4, a pointing overshoot was found in the presence of an array of dots or a thin line. CONCLUSIONS: It is concluded that extraretinal eye position information is not the primary determinant of visuomotor localization in the presence of a horizontal contour. The overshoot produced by a horizontal contour may be related to a length illusion brought about by spatial filtering in the visual system or inaccurate distance judgments.

Accommodation, Ocular↗
PubMed1996

[Detection of hearing loss in patrons of a discoteque using TEOAE and DPOAE].

BACKGROUND: The aim of the study was to investigate the potential and difference of pure tone audiogram, TEOAE and DPOAE in the detection of temporary threshold shift. METHODS: 46 disco visitors who were exposed to disco music at an average intensity of 105 dB (A) for 1, 1 1/2 and 2 hours respectively underwent audiological examination before and after noise exposure. Audiological measurements performed were an audiogram and measurements of the TEOAE and DPOAE using the system ILO 92 (Otodynamics). RESULTS: The frequency range where the threshold shift occurred was around 4000 Hz in the 1 hour group and spread over all frequencies when the exposure time increased. The average threshold shift over all frequencies and probands was 6.2 dB for the 1 hour group, 7.1 dB for the 1 1/2 hour group and 10.1 dB after 2 hours of noise exposure. TEOAE amplitudes showed significant reduction only at 2000 and 3000 Hz. Even at threshold shifts exceeding 15 dB, however not in all cases, a reduction of TEOAE amplitudes occurred. Similar results were obtained regarding the DPOAE measurements. CONCLUSIONS: We conclude that TEOAE and DPOAE are not ideal instruments in the detection of temporary threshold shift after noise exposure.

Adolescent↗
PubMed2000

Influence of height on the spatial orientation and equilibrium of the body.

The sway of the center of gravity for 30 seconds with a stabilometer was examined in 30 volunteers under 3 visual conditions (eyes open with and without fixation and eyes closed) at heights of 0, 1, and 2 m and under 2 visual conditions (eyes open with fixation and eyes closed) at a height of 10 m 22 cm. Eight of the subjects had acrophobia. The sway worsened at 10 m 22 cm but showed no change at 1 or 2 m. The acrophobic group became clearly worse at 10 m 22 cm. In another group of 12 volunteers, the subjects were guided to the roof with the eyes closed, and sway was measured. Sway was also measured with the eyes uncovered and open and again with the eyes closed. The first measurement with the eyes closed showed worse sway, and the second with the eyes open was better, except in 2 subjects who were acrophobic.

Adult↗
PubMed1977

Serial adaptation to conflicting prismatic rearrangement effects in monkey and man.

Seven adult male squirrel monkeys adapted successfully to prisms displacing in equal and opposite directions. After protracted training under certain conditions, they succeeded in conserving adaptation to both prisms without benefit of readaptation trials. Results obtained with thirty-six undergraduates under similar conditions of test (although for a much shorter period) are also reported.

Adaptation, Ocular↗
PubMed1977

Stability of Wilkinson's linear model of prism adaptation over time for various targets.

Prism adaptation as measured by negative aftereffects (NA), proprioceptive shifts (PS), and visual shifts (VS) was assessed as a function of amount of exposure time and target specificity, whether an exposure and a test target background were the same or different, to determine the validity of Wilkinson's linear model (NA = PS + VS). With few exceptions the model was found to hold well up to 40 min of prism viewing regardless of type of exposure background. In addition target specificity affected magnitude of the NA component of adapation but not the PS and the VS components.

Adaptation, Ocular↗
PubMed1978

A possible explanation as to why the newly sighted commonly perform well on pseudoisochromatic colour vision tests.

Patients whose vision has been restored after long periods of blindness commonly experience difficulty in perceiving. Parodoxically, such patients often perform well on pseudoisochromatic colour-vision tests. A well-known example is Gregory and Wallace's subject, S.B. who performance on the Ishihara test was perfect. It is suggested that restoration of vision may be associated with relatively poor visual acuity and that this, by filtering higher spatial frequencies, enhances the legibility of pseudoisochromatic test patterns. Two experiments confirm that the Ishihara plates are more legible when seen as defocused images.

Blindness↗
PubMed1979

Recalibration of the convergence system.

Adaptation to convergence-altering prism spectacles was studied. The subjects were trained for 8 min with either convergence-increasing or convergence-decreasing prisms. Before and after training they estimated the distance to a binocular dot varying in the stimulus it provided to convergence. Both the preadaptation and postadaptation estimates showed that the reciprocal of estimated target distance is linearly related to convergence. Further there was a consistent change in the direction of adaptation expected from the preadaptation to the postadaptation test. This change was accounted for in terms of a recalibration of the effective absolute convergence level.

Adaptation, Ocular↗
PubMed1979

Adaptation to displacing prisms in human infants.

This research reports a first attempt to study adaptation to laterally displacing prisms in human infants of ages six to ten months. Twenty infants were tested over four days under conditions similar to those used in adult adaptation studies. Evidence was found of vigorous adaptation when infants were exposed to base-right prisms under conditions of active exposure. Detailed consideration is given to the conditions and methods of studying adaptation in infants and implications for adult studies.

Adaptation, Psychological↗