Monaural sound localization : mechanisms and processes

A review of the literature established that localization acuity measured during monaural listening conditions was directly related to various methodological considerations. These included method of attenuation, segment of auditory space where monaural localization was measured, and the presence or absence of head movements. An extensive measurement of monaural localization was made with due consideration of these factors, allowing a more comprehensive evaluation of monaural acuity and the underlying processes that were involved. Establishing a monaural condition is dependent both on the attenuation level of the occluded ear and the signal level, both of which are clearly inter-related since the attenuation level of the occluded ear sets the maximum level of die stimulus. In a series of experiments it was established that there was a minimum signal level for accurate localization. Testing on both sides of the head revealed that there were three regions of monaural localization acuity. The first was about the interaural axis on the ipsilateral ear where monaural localization was relatively accurate, the second a region either side of the MSP where there was some loss of localization, and a third about the interaural axis on the ipsilateral side where virtually no monaural localization ability existed. In the final series of experiments it was established that head-movements allowed subjects to extend the accuracy of the first region by minimizing the distance between the sound and the ipsilateral interaural axis, thus compensating for the loss of localization ability in the second and third regions. This was determined from changes recorded in the error data, and also the extent and direction of measured head-movements. The results of this series of experiments demonstrated the relationship between spectral cues and monaural localization. Firstly, monaural localization was not possible in the absence of accurate spectral information. Thus large errors were observed in the third region where there was blockage of the high-frequencies by the head, and in all regions during the presentation of low signal levels where the high-frequencies fell below threshold. Secondly, the inaccuracy of the second region due to the loss of information from the second pinna suggested that there was a binaural component with relation to pinna cues. It seems that for sounds in this region the spectral modifications from both pinnae are processed to determine a sound's location in space.

Auditory localisation reversals and the role of torso-related cues

Human auditory localisation reversals are explored using mixture distribution analysis techniques. This is validated for front/back reversals and subsequently shown to provide evidence for up/down reversals as distinct classes of mis-localisation. Torso-related localisation cues are identified and also shown to provide a source for resolving these reversals in some listeners.

Category politics: deaf students' inclusion in a 'hearing university'

This article investigates the way in which deaf tertiary students' identity is constructed within the university - an overwhelmingly 'hearing' institution. It is a descriptive and analytical account of the experiences of two deaf teacher education students as they reflect on their progress and experiences in higher education. Data have been analysed within an interpretive framework of category politics and the construction of difference. The study found that providing the same access to the same information in the same form did little to address the discursive marginality of these students.

An autonomous trimming system of large glass fiber reinforced plastics parts using an omni-directional mobile robot and its control

This paper describes an automated trimming system of large glass fiber reinforced plastic (GFRP) using an omni-directional wheeled mobile robot (WMR) and its path control method. In trimming GFRP parts, much glass fiber and plastic powder dust occur and it becomes bad visible in environment. It is necessary to correct dead-reckoning errors of the WMR in order to control its moving path. We have discussed an external correction method of the dead-reckoning errors for the WMR using ultrasonic sensor.

Hearing what older consumers say about participation in their care

A study exploring older people's participation in their care in acute hospital settings reveals both consumers' and nurses' views of participation. Using a critical ethnographic design, data were collected through participant observation and interviews from consumers in acute care settings who were over 70 years old and nurses who were caring from them. Thematic analysis identified that older people equated participation with being independent. Importantly, consumers highlighted the complexity of the notion of participation when describing situations where they were unable to participate in their own care. The difficulties in communicating with health professionals and an inability to administer their own medications in inpatient settings were identified as barriers to participation. Understanding what consumers believe participation means provides a starting point for developing meaningful partnerships between health professionals and people receiving care.

Pretend play and maternal scaffolding : comparisons of toddlers with advanced development, typical development, and hearing impairment

This study used measures of pretend play and maternal scaffolding to explore and compare the early development of deaf children, typically developing children, and children showing advanced intellectual development. Marked differences were found among the groups in both play development and characteristics of mother-child interactions. In particular, children who scored above 130 IQ at four years of age were found, as toddlers, to have demonstrated significantly advanced pretend play. In addition, the mothers of the high IQ children engaged in scaffolding behaviors involving higher stages of pretend transformations, verbal analogies and world links. The findings are discussed in relation to children's learning in Vygotsky's Zone of Proximal Development, as well as possible implications for future research on early gifted development.

The effects of phonological and morphological training on speech perception scores and grammatical judgments in deaf and hard-of-hearing children

Seventeen primary school deaf and hard-of-hearing children were given two types of training for 9 weeks each. Phonological training involved practice of /s, z, t, d/ in word final position in monomorphemic words. Morphological training involved learning and practicing the rules for forming third-person singular, present tense, past tense, and plurals. The words used in the two training types were different (monomorphemic or polymorphemic) but both involved word final /s, z, t, d/. Grammatical judgments were tested before and after training using short sentences that were read aloud by the child (or by the presenter if the child was unable to read them). Perception was tested with 150 key words in sentences using the trained morphemes and phonemes in word final position. Grammatical judgments for sentences involving the trained morphemes improved significantly after each type of training. Both types of training needed to be completed before a significant improvement was found for speech perception scores. The results suggest that both phonological and morphological training are beneficial in improving speech perception and grammatical performance of deaf and hard-of-hearing children and that both types of training were required to obtain the maximum benefit.

Separating the contributions of hearing, lexical knowledge and speech production to speech perception scores in children with hearing impairments.

Open-set word and sentence speech-perception test scores are commonly used as a measure of hearing abilities in children and adults using cochlear implants and/or hearing aids. These tests are usually presented auditorily with a verbal response. In the case of children, scores are typically lower and more variable than for adults with hearing impairments using similar devices. It is difficult to interpret children's speech-perception scores without considering the effects of lexical knowledge and speech-production abilities on their responses. This study postulated a simple mathematical model to describe the effects of hearing, lexical knowledge, and speech production on the perception test scores for monosyllabic words by children with impaired hearing. Thirty-three primary-school children with impaired hearing, fitted with hearing aids and/or cochlear implants, were evaluated using speech-perception, reading-aloud, speech-production, and language measures. These various measures were incorporated in the mathematical model, which revealed that performance in an open-set word-perception test in the auditory-alone mode is strongly dependent on residual hearing levels, lexical knowledge, and speech-production abilities. Further applications of the model provided an estimate of the effect of each component on the overall speech-perception score for each child.