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R M Cox

Publications and source records attributed to R M Cox.

At least 19 recordsLinked to original sources
PubMed2006

A computer method for assessing satisfaction with hearing aids.

The purpose of this study was to evaluate a new clinical assessment, the Dynamic Assessment of Hearing Aids (DAHA), for a large clinical population. Unlike traditional questionnaire methods, the DAHA has patients use an intuitive graphical computer interface to record visual analogue ratings of satisfaction with various features of their hearing aids (e.g. clarity, cost, appearance). Data were collected from 191 participants.A subset of participants returned for retest. The DAHA items assess satisfaction with hearing aids within four domains: communication, physical features, sound quality, and personal reactions. The concurrent validity was determined by comparing DAHA results to those obtained with the satisfaction with amplification in daily life (SADL). Ratings for personal reactions to hearing aids indicate the most satisfaction, and ratings for communication (especially group conversations and phone use) indicate the least satisfaction. The DAHA total score was found to have good test/retest and high internal consistency. Concurrent validity was supported by a strong correlation between total scores on the DAHA and the SADL. Results suggest the DAHA maybe an effective tool for clinical use.

Activities of Daily Living↗
PubMed2006

A test of the reproductive cost hypothesis for sexual size dimorphism in Yarrow's spiny lizard Sceloporus jarrovii.

1. Trade-offs between reproduction and growth are central assumptions of life-history theory, but their implications for sexual size dimorphism (SSD) are poorly understood. 2. Adult male Yarrow's spiny lizards Sceloporus jarrovii average 10% larger than adult females. In a low-altitude (1700 m) population, this SSD develops because males grow more quickly than females during the first year of life, particularly during the first female reproductive season. This study tests the hypothesis that SSD develops because female growth is constrained by energetic costs of reproduction. 3. To test for a growth cost of reproduction, I compared growth rates of free-living females that differed, either naturally or experimentally, in reproductive status. Females that naturally delayed reproduction until their second year grew more quickly than females that reproduced as yearlings, and ovariectomized yearlings grew more quickly and to larger sizes than reproductive controls. 4. To determine whether SSD develops in the absence of this inferred reproductive cost, I also studied a high-altitude (2500 m) population in which all females delay reproduction until their second year. Sex differences in growth trajectories were similar to those observed at low altitude, such that males averaged 10% larger than females even prior to female reproduction. 5. Although female growth may be constrained by reproduction, multiple lines of evidence indicate that this cost is insufficient to explain the full magnitude of SSD in S. jarrovii. First, differences in growth of reproductive and nonreproductive females are not observed until the final month of gestation, by which time SSD is already well developed. Second, the growth benefit accruing from experimental inhibition of reproduction accounts for only 32% of the natural sex difference in body size. Finally, SSD develops well in advance of female reproduction in a high-altitude population with delayed maturation.

Altitude↗
PubMed2005

Training in neonatal cranial ultrasound: a questionnaire survey.

A questionnaire was sent to every paediatric specialist registrar in the West Midlands to assess the training of paediatric specialist registrars in neonatal cranial ultrasound. 26% had never carried out supervised scans. 51% lacked confidence in performance and 57% in interpretation of scans. The current pattern of training in neonatal cranial ultrasound lacks structure, supervision and assessment of competency.

Echoencephalography↗
PubMed2003

Effects of simulated thaw on xylem cavitation, residual embolism, spring dieback and shoot growth in yellow birch.

Yellow birch seedlings (Betula alleghaniensis Britt.) that had lost more than 90% of their stem hydraulic conductivity during ambient winter temperatures were exposed to 0 and 20 days of a simulated winter thaw followed by a 48-h freezing treatment at 0, -5, -10, -20 and -30 degrees C. After measuring freezing injury to shoots and roots, the seedlings were placed in a greenhouse where recovery of xylem conductivity and new growth were measured. Shoot xylem cavitation was measured as percent loss of hydraulic conductivity. Shoot freezing injury was assessed by electrolyte leakage (EL) and root freezing injury was assessed by EL and triphenyl tetrazolium chloride reduction. Seedlings pretreated with thaw had higher stem water contents and suffered more freezing damage to roots and shoots (at -20 and -30 degrees C, respectively) than unthawed seedlings. After 3 weeks in a greenhouse, seedlings from the 0, -5 and -10 degrees C freezing treatments showed complete recovery of xylem conductivity, with substantially increased stem water contents. Poor recovery of hydraulic conductivity was observed only in seedlings that were subjected to freezing treatments at -20 and -30 degrees C, regardless of thaw treatment. Of these embolized seedlings, however, only those not previously thawed showed recovery of hydraulic conductivity or regained stem water content after 9 weeks in the greenhouse. Shoot dieback, bud burst and length of new shoots were significantly related to the extent of stem xylem cavitation and freezing injury. We conclude that (1) the simulated winter thaw predisposed yellow birch seedlings to freezing damage in shoots and roots by dehardening tissues and increasing their water content; (2) root freezing damage in turn affected the seedlings' ability to refill embolized stem xylem, resulting in considerable residual xylem embolism after spring refilling; (3) further recovery of stem xylem conductivity was attributable to growth of new vessels; (4) and the permanent residual embolism, together with root and shoot freezing injury, caused increased dieback, bud mortality and reduced growth of new shoots.

Betula↗
PubMed2001

Sampling ozone exposure of Canadian forests at different scales: some case studies.

The use of passive samplers in extensive monitoring, such as that used in national forest health monitoring plots, indicates that these devices are able to determine both spatial and temporal differences in ozone exposure of the plots. This allows for categorisation of the plots and the potential for cause-effect analysis of certain forest health responses. Forest exposure along a gradient of air pollution deposition demonstrates large variation in accumulated exposures. The efficacy of using passive samplers for in situ monitoring of forest canopy exposure was also demonstrated. The sampler data produced weak relationships with ozone values from the nearest "continuous" monitor, even though data from colocated samplers showed strong relationships. This spatial variation and the apparent effect of elevation on ozone exposure demonstrate the importance of topography and tree canopy characteristics in plant exposure on a regional scale. In addition, passive sampling may identify the effects of local pollutant gases, such as NO, which may scavenge ozone locally only to increase the production of this secondary pollutant downwind, as atmospheric reactions redress the equilibrium between concentrations of this precursor and those of the generated ozone. The use of passive samplers at the stand level is able to resolve vertical profiles within the stand and edge effects that are important in exposure of understorey and ground flora. Recent case studies using passive samplers to determine forest exposure to ozone indicate a great potential for the development of spatial models on a regional, landscape, and stand level scale.

Canada↗
PubMed2001

Verifying loudness perception after hearing aid fitting.

During the verification phase of a hearing aid fitting, clinicians often want to assess the extent to which loudness perceptions for amplified sounds are similar to those typical of normal hearers. This type of verification calls for a criterion for "normal" loudness perception of sounds presented in a sound field. This research sought to answer several questions about the parameters of a valid "normal" criterion for a verification procedure using the Contour test of loudness perception. Loudness data were obtained from 30 listeners with normal hearing. Results indicated that a loudness growth function obtained with earphone listening is not an appropriate normative reference for hearing aid fitting verification. Instead, the normative data should be based on sound field listening. Results also indicated that the same normative function could be used to assess both unilateral and bilateral fittings. Further, it is likely that the same normative function can be used for most frequency responses that are likely to be used in feasible fittings. Finally, it was found that a previously published normative function obtained using an automated test procedure was not faithfully replicated using a carefully executed fully manual test procedure. We concluded that, until a replicable normative function is established, practitioners will need to generate their own local norms to perform postfitting verification of loudness normalization.

Adult↗
PubMed2001

Validation of the SADL questionnaire.

OBJECTIVE: To cross-validate the psychometric characteristics of the Satisfaction with Amplification in Daily Life (SADL) questionnaire (Cox & Alexander, 1999), and to explore the SADL's construct validity. DESIGN: Thirteen private practice Audiology clinics each distributed SADL questionnaires, by mail, to 20 adults who had recently obtained hearing aids. The completed questionnaires were returned to a central site and subject anonymity was assured. There were 196 usable responses. RESULTS: Psychometric characteristics of the items were found to be very similar to those reported previously. Thus, the internal validity of the instrument was strongly supported. The assumption that the SADL quantifies satisfaction by assessing its components was evaluated by examining the relationship between SADL scores and scores on a traditional single-item satisfaction measure. A logical and statistically significant relationship was seen between the two measures, thereby supporting the construct validity of both types of data. For private-pay clients, satisfaction scores were very similar to the interim norms published by Cox and Alexander (1999). However, clients whose hearing aids were partly or fully purchased by insurance or benefits programs tended to be more satisfied than interim norms for third-party pay clients derived 5 yr ago. For most types of clients, there was a tendency toward more satisfaction in the Negative Features subscale than observed in our previous research. CONCLUSIONS: Both construct and internal validity of the SADL questionnaire were supported by this research. The previously published interim norms appear to be mostly appropriate for private-pay clients, but might require adjustment in the Negative Features subscale. Further research is needed to explore the relationship between satisfaction and device purchase issues (third-party versus private pay).

Adult↗
PubMed2001

Evaluation of a Revised Speech in Noise (RSIN) test.

A revised version of the Speech in Noise (SIN) test was developed by reallocating the recorded test material on the compact disc into different lists (blocks). The goal was to increase the equivalence and reliability of the test blocks to enhance their usefulness in research settings. The Revised Speech in Noise test has four blocks of sentences. Each block comprises twice as many sentences as in the original SIN test. There are also practice sentences for each condition. Forty-two elderly subjects with normal hearing for their age and gender provided data on the equivalence of the new test blocks. The remaining inequalities in mean scores were mostly eliminated using score weighting. Critical differences were developed to promote interpretation of scores from the same individual under different conditions. The revisions substantially improved the equivalence of test blocks and their sensitivity to performance changes. Increased test time is the associated drawback.

Aged↗
PubMed1999

Measuring Satisfaction with Amplification in Daily Life: the SADL scale.

OBJECTIVE: To develop a self-report inventory to quantify satisfaction with hearing aids. DESIGN: The inventory was developed in several stages. To determine the elements that are most important to satisfaction for most people, we conducted structured interviews and then designed a questionnaire. Hearing aid owners responded to the questionnaire, indicating the relative importance of 14 different elements in their hearing aid satisfaction. Analyses indicated that the elements could be placed into four importance content areas. Trial satisfaction items were designed for each content area and submitted to focus groups to identify highly salient items as well as ambiguous items. A 25-item satisfaction questionnaire then was developed and disseminated to hearing aid owners. Results were obtained from 257 individuals. These data were analyzed to generate the final questionnaire. RESULTS: Fifteen items, divided into four subscales, were selected for the final Satisfaction with Amplification in Daily Life (SADL) questionnaire. The questionnaire yields a Global satisfaction score and a profile of subscale scores, which address Positive Effects, Service and Cost, Negative Features, and Personal Image. A preliminary evaluation of retest stability was conducted with 104 subjects. Ninety percent critical differences for the various scores ranged from 0.9 to 2.0 score intervals on a 7 point scale. CONCLUSIONS: The SADL scale is both brief enough to be clinically acceptable and comprehensive enough to provide a valid assessment of an inherently multidimensional variable. Additional assessment is necessary to refine understanding of its test-retest properties, explore validity issues, and determine clinical, research, and administrative applications of the data.

Aged↗
PubMed1999

Personality and the subjective assessment of hearing aids.

Relatively little is known about the influence of patients' personality features on the responses they make to self-assessment items used to measure the outcome of a hearing aid fitting. If the personality of the hearing aid wearer has a significant influence on self-report outcome data, it would be important to explore the relevant personality variables and to be cognizant of their effects when using subjective outcome data to justify decisions about clinical services or other matters. This investigation explored the relationship between several personality attributes and responses to the Abbreviated Profile of Hearing Aid Benefit (APHAB). It found that more extroverted patients tend to report more hearing aid benefit in all speech communication situations. In addition, patients with a more external locus of control tend to have more negative reactions to loud environmental sounds, both with and without amplification. Anxiety also played a small additional role in determining APHAB responses. Although personality variables were found to explain a relatively small amount of the variance in APHAB responses (usually around 10%), these outcomes should alert practitioners and researchers to the potential effects of personality variables in all self-report data.

Aged↗
PubMed1998

Accuracy of predicted ear canal speech levels using the VIOLA input/output-based fitting strategy.

OBJECTIVE: The Visual Input/Output Locator Algorithm (VIOLA) is a software-assisted method for prescribing amplification targets and selecting a hearing aid to match the targets. Although the procedure calls for selection and fitting of hearing aids in terms of their pure-tone input/output functions in a coupler, it is assumed that a hearing aid that matches the coupler prescription targets will produce specific amplified speech levels in the patient's ear canal. This investigation evaluated the validity of that assumption. DESIGN: Six hearing aids were evaluated. They were representative of linear and compression processing as well as single- and 2-channel designs. The "subject" was a KEMAR manikin with realistic assumed hearing loss and loudness perception characteristics. Each hearing aid was configured to match the subject's VIOLA prescription as closely as possible. Predicted ear canal speech levels were determined using the prescription rules and modified by the differences between coupler prescription targets and coupler performance of the actual hearing aids. With the subject wearing each hearing aid coupled to an unvented earmold, continuous speech was presented in the sound field and measured, after amplification, in the ear canal. The match between observed and predicted levels of amplified speech indicated the validity of the VIOLA assumptions under examination. RESULTS: The match between predicted and observed levels was good for soft speech input levels. As speech input levels increased, the differences between observed and predicted levels also increased, with the largest differences seen for loud speech inputs. When differences were seen between observed and predicted levels, they were always in the direction of lower than predicted ear canal levels. The differences between observed and predicted levels were attributed to the effects of limiting, effects of compression ratio in wide range compression, the individual subject's field-to-microphone transfer function, and the subject's individual real-ear-to-coupler level difference. CONCLUSIONS: Ear canal speech levels were reasonably close to predicted values, and the deviations from predicted levels were plausibly accounted for by consideration of hearing aid performance. Thus, the approach used by the VIOLA procedure holds considerable promise for extending clinical control over the complex and interactive parameters of nonlinear hearing aids. The results of this study indicate that selection and fitting of hearing aids using the current VIOLA procedure usually will result in the generation of lower than predicted ear canal speech levels, especially for loud speech inputs. However, the accuracy of the procedure could be improved substantially by modification of the software to account for the effects of limiting and those of the compression ratio in systems with compression thresholds lower than the level of unamplified loud speech.

Ear Canal↗
PubMed1997

Effects of duration of a simulated winter thaw on dieback and xylem conductivity of Betula papyrifera.

Stems or roots + stems of potted, 2-year-old paper birch (Betula papyrifera L.) were subjected to simulated winter thaws of various durations in climate-controlled chambers. The simulated thaws induced dieback of shoots of the treated plants. Although the stem thaw treatment did not significantly increase dieback, there were significant (P < 0.05) correlations between growing degree days above 4 degrees C and both shoot dieback and percent reduction in conductive xylem. All trees that received > 60 growing degree days (GDD) > 4 degrees C died back to some extent. Plants in the root + stem thaw treatment that received more than 60 GDD > 4 degrees C showed a significant (P < 0.05) increase in dieback and a significant (P < 0.05) loss of conducting xylem after a period of growth and recovery in the greenhouse, especially in the xylem of 1-year-old stems. Furthermore, higher correlations between GDD > 4 degrees C during a thaw and both the extent of dieback and the loss in conductive xylem were found in trees subjected to the root + stem thaw treatments than in trees exposed only to the stem thaw treatments (P < 0.05). The root + stem thaw treatments also resulted in highly significant relationships (P < 0.05-0.001) between loss in conductive xylem and dieback. The occurrence of dieback in response to winter thaws, and its close correlation with irreversible losses of xylem conductivity due to embolisms, coupled with an inability to refill the xylem because of root damage, support the view that these processes may be key factors in initiating birch decline.

Journal Article↗
PubMed1997

The contour test of loudness perception.

OBJECTIVE: This article presents the underlying rationale, normative data, and reliability data for a test of loudness perception (the Contour Test) that was devised for use in clinical hearing aid fitting. The Contour Test yields data describing the sound level required for each of seven categories of loudness ranging from very soft to uncomfortably loud. DESIGN: Two experiments are described. Experiment 1 yielded norms for the test. The subjects were 23 male and 22 female normal-hearing listeners. Test stimuli included warble tones at six frequencies and broad band speech. Experiment 2 assessed the reliability of the test results. Ten hearing-impaired listeners responded to the test at two frequencies on two occasions separated by several days. Both experiments also evaluated the effect of using different stimulus increment sizes on the measured levels of loudness categories. RESULTS: Based on the data from experiment 1, norms for each category of each stimulus are reported in terms of mean level and typical between-subject variation in responses. Data are provided in HA-12 cm3 coupler levels as well as in hearing levels (dB HL). The shape of the loudness growth function for warble tones was somewhat different from that for speech. When data were expressed in HL, there were no differences in mean loudness category levels across warble tone test frequencies. Thus, test frequencies were combined and equations were generated to describe the upper and lower limits of typical normal performance for warble tone stimuli. These equations can be used to construct a template for clinical comparison of normative values to patient loudness growth curves. Experiment 2 provided information about the test-retest variability of data yielded by the Contour Test. Reliability appears to be similar to that of the few other category scaling tests described in the literature. Most test-retest differences were 6 dB or less. Although a moderate variation in test increment size did not significantly affect the loudness category levels for young normal-hearing listeners, levels corresponding to loudness categories were significantly higher when larger increments were used with elderly hearing-impaired listeners. CONCLUSIONS: Evidence from this and other research indicates that standardized measurement of loudness perception is an achievable goal for clinical practice. The Contour Test appears to offer a viable approach to clinical measurement of loudness perception: It has good patient acceptance and combines fairly rapid administration with acceptable reliability. Details of test procedures and scoring sheets for manual administration can be downloaded from the Internet at www.ausp.memphis.edu/harl. However, it is important to keep in mind that the application of loudness perception data for narrowband stimuli (such as warble tones) to hearing aid prescription is complicated by the need to account for the effects of loudness summation across bandwidth. There is a need for additional research to establish an empirical link between clinically measured loudness perception and optimal amplification characteristics.

Adolescent↗
PubMed1996

A review of past research on changes in hearing aid benefit over time.

Hearing aid benefit refers to a relative change in performance on a particular measure between aided and unaided listening conditions. A number of studies in recent years have investigated the hypothesis that hearing aid benefit increases over time after the initial fitting of the aid. Both objective (speech recognition) and subjective (questionnaire) measures have been used to measure hearing aid benefit. Some studies have reported a positive increase over time in group mean benefit, and some have reported no change in benefit, whereas none have reported a group mean negative change in benefit. However, individual subjects in these studies can show changes in benefit in either a positive or negative direction. The variability across subjects in each study has been large in comparison with the observed amount of benefit increase. In this review of the literature, it is argued that the studies present essentially similar results and the range of values across subjects in the various studies shows considerable overlap. Although there does appear to be a tendency for hearing aid benefit to increase over time, there are other, much stronger, factors influencing changes in hearing aid benefit that make it impossible at present to predict which patients will show a reliable increase (or decrease) in hearing aid benefit over time.

Deafness↗
PubMed1996

Report of the Eriksholm Workshop on auditory deprivation and acclimatization.

The terminology used in studies documenting changes in auditory performance following fitting of hearing aids has been diverse. Definitions for the auditory deprivation effect and auditory acclimatization are offered as a first step in rationalization. Two statements summarize current knowledge concerning auditory deprivation effects and auditory acclimatization, as well as considering the potential implications for research, field trial and clinical practice applications. Potential areas for future research are identified.

Auditory Perception↗
PubMed1996

Benefit acclimatization in elderly hearing aid users.

A previous study from this laboratory indicated that the benefit obtained from a hearing aid in a noisy environment might increase over the first few months of hearing aid use. It was hypothesized that this acclimatization of benefit was due to a process in which the individual optimized his/her use of modified or newly available high-frequency acoustic speech cues. This investigation further explored the effect in 22 elderly individuals with mild to moderate sensorineural hearing losses, fitted unilaterally with hearing aids. None of the subjects was a current or recent hearing aid wearer. Speech intelligibility testing over a 12-week post-fitting period indicated that a significant improvement in benefit was seen for the group as a whole, probably beginning after about 6 weeks of regular hearing aid use. However, the magnitude of improvement was very small for most subjects. Only three individuals experienced a dramatic improvement in their benefit for speech in noise over this period. No evidence was found for a specific role of high-frequency cues. Seven subjects participated in a long-term follow-up in which benefit was measured after several months of use of their newly acquired personal hearing aids. Further increase in benefit was noted but was due exclusively to a decline in performance for unaided listening.

Aged↗
PubMed1995

The abbreviated profile of hearing aid benefit.

OBJECTIVE: To develop and evaluate a shortened version of the Profile of Hearing Aid Benefit, to be called the Abbreviated Profile of Hearing Aid Benefit, or APHAB. DESIGN: The Profile of Hearing Aid Benefit (PHAB) is a 66-item self-assessment, disability-based inventory that can be used to document the outcome of a hearing aid fitting, to compare several fittings, or to evaluate the same fitting over time. Data from 128 completed PHABs were used to select items for the Abbreviated PHAB. All subjects were elderly hearing-impaired who wore conventional analog hearing aids. Statistics of score distributions and psychometric properties of each of the APHAB subscales were determined. Data from 27 similar subjects were used to examine the test-retest properties of the instrument. Finally, equal-percentile profiles were generated for unaided, aided and benefit scores obtained from successful wearers of linear hearing aids. RESULTS: The APHAB uses a subset of 24 of the 66 items from the PHAB, scored in four 6-item subscales. Three of the subscales, Ease of Communication, Reverberation, and Background Noise address speech understanding in various everyday environments. The fourth subscale, Aversiveness of Sounds, quantifies negative reactions to environmental sounds. The APHAB typically requires 10 minutes or less to complete, and it produces scores for unaided and aided performance as well as hearing aid benefit. Test-retest correlation coefficients were found to be moderate to high and similar to those reported in the literature for other scales of similar content and length. Critical differences for each subscale taken individually were judged to be fairly large, however, smaller differences between two tests from the same individual can be significant if the three speech communication subscales are considered jointly. CONCLUSIONS: The APHAB is a potentially valuable clinical instrument. It can be useful for quantifying the disability associated with a hearing loss and the reduction of disability that is achieved with a hearing aid.

Adult↗