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Biomedical subjects

H Dillon

Publications and source records attributed to H Dillon.

At least 37 records · Page 2Linked to original sources
PubMed1993

Hearing aid evaluation: predicting speech gain from insertion gain.

In this study, hearing aid gain for speech was defined as the difference in level between the aided and unaided performance-intensity functions measured at any specific value of percentage of items correct. The articulation index method was used to predict speech gain based on the subject's unaided sound field thresholds, ambient room noise, hearing aid internal noise, hearing aid insertion gain, and the subject's unaided performance-intensity function. Predicted speech gain agreed with measured speech gain with rms errors of only 3 dB for 11 subjects with mild or moderate hearing loss tested with monosyllabic words and continuous discourse. The speech gain provided by a hearing aid can thus be predicted from electroacoustic measures, which generally can be obtained in a shorter time. Importance functions believed to be applicable to nonsense syllables, words, and continuous discourse were used to make the predictions, but prediction accuracy was not affected by the importance function chosen. Speech gain measured with the monosyllabic word test was highly correlated with speech gain measured with the continuous discourse test, provided that similar presentation levels were used.

Aged↗
PubMed1992

Cephalexin and penicillin in the treatment of group A beta-hemolytic streptococcal throat infections.

OBJECTIVE: To determine whether cephalexin or penicillin is more effective in the treatment of group A beta-hemolytic streptococcal tonsillopharyngitis in children. DESIGN: Randomized, double-blind, crossover study conducted from 1981 to 1984. SETTING: Seven pediatric practices in the United States, including private offices and pediatric clinics. PARTICIPANTS: Of the 654 patients, 525 children and adolescents with clinical evidence of tonsillitis or pharyngitis and throat cultures positive for group A beta-hemolytic streptococcal infection were evaluable. Eighty percent of patients completed the study; none were withdrawn because of adverse reaction. SELECTION CRITERIA: Children and adolescents who had acute illness suggestive of group A beta-hemolytic streptococcal infection were enrolled in the study. Treatment was continued if the throat culture was positive for group A beta-hemolytic streptococcal infection. INTERVENTIONS: Four doses of cephalexin and penicillin (27 mg/kg per day) were prescribed to be taken on an empty stomach for 10 days. MEASUREMENTS/MAIN RESULTS: Symptomatic clinical failure occurred in 8% of penicillin-treated patients and in 3% of cephalexin-treated patients. Bacteriologic failure rates were 11% in the penicillin treatment group and 7% in the cephalexin treatment group. The combined treatment failure rate of clinical relapse plus asymptomatic bacteriologic failure was 19% in the penicillin treatment group and 10% in the cephalexin treatment group. Paired antistreptolysin-O titer increased significantly in 62.3% of penicillin-treated patients and in 64.2% of cephalexin-treated patients. Similarly, anti-DNase B titers rose 52.2% in penicillin-treated patients and 52.4% in cephalexin-treated patients. CONCLUSION: Cephalexin is a more effective drug than penicillin in the treatment of group A beta-hemolytic streptococcal throat infection in children.

Adolescent↗
PubMed1991

Allowing for real ear venting effects when selecting the coupler gain of hearing aids.

Vents in hearing aids have two major effects on the insertion gain of a hearing aid: they let low-frequency sound in without amplification, and they reduce the low-frequency gain of sound transmitted through the hearing aid. Their net effect on low-frequency gain can thus be either negative or positive. This paper shows how to allow for both of these effects. One of the results is that for many hearing-impaired clients, there is a range of coupler gain curves which will result in the required insertion gain. The tables in this article are arranged to enable the user to specify a desired vent, and then determine the allowable range of coupler gains that will achieve a desired insertion gain to within a specified tolerance. The results of various studies comparing coupler gain and insertion gain are also compared and combined. The calculation method outlined in this paper can predict low-frequency real ear insertion gain for the individual subject with a prediction accuracy (root-mean-square-error) of 3.6 dB.

Ear↗
PubMed1987

Accuracy of twelve methods for estimating the real ear gain of hearing aids.

The gain of a hearing aid was measured on each of eight subjects using a variety of functional (subjective) and insertion (objective) gain methods. Each measurement was repeated on subsequent days and the hearing aid gain was also determined in several couplers and on KEMAR. The multiple measurements enabled an accurate estimate of the "true" gain of the aid on each subject to be determined. The real ear gain measured by each of the individual methods was then compared with this true gain estimate and the relative accuracy of each method was quantified. Of the clinically feasible methods, probe microphone measurement of insertion gain proved to be the most accurate. Few significant differences were found between functional gain and insertion gain. Estimation of real ear gain on the basis of coupler gain appeared to be a reasonable, though not recommended approach.

Audiometry↗
PubMed1986

The National Acoustic Laboratories' (NAL) new procedure for selecting the gain and frequency response of a hearing aid.

A new procedure is presented for selecting the gain and frequency response of a hearing aid from pure-tone thresholds. This was developed from research which showed that a previous procedure did not meet its aim of amplifying all frequency bands of speech to equal loudness but that frequency responses which did so were considerably more effective. Measurements of 30 sensorineurally hearing-impaired ears (27 subjects), together with data from other studies, were analyzed to determine the best formula for predicting the optimal frequency response, for each individual, from the audiogram. The analysis indicated that a flat audiogram would require a rising frequency response characteristic of about 8 dB/octave up to 1.25 kHz and thereafter a falling characteristic of about 2 dB/octave. Variations in audiogram slope required about one-third as much variation in response slope. Three frequency average (3FA) gain was calculated to equal the 3FA gain of the previous procedure. Forty-four subjects (67 aided ears) fitted by the new procedure were evaluated by paired comparison judgments of the intelligibility and pleasantness of speech. The prescribed frequency response was seldom inferior to, and usually better than, any of several variations having more, or less, low and/or high-frequency amplification. On the average, used gain was approximately equal to prescribed gain. It is concluded that the new formula should prescribe a near optimal frequency response with few exceptions.

Audiometry, Pure-Tone↗
PubMed1986

Updated performance requirements for hearing aids.

This article updates the design specifications for a family of hearing aids required by the National Acoustic Laboratories (NAL) in order to meet the needs of its clients. The required range of coupler gains and frequency responses of behind-the-ear (BTE), in-the-ear (ITE) and body-level (BL) hearing aids has been recalculated on the assumption that the aids will be fitted using the new Byrne-Dillon procedure for selecting gain and frequency response. In the light of recently acquired data, the specification of maximum allowable internal noise has been changed slightly and no relaxation of the equivalent input noise criterion for high gain aids is allowed. Since the Byrne-Dillon procedure demands a somewhat smaller (though still quite substantial) range of hearing aid response shapes, the subdivision of the total response requirements has also been repeated. The number of hearing aid models specified is still 18, but the number of fitter-adjusted controls has been reduced from 6 to 4. The fitter-adjusted controls comprise a maximum power output (MPO) level control, an MPO shape control, a low-tone cut control and a high-tone cut control, with MPO control being achieved by means of low-distortion compression limiting.

Australia↗
PubMed1986

Performance requirements for hearing aids.

The requirements for hearing aid frequency responses, SSPL characteristics, compression limiting, directional response, and internal noise are examined. On the basis of the assumptions made, aids would best serve the hearing impaired if they had flat very-low-frequency gains (and various mid- and high-frequency gains), SSPL responses adjustable in shape and level, directional responses, and internal noise levels below a recommended criterion level.

Aged↗
PubMed1984

The effects of multichannel compression/expansion amplification on the intelligibility of nonsense syllables in noise.

The effects of six-channel compression and expansion amplification on the intelligibility of nonsense syllables embedded in speech spectrum noise were examined for four hearing-impaired subjects. For one condition (linear) the stimulus was given six-channel amplification with frequency shaping to suit the subject's hearing loss. The other condition (nonlinear) was the same except that low level inputs, to any given channel, received expansion amplification and high level inputs received compression. For each condition, each subject received the nonsense syllables at three different input levels, representing low, average, and high intensity speech. The results of this study, like those of most other studies of multichannel compression, are mainly negative. Nonlinear processing (mainly expansion) of low intensity speech resulted in a significant degradation of speech intelligibility for two subjects and in no improvement for the others. One subject showed a significant improvement in intelligibility for the nonlinearly processed average intensity speech and another subject showed significant improvement for the high intensity input (mainly compression). Clearly, nonlinear processing is beneficial for some subjects, under some listening conditions, but further research is needed to identify the relevent characteristics of such subjects. An acoustic analysis of selected items revealed that the failure of expansion to improve intelligibility was primarily due to the very low intensity consonants /e/ and /k/, in final position, being presented at an even lower intensity in the expansion condition than in the linear condition. Expansion may be worth further investigation with different parameters. Several other problems caused by the multichannel processing were also revealed. These included alteration of spectral shapes and band interaction effects. Ways of overcoming these problems, and of capitalizing on the likely advantages of multichannel amplification, are currently being investigated.

Hearing Aids↗
PubMed1984

Pharmacokinetics of cefoperazone in newborn infants.

We studied the disposition of two 100 mg/kg doses of cefoperazone given intravenously 12 hr apart in ten newborn infants. Peak levels were a mean 352 +/- SD 75 and 371 +/- 68 micrograms/ml immediately after the first and second dose, respectively, with corresponding troughs of 60 +/- 10 and 76 +/- 28 mcg/ml 12 hr later. Mean half-life was 6.5 +/- 0.9 hr and decreased with increasing gestational age and birthweight. Steady-state volume of distribution averaged 410 +/- 40 ml/kg and total clearance 0.78 +/- 0.13 ml/min X kg and neither varied with gestational age nor birthweight. No untoward physical or laboratory effects were noted. Additional studies including postnatal age effects on kinetics, efficacy, and cerebrospinal fluid penetrance are necessary prior to widespread use of this potentially valuable antibiotic in newborn infants.

Cefoperazone↗
PubMed1983

The effect of test difficulty on the sensitivity of speech discrimination tests.

The sensitivity of speech discrimination tests is defined as being large if a small change in experimental conditions causes a large and repeatable change in test score. The aim of this paper is to investigate ways by which test sensitivity can be maximized. The effect of test difficulty on sensitivity is examined by the use of a model based on signal detection theory and subjective similarity rating concepts. For several sets of assumptions about the parameters underlying the perceptual processes, the model indicates that test difficulty should be in the range 73% to 87% to achieve the maximum sensitivity with speech tests using between four and eight response foils. The model results also indicate that the sensitivity increases with the number of response foils. When the variation of test reliability with test difficulty is taken into account, the test difficulty which maximizes the sensitivity/reliability trade-off lies in the range 85% to 90%. It is argued that irrespective of the optimum test difficulty, a maximally sensitive test will contain items equal to one another in difficulty.

Humans↗
PubMed1983

The selection of modulation rates for frequency modulated sound field stimuli.

Frequency modulated (FM) tones are used in sound field audiometry in order to avoid problems caused by standing waves. The FM stimuli to be used must be specified in terms of bandwidth (twice the frequency deviation), modulation rate and modulation waveform. This paper deals with selection of the modulation rate. Improved field uniformity obtained with FM tones relies upon the ear averaging the sound intensity as the frequency sweeps. The modulation rate must be less than about 1/3 of the frequency deviation in order to provide sufficient spectral components to ensure reasonable averaging across the frequency band. If the rate is too low threshold will be determined by the peak intensity during the sweep. For normal listeners a modulation rate of 5 Hz is just satisfactory but in the hearing impaired a higher rate is required because of their altered temporal integration characteristics. A suitable value for the modulation rate can be inferred from the literature on temporal integration and the acoustic characteristics of typical test rooms. The optimum rate increases with the stimulus centre frequency, but a constant rate of 20 Hz appears to be acceptable.

Audiometry↗