Biomedical subjects

R C Beattie

Publications and source records attributed to R C Beattie.

At least 37 records · Page 2Linked to original sources

PubMed1989

Electrode placement and mode of recording (differential vs. single-ended) effects on the early auditory-evoked response.

The effects of electrode placement and mode of recording (single-ended vs. differential) on latencies and amplitudes of the early auditory-evoked response were studied. The following electrode arrays were evaluated (1) vertex-neck, (2) forehead-ear canal (Enhancer I), and (3) vertex-nape. Responses were obtained on 10 normally hearing subjects at sensation levels (SLs) ranging from 15 to 75 dB. Test-retest reliability was excellent for absolute and interwave latencies for all conditions. The reliability of absolute amplitude was poor, and the stability of the amplitude ratios between waves I and V was even worse. No consistent absolute or interwave latency differences were found among electrode montages. The amplitude data suggest that the forehead-ear canal montage is preferred for differential diagnosis because it enhances the probability of detecting wave I. The electrophysiologic threshold for wave I was 5-10 dB lower with the Enhancer I. However, the vertex-neck and vertex-nape combinations are best for estimating auditory sensitivity because they gave the largest wave V amplitudes and 10-dB lower electrophysiologic thresholds. Although the differential vertex-neck and single-ended vertex-nape recordings yielded comparable results, the single-ended montage employs only two electrodes and the test leads do not require rearrangement when the test ear changes.

Adult↗

PubMed1988

Interaction of click polarity, stimulus level, and repetition rate on the auditory brainstem response.

The present study investigated the interaction of click polarity (compression, rarefaction, alternating), repetition rate (2.3 and 9.2 clicks per second), and stimulus level (60, 75, and 90 dB nHL) on auditory brainstem responses. Two tracings (trials) were obtained for each condition using 45 normally hearing subjects. Although no systematic Wave I, III, or V latency or amplitude differences were observed among polarities or repetition rates at the three intensities, statistically significant differences were observed for the following conditions: (1) Wave III latency at 90 dB nHL was longer for the 9.2 repetition rate than for the 2.3 rate, and latencies for compression clicks were shorter than rarefaction clicks; (2) Wave V latencies at 75 dB nHL were longer with compression clicks than with rarefaction clicks; (3) mean Wave V latencies at 60 and 75 dB nHL were slightly longer for the 2.3 click rate than for the 9.2 rate; and (4) Wave V amplitudes at 90 dB nHL were larger for rarefaction clicks than for compression clicks. Because latency and amplitude differences were small and only found in a few conditions, the results indicate that polarity is not a significant variable in normally hearing subjects when using slow repetition rates (less than or equal to 10 clicks per second) at moderate to high intensities (60 to 90 dB nHL). Because repetition rates of less than 10 clicks per second increases examination time but does not improve wave morphology, rates of 10 per second or faster are recommended for gathering normative data. Absolute amplitudes showed considerable intersubject variability, especially for Waves I and III. Intrasubject variability (test-retest) also was substantial. These findings suggest that absolute amplitudes may be of little use for distinguishing normal from pathologic populations.

Acoustic Stimulation↗

PubMed1987

Effects of amplifier type (single-ended vs. differential) and electrode placement on early auditory evoked potentials.

The effects of amplifier type (single-ended versus differential) and electrode location on early auditory evoked potentials were investigated in normally hearing subjects. Each subject was tested with six electrode combinations using 70 dB nHL clicks. One differential recording was made for each subject by placing the non-inverting (A+), inverting (A-), and common (C) electrodes on the vertex, ipsilateral neck, and contralateral neck, respectively. Five single-ended recordings were obtained from each subject. One electrode (positive) was situated on the vertex, whereas the second electrode (negative) was variously placed on (1) ipsilateral mastoid, (2) ipsilateral neck, (3) seventh cervical vertebra, (4) ipsilateral wrist, and (5) lower forehead. Because the vertex-lower forehead montage yielded identifiable responses in only one of 13 subjects, this condition was omitted from data analyses. No statistically significant latency or amplitude differences were observed among the remaining five electrode combinations for Waves I, III, or V. These data suggest that any of the five electrode combinations may be used for recording early auditory evoked potentials. Moreover, it is important to note that the single-ended recordings can yield auditory evoked potentials comparable to conventional differential recordings.

Adult↗

PubMed1986

Latency and amplitude effects of electrode placement on the early auditory evoked response.

This study examined the effects of electrode placement on the early auditory evoked response in normally hearing subjects. The electrodes are termed noninverting, inverting, and common. Ten commonly used electrode combinations were evaluated. Both amplitudes and latencies of Waves I, III, and V were measured for each electrode combination. No mean differences in latencies were observed for Waves I, III, or V with any of the 10 electrode combinations. Similarly, no statistically significant Wave I or Wave III amplitude differences were found among the 10 electrode montages. However, larger Wave V amplitudes were found with placement of the noninverting electrode at the vertex (0.53 mu v) as compared to the upper forehead (0.39 mu v). Moreover, Wave V amplitudes were larger for inverting/common electrode placements at the seventh cervical vertebra/forehead, neck/forehead, and neck/neck (approximately 0.50 mu v) than for mastoid/mastoid and mastoid/forehead placements (approximately 0.40 mu v). Thus, three combinations of electrodes gave the largest Wave V amplitudes. These placements for the noninverting, inverting, and common electrodes, respectively, were (a) vertex-seventh-forehead, (b) vertex-neck-forehead, and (c) vertex-neck-neck.

Adolescent↗

PubMed1986

Relationship between pure-tone and speech loudness discomfort levels among hearing-impaired subjects.

The purpose of this study was to investigate how accurately pure-tone (250-6000 Hz) loudness discomfort levels (LDLs) predict speech (CID Test W-22) LDLs. One ear was tested in each of 50 elderly subjects with mild-to-moderate sensorineural hearing loss. The results revealed poor-to-fair correlations (r = 0.00 to 0.42) and large standard errors of estimate (approximately 9.5 dB). Thus, it was concluded that pure-tone LDLs are not accurate predictors of the speech LDL, and, if the clinician wants to ascertain the upper intensity for listening to speech, this measurement must be made directly.

Aged↗

PubMed1986

Earphone sound pressure output as measured in a standard coupler: effects of microphone protection grid and coupler adapter ring.

The present investigation compared grid and adapter-ring sound pressure levels using two microphones (B&K, models 4132 and 4144) and three earphones (Telephonics, TDH-39P, TDH-49P, and TDH-50). Results revealed greater sound pressure levels with the adapter-ring than with the grid. Mean differences of less than 0.30 dB (SDs approximately 0.1 dB) between adapter-ring and grid conditions were observed below 6000 Hz for the TDH-39P and TDH-49P earphones. Grid/adapter-ring differences for all earphones usually were less than 0.5 dB for frequencies less than or equal to 4000 Hz, and the largest mean difference (2.1 dB) was observed at 6000 Hz. Although these differences between grid and adapter-ring conditions are not clinically significant, several uncontrolled variables can combine to yield cumulative differences that are significant. Investigators should specify whether their instruments were calibrated with the protection grid or the adapter-ring on the microphone.

Audiometry↗

PubMed1986

Normal intelligibility functions for the Auditec CID W-22 test at 30% and 60% time-compression.

Time-compressed speech has been used to identify the site of central auditory disorders and auditory processing problems. Some authors suggest that the determination of audiometric normalcy should include satisfactory performance on a speech intelligibility test sensitive to central auditory dysfunction, such as time-compressed speech. Before scores from patients with auditory disorders can be meaningfully interpreted, however, it is necessary to establish normal performance on standardized recordings. Thus, this study was undertaken to generate speech intelligibility functions in a normal-hearing population using the Auditec CID W-22 recordings with 30% and 60% time-compression. The 30% condition revealed a slope of 3.24% per decibel and the function approached a plateau at 35 dB sensation level (SL). The 60% condition produced a function that increased gradually at 1.8% per decibel over the 20 to 80% intelligibility range. An intelligibility score of 82% was observed at 46 dB SL where the function approached an asymptote. These functions provide a standard against which subjects with central auditory dysfunctions can be compared. The relative difficulty that normal subjects had with the 60% time-compressed speech suggests that this condition may be too difficult for some subjects with central auditory disorders.

Adult↗

PubMed1985

Reliability of threshold, slope, and PB max for monosyllabic words.

The Auditec recordings of the CID W-22 monosyllables were used to generate test and retest intelligibility functions on normally hearing listeners and subjects with mild-to-moderate sensorineural hearing loss. The normally hearing subjects were tested with 50-word lists at SPLs ranging from 15 to 50 dB. Lists of 25 words were used with the hearing-impaired group. The functions were analyzed to assess the reliability of threshold (50% point), slope (20%-80% points), and maximum intelligibility (PB max). The 50% point was obtained at 28 dB SPL for the normally hearing listeners and at a sensation level (SL) of 12 dB respondaic thresholds for the hearing-impaired group. Very stable monosyllabic thresholds were found because 95% of the test-retest values were within 6 dB for both subject groups. Slopes of 4.9% per dB and 2.7% per dB were obtained for the normally hearing and hearing-impaired groups, respectively. Fair reliability was observed; 95% of the test-retest values encompassed a range of +/- 1.9% per dB for the normally hearing subjects and +/- 1.1% per dB for the hearing-impaired group. Although group slopes provide useful information for selecting the range and step size for generating psychometric functions, the value of routinely obtaining slope on an individual basis has not been demonstrated. Even though the same word lists were used for both test and retest measurements, reliability closely agreed with predicted results based on the binomial theorem. In contrast to the large variability for a single list of 25 words, very stable PB max scores were found when two or three scores were averaged on the plateau of the function.

Adult↗

PubMed1985

Early/middle evoked potentials to tone bursts in quiet, white noise and notched noise.

Early/middle auditory-evoked potentials were recorded on 10 normal-hearing adults using 500-, 1 000, and 2 000-Hz tone bursts having 4-ms rise-fall and 1-ms plateau times. The stimuli were presented in quiet, white noise and notched noise at 50, 40, 30, 20 and 10 dB nHL. The noises were selected to improve frequency specificity by masking those regions of the cochlea that do not correspond to the test stimulus. The recording-amplifier system had a bandpass of 55-1 500 Hz; electric activity was measured during the 25-ms post-stimulus interval. The three waves observed during this time interval (P10, N15, and P20) were labeled to reflect polarity and latency. The results revealed no differences among stimulus conditions (quiet, white noise, notched noise) in the number of identifiable responses for any wave at any intensity. Moreover, no P10, N15 or P20 latency differences were observed among conditions at 40 dB nHL and below. When 500-Hz tone bursts were presented at 50 dB nHL, however, significantly shorter response latencies were observed in quiet than when the tone bursts were mixed with white noise or notched noise. It was concluded that frequency specificity can be improved when tone bursts are mixed with notched noise or white noise. White noise is preferred, however, because it can be implemented with less complex instrumentation and calibration than notched noise.

Adult↗

PubMed1984

Effects of rise-fall time, frequency, and intensity on the early/middle evoked response.

Auditory evoked responses to tone pips were recorded on 10 normally hearing adults. Tone pips centered at 500 and 2000 Hz with 1, 2, and 4 ms rise-fall times were presented at intensities of 40, 30, 20, and 10 dB nHL. The band-pass of the recording-amplifier system was set to 55 and 3000 Hz. Responses were measured during the first 25 ms following the onset of the stimulus and the first three prominent waves were labeled P10, N15, and P20. The results indicated that varying rise-fall times from 1 to 4 ms had little effect on the detectability of these waves. Consequently, the 4-ms rise-fall time was recommended because of its greater frequency specificity. The number of identifiable responses was similar for both 500 and 2000 Hz for waves P10, N15, and P20. The similarity in the number of detectable responses suggests that any of these waves may be used as a threshold indicator. The acoustic/physiologic mechanisms underlying the latency changes are discussed.

Acoustic Stimulation↗

PubMed1984

Effects of click duration of the latency of the early evoked response.

The effect of click duration on the latency of waves I, III, and V was investigated by testing 20 normal-hearing subjects at 60 dB HL using electric pulses of 25, 50, 100, 200, and 400 microseconds. Alternating condensation and rarefaction clicks were used. The results revealed similar and nonsignificant latency differences for the 25-, 50-, and 100-microseconds pulses. However, the 100 microseconds duration is preferred to the 25-microseconds pulse because the latter reduced the maximum measurable hearing loss by about 13 dB. The results also showed that latencies increased approximately 0.10 ms as duration increased from 100 to 200 microseconds and by 0.20 ms when duration increased from 100 to 400 microseconds. Although such differences by themselves are small, they can combine with other stimulus or recording variables to be clinically significant. Therefore, it is important to control click duration when normative data are generated. A second experiment was conducted to assess the interaction of polarity (condensation, rarefaction, and alternating) and pulse duration (100 and 400 microseconds) on the wave V latency. These data revealed no latency differences among polarities at either duration.

Acoustic Stimulation↗

PubMed1984

Comfortable loudness levels for speech: effects of signal-to-noise ratios and instructions.

The effect of S/N from +20 to -10 db on loudness levels of connected discourse with or without background cafeteria noise was investigated for one set of instructions sampling the most comfortable loudness level (MCLL) and a second set sampling the upper limit of CLL. Normal young adults (N:16) showed no significant differences for either set of instructions in quiet or from 20 to 0 db S/N but mn MCLL was about 5 db lower at -10 db. Elderly hearing-aid wearers (N:10, mn age: 77 yrs) yielded mn differences across S/N of less than 5 db for either set of instructions. No data indicate that the speech CLL accurately predicts optimal hearing-aid gain, while the literature indicates that occasionally the desired maximum intelligibility frequently is not obtained at the MCLL. We question whether MCLL for speech justifies its measurement. A discussion is presented of the Comfort Level Method of adjusting gain in hearing-aid evaluations and a perhaps preferable Threshold Level Method in which the test stimulus is presented at a level corresponding to the predicted threshold and the aid's volume control is adjusted until S just perceives the signal.

Adult↗

PubMed1983

Slope characteristics of CID W-22 word functions in elderly hearing-impaired listeners.

Some variables affecting the slope of monosyllabic word functions were investigated among subjects having mild-to-moderate sensorineural hearing loss. Slope is an important variable because it determines the intensity range and the step size that is likely to accurately and efficiently describe the function. Eighty-one ears from 60 elderly subjects were tested with the Auditec recordings of the CID W-22 words. Slopes were computed between the 20 and 80% intelligibility points from the individual functions. The results indicated that the magnitude of hearing loss did not affect the slope of the intelligibility function. That is, slopes remained at approximately 3% per dB even though spondaic thresholds varied over a 45-dB range (15-60 dB HTL). The audiometric configuration was found to affect slope, although this relationship was weak (r = .30). As the audiogram progressed from flat to steeply falling, the slope decreased from about 3.5% per dB to 2.5% per dB. With subjects having flat and falling audiograms, slope was steeper for the 20-50% intelligibility segment (4.3% per dB) than for the 50-80% interval (2.9% per dB). These subjects also exhibited substantial differences in mean slope, depending on the procedure selected for computations. The mean of individual slopes was steepest (3.3% pr dB), whereas the mean slope was only 2.4% per dB when computed from the function derived in the conventional manner by averaging intelligibility scores at fixed intensities.

Aged↗

PubMed1982

Comfortable speech listening levels: effects of competition and instruction.

This study was designed to investigate the effects of a background four=falker babble on the comfortable loudness level (CLL) for speech (California Consonant Test stimuli) using three sets of instructions. Three groups of twelve normal-hearing subjects each were tested using an adjustment psychophysical method. Each group received one of three sets of instructions, which were selected to sample the lower limit, most comfortable, or upper limit of the CLL range. Speech CLLs were initially obtained in quiet, then in the presence of four levels of competition (50 to 80 dB SPL, or 70 to 100 dB SPL), and finally in quiet again. Very similar means were found for the two quiet conditions for all instructions, indicating that the intervening four-talker conditions did not alter the final quiet CLL. The four-talker babble resulted in very substantial CLL shifts fro the lower limit instructions, although relatively little effect was observed on the upper limit of the CLL range. These differential effects were reflected as a systematic reduction in th CLL range with increasing competition levels. Whereas there was approximately 60-dB CLL range when the lower and upper limits were measured in quiet, introduction of the 80-dB SPL competition reduced this range to 16 dB. These data raise questions as to which instructions are most appropriate when CLLs are used to select and evaluate hearing aids, and how much, if any, background competition should be employed when making these measurements.

Adult↗

PubMed1982

Relationships among speech threshold, loudness discomfort, comfortable loudness, and PB max in the elderly hearing impaired.

The purposes of this study were (1) to determine the effect of the severity of hearing loss on the most comfortable loudness level (MCL) and the loudness discomfort level (LDL), and (2) to assess the efficacy of obtaining maximum intelligibility (PB max) at MCL and/or LDL. One hundred twenty-nine ears were tested from seventy-four elderly subjects having mild to moderate sensorineural hearing losses. The results showed that mean MCLs and LDLs remained fairly constant as spondaic thresholds increased from 5 to 55 dB HTL. The data also exhibited considerable intersubject variability and indicated that MCLs and LDLs could not be closely predicted from threshold. Thus, for most clinical purposes MCL and LDL must be measured directly. This study also indicated that measuring speech intelligibility at MCL approximated PB max (+/- 12 percent) only about two-third of the time. Thus, decisions concerning auditory functioning may frequently be inaccurate if intelligibility is measured only at MCL. Neither can LDL be the single intensity at which speech intelligibility is measured, at least with elderly patients, since one in ten scores did not closely approximate PB max. Consequently, we concur with previous investigators who recommend generating an entire intelligibility function. The present findings also suggest that hearing aid users may not receive optimal benefit if their hearing aid is adjusted to MCL, and that improved intelligibility may be achieved a higher volume control settings. The hearing aid evaluation process should investigate this possibility.

Aged↗

PubMed1982

Bone-conduction force values for the sensorineural acuity level (SAL) test.

The sensorineural acuity level (SAL) test has the advantages of eliminating the questions of when to mask and how much masking to use in audiometry, greater efficiency in assessing cochlear sensitivity than conventional bone-conduction (bc) testing, and fewer and less serious errors in measuring cochlear sensitivity. However, a major limitation of the SAL test is that norms are generally determined using the time-consuming real-ear calibration method. A more satisfactory procedure is to establish normative force levels using an artificial mastoid. Normal-hearing young adults (N:18) were tested with pure tones and with spondees, in the presence of bc white noise delivered to a Radioear B-70-AA vibrator and calibrated with a Bruel & Kjaer 4930 artificial mastoid. Force levels in db re 1 mu Newton found to produce a 30-db HTL in bc white noise were: 104, 94, 94, 94, and 100 for tones of .5, 1, 2, and 4 kc/s, and for spondees, in that order. Force levels for narrow bands of noise centered at .5, 1, 2, and 4 kc/s were 104, 84, 76, and 86 db in that order. Clinicians are cautioned to use these force values with reservation unless their bone vibrator, artificial mastoid, and noise spectra are similar to those used in the present study. If clinics choose to obtain their own baseline data, artificial mastoid measures can still serve as a convenient reference to monitor equipment stability. The use of the SAL is urged as part of a test battery for assessing the presence and degree of conductive pathology.

Adult↗

PubMed1982

Effects of white noise on the most comfortable level for speech with normal listeners.

This study assessed the effects of noise level on the most comfortable level (MCL) for discursive speech. Normal young adults (N:25) were instructed to search thoroughly around their MCL by Bekesy tracking. Mean MCL in quiet was 82.5 db SPL (S.D. = 11.1 db) which was statistically indistinguishable from group MCLs in noises of 55 and 70 db SPL. However, MCL rose to 90.9 and 100.3 db in noises of 85 and 100 db SPL, respectively. These mean MCLs were somewhat higher than observed previously and may be due to differences in instructions and procedures in threshold-tracking.

Adult↗

PubMed1981

Test-retest stability and effects of psychophysical methods on the speech loudness discomfort level.

It is generally agreed that the saturation sound pressure level of a hearing aid should not exceed the patient's loudness discomfort level (LDL) for speech. This study investigated (1) the stability of the test and retest LDLs when obtained on different days using McCandless's and Berger's instructional sets and (2) the effects of a psychophysical method (adjustment versus limits) on the speech LDL using McCandless's instructions. Good reliability was observed since one-half of the listeners had test-retest differences of 2 dB or less and nearly all subjects obtained LDLs within 8 dB. The mean LDLs for the respective methods of adjustment and limits were 86.8 and 92.9 dB SPL, and statistically significant. Additionally, a significant interaction between the two methods was observed. The LDL measurement is also discussed in relation to other tests used to evaluate hearing aid performance.

Adolescent↗