Biomedical subjects

R C Beattie

Publications and source records attributed to R C Beattie.

At least 19 recordsLinked to original sources

PubMed2001

Normative behavioral thresholds for short tone-bursts.

Although tone-bursts have been commonly used in auditory brainstem response (ABR) evaluations for many years, national standards describing normal calibration values have not been established. This study was designed to gather normative threshold data to establish a physical reference for tone-burst stimuli that can be reproduced across clinics and laboratories. More specifically, we obtained norms for 3-msec tone-bursts presented at two repetition rates (9.3/sec and 39/sec), two gating functions (Trapezoid and Blackman), and four frequencies (500, 1000, 2000, and 4000 Hz). Our results are specified using three physical references: dB peak sound pressure level, dB peak-to-peak equivalent sound pressure level, and dB SPL (fast meter response, rate = 50 stimuli/sec). These data are offered for consideration when calibrating ABR equipment. The 39/sec stimulus rate yielded tone-burst thresholds that were approximately 3 dB lower than the 9.3/sec rate. The improvement in threshold with increasing stimulus rate may reflect the ability of the auditory system to integrate energy that occurs within a time interval of 200 to 500 msec (temporal integration). The Trapezoid gating function yielded thresholds that averaged 1.4 dB lower than the Blackman function. Although these differences are small and of little clinical importance, the cumulative effects of several instrument and/or procedural variables may yield clinically important differences.

Acoustic Stimulation↗

PubMed2000

Effects of sample size on the noise floor and distortion product otoacoustic emissions.

This study investigated the effects of sample size on the noise floor and distortion product otoacoustic emissions (DPOAEs) in 55 normal-hearing subjects as a function of intensity. More specifically, we investigated the effects of sample size (12-400 sweeps) as a function of intensity (L1 = L2 = 35, 45 and 55 dB SPL), firstly, on the identifiability of DPOAEs (2F1-F2), secondly, on the noise floor adjacent to DPOAEs, and thirdly, on the magnitude of DPOAEs centred around geometric means of 531 Hz, 1,000 Hz, 2,000 Hz and 4,000 Hz. Testing was conducted with a commercially available system for measuring DPOAEs (Grason-Stadler, GSI-60). A constant F2:F1 ratio of 1.21 was used. As sample size increased from 12 to 400 sweeps, the noise floors decreased by about 13 dB; this closely corresponds to the expected 15 dB reduction based on the square root rule of noise reduction. The highest noise floors were measured at 531 Hz and the lowest noise floors at 2,000 Hz and 4,000 Hz. Identifiability increased as intensity increased from 35 to 55 dB SPL and as sample size increased from 12 to 400 sweeps for all stimulus conditions. Mean DPOAEs for all frequencies (531-4,000 Hz) appeared to decrease as sample size increased, particularly at stimulus levels of 35 dB and 45 dB SPL. These results may be explained by a reduction in the noise levels within the bandwidth of the DPOAE bin. That is, the DPOAE bin is comprised of the DPOAE plus background noise and these two quantities are not separated within the measured bin. Because the magnitude of bin containing DPOAEs is critically dependent on sample size, clinicians should carefully document this variable when collecting normative data. Similarly, clinicians who compare the magnitude of their DPOAEs to published data should note the sample size employed.

Acoustic Stimulation↗

PubMed2000

Effects of sample size on the reliability of noise floor and DPOAE.

This study investigated the effects of sample size on the test-retest reliability of the amplitude of distortion product otoacoustic emissions (DPOAE) (2f1-f2) and on the noise floor. Four pairs of primary frequencies (fl and f2) with geometric means of 531, 1000, 2000 and 4000 Hz were presented to 55 normal-hearing women at intensity levels of 35, 45 and 55 dB SPL (L1 = L2). Sample sizes of 12, 25, 50, 100, 200 and 400 sweeps were averaged. The results revealed that sample size, frequency, and intensity had little effect on the standard error of measurement. Thus, the DPOAE data were combined across all conditions and yielded a standard error of measurement of 2.2 dB. To assess whether two DPOAE measurements are statistically significant (e.g. before and after drug administration), the standard error of measurement of the difference between two values was calculated (3.1 dB). Thus, by use of the 95% confidence interval, the difference between two DPOAE is statistically significant if it exceeds approximately 6 dB.

Acoustic Stimulation↗

PubMed1998

Normative Wave V latency-intensity functions using the EARTONE 3A insert earphone and the Radioear B-71 bone vibrator.

Early auditory evoked response (ABR) audiometry is useful for estimating auditory sensitivity in infants and other difficult-to-test populations. Several investigations advocate using bone-conducted stimuli, in addition to air-conducted stimuli, for screening infants with hearing loss or for ascertaining the presence and magnitude of a conductive hearing loss. The present study was designed to gather normative Wave V latency-intensity data with an insert earphone (EARTONE 3A) and a bone vibrator (Radioear B-71). Forty normal-hearing subjects were tested with air-conducted and bone-conducted clicks at intensities of 55, 40, 30, 20, and 10 dB SL. The stimulus waveforms showed a click onset delay of 0.1 ms for the 3A insert earphone. It is important to note that our ABR latencies were not adjusted to account for these differences. The results revealed that both the air-conduction and bone-conduction functions exhibited Wave V latencies of 7.0 ms at 55 dB SL. Although both functions exhibited increased latencies as intensity decreased to 10 dB SL, the air-conducted clicks yielded somewhat longer latencies than the bone-conducted clicks. To allow direct comparison of the air-conduction and bone-conduction latency-intensity function, the bone-conduction function must be corrected by approximately +0.3 ms at 40 dB, +0.4 ms at 30 dB, +0.5 ms at 20 dB, and +0.8 ms 10 dB nHL. No correction is needed at 55 dB. The present study suggests that it may not be appropriate to apply a single correction value (e.g., 0.5 ms) to the entire latency-intensity function. If clinicians elect to use published latency-intensity data, they must employ procedure similar to those that were used to collect the normative data. Otherwise, individual clinics should generate normative latency-intensity data using well-defined procedures. An alternative to generating latency-intensity functions is to compare ABR air-conduction and bone-conduction thresholds. This procedure is advantageous because threshold responses are not as sensitive as latency measures to slight changes in instrumentation and procedures. The normative air-conduction and/or bone-conduction values presented in this investigation are offered as a baseline for either latency-intensity or threshold comparisons.

Acoustic Impedance Tests↗

PubMed1997

Effects of rise-fall time and repetition rate on the auditory brainstem response to 0.5 and 1 kHz tone bursts using normal-hearing and hearing-impaired subjects.

This study was designed to compare normal-hearing and hearing-impaired auditory brainstem response (ABR) thresholds using 1 msec rise-plateau-fall times with ABR thresholds using two-cycle rise-fall times and a one-cycle plateau. Because tone bursts of 500 Hz and 1000 Hz were selected for study, the respective two-cycle rise-fall times were 4 msec and 2 msec. This study also compared ABRs using repetition rates of 25.6/sec and 40/sec to determine if these two rates yield different ABR thresholds. Sixteen normal-hearing subjects and 13 subjects with mild-to-moderate sensorineural hearing loss participated in this study. The results revealed that increasing rise-fall time from 1 msec to 4 msec at 500 Hz, and from 1 msec to 2 msec at 1000 Hz, had little or no effect on the ABR threshold. Moreover, no differences in ABR thresholds were observed for the two repetition rates. Thus, these data suggest that differences in repetition rate do not account for the discrepancies in thresholds among studies. The predication of pure-tone thresholds in dB HL from ABR thresholds in dB nHL was assessed using correction factor and regression procedures. Both methods yielded a reasonable approximation of the degree and configuration of hearing loss. Approximately 85% of pure-tone thresholds were predicted within +/- 10 dB at 500 Hz and 1000 Hz. The present investigation suggests that either the 1 msec or 2-cycle-rise-fall times may be used for clinical purposes.

Adolescent↗

PubMed1997

Normal and hearing-impaired word recognition scores for monosyllabic words in quiet and noise.

The effects of noise on word recognition scores were assessed with normal-hearing and hearing-impaired subjects. Fifty-one normal-hearing subjects were tested at 50 dB HL using signal-to-noise ratios (S/Ns) of 5, 10, and 15 dB. Thirty subjects with mild-to-moderate sensorineural hearing losses were tested in quiet and in noise at S/Ns of 10 dB and 15 dB. Monosyllabic words in a Multitalker Noise were selected for testing. Mean scores for the normal-hearing subjects were 45% at the 5 dB S/N, 74% at the 10 dB S/N, and 87% at the 15 dB S/N. For the hearing-impaired subjects, scores were 85% in quiet, 60% at the 15 dB S/N, and 40% at the 10 dB S/N. These results suggest that background noise which is mildly disruptive for normal hearing subjects can be highly disruptive to hearing-impaired subjects. Moreover, these findings indicate that subjects with mild-to-moderate sensorineural hearing loss require a more favourable S/N than normal listeners to achieve comparable word recognition scores. Test-retest differences for word recognition scores revealed variability that agreed closely with predictions based on the binomial distribution for both groups of subjects. Speech-in-noise abilities must be measured directly because regression equations revealed that speech-in-noise scores cannot be predicted accurately from either puretone thresholds or speech-in-quiet scores. Word recognition functions are presented from several hearing-impaired subjects and demonstrate the value of testing in noise.

Adolescent↗

PubMed1997

IHAFF loudness contour test: reliability and effects of approach mode in normal-hearing subjects.

This study investigated the effects of approach mode (ascending, descending, random) on the normal loudness function using the Loudness Contour Test suggested by the Independent Hearing Aid Fitting Forum. We also assessed how increasing the number of trials from one to five affects the short-term reliability of the Loudness Contour Test. Additionally, we examined the relationship between loudness judgments (very soft to uncomfortably loud) for warble tones and loudness judgments for speech. Thirty-one normal-hearing subjects were tested using 500-Hz and 3000-Hz tones and speech (CID W-22 words preceded by a carrier phrase). The results revealed that 5- to 12-dB higher SPLs were found with the descending approach than with the ascending approach. The reliability results suggest that it is not beneficial to present more than one or two trials when administering the Loudness Contour Test. The true sound pressure level (SPL) for a given loudness category will fall within +/-10 to 12 dB of the obtained SPL approximately 95 percent of the time. This 20- to 24-dB range is fairly large and it is questionable whether reliability is sufficient to justify obtaining individual loudness measurements. When the relationship between warble tones and speech was investigated, the results revealed an overall standard error of estimate of approximately 8 dB. These data suggest that warble tones are not accurate predictors of the corresponding loudness categories for speech. If the clinician wants to ascertain SPLs that correspond to the various loudness categories for speech, then direct measurement with a speech stimulus appears necessary.

Audiometry, Pure-Tone↗

PubMed1994

Effects of signal-to-noise ratio on the auditory brainstem response to tone bursts in notch noise and broadband noise.

This study investigated the effects of signal-to-noise ratio (S/N) on the latency and amplitude of the auditory brainstem response (Wave V) using 1 and 4 kHz tone bursts in notch noise and broadband noise. Normal listeners were presented with 40 dB and 80 dB nHL tone bursts in quiet and in noise at S/Ns of 10, 15, 20, and 25 dB. The latency data suggest that at low intensity levels tone bursts in quiet may be preferred to testing in noise. At moderate and high intensities, however, notch noise or broadband noise is preferred to the quiet condition because of the improved frequency specificity provided by the masking. When testing patients with flat or gradually sloping audiometric configurations at moderate to high intensities with 4 kHz, either notch noise or broadband noise with an S/N of 15 to 25 dB may be used. When presenting 1 kHz tone bursts at high intensities to patients having flat and gradually sloping losses, a notch noise at S/Ns of 10 to 25 dB is preferred to broadband noise. The use of a notch noise at 10 dB S/N may be the stimulus of choice when testing patients with moderately to steeply sloping audiometric configurations with 1 or 4 kHz tone bursts.

Acoustic Stimulation↗

PubMed1994

Effects of signal-to-noise ratio on the auditory brainstem response to 0.5 and 2 kHz tone bursts in broadband noise and highpass noise or notch noise.

This study investigated the effects of signal-to-noise ratio (S/N) on the latency and amplitude of th3 auditory brainstem response (Wave V) using 0.5 and 2 kHz tone bursts in highpass/notch noise and broadband noise. Normal listeners were presented with 40 and 80 dB nHL tone bursts in quiet and in noise at S/Ns of 10, 15, 20, and 25 dB. The latency data suggest that, at moderate and high intensities, highpass/notch noise or broadband noise is preferred to the quiet condition because of the improved frequency specificity provided by the masking. Highpass/notch noise appears preferable to broadband noise when testing at moderate to high levels because the former produced larger Wave V amplitudes to 0.5 and 2 kHz tone bursts at 80 dB nHL. The 80 dB nHL data also suggest that S/Ns of 15-25 dB should be selected when the highpass/notch noise is mixed with moderate to high level 0.5 and 2 kHz tone bursts. In contrast to the 80 dB nHL data, Wave V amplitudes to the 40 dB nHL tone bursts suggest that testing in quiet may be preferred to testing in noise when 0.5 and 2 kHz tone bursts are presented at low levels. This is because of the simplicity of instrumentation and because larger amplitudes were observed in quiet than in noise.

Acoustic Stimulation↗

PubMed1992

Effects of notch noise bandwidth on the auditory brainstem response to clicks.

The effects of notch width of notch masking noise on the auditory brainstem response (ABR) were investigated with ten normal-hearing subjects. Wave V latencies and amplitudes were measured to a click in quiet and in the presence of noise with notches centered around 1000 Hz and 4000 Hz. Notch width was either 0.5, 1.0, 1.5, 2.0, or 2.5 octaves. A 95 dB SPL broadband noise was necessary to mask a 65 dB nHL click at an effective level of 73 dB nHL. All ten subjects at both 1000 Hz and 4000 Hz yielded identifiable responses for the click in quiet and for the 2.5 octave and 2.0 octave conditions, and eight or nine subjects responded to the 1.5 octave notch noise. In contrast, no responses were observed to the 0.5 octave condition, and only three or four subjects responded to the 1.0 octave notch noise. These findings suggest that when ABRs are obtained to 65 dB nHL clicks in notch noise, the notch width should exceed 1.0 octave. Moreover, because of the relatively low amplitudes elicited with the 1.5 octave bandwidth, it appears preferable to select notches that are 2.0 to 2.5 octaves wide. Considering the wide bandwidth required, the high noise levels necessary to mask clicks, high ABR thresholds, and the difficulty setting the signal-to-noise ratio, it appears that tonepips are more promising than clicks in notch noise for assessing frequency specific ABRs.

Acoustic Stimulation↗

PubMed1992

Effects of interstimulus interval on slow phase velocity to ipsilateral warm air caloric stimulation in normal subjects.

This study investigated the effects of interstimulus interval on slow phase velocity (SPV) to ipsilateral warm air caloric stimulation in normal subjects. Results suggest that about 3 minutes should intervene between the offset of one irrigation and the onset of the second irrigation. This finding supports the hypothesis that carryover effects are likely only when nystagmus from the preceding irrigation overlaps the subsequent irrigation. If correct, clinicians do not have to wait a fixed time period between stimuli, but can initiate caloric stimulation as soon as nystagmus has ceased from the preceding irrigation. This recommendation compensates for individual and procedural differences. Test-retest reliability also was investigated. Findings suggest that when immediate test-retest differences exceed approximately 6 degrees/second (95% confidence interval), the examiner should administer additional trials until stability is ascertained. Moreover, unusual or significant findings should be verified with repeat testing.

Adult↗

PubMed1992

Auditory brainstem response to tone bursts in quiet, notch noise, highpass noise, and broadband noise.

This study investigated the effects of tone bursts (1000 Hz, 2000 Hz, and 4000 Hz) in quiet, notch noise, highpass noise, and broadband noise on the identifiability, latency, and amplitude of the auditory brainstem response (wave V). Normal listeners were presented with 40 dB and 80 dB nHL tone bursts having rise-plateau-fall times of 1 msec. Wave V was observed in all subjects at 40 dB and 80 dB nHL for the quiet and noise conditions. The latency findings suggest that responses elicited by the 80 dB nHL tone bursts in quiet were, in part, mediated by regions on the basilar membrane that did not correspond to the center frequency of the tone burst. To increase frequency-specificity, high-level tone bursts (e.g., 80 dB nHL) should be mixed with notch, highpass, or broadband noise. The use of noise conditions for low intensity levels (e.g., 40 dB nHL) does not appear necessary for isolating the response because both the notch and the highpass conditions yielded latencies similar to the quiet condition. Although similar wave V amplitudes were found at all frequencies, amplitudes were smaller for the broadband noise than for the quiet, notch, and highpass conditions. Thus, the latter conditions seem preferred.

Acoustic Stimulation↗

PubMed1992

Effects of sample size on the latency and amplitude of the auditory evoked response.

Experiment I investigated the effects of sample size (500 to 1500 stimulus repetitions) on the auditory brainstem response as a function of intensity (20 to 80 dB nHL) on a group of 10 normally hearing subjects. There was little change in identifiability, reliability, latencies, or amplitudes of Waves I, III, and V as the sample size increased from 500 or 750 to 1500 repetitions. These results suggest that 500 to 750 repetitions may be adequate when methods similar to those in the present study are used, and that the common clinical practice of employing approximately 1500 repetitions may unnecessarily prolong testing. Experiment II employed 12 hearing-impaired subjects who were tested at 10 to 40 dB SL using sample sizes from 250 to 4500 stimulus repetitions. Identifiability of all waves increased as sample size increased from 250 to 4500 repetitions. The largest changes in identifiability occurred when sample size increased from 250 to 1500 or 3000 repetitions, with little improvement as sample size increased from 3000 to 4500 repetitions. Examiners should monitor averaged responses and terminate testing as soon as a wave is identified. Contrary to expectation, there was no systematic change in the standard error of measurement for latency (approximately 0.07 ms) as sample size increased from 250 to 4500 repetitions. The standard error of measurement for amplitude decreased from approximately 100 nV with 500 repetitions to approximately 45 nV at 3000 repetitions. The improvement in reliability with increasing sample size may be explained by a decrease in the variability of background noise. A systematic decrease in amplitude also was observed as sample size increased. This observation may be explained by a reduction in the residual noise levels or because of time jitter or adaptation within the auditory pathways. Nonetheless, investigators who wish to use ABR amplitude measures for diagnosis may benefit from using a relatively large sample size.

Adult↗

PubMed1991

Auditory brainstem response to clicks in quiet, notch noise, and highpass noise.

Auditory brainstem responses to clicks in quiet, notch noise, and highpass noise were recorded from 10 normal-hearing adults. Contrary to some reports, the latency of wave V increased as the center frequency of the notch decreased. Response identifiability and wave V amplitudes were similar for the notch and highpass noises. Thus, the additional frequencies below the notch did not contribute sufficiently to the response to alter identifiability or amplitude. Notch noise, as compared to the highpass noise, is advantageous because of the increased frequency-specificity provided by the low-frequency masking noise. Presenting clicks in highpass or notch noise centered at 500 Hz is of limited value for assessing auditory sensitivity. This is because the range of testable hearing levels is restricted by (1) a high normal ABR threshold (approximately 65 dB nHL) and (2) the high noise levels required to mask the click. This limited dynamic range for assessing hearing loss is a major limitation of click in noise testing, particularly for 500 Hz. Generating a two-point audiogram by presenting clicks in noise with notches centered around 1000 Hz and 4000 Hz may prove promising for assessing auditory sensitivity.

Acoustic Stimulation↗

PubMed1991

Effects of stimulus duration on air caloric slow phase velocity.

This study was designed (1) to assess the test-retest reliability of the slow phase velocity (SPV) in response to air calorics, (2) to compare four procedures for calculating the SPV (average of 3 beats, average of 10 beats, average of all beats in a 10 second period, and the single largest beat), and (3) to investigate the effects of the duration of air irrigation (45, 60, and 75 seconds) on the SPV. Three groups of 10 subjects each were administered test and retest air irrigations (8 L/min) in each ear at 24 degrees C and 50 degrees C. Reliability was assessed with the standard error of measurement, which was approximately 4 degrees/second for all SPV calculations. This value is consistent with previous research. The 1-beat and 3-beat measurements revealed larger SPVs (approximately 24 degrees/sec) than the 10-beat and 10-sec measurements (approximately 20 degrees/sec). Considering time efficiency, and to avoid the effects of an artifact on the single largest beat, the 3-beat average may be preferred for calculating the SPV. Finally, our data do not allow recommendation of a preferred stimulus duration from among those evaluated (45, 60, 75 seconds).

Acoustic Stimulation↗

PubMed1990

Range of intensities yielding PB Max and the threshold for monosyllabic words for hearing-impaired subjects.

Characteristics of the range of intensities yielding PB Max and of the threshold for monosyllabic words (PBT) were investigated in 110 elderly subjects with mild-to-moderate sensorineural hearing loss. Word recognition functions were generated using the Auditec recordings of the CID W-22 words with 50 words per level. The results indicated that (a) the range of intensities yielding PB Max was approximately 33 dB at a level corresponding to 12% below PB Max, (b) the PB Max range decreased as the magnitude of hearing loss increased, (c) testing at the loudness discomfort level was likely to provide a more accurate estimate of PB Max than testing at most comfortable listening level, (d) word recognition scores should be obtained at a minimum of two intensities in order to estimate PB Max, (e) the PBT in dB SL re the spondaic threshold increased as the steepness of the audiogram increased, and (f) the PBT should not be considered unusual unless it exceeds the predicted value by about 14 dB.

Aged↗

PubMed1990

Effects of electrode placement on the auditory brainstem response using ear canal electrodes.

The effects of electrode placement on the latency and amplitude of the auditory brainstem response (ABR) were investigated in normal-hearing subjects. Ear canal (EC) electrodes were used in conjunction with surface electrodes to obtain ABRs. Three electrode combinations were evaluated: (1) vertex-EC-EC; (2) vertex-EC-neck; and (3) forehead-EC-neck. Absolute and interwave latencies and absolute and relative amplitudes were computed for Waves I, III, and V at 75 dB SL. Standard errors of measurement (SEmeas) revealed excellent test-retest reliability for latency (SEmeas = 0.06 ms) but only fair reliability for amplitude (SEmeas = 55 nv). No reliability differences were observed among the three electrode combinations. No significant latency or interwave latency differences were found among the three montages. No amplitude differences were found for Waves I and III among the montages. However, the Wave V amplitude was larger for the vertex-EC-EC and vertex-EC-neck montages than for the forehead-EC-neck montage. Because the vertex-EC-EC montage does not require additional electrodes on the contralateral neck, this montage is recommended.

Acoustic Stimulation↗

PubMed1989

Word recognition functions for the CID W-22 test in multitalker noise for normally hearing and hearing-impaired subjects.

Word recognition functions for Auditec recordings of the CID W-22 stimuli in multitalker noise were obtained using subjects with normal hearing and with mild-to-moderate sensorineural hearing loss. In the first experiment, word recognition functions were generated by varying the signal-to-noise ratio (S/N); whereas in the second experiment, a constant S/N was used and stimulus intensity was varied. The split-half reliability of word recognition scores for the normal-hearing and hearing-impaired groups revealed variability that agreed closely with predictions based on the simple binomial distribution. Therefore, the binomial model appears appropriate for estimating the variability of word recognition scores whether they are obtained in quiet or in a competing background noise. The reliability for threshold (50% point) revealed good stability. The slope of the recognition function was steeper for normal listeners than for the hearing-impaired subjects. Word recognition testing in noise can provide insight into the problems imposed by hearing loss, particularly when evaluating patients with mild hearing loss who exhibit no difficulties with conventional tests. Clinicians should employ a sufficient number of stimuli so that the test is adequately sensitive to differences among listening conditions.

Adult↗