Acoustic-Reflex Adaptation

1984 ◽  
Vol 27 (4) ◽  
pp. 586-595 ◽  
Author(s):  
Richard H. Wilson ◽  
June K. McCullough ◽  
David J. Lilly
Keyword(s):  
Half Life ◽  
Onset Time ◽  
Life Time ◽  
Broadband Noise ◽  
Acoustic Reflex ◽  
Individual Subject ◽  
Baseline Drift ◽  
Reflex Threshold ◽  
The Individual ◽  
Life Function

Acoustic-reflex adaptation was studied in 35 subjects with normal hearing using nine pure-tone activators (250-6000 Hz) and a broadband-noise activator. The individual subject data generated by the 31-s activators presented 10 dB above the reflex threshold were digitized, corrected for baseline drift and ear Canal volume, and analyzed in terms of the acoustic-admittance change in acoustic mmhos and in terms of the percentage of maximum-reflex magnitude. Reflex adaptation increased as a function of frequency. The adaptation functions for the lower frequencies (⩽1500 Hz) were essentially linear over the 31-s activator period, whereas the functions for the higher frequencies (⩾2000 Hz) were curvilinear over the activator period. The experimental half-tile data are compared with a theoretical half-life function that was generated to estimate normal acoustic-reflex adaptation as a function of activator frequency. Finally, the means and standard deviations are reported and discussed for (a) the onset time of adaptation; (b) the half-life time, and (c) the percentage of maximum reflex magnitude at 5-s intervals from 5 to 30 s.

Aural Acoustic-Immittance Measurements

1981 ◽  
Vol 46 (4) ◽  
pp. 413-421 ◽  
Author(s):  
Richard H. Wilson ◽  
Janet E. Shanks ◽  
Therese M. Velde
Keyword(s):  
Sound Pressure ◽  
Broadband Noise ◽  
Intensity Level ◽  
Growth Data ◽  
Acoustic Reflex ◽  
Individual Subject ◽  
Acoustic Admittance ◽  
Sound Pressure Levels ◽  
Pure Tones ◽  
The Individual

Bilateral measurements of the aural acoustic-immittance characteristics of the middle-ear transmission systems of 48 subjects were made with an acoustic-admittance meter. The measurements, including static acoustic-immittance, acoustic-reflex thresholds, and acoustic-reflex growth functions, were made using a 220-Hz probe. The contralateral reflex data for three pure tones (500, 1000, and 2000 Hz) and for broadband noise were acquired in 2-dB steps at sound-pressure levels from 84–116 dB (tones) and 66–116 dB (noise) during ascending- and descending-intensity level runs. For all acoustic-immittance measurements, right ear and left ear comparisons were made and found not to be significantly different. The individual subject data then were expressed as the absolute differences between ears. In this manner normative inter-aural immittance differences were defined. The peak static immittance data were analyzed in terms of median inter-aural differences and upper 80% cut-off values. The 80% range for normal immittance values were smaller for a within subject versus an across subject comparison. For acoustic-reflex thresholds, a disparity between ears of >10 dB was suggested as indicative of an abnormality in the auditory mechanism. Finally, the reflex-growth data indicated mean inter-aural absolute differences that ranged to .040–.043 acoustic mmhos (300–400 acoustic ohms) at the higher reflex activator sound-pressure levels.

Acoustic-Reflex Growth and Loudness

1979 ◽  
Vol 22 (2) ◽  
pp. 295-310 ◽  
Author(s):  
Michael G. Block ◽  
Terry L. Wiley
Keyword(s):  
Acoustic Impedance ◽  
Dynamic Range ◽  
Broadband Noise ◽  
Reflex Response ◽  
Impedance Change ◽  
Acoustic Reflex ◽  
Growth Functions ◽  
The Mean ◽  
Standard Deviations ◽  
The Individual

Acoustic-reflex growth functions and loudness-balance judgments were obtained for three normal-hearing subjects with normal middle-ear function. The hypothesis that acoustic reflex-activating signals producing proportionately equal acoustic-impedance changes are judged equal in loudness was evaluated. The mean acoustic impedance and associated standard deviations were computed for the baseline (static) and activator (reflex) portions of each reflex event. An acoustic-impedance change exceeding two standard deviations of baseline was defined as the criterion acoustic-reflex response. Acoustic impedance was measured as a function of activator SPL for broadband noise and a 1000-Hz tone from criterion magnitude to the maximum acoustic impedance (or 120-dB SPL). This was defined as the dynamic range of reflex growth. Loudness-balance measurements were made for the 1000-Hz tone and broadband noise at SPL’s representing 30, 50, and 70% of the individual dynamic range. The data supported the hypothesis.

Temporal Integration of the Contralateral Acoustic Reflex Threshold for a 1000 Hz Tonal Activator and Its Age-Related Changes

2009 ◽  
Vol 20 (04) ◽  
pp. 225-228 ◽  
Author(s):  
Michele B. Emmer ◽  
Shlomo Silman ◽  
Carol A. Silverman ◽  
Harry Levitt
Keyword(s):  
Temporal Integration ◽  
Age Effect ◽  
Broadband Noise ◽  
Hearing Level ◽  
Acoustic Reflex ◽  
Hearing Sensitivity ◽  
Age Related ◽  
Main Effect ◽  
Reflex Threshold ◽  
Acoustic Reflex Threshold

Background: Previous research has noted an age effect on the temporal integration of the acoustic reflex for a noise activator. Purpose: To determine whether the age effect earlier noted for a noise activator will be noted for a tonal activator. Research Design: Comparison of ARTs of younger and older groups at activating stimulus durations of 12, 25, 50, 100, 200, 300, 500, and 1000 msec. Study Sample: Two groups of adults with normal-hearing sensitivity: one group of 20 young adults (ten males and ten females, ages 18–29 years, with a mean age of 24 years) and one group of 20 older adults (ten males and ten females, ages 59–75 years, with a mean age of 67.5 years). Results: A significant main effect for duration was obtained. That is, as the duration increased, the acoustic reflex threshold for the 1000 Hz tonal activator decreased. The interactions of duration × age group and duration × hearing level were not significant. There was a nonsignificant main effect (p = .889) for the between-subjects factor of age. Conclusion: Results contradict the findings for broadband noise.

Newborn Acoustic Reflexes to Noise and Pure-Tone Signals

1982 ◽  
Vol 25 (3) ◽  
pp. 383-387 ◽  
Author(s):  
Michael J. Bennett ◽  
Lynn A. Weatherby
Keyword(s):  
Pure Tone ◽  
Broadband Noise ◽  
Acoustic Reflex ◽  
Acoustic Reflexes ◽  
Auditory Response ◽  
Reflex Activation ◽  
The Mean ◽  
Reflex Threshold ◽  
Filtered Noise ◽  
High Pass

A variable-frequency probe-tone acoustic-impedance bridge has been developed to enable an artifact-free pure-tone acoustic reflex study to be carried out on neonates. Contralateral reflex thresholds for pure tones, broadband noise, and filtered noise were measured in 28 newborns aged 4–8 days. The mean reflex threshold for the broadband noise was 73 dB SPL, 4 dB lower than the reflex threshold for the 2600-Hz low- and high-pass noise bands. Reflex activation at 500, 1000, 2000, and 4000 Hz gave responses that closely followed the normal adult pattern although reflex thresholds were approximately 10 dB higher. Two infants failed to demonstrate reflexes. One of these failed a behavioral-response test using the Auditory Response Cradle and was found to have mild jaundice. The second infant passed the behavioral test and had measurable reflexes 5 weeks later. A third baby with elevated reflex thresholds also was jaundiced but had normal behavioral responses and was discharged. Discussion of these results emphasizes their value to those engaged in neonatal auditory assessment.

The Effects of Aging on the Magnitude of the Acoustic Reflex

1981 ◽  
Vol 24 (3) ◽  
pp. 406-414 ◽  
Author(s):  
Richard H. Wilson
Keyword(s):  
Sound Pressure ◽  
Age Groups ◽  
Sampling Technique ◽  
Pressure Level ◽  
Broadband Noise ◽  
Individual Growth ◽  
Growth Data ◽  
Ear Canal ◽  
Acoustic Reflex ◽  
The Individual

Aural acoustic-immittance (admittance and impedance) measurements during the quiescent and reflexive states were made using a computer sampling technique on 18 subjects with normal hearing in each of two age groups (< 30 years and > 50 years). Seven pure-tones (250–6000 Hz) and broadband-noise stimuli served to elicit the acoustic reflex at sound-pressure levels from 84–116 dB (tones) and 66–116 dB (noise) in 2-dB steps during ascending and descending runs. The contralateral middle-ear activity, was monitored with a 220-Hz probe by digitizing the conductance and susceptance outputs of an acoustic-admittance meter. The computer corrected for the immittance characteristics of the ear-canal volume by utilizing measurements made at an ear-canal pressure of -350 daPa and then by converting the conductance and susceptance values into admittance and impedance units. The results are reported as the immittance change between the quiescent and reflexive states as a function of both the activator sound-pressure level and the activator-pressure level above the reflex threshold. There were no significant differences between the static-immittance values for the two groups, Although acoustic-reflex thresholds for the two groups were the same in the low- to mid-frequency region (250–2000 Hz), the reflex thresholds for the > 50-years group were elevated significantly ( 8 dB) for 4000 Hz, 6000 Hz, and noise activators. In all conditions, the magnitude of the acoustic reflex was substantially smaller for the > 50-years group as compared with the < 30-years group. The variability of the reflex magnitude was large for both groups of subjects. Saturation of the individual growth functions, which was frequency dependent, occurred twice as often with the > 50-years group as with the < 30-years group. The relationship between the magnitude changes in conductance and susceptance from the quiescent to the reflexive state was the same for the two groups. Finally, the magnitude differences among the reflex-growth data were not related to differences in static immittance.

Loudness Discomfort Level and Acoustic Reflex Threshold for Speech Stimuli

1979 ◽  
Vol 22 (4) ◽  
pp. 849-861 ◽  
Author(s):  
Donald E. Morgan ◽  
Donald D. Dirks ◽  
Deborah Bower ◽  
Candace A. Kamm
Keyword(s):  
Broad Band ◽  
Wide Band ◽  
Acoustic Reflex ◽  
Individual Subject ◽  
Speech Stimuli ◽  
Wide Variability ◽  
Reflex Threshold ◽  
Mean Differences ◽  
Acoustic Reflex Threshold ◽  
Wide Band Noise

Loudness discomfort level (LDL) and acoustic reflex threshold (ART) measurements were obtained from subjects with normal hearing using several speech stimuli, as well as broad-band and speech-spectrum noise. The purpose of the investigation was to determine the LDL for a variety of representative speech samples, and to determine the relationship between the LDL and ART for selected speech and noise stimuli. For all stimuli, LDL measurements were relatively constant, but ART measurements decreased significantly for wide-band noise stimuli as compared with the speech stimuli. Mean differences between the two measures were consistent, but individual subject data were characterized by wide variability precluding accurate prediction of the LDL from ART measurements.

Factors Influencing the Acoustic-Immittance Characteristics of the Acoustic Reflex

1979 ◽  
Vol 22 (3) ◽  
pp. 480-499 ◽  
Author(s):  
Richard H. Wilson
Keyword(s):  
Middle Ear ◽  
Sound Pressure ◽  
Broadband Noise ◽  
Intensity Level ◽  
Ear Canal ◽  
Acoustic Reflex ◽  
Impedance Characteristics ◽  
Reflex Threshold ◽  
Acoustic Reflex Threshold ◽  
Tonal Stimuli

Measurements of the aural acoustic-immittance (admittance and impedance) characteristics of the middle-ear transmission system in humans during the quiescent (static) and reflexive states were made (N = 36) utilizing a signal-averaging technique. Three pure tones (750, 1000, and 2000 Hz) and broadband noise stimuli elicited the acoustic reflex in 2-dB steps at sound-pressure levels from 84–116 dB (tones) and 66–116 dB (noise) during ascending- and descending-intensity level runs. The contralateral middle-ear activity was monitored with a 220-Hz probe by digitizing the conductance and susceptance outputs of an admittance meter. A computer corrected for the ear-canal volume utilizing measurements made at ear-canal pressures of 0 and −350 daPa and then converted the conductance and susceptance values into admittance and impedance units. The results were reported in absolute and relative immittance units, including components, as a function of both stimulus sound-pressure level and intensity level above the acoustic-reflex threshold. The static immittance of the middle ear changed nonlinearly over time to lower admittance or higher impedance values. The influence of this static-immittance shift on the reflex magnitude was discussed. The largest mean reflex magnitude and the slowest rate of growth were observed with broadband noise, although eight of the 36 subjects demonstrated the largest reflex magnitude in response to one or more of the tonal stimuli. Although static-immittance values and acoustic-reflex thresholds were poorly correlated, the reflex magnitudes were proportional to static immittance. The variability of the reflex measures was similar to the variability of the static-immittance values. Finally, bi-directional changes in resistance during the reflexive state were observed and discussed.

Acoustic-Reflex Dynamics for Pulsed Signals

1978 ◽  
Vol 21 (2) ◽  
pp. 295-308
Author(s):  
Terry L. Wiley ◽  
Raymond S. Karlovich
Keyword(s):  
Duty Cycle ◽  
Acoustic Impedance ◽  
Normal Hearing ◽  
Broadband Noise ◽  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Acoustic Reflex ◽  
Stapedius Muscle ◽  
Duty Cycles

Contralateral acoustic-reflex measurements were taken for 10 normal-hearing subjects using a pulsed broadband noise as the reflex-activating signal. Acoustic impedance was measured at selected times during the on (response maximum) and off (response minimum) portions of the pulsed activator over a 2-min interval as a function of activator period and duty cycle. Major findings were that response maxima increased as a function of time for longer duty cycles and that response minima increased as a function of time for all duty cycles. It is hypothesized that these findings are attributable to the recovery characteristics of the stapedius muscle. An explanation of portions of the results from previous temporary threshold shift experiments on the basis of acoustic-reflex dynamics is proposed.

Covalent Complexes Between Low Molecular Weight Heparin Fragments and Antithrombin III – Inhibition Kinetics and Turnover Parameters

1983 ◽  
Vol 49 (02) ◽  
pp. 109-115 ◽  
Author(s):  
M Hoylaerts ◽  
E Holmer ◽  
M de Mol ◽  
D Collen
Keyword(s):  
Molecular Weight ◽  
Half Life ◽  
Low Molecular Weight Heparin ◽  
Antithrombin Iii ◽  
Factor Xa ◽  
Life Time ◽  
Low Molecular Weight ◽  
High Affinity ◽  
Plasma Half Life ◽  
Covalent Complex

SummaryTwo high affinity heparin fragments (A/r 4,300 and M, 3,200) were covalently coupled to antithrombin III (J. Biol. Chem. 1982; 257: 3401-3408) with an apparent 1:1 stoichiometry and a 30-35% yield.The purified covalent complexes inhibited factor Xa with second order rate constants very similar to those obtained for antithrombin III saturated with these heparin fragments and to that obtained for the covalent complex between antithrombin III and native high affinity heparin.The disappearance rates from plasma in rabbits of both low molecular weight heparin fragments and their complexes could adequately be represented by two-compartment mammillary models. The plasma half-life (t'/j) of both low Afr-heparin fragments was approximately 2.4 hr. Covalent coupling of the fragments to antithrombin III increased this half-life about 3.5 fold (t1/2 ≃ 7.7 hr), approaching that of free antithrombin III (t1/2 ≃ 11 ± 0.4 hr) and resulting in a 30fold longer life time of factor Xa inhibitory activity in plasma as compared to that of free intact heparin (t1/2 ≃ 0.25 ± 0.04 hr).

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