Reflex Threshold Shift in Chinchillas Following a Prolonged Exposure to Noise

The acoustic reflex is considered to reduce transmission across the middle ear and thereby protect the inner ear from intense sounds. The dynamic properties of this reflex seem to be a function of the duration of the eliciting stimulus. Assessment of the protective action afforded by middle-ear muscle contractions for long-term noise exposures requires the knowledge of how these dynamic properties change under such conditions. Round window electrodes were implanted in eight chinchillas. Changes in the threshold of the acoustic reflex were measured during an eight-hour exposure at 95 dB SPL to an octave-band noise centered at 0.5 kHz. The criterion measure of the acoustic reflex was a change in the amplitude of the cochlear microphonic generated by a 0.5 kHz eliciting tone. Thresholds of the acoustic reflex increased systematically throughout the noise exposure up to approximately 14 dB after 8 hours. The time course of the changes in the threshold of the acoustic reflex was nearly identical to the time course of behaviorally measured changes in the auditory sensitivity as reported by Carder and Miller (1972).

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Acoustic Reflex as a Predictor of Middle Ear Effusion

Annals of Otology Rhinology & Laryngology ◽

10.1177/00034894800890s345 ◽

1980 ◽

Vol 89 (3_suppl) ◽

pp. 196-199 ◽

Cited By ~ 7

Author(s):

Georges E. Freyss ◽

Yves Manac'H ◽

Philippe P. Narcy ◽

Michel G. Toupet

Keyword(s):

Nitrous Oxide ◽

Middle Ear ◽

Middle Ear Effusion ◽

General Anesthetic ◽

Comparative Efficacy ◽

Acoustic Reflex ◽

Reflex Threshold ◽

Acoustic Reflex Threshold ◽

Youden’S Index ◽

Ear Effusion

The comparative efficacy of tympanometry and the acoustic reflex (threshold and supraliminal amplitude) in predicting the presence of fluid in the middle ear was studied just before myringotomy in 50 children (99 ears) prior to adenoidectomy. Impedance audiometry was carried out under a general anesthetic (ketamine and nitrous oxide) in 60%, and without anesthesia in 40% of the cases. The comparative efficacy of this test was assessed using objective criteria which were independent of the cut-off point between normal and abnormal groups. The prediction efficacy of acoustic reflex threshold and amplitude (Youden's index = 0.58) was superior to that of tympanometry peak amplitude and pressure (Youden's indexes = 0.29 and 0.36). The efficacy of the gradient was 0.41. Modifications due to anesthesia were not statistically significant for the whole group, but temporary abolition of the acoustic reflex at the start of anesthesia is probably related to the high percentage of false positives noted when the acoustic reflex is used alone in patients given a general anesthetic.

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Extra-auditory responses to long-term intermittent noise stimulation in humans

Journal of Applied Physiology ◽

10.1152/jappl.1980.49.6.985 ◽

1980 ◽

Vol 49 (6) ◽

pp. 985-993 ◽

Cited By ~ 4

Author(s):

B. Fruhstorfer ◽

H. Hensel

Keyword(s):

Heart Rate ◽

Time Course ◽

Noise Exposure ◽

Physiological Noise ◽

Auditory Responses ◽

S 100 ◽

Intermittent Noise ◽

Electroencephalogram Eeg ◽

Cutaneous Blood

Respiration, heart rate, cutaneous blood flow, and electroencephalogram (EEG) reactions to long-term intermittent noise exposure were recorded from 13 volunteers (20-29 yr) with normal hearing and vegetative reactivity. They received daily within 1 h 12 noise stimuli (16 s 100 dB (A) white noise) for 10 or 21 days, respectively. Most subjects reported partial subjective adaptation to the noise. Heart rate adapted within a session but did not change considerably during successive days. Vascular responses did not change during one session but diminished mainly during the first 10 days. Noise responses in the EEG remained constant, but a decrease in vigilance occurred during the whole experimental series. Respiration responses were unpredictable and showed no trend within the sessions. It was concluded that certain physiological responses adapt to loud noise but that the time course of adaptation is different. Therefore a general statement about physiological noise adaptation is not possible.

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Effects of External Ear Canal Pressure on the Middle-Ear Muscle Reflex Threshold

Journal of Speech and Hearing Research ◽

10.1044/jshr.1703.526 ◽

1974 ◽

Vol 17 (3) ◽

pp. 526-530 ◽

Cited By ~ 3

Author(s):

Frederick N. Martin ◽

Sherry Coombes

Keyword(s):

Tympanic Membrane ◽

Middle Ear ◽

External Auditory Canal ◽

Acoustic Impedance ◽

Normal Hearing ◽

Air Pressure ◽

External Ear ◽

Ear Canal ◽

Acoustic Reflex ◽

Reflex Threshold

Twenty normal-hearing individuals served as subjects in an experiment designed to determine the relationships between positive and negative air pressure in the external auditory canal and the intensity required to elicit the acoustic reflex. Pressure was varied from +240 to −240 mm H 2 O. Changes in the magnitude of acoustic impedance were measured on an acoustic impedance meter and displayed graphically on a Y-T recorder. As air pressure was varied in the canal and the tympanic membrane was displaced from its position of greatest compliance, systematic increases in the intensity required to elicit the reflexes were noted. The magnitude of the differences was smaller than might have been anticipated, not exceeding a mean of 5.1 dB at −240 mm H 2 O.

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Stapedius Reflex in Patients with an Inner Ear Prosthesis

The International Journal of Artificial Organs ◽

10.1177/039139889201500712 ◽

1992 ◽

Vol 15 (7) ◽

pp. 436-439 ◽

Cited By ~ 3

Author(s):

K. Stephan ◽

K. Welzl-Muller

Keyword(s):

Electrical Stimulation ◽

Cochlear Implant ◽

Inner Ear ◽

Time Course ◽

Temporal Integration ◽

Fast Response ◽

Acoustic Stimulation ◽

Acoustic Reflex ◽

Stapedius Reflex ◽

Reflex Threshold

The stapedius reflex elicited by electrical stimulation was investigated in 21 deaf individuals supplied with an inner ear prosthesis. All patients were implanted with the Vienna cochlear implant using intra or extracochlear electrodes. Analog stimulation with sinus bursts of various durations (25, 50, 100, 300, 500 ms) and frequencies (125, 500, 1000, 2000 Hz) was used. The time course of the contralateral acoustic reflex was monitored using a fast-response impedance meter. The stapedius reflex was observed in about half of the cases. Reflex threshold was observed at a stimulation level close to uncomfortable loudness. The time course in case of electrical stimulation differs in some aspects (rise time, onset) from acoustic stimulation in hearing individuals. Temporal integration of the stapedius reflex was observed also in case of electrostimulation through the cochlear implant.

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The Role of the Clinically Obtained Acoustic Reflex as a Research Tool for Subclinical Hearing Pathologies

Trends in Hearing ◽

10.1177/2331216520972860 ◽

2020 ◽

Vol 24 ◽

pp. 233121652097286

Author(s):

Andrew Causon ◽

Kevin J. Munro ◽

Christopher J. Plack ◽

Garreth Prendergast

Keyword(s):

Middle Ear ◽

Noise Exposure ◽

Quantitative Measure ◽

Auditory Function ◽

Acoustic Reflex ◽

Normal Range ◽

Probe Tone ◽

Growth Functions ◽

Clinically Normal

The acoustic reflex (AR) shows promise as an objective test for the presence of cochlear synaptopathy in rodents. The AR has also been shown to be reduced in humans with tinnitus compared to those without. The aim of the present study was twofold: (a) to determine if AR strength (quantified as both threshold and growth) varied with lifetime noise exposure, and thus provided an estimate of the degree of synaptopathy and (b) to identify which factors should be considered when using the AR as a quantitative measure rather than just present/absent responses. AR thresholds and growth functions were measured using ipsilateral and contralateral, broadband and tonal elicitors in adults with normal hearing and varying levels of lifetime noise exposure. Only the clinical standard 226 Hz probe tone was used. AR threshold and growth were not related to lifetime noise exposure, suggesting that routine clinical AR measures are not a sensitive measure when investigating the effects of noise exposure in audiometrically normal listeners. Our secondary, exploratory analyses revealed that AR threshold and growth were significantly related to middle-ear compliance. Listeners with higher middle-ear compliance (though still in the clinically normal range) showed lower AR thresholds and steeper AR growth functions. Furthermore, there was a difference in middle-ear compliance between the sexes, with males showing higher middle-ear compliance values than females. Therefore, it may be necessary to factor middle-ear compliance values into any analysis that uses the AR as an estimate of auditory function.

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Factors Influencing the Acoustic-Immittance Characteristics of the Acoustic Reflex

Journal of Speech Language and Hearing Research ◽

10.1044/jshr.2203.480 ◽

1979 ◽

Vol 22 (3) ◽

pp. 480-499 ◽

Cited By ~ 12

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.

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