The role of the middle ear in acoustic trauma from impulses.
Eames-BL; Hamernik-RP; Henderson-D; Feldman-A
Laryngoscope 1975 Sep; 85(9):1582-1592
Changes in the middle ear mechanism after impulse noise exposure in nine monoaural chinchillas were related to audiometric and histological effects. Exposure was to either 161 or 166 decibel peak sound pressure level impulses of 1 millisecond "A" duration, presented at a rate of 1 per minute for 50 minutes. The conductive mechanism of the chinchilla was assessed using standard clinical measures of static and dynamic impedance before and after the noise exposure. Auditory thresholds were measured before and after noise exposure using the average evoked response (AER) technique. At 30 days post exposure, the animals were sacrificed for histology. Pre exposure tympanometry showed that the total mean impedance of the chinchilla ear is considerably lower than that of man; a method related hysterisis effect is present in both the susceptance and conductance tympanograms; and sedation has a significant effect on the total impedance of the ear and on the shape of the tympanograms. After exposure to high level impulse noise: tympanograms become irregular and double peaked, indicating tympanic membrane stress; for the given exposure, 166 decibels is the impulse intensity needed to rupture consistently the tympanic membrane; and audiometric and histological data correlate with the tympanometric findings and demonstrate a protective effect of a tympanic membrane rupture on the cochlea. (Grant No. R01-OH-00364)
NIOSH-Publication; NIOSH-Grant; Noise-induced-hearing-loss; Physiological-function; Histological-changes; Ear-disorders; Histology; Physiological-measurements; Cell-reactions; Acoustic-trauma; Hearing-disorders; Tympanum; Trauma; Methodology; Audiometry
Otolaryngology Upstate Medical Center Departm 750 E Adams Street Syracuse, N Y 13210
Upstate Medical Center, Syracuse, New York