An Experimental Study of Middle-ear Vibrations in Gerbils

RÉSUMÉ ABSTRACT The Mongolian gerbil has become increasingly popular in middle-ear research, as it is low in cost and has easily approachable middle-ear structures. The goal of this thesis is to present vibration measurements on the gerbil eardrum. Displacement frequency responses are acquired in five gerbils at three or four points along the manubrium and at up to 8 points on the eardrum. We use a Polytec laser Doppler vibrometer to perform measurements with a sinusoidal-sweep stimulus. Displacements, normalized with respect to the sound pressure level measured near the eardrum, are presented over the frequency range from 0.15 to 10 kHz, and compared with measurements published in the literature. Spatial displacement patterns along the manubrium and on the tympanic membrane are presented. The variability and repeatability of the measurements are investigated with an emphasis on temporal effects due to the drying and rehydration of middle-ear structures.The Mongolian gerbil has become increasingly popular in middle-ear research, as it is low in cost and has easily approachable middle-ear structures. The goal of this thesis is to present vibration measurements on the gerbil eardrum. Displacement frequency responses are acquired in five gerbils at three or four points along the manubrium and at up to 8 points on the eardrum. We use a Polytec laser Doppler vibrometer to perform measurements with a sinusoidal-sweep stimulus. Displacements, normalized with respect to the sound pressure level measured near the eardrum, are presented over the frequency range from 0.15 to 10 kHz, and compared with measurements published in the literature. Spatial displacement patterns along the manubrium and on the tympanic membrane are presented. The variability and repeatability of the measurements are investigated with an emphasis on temporal effects due to the drying and rehydration of middle-ear structures. RÉSUMÉ Le gerbil mongolien est devenu de plus en plus populaire dans la recherche sur l'oreille moyenne, car il n’est pas trop couteux, et les structures de l'oreille moyenne sont facillement accessibles. Le but de cette thèse est de présenter des mesures de vibration de tympan du gerbil. Des réponses fréquentielles des déplacements sont acquises dans cinq gerbils à trois ou quatre points le long du manubrium, et à autant que 8 points sur le tympan. Nous employons un vibromètre à laser Doppler de Polytec pour effectuer des mesures avec un stimulus à balayage sinusoïdal. Des déplacements, normalisés par le niveau de pression acoustique mesuré près du tympan, sont présentés sur la gamme de fréquence de 0.15 à 10 kilohertz, et comparés aux mesures publiées dans la littérature. Des motifs spatiaux de déplacement le long du manubrium et sur la membrane tympanique sont présentés. La variabilité et la répétabilité des mesures sont étudiées avec une emphase sur les effets temporels dus à la déshydratation et à la ré-humidification des structures de l’oreille moyenne.