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Chapter 15 Audiology
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
This is a technique for measuring the integrity of the conduction between the eardrum and the oval window to the inner ear by measuring the acoustic impedance of the eardrum (see figure 15.1). The primary function of the middle ear is that of an impedance matching system, designed to ensure that the energy of the sound wave is transmitted smoothly (with minimum reflection) from the air in the outer ear to the fluid in the inner ear. Middle-ear impedance audiometry (tympanometry) is a technique for measuring the integrity of this transmission system. If the middle ear is defective (whether due to a mechanical defect or physical inflammation) then the impedance matching might be lost and most of the energy of an applied sound will be absorbed or reflected. The acoustic impedance (see section 3.4.2) of the eardrum and middle ear is analogous to an electrical impedance. If the ear has a low impedance then an applied sound will be transmitted with very little absorption or reflection. If the middle ear is inflamed then the impedance may be high and most of an applied sound will be absorbed or reflected.
Effectiveness of hearing protection apparatus in preventing noise induced vestibular loss
Published in International Journal of Environmental Health Research, 2022
Süha Ertugrul, Emre Soylemez, Tuğçe Gurel
Audiological and immitansmetric evaluations were conducted for all individuals who underwent an otological examination. A 226-Hz probe-tone tympanometry test was performed (Interacoustics AZ 26 Middelfart, Denmark) in all individuals to evaluate middle ear pressure, eardrum, and static acoustic admittance. Then, pure tone audiometry test was performed in all individuals with an audiometer (Interacoustics AC40) in a silent cabin. The air conduction hearing thresholds of the individuals were determined bilaterally between 125–8000 Hz using TDH 39 supra-aural headphones. Bone conduction thresholds were detected bilaterally between 500–4000 Hz using a radio ear B71 bone vibrator. The pure tone average (PTA) of the individuals was calculated by taking the average of the air conduction hearing thresholds at 500, 1000, 2000, and 4000 Hz. Hearing of individuals with PTA between 0–20 dB was considered normal. The PTA was considered mild hearing loss between 21–40 dB, moderate hearing loss between 41–55 dB, moderate to severe hearing loss between 56–70 dB, and severe hearing loss between 71–90 dB. The hearing loss degree of the individuals was classified according to the ear with more hearing loss.