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Conclusions: The validated finite element model of human middle ear can be used as a tool in hearing loss research. Objective: To establish an accurate finite element model of the external ear canal and middle ear through micro-computer tomography and test its feasibility in the human. Methods: A fresh specimen of human temporal bone was scanned by micro-computer tomography. The finite element model was established based on the images, and then the simulation results were compared with published experimental data. Results: After a series of simulations were conducted, the simulated results were compatible with the published experimental data and this confirms the validation of the finite element model.

The human ear is very resistant against noise-induced damage in the low frequency range. The aim of the present study was to investigate whether or not the stapedium reflex is of any importance for this resistance. Subjects with peripheral facial palsy (Bell's palsy) including unilateral stapedius muscle paralysis were exposed to several different levels of narrow band noise centered at 0.5 and 2.0 kHz. Temporary threshold shift (TTS) at 0.75 kHz was significantly higher in the affected than in the nonaffected ear after 0.5 kHz noise at and above 110 dB SPL. After the exposure with 2.0 kHz narrow band noise there was no difference in TTS at 3.0 kHz between the affected and nonaffected ear. It is concluded that the attenuation provided by the stapedius reflex reduces TTS after low frequency noise exposure. An implication is that the stapedius reflex also may have the function of protecting the ear from hearing damage caused by low frequency noise exposure.

Many techniques have been proposed for reconstruction of the posterior canal wall and/or obliteration of the mastoid bowl after radical mastoidectomy. The variety of materials that have been used, biological as well as foreign materials of different kinds, indicates that the ideal solution has yet to be found. Plaster of Paris, a biocompatible, degradable ceramic material prepared from CaSO4, may have an osteogenic property and become an alternative implant material for ear surgery. However, its possible ototoxicity has not been studied previously. Plaster was implanted in the tympanic cavity of guinea pigs. On investigation in the scanning electron microscope after 4.5 to 8 months, no toxic damage to the hair cell morphology was observed. Thus, from an ototoxic point of view, plaster of Paris would seem suitable for use as an implant material in ear surgery. Studies concerning the possible osteogenic property of plaster of Paris and its clinical application in human ear surgery are in progress.

The fetal development of both the vestibular and cochlear aqueducts will be followed in otological series beginning with tlie 4-month stage. Postnatal progress and mature structure will be traced from the newborn infant to the adult of 70 years (in dissections, serial sections and reconstructions prepared from the latter).These features will be emphasized: histology of the osseous wall and the contained connective tissue; source and course of blood vessels derived from labyrinthine periotic tissue internally and meningeal layers externally; normal range in adult anatomy. On these structural bases, the two channels will be compared, with special reference to their present and prospective role in otological surgery.

The functional influence of non-otosclerotic fixating lesions of the middle ear is investigated by reviewing two unusual cases and, experimentally, by creating such lesions in human temporal bones and observing the subsequent alteration in sound transmission. The effect of experimental fixation at each of five specific sites on the ossicular chain is discussed with respect to clinical observations.

(1957). Frequency Modulation and The Human Ear. Acta Oto-Laryngologica: Vol. 47, No. 5, pp. 421-430.

A new method for producing pressure variations in the pneumatic system of the human ear under control is described, i.e. the mastoid puncture technique. Several investigations are made; the volume displacement capacity of the normal ear drum, the role of the drum as a middle ear pressure regulator, vacuum effects on hearing and transudation, all these changes arc produced by intra-aural pressure variations under control. The accuracy of the previous methods for indirect determination of the middle tar pressure is analysed.

During continuous tone stimulation a gradual decrease of the provoked impedance change in the normal human ear occurs. The reactivation from this reflex fatigability when superimposing a second tone is studied by means of an electroacoustic impedance bridge. The assumption that the reactivation implies a frequency difference between the two tones is not confirmed in our investigations.

An experimental set-up in which an automatic sound level recorder is employed has been used to obtain a graphic representation of the sound conduction in specimens of human temporal bones. The influence of application of various forces to the stapedius and tensor tympani muscles has been investigated with special respect to output to input ratio and the formation of harmonics.

A review is given of the intra-aural muscular reflexes elicited by air current stimulation of the external human ear. Air current stimulation is advantageous compared with acoustic stimulation, being independent of the hearing in the contralateral ear, provided the reflex path is intact. The diagnostic scope of impedance measurements is thus substantially increased.

Since Zwaardemaker (i) stated that older people grow increasingly less sensitive to tones of high frequency, several authors (2-5) have determined the hearing losses as functions of age and sex. Moreover, Crowe and co-workers (6), and Fieandt & Saxen (7) have studied the pathological anatomy of the human ear affected by high tone deafness. From the functional standpoint, the recent experimental and clinical works of Schuknecht (8, 9) have also provided additional information on this type of hearing impairment.The object of this investigation was to determine the effects of loudness and age on the differential sensitivity to frequency for an unselected, non-clinical population.The data were collected under the single comparison standard procedure or method of constant stimuli (A-X method). All listening tests were monaural. The listeners were classified in groups of 10 individuals for each age decade, the number of men and women in each age-group being more or less equal.Ten untrained observers between the...

The structural and functional peculiarities of the middle ear, taken from various species of birds, have been studied on 80 preparations. The results of a morphological and functional study of the avian middle ear have been compared to the anatomy and physiology of the human ear in its normal status as well as after tympanoplasty. An analogous model of the avian tympanic apparatus has been designed.

The transmission of sound in the ear in post-mortem human temporal bones was measured before and after insertion of stapedial prosthesis of different material. It is shown that the increasing weight of the prosthesis does not improve the transmission in the high-frequency range. Exposure to violent sound results in permanent transmission loss. The cause of this was identified in microscopic examination as a dislocation of the prosthesis, and is shown in a film.

By means of an experimental set-up in which an automatic sound level recorder is employed, it is possible to obtain a graphic representation of the sound conduction in the ear of post-mortem human temporal bones. A change in the sound path produces a change in the response.

A survey presenting the anatomic and the pathologic size variation theories for the pneumatization of the mastoid air cell system and its size variation in the population is given. It shows the fundamental prerequisites for the two controversial theories. The inadmissability of claiming a gradual decrease of a size previously existing as caused by a productive mastoiditis is illuminated.A destructive or productive and obliterating mastoiditis cannot be claimed to cause a gradual narrowing of the size of the mastoid air cell system. Such a theory cannot be supported by conclusions of analogy between the obliteration of the bulla of the ear in the guinea pig in experimental studies of induced infections and the effect of a mastoiditis in the human ear. In the bulla we are dealing with one single air cell, whereas in the mastoid we have quite a number of communicating air cells. In addition, the bulla experiment must show signs of the infectious productive and obliterating process both on the X-ray and histo...

Age and certain post-mortem factors have been investigated and found to have apparently no systematic effect upon measurements of sound transmission in human temporal bone preparations.