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At least 235 records · Page 13Linked to original sources
PubMed1989

Open-cavity mastoid surgery: its effect on the acoustics of the external ear canal.

Temporal bone studies have demonstrated that a modified radical mastoidectomy changes the resonant characteristics of the external auditory canal, but the effect has not been reported in patients. In 12 patients, performing open-cavity mastoid surgery for cholesteatoma changed the mean peak resonant frequency of the external ear canal from 2.5 to 2.2 kHz (p less than 0.02). This is in comparison with creating a modified radical mastoid cavity in 6 temporal bones which changed the mean peak resonant frequency of the external ear canal from 3.9 to 1.9 kHz. It is concluded that open-cavity mastoid surgery in patients changes the acoustics of the external ear canal less than in temporal bone studies.

Acoustics↗
PubMed2002

Changes in external ear resonance after mastoidectomy: open cavity mastoid versus obliterated mastoid cavity.

The creation of an open mastoid cavity changes the acoustic characteristics of the external ear. The aim of this study was to ascertain the acoustic change in the external auditory canal caused by an open mastoid cavity and to compare it with mastoid obliteration. The external ear resonance characteristics were measured in 40 normal adult ears, 20 ears with an open mastoid cavity and 40 ears with an obliterated mastoid. The measurement of resonance characteristics was performed using a real ear analyser. An open mastoid cavity changed the mean peak resonant frequency of the external ear from 2.1 kHz to 2.3 kHz (P < 0.02), with a mean attenuation of 8 dB SPL at 4 kHz. An obliterated mastoid produced higher resonance frequencies from 2.5 kHz to 2.8 kHz. The sound pressure gain of the external auditory canal with an open mastoid cavity was higher than with an obliterated mastoid. The author concludes that an open mastoid cavity can affect the resonance frequency, and that this effect is reduced by mastoid obliteration. Therefore, mastoid obliteration results in a more normal ear canal both anatomically and functionally.

Adult↗
PubMed1996

Sound-power collection by the auditory periphery of the mongolian gerbil Meriones unguiculatus. II. External-ear radiation impedance and power collection.

Acoustic power flow into the external and middle ear of the gerbil is computed from acoustic measurements and models of the external ear and used to predict the behavioral auditory threshold. The external-ear radiation impedance from the tympanic ring ZE measured in six gerbil ears with a calibrated acoustic source at frequencies from 10 Hz to 18 kHz is mass dominated below about 8 kHz, with a mean mass of 2720 kg/m4. ZE shows resonant behavior near 8 and 14 kHz. The frequency dependence of ZE is similar to that measured in cat, chinchilla, and models of the human external ear, but the mass and the resonant frequencies are higher. The power utilization ratio (PUR) computed from ZE and measurements of the middle-ear input impedance ZT presented previously [Ravicz et al., J. Acoust. Soc. Am. 92, 157-177 (1992)] suggests that appreciable power is transmitted to the middle ear only above 1.5 kHz. Mathematical external-ear models, consisting of tube segments and conical horns that include viscous and thermal losses, were developed from anatomical dimensions to match ZE over the entire frequency range of measurement. The radiation efficiency eta R computed from the models is near unity only above 12 kHz and falls to 10(-5) as frequency decreases to 10 Hz. Predictions of the mean pressure gain from an external diffuse sound field to the tympanic membrane resemble measurements in another gerbilline species. The effective area of the ear in a diffuse sound field at the tympanic membrane EATMDF computed from PUR and eta R approaches the anatomical area of the pinna opening, 71 mm2, above 1.5 kHz and the geometric limit of lambda 2 /4 pi determined by the wavelength lambda above 12 kHz but decreases sharply below 1.5 kHz to 0.002 mm2 at 10 Hz. The diffuse-field sound pressure required to deliver 5 x 10(-17) W to the middle ear between 10 Hz and 18 kHz resembles the behavioral auditory threshold [Ryan, J. Acoust. Soc. Am. 54, 1222-1226 (1976)]. This result supports the idea that the cochlea acts as a power detector at the auditory threshold.

Acoustics↗
PubMed1988

Treatment of angiolymphoid hyperplasia of the external ear with carbon dioxide laser.

Two women with long histories of angiolymphoid hyperplasia involving the left external ear were successfully treated with carbon dioxide laser vaporization. In one of these patients a previous treatment with argon laser photocoagulation had proved unsuccessful. Carbon dioxide laser vaporization can be advantageous in the treatment of angiolymphoid hyperplasia, especially when the patient is not a good candidate for cold steel surgery or when the disease process involves confined or convoluted structures such as those on the external ear.

Aged↗
PubMed1993

[Reconstruction of a malformed external ear by an endoprosthesis of porous polyethylene with an integrated suction system].

Complete reconstruction of the external ear is one of the most difficult tasks in plastic and reconstructive surgery. The risk of frame protrusion inherent in all alloplastic materials is reduced by using a new premoulded endoprosthesis with an integrated suction system. It consists of tissue-compatible porous polyethylene. A conventional suction drainage can be attached to a hollow canal system within the endoprosthesis that empties from defined spaces corresponding to the natural concavities of the external ear. In combination with a preceding expansion the overlying skin is then adapted evenly and completely to the frame by suction. As a result of this vacuum seromas and haematomas can be prevented. Furthermore, infections and pressure necroses due to matress sutures cannot develop. The use of this endoprosthesis obviates the removal of autogenous cartilage and all the complications and scars that are connected with this procedure. The frame itself is stable and has a relief that is largely similar to the natural form of the auricle. Thus, an aesthetically satisfying result can be achieved also in the hand of the surgeon who is not often engaged in this field of plastic surgery.

Adolescent↗