Outer and Middle Ear

Allen S (2006) Outer and middle ear problems. The Pharmaceutical journal 276 83-86. 

Tympanic membrane Membrane separating the outer and middle ear. 

The primary means for hearing is sound traveling through the outer and middle ear to the inner ear. A small amount of hearing occurs through bone conduction to the inner ear. 

Figure 9.3. The human ear is divided into three main parts. The outer ear collects sound and directs it down the ear canal towards the eardrum. The size of the eardrum, comhined with the lever action of the three hones of the middle ear, ensures the efficient conduction of sound from the ear canal, which is filled with air, to the inner ear, which is filled with a liquid. Very small muscles, not shown here, are cormected to these bones to protect the ear from very lond sounds. The inner ear consists of two parts. Only the cochlea is shown, which is the part of the human ear that is responsible for converting sound into electrical signals in the auditory nerve. The other part of the inner ear, the vestibular organ, is involved in balance.

The ear is divided into three sections, these being the outer, middle, and inner ear. The outer ear consists of the pinna and ear canal. The sound wave enters the pinna and travels through the ear canal to the ear drum (tympanic membrane). The outer ear... 

Figure 8.2 is a cross-sechon of the human ear. Sound is collected and funneled into the ear canal by the outer ear. At the end of the ear canal, the sound impinges upon a membrane called the ear drum. The bones of the middle ear convey the ear drum s vibration to the inner ear. The inner ear consists of a fluid filled Basilar membrane that has tiny hair cells on the inside. The hair cells sense the vibrahon conveyed to the Basilar membrane and convert this into electrical signals that are then conveyed to the brain. 

Abu Bakar et al. 1999), polyhydroxybutyrate (Luklinska and Bonfield 1997) and polysulfone (Wang et al. 2001). These composites are easily formed and are used in maxillofacial augmentation. More specific uses include nasal reconstruction (Lovice et al. 1999), middle ear reconstruction (Geyer 1999, Meijer et al. 2002) and repair of orbital fractures (Tanner et al. 1994). Recently, a pilot study has been conducted to examine the feasibility of thin sheets for the outer ear canal (Zanetti et al. 2001). The bone grows up to the composite and establishes a bond with the low resorbable HAp particles. 

The middle ear begins on the inner side of the ear drum. The middle ear is an air-filled chamber that vents to the throat through the Eustachian tube. It contains three small bones (ossicles) and two suspensory muscles for them. The three bones are the maleus (hammer), the incus (anvil), and the stapes (stirrup). Sound energy travels across the three bones from the tympanic membrane of the outer ear to the oval window of the inner ear. The action of these three bones produces an amplification of about 2.5 dB. The suspensory muscles are the tensor tympani and the stapedius. When there is a loud sound, these muscles contract and provide some attenuation of energy transmitted across the three bones. 

The external ear (pinna) and the external auditory meatus form the outer ear. The eardrum, a membrane of connective tissue 0.1 mm thick and 8-10 mm in diameter, divides the external ear from the middle ear. The eardrum acts as a resonator with an inherent frequency of approximately 3000 Hz. The middle ear consists of an air-filled cavity, the... 

There are three sections of the ear - the outer (or external) ear, the middle ear and the inner (or irrternal) ear. The sound pressure wave passes into and through the outer ear and strikes the eardrum causing it to vibrate. The eardrum is situated approximately 25 mm inside the head. The vibration of the eardrum causes the proportional movement of three interconnected small bones in the middle ear thus passing the sound to the cochlea situated in the inner ear. 

First sound is gathered by the outer ear and fiinneled down the middle ear to the eardrum. 

In common with other power system equipment, motors need to be derated to suit a high ambient temperature. Equipment that is manufactured in America, UK and Europe is usually based on a maximum design temperature of 40°C. For higher ambient temperatures, e.g. 50°C as found in the Middle East and Ear East, the continuous duty output power and supply current would need to be reduced. The continuous duty is that as defined as type SI in IEC60034 part 1. International standards recommend performance and design criteria suitable for 40°C. Although most of these standard requirements will apply to ambient temperatures above 40°C there may be some addition restrictions to apply. In particular aspects of full-load current, duty, radiation of heat loss and outer surface temperature will need to be considered, see for example IEC60034 part 1 clauses 11 and... 

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