Conduction, bone

There are three widely accepted routes by which bone-conducted sound stimulates the cochlea. These are the compres-sional, inertial and osseotympanic theories of bone conduction (12). Compressional bone conduction implies that the cochlear shell is compressed slightly in response of the pressure variation caused by a sound. Inertial bone conduction alludes to a relative motion between the ossicular chain and the temporal bone for low frequency vibrations. The osseotympanic theory denotes a mechanism by which relative movement of the skull, with respect to the mandible, sets up pressure variation in the air present in the auditory meatus. Since perception of microwave pulses are correlated with the capacity to hear high-frequency sound, it rules out inertial or osseotympanic bone conduction as potential mechanisms for microwave acoustic effect. 

A mathematical analysis of pressure waves created by thermoelastic expansion of brain matter showed that the sound pressure required for human subjects to barely perceive microwave pulses is about the same as the known minimum audible sound pressure for bone conduction (1 3,27). The frequency of sound provides another line of evidence. It was shown that the fundamental frequency of sound is given by... 

There are two alternate routes that might be taken by the microwave-induced thermoelastic pressure wave to reach the cochlea the well-known bone conduction route and a yet unspecified but perhaps a direct route from brain matter to the cochlea. While current information precludes elaboration of the latter, compressional bone-conduction appears to be the most likely candidate for the former, since the frequency of microwave-induced sound is very high and is inversely proportional to the radius or circumference of the head (15,26,27). 

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. 

A fundamental problem of binaural hstening is known as in-head localization (IHL) and is apparently due to the lack of a dispersed wavefront striking the aural cavity. Other problems such as bone conduction (BC), the frequency response and resonance challenges of small aperture assemblies, variable leakage... 

Vibrations in solid or semi-solid material, or movement in liquid, can produce a series of minute changes in the pressure of the air which is in contact with the material. When this series of small air pressure variations reaches the ear and triggers a message in the auditory nerve, the brain registers this as sound. Sound waves can also travel as vibrations through solid materials such as steel, and Uquid materials such as water. We can hear the sound in steel if we put part of our skull in contact with the steel. This is known as bone conduction of the sound. Some of the pressure waves reaching us through the air can also travel to the inner ear by bone conduction rather than up the ear canal. 

Frequency Allergic skin reactions to titanium are rare. In 445 patients who had received bone-anchored skin-penetrating tkanium implants for anchorage of facial prostheses or bone-conducting hearing aids, nine had adverse skin reactions around the titanium implants none had delayed hypersensitivity to titanium [65 "]. In these and other cases [66 ] skin reactions have been attributed to infections with Staphylococcus aureus. 

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