How is the human ear works?
Answers
Answer:Here is how the ear works normally:
The sound waves are gathered by the outer ear and sent down the ear canal to the eardrum. The sound waves cause the eardrum to vibrate, which sets the three tiny bones in the middle ear into motion. The motion of the bones causes the fluid in the inner ear or cochlea to move.
Answer:
The ear has three main parts. They are called the outer, middle, and inner ears.
The outer ear consists of the organ on the side of our heads that we usually call simply "the ear". (The scientifically accurate name for this structure is the pinna.) Also included in the outer ear is the ear canal. This is the hollow tube that leads from the pinna into the head. It terminates in the eardrum which is technically known as the tympanic membrane. The purpose of the external ear is to transmit sounds from the outside world into the more internal parts of the auditory system. While one can simply think of the pinna and ear canal as a simple funnel for collecting sounds, in reality they perform some important functions. The pinna has various ridges and folds that act to reflect and absorb certain frequency components of the sound wave . Because the pinna is not circularly symmetric, sounds which come from different directions will have slightly different spectral characteristics. (This means that certain frequencies will be slightly louder or softer depending on the direction they enter the ear.) As a result, sounds which come from above our heads seem slightly different than sounds coming from below. This allows us to localize (pinpoint the direction of) a sound source. We therefore immediately look up when someone calls us from an upper story window.
The ear canal also plays a role in shaping the spectrum of incoming sounds (emphasizing certain frequencies and attenuating others). It does this in a manner similar to an organ pipe where certain wavelengths tend to reflect back in such a manner so as to cause constructive interference which acts to strengthen the sound. Others frequencies reflect back in a way which causes destructive interference and are thereby weakened. So the net result is that some signal processing already occurs in the outer ear.
At the inner end of the ear canal is the eardrum which is a small membrane about 1 cm in diameter. Its purpose is to seal off the delicate organs of the inner parts of the auditory system so that foreign matter and bacteria don’t enter which could otherwise clog the system and cause harmful infections, as well. However, it is designed to efficiently transmit sound across it.
The middle ear begins at the inner surface of the eardrum. It is connected to a chain of three small bones called the ossicles. Their names are the malleus (hammer) incus (anvil) and stapes (stirrup) since they resemble those objects in shape. Their purpose is to act as a mechanical transformer. The reason for this is that sound waves are vibrations of air molecules. However, the organ which performs the actual transduction (conversion of acoustic energy into electrochemical impulses) is a fluid filled bony coil called the cochlea. Because air is much less dense than liquid, and is also more compressible, most of the energy of the sound wave would simply be reflected back into the ear canal. A rough analogy would be throwing a rubber ball at the sidewalk. Most of the energy simply is reflected in the bounce of the ball back to the thrower. Very little is transmitted to the massive earth. In order to efficiently transmit sound from air into liquid, a lever system is needed to help the move the fluid. The middle bone acts as a sort of pivot for the malleus which is attached to the eardrum, and the stapes which is attached to the cochlea. The two lever arms have different lengths giving a mechanical advantage.
The inner ear refers to the cochlea which is a helically shaped bony structure that resembles a snail in appearance. It is the most complicated part of the auditory system, and papers are continually being published in an attempt to elucidate its complex workings. Basically, it has three parallel fluid filled channels that coil the around the axis of the cochlea.The last of the middle ear bones, the stapes, acts like a piston, and pushes on the fluid in the first channel, the scala vestibuli, through an opening in the base of the cochlea called the oval window, setting up a pressure wave. The pressure wave propagates in this fluid which is called perilymph toward the end of the cochlea which is called the apex. At the apex, the scala vestibuli connects through an opening called the helicotrema to the third channel which is called the scala tympani. The scala tympani acts as a return path for the pressure wave back towards the base of the cochlea. There is a flexible termination at the basal end of this channel called the round window which bulges in and out with the flow of fluid to allow the wave to flow unimpeded. Otherwise, the incompressible fluid would not have any freedom to cause much motion.