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Human ear - structure & working | Sound | Physics | Khan Academy - YouTube
Channel: Khan Academy India - English
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[Music]
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how are you listening to this music
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right now
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well you might know that your speakers
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are creating sound and your ears are
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listening to it but there's a lot more
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going on over here
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you see all your speakers are doing
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right now is vibrating the particles of
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the air close to it
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then they vibrate the air molecules
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close to them and so on and so forth
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and we call this a sound wave
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and eventually when the air molecules
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close to your ears start vibrating we
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hear sound
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but how does something as boring
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as air molecules going back and forth
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make us experience something like this
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[Music]
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well
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for that we need to look at our ear
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carefully
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i mean the entire structure of the year
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so let's look at how the different parts
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of the ear
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work together to make us experience
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sound
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so our ear can be divided into three
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parts
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the outer ear
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the middle ear
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and the inner ear
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the outer ear starts with the pinna
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it's the part that you can see and touch
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or in my case the part that my mom would
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twist quite often
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its job is to collect as much sound
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waves as possible and channel it into
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the auditory canal
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the sound waves pass through the
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auditory canal and eventually meet the
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eardrum which is shown in green over
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here
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the eardrum is a transparent membrane
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which is super sensitive to the
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vibrations of the air so as the air
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vibrates even the eardrum starts
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vibrating just like the skin of a drum
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and as you can see the eardrum also
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separates
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the outer ear
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from the middle ear
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this brings us to the middle ear
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the middle ear consists of the three
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tiniest bones of the human body and
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they're together called
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the ossicles
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and they have pretty cool names they're
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called the malleus
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the incus
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and stapes
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and here's the actual picture of these
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three bones
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and because of their shapes they're also
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commonly called as the hammer
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the anvil
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and the stirrup
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steer up is where you rest your feet
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when you're riding your horse
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all right so as the eardrum vibrates you
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can see the ossicles also start
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vibrating transferring the vibrations
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from the eardrums to the inner ear
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now their main job is to increase or
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amplify the pressure of the sound waves
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when it reaches the inner ear
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but why do we need to increase the
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pressure of the sound waves
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because as we will see the inner ear
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consists of a liquid
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not air
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so the vibrations must transfer into a
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liquid
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and you might already know that
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vibrating or moving particles of liquid
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is much harder than moving particles of
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air
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which is why it's very easy for you to
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swing your arms in the air but it's
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pretty difficult to do that inside water
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like say in a swimming pool
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and so to set this liquid in vibration
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the pressure has to be high enough
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and in fact it turns out that our
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ossicles increase the pressure of the
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sound about 20 times
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but how do they do that
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well just take a look at the base of the
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stapes
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it has such a small area compared to
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that of the eardrum
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so when the force gets transmitted from
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the eardrum to the stay piece it gets
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concentrated in a very tiny
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area and you might know when you
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concentrate force in a very tiny area
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you increase its pressure
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and that brings us to the inner ear
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the inner ear consists of a bony
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structure which is shown in purple
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now as you can see the top part of the
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structure consists of three semicircular
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rings
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they help us in maintaining our balance
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when walking or dancing or whatever we
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do so they're not involved in hearing so
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not so important for us
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the part that's involved in hearing is
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this snail-like structure this is called
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the cochlea
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what does it do
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well although these bones have already
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started dancing to the music nothing
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gets heard until these vibrations are
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converted to electricity and sent to our
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brain
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and that's exactly what the cochlear
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does
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now the cochlea is super complex and
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it's also a little mysterious
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even today there are certain things
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about it we just don't know
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and so we'll definitely not go into the
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details but as mentioned earlier it
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contains a liquid
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and when the stirrup hits our cochlea
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this liquid starts vibrating
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and then there are some specialized
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cells in the cochlea that convert these
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vibrations
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into electrical signals
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and these electrical signals go through
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the auditory nerves
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all the way to your brain
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where it gets finely interpreted as
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sound
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and the cells of your cochlea are
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amazing
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the electrical impulses that they
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generate are super sensitive to how loud
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the sound is or how feeble the sound is
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whether it is high frequency or low
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frequency
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and as a result your brain can
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differentiate the tiniest differences in
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the sound and so you can understand
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different letters or words or even
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understand what i'm saying right now
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or hear the different notes of this
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music
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and so to summarize the outer ear
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collects the sound waves through the
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pinna and directs them to the eardrums
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the three optical bones of the middle
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ear amplify these sound waves
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transferring it into the cochlea
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and the cochlea converts the back and
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forth vibrations of the particles into
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electrical signals and sends it to our
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brain
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and regardless of how many words i use
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to describe what's going on
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the very fact that the back and forth
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movement of the air can be converted
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into this amazing experience we call
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sound is truly unfathomable and beyond
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words
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[Music]
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you
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