Outer Ear
Overview of unit and week
Peripheral vs. Central auditory pathways
Peripheral auditory pathway
Outer ear
Middle ear
Inner ear
Central auditory pathway
Cochlear nucleus
Superior olivary complex
Inferior colliculus
Medial geniculate body
Auditory cortex
Anatomy of the temporal bone
External auditory canal
Tympanic membrane
Ossicles (malleus, incus, stapes)
Cochlea
Vestibular system
Changes in sound transmission
Conductive hearing loss
Causes
Symptoms
Treatment
Sensorineural hearing loss
Causes
Symptoms
Treatment
Detailed Overview of Unit and Week
In this unit, we will delve into the intricate workings of the auditory system, focusing on the differentiation between peripheral and central auditory pathways. The Peripheral Auditory Pathway consists of the outer ear, middle ear, and inner ear. Each component plays a crucial role in capturing and transmitting sound signals to the brain.
Conversely, the Central Auditory Pathway involves a more complex route, starting from the cochlear nucleus, passing through the superior olivary complex, inferior colliculus, medial geniculate body, and finally reaching the auditory cortex where sound perception occurs.
Furthermore, we will explore the Anatomy of the Temporal Bone, which houses essential structures like the external auditory canal, tympanic membrane, ossicles (malleus, incus, stapes), cochlea, and the vestibular system. Understanding the temporal bone's anatomy is pivotal in comprehending how sound is processed and balanced within the ear.
As we progress through the week, we will investigate the Changes in Sound Transmission, specifically focusing on conductive and sensorineural hearing loss. Conductive hearing loss stems from issues in sound conduction within the outer or middle ear, leading to various causes, symptoms, and treatment options. On the other hand, sensorineural hearing loss involves damage to the inner ear or auditory nerve, resulting in distinct causes, symptoms, and treatment approaches. By the end of this unit, you will have a comprehensive understanding of the auditory system and the complexities associated with hearing impairments.
The transcript of the video:
Welcome back to communication sciences.
Mosley, Cornetta 0 minutes 11 seconds
Going to give my captioning and my video a bit more time to get started and I think we're good to go.
Mosley, Cornetta 0 minutes 19 seconds
So this video is going to be all about the outer ear.
Mosley, Cornetta 0 minutes 23 seconds
OK, so the outer ear is composed of the panel, which is what you see when you just take a look at in here.
Mosley, Cornetta 0 minutes 30 seconds
But it's also composed of something called the ear canal.
Mosley, Cornetta 0 minutes 34 seconds
So I have the Merck Manual pulled up here.
Mosley, Cornetta 0 minutes 37 seconds
I would not use the Merck Manual to understand the anatomy of the pinna just because it gives a pretty gross representation.
Mosley, Cornetta 0 minutes 45 seconds
It doesn't show many of the landmarks on the Pennant that you'd be responsible for learning, and that we want you guys to know.
Mosley, Cornetta 0 minutes 53 seconds
However, if we turn this to the side, it does give us a pretty good image of the ear canal.
Mosley, Cornetta 0 minutes 59 seconds
So there are some aspects of the ear canal that I want you to see here.
Mosley, Cornetta 27 minutes 16 seconds
I'm gonna just stop writing because it looks so bad that it's driving me nuts, but you get the gist of where I'm going here.
Mosley, Cornetta 27 minutes 23 seconds
We worked through this in class and so the wavelength when we when we use those formulas, we know that a point A the uh wavelength of a tube that's closed on one end.
Mosley, Cornetta 27 minutes 40 seconds
If the tube is 25 millimeters long, the wavelength is .1 meters, and if the tube is 35 millimeters long, the wavelength is .14 meters.
Mosley, Cornetta 27 minutes 53 seconds
Just by using that formula.
Mosley, Cornetta 27 minutes 55 seconds
OK, so when we divide .25 when we multiply .25 by 4, we get .1.
Mosley, Cornetta 28 minutes 3 seconds
When we multiply .3554 we get .14.
Mosley, Cornetta 28 minutes 7 seconds
OK.
Mosley, Cornetta 28 minutes 8 seconds
So just moving, changing our, converting our millimeters to meters and then applying that formula, now knowing our wavelength when we divide our, when we divide the speed of sound by that wavelength, we're able to calculate the frequency.
Mosley, Cornetta 28 minutes 24 seconds
So when we divide 343, the speed of sound by .1 we get 2450 Hertz.
Mosley, Cornetta 28 minutes 34 seconds
When we divide .1, the speed of sound by .14 we get 303,400 and I'm sorry that's backwards.
Mosley, Cornetta 28 minutes 43 seconds
This yields this and this yields this OK cause the shorter wavelength means a higher frequency.
Mosley, Cornetta 28 minutes 53 seconds
OK, so when we apply our formula which divide within which we divide the speed of sound by our wavelength, this is what we get in frequency.
Mosley, Cornetta 29 minutes 4 seconds
OK, so we usually generalize this to say that the ear canal has a resonance between 2500 and 4000 Hertz.
Mosley, Cornetta 29 minutes 15 seconds
OK, so the gain is the gain and the 25 thousand 2500 to 4000 Hertz area is an important factor in making the human ear more sensitive.
Mosley, Cornetta 29 minutes 27 seconds
And what the outer ear does is it enhances though that mid frequency range.
Mosley, Cornetta 29 minutes 34 seconds
It acts as what we call a bandpass filter.
Mosley, Cornetta 29 minutes 38 seconds
So remember, a bandpass filter allows for it boosts certain frequencies.
Mosley, Cornetta 29 minutes 43 seconds
So if we had our graph here where this is frequency and this is gain or amplitude like increases in amplitude, then it would look something our our ear canal would do something like this.
Mosley, Cornetta 29 minutes 58 seconds
A bandpass filter where the cutoff frequencies are between 2500.
Mosley, Cornetta 30 minutes 4 seconds
Oh my goodness.
Mosley, Cornetta 30 minutes 6 seconds
You guys know that this supposed to be 2500 and this one is supposed to be 4000.
Mosley, Cornetta 30 minutes 12 seconds
So oops, sorry right here.
Mosley, Cornetta 30 minutes 14 seconds
Should be or 1000.
Mosley, Cornetta 30 minutes 23 seconds
Abstinence.
Mosley, Cornetta 30 minutes 28 seconds
Alright, so our graph.
Mosley, Cornetta 30 minutes 36 seconds
Right.
Mosley, Cornetta 30 minutes 37 seconds
We have our 2500 and then this cut off would be 4000.
Mosley, Cornetta 30 minutes 47 seconds
I am so sorry guys, I need to get a better tool for this, but you get the gist of what I'm saying.
Mosley, Cornetta 30 minutes 54 seconds
So when we look at that band pass filter, it has cutoff frequencies of two 2500 and 4000 Hertz.
Mosley, Cornetta 31 minutes 1 second
That's just due to the residents of the ear canal, caused by its size and shape.
Mosley, Cornetta 31 minutes 8 seconds
All right, so this is another a much better image of what I was just trying to do.
Mosley, Cornetta 31 minutes 14 seconds
So it's showing the amount of gain and decibels and notice that that peak is between 2500 and about 4000 Hertz.
Mosley, Cornetta 31 minutes 23 seconds
That's just caused by by the ear canal.
Mosley, Cornetta 31 minutes 28 seconds
However, you do have some extra resonance around 5000 Hertz from the pinna that you're that you're canal adds about 10 decibels between 2 and 4000 Hertz.
Mosley, Cornetta 31 minutes 41 seconds
And together they produce a gain in acoustic pressure.
Mosley, Cornetta 31 minutes 45 seconds
In between 2000 and 5000, Hertz.
Mosley, Cornetta 31 minutes 48 seconds
OK, so these are the combined effects of the outer ear.
Mosley, Cornetta 31 minutes 52 seconds
So the pinna and the ear canal together.
Mosley, Cornetta 31 minutes 55 seconds
This is particularly important for speech sounds.
Mosley, Cornetta 31 minutes 59 seconds
Many speech sounds are within this range, and so by having the added boost of the boost that our external ear that our external auditory veidis and pinna provide, that extra boost gives us better access to those speech sounds.
Mosley, Cornetta 32 minutes 18 seconds
Alright, so we've talked about the outer ear as a part of our peripheral auditory system.
Mosley, Cornetta 32 minutes 24 seconds
The next thing that we'll discuss is the middle ear.
Mosley, Cornetta 32 minutes 27 seconds
The next video, we'll discuss the anatomy and Physiology of the middle ear.
Mosley, Cornetta 32 minutes 32 seconds
Thank you for listening.