Human Hearing.

What is sound and hearing? What is the difference?

Sound is a form of different frequencies and is made up of vibrations. These vibrations travel through the air in a compression and refraction form. Sound can be hard by humans and animals, even fish and any living creature.

A way of describing hearing is by the blooms taxonomy. This is a triangular diagram that shows you the way you understand things and listen and hear different things.

Hearing is when you are able to hear the different sounds and the first step I to remember something. For example you remember what people tell you. When we were growing up we were learning to speak and we may not have known what it meant. For example mummy and daddy we learn as a child. This does not mean we knew what they word meant we were just being told to repeat something. And as we grown up we learn the definition. So this means that after remembering something we then understand it. For example if we are told to get a certain train or bus, this is because you need to be at a certain place at a certain time. Then after we understand something we then apply that knowledge to something. Learning what time things are for example we will then know that we need to get to a place for a certain time and how long it will take and what time travel I will need to get there for that specific time.

For the next part we will use the example of a human ear. Once we are told the name we can recall the name. Then we search up what part is where in the ear. Then we learn what part does what and analyse what we have learnt and put each part of the ear together. In what way is a certain part used to pass information onto another part of the ear. For example the cochlea transmits noise to the brain nerves helping us understand what we are hearing. Then the next part is making judgments on what we analyse making more sense of it and then we put all of the information together.

So that is the different parts of hearing and how it is different to sound. Sound is a noise that we hear through vibrations and hearing is understanding the sound. Like a scream we might relate to as danger nearby we need to help or flee the situation. Also listening is how we understand what we hear.

How does the human ear work?

The human ear has different sections to it. It has the outer ear part, the middle ear section and the inner ear section. All of these sections contain different parts of the ear that lets us hear what’s around us.

Pinna

The pinna is also known as an “or auricle” (Partners 1997-2015) is a part of the ear that is on each side of our head. This also helps us for direction from where noise I s coming from. More about that later. It is made of skin and cartilage and soft tissue. This is so that it keeps the shape (different people have different shaped ears) and is also flexible. The pinna serves the purpose of collecting vibrations of sound and guides the vibrations into our ear canal. This helps us to determine where the sound is coming from.

Ear canal

The ear canal (also called the external acoustic meatus) is a passage way in which sound travels into the ear. It is a form of bone and skin that leads to the eardrum. The ear canal is a passage way for the entry of sound waves to enter into the middle ear section. “Which get propelled toward the tympanic membrane, known as the eardrum.” (annonymous 2005-2015)

Ear drum

The ear drum is a thin piece of tissue that marks the point between the outer ear and the inner ear. This is also known as the tympanic membrane. The size is said to be around 0.1mm thick and 8-10mm in diameter. Despite how small that may seem, in fact the ear drum is very flexible and tough and is less prone to being damaged beyond repair. A tough and flexible piece of tissue, called the cartilage, hold the eardrum in place.

The eardrum has three layers. These layers being cutaneous layer (outer), fibrous (middle layer) and the mucous membrane on the inner part of the ear drum. This makes the eardrum tough and less likely to damage. Although the eardrum is tough, you can pop/burst it which in some cases can cause a lot of pain. This can affect your hearing. In my case, in the past I was always getting an ear infection, and that lead to damage inside the ear, which has left me with hearing loss in my left ear. However I think they can fix this my maybe doing an extraction of maybe left behind wax inside the ear clearing the ear of any blockage left behind.

The process in which we hear from the eardrum is by sound waves that travel into the ear, hit the eardrum which causes it to vibrate and then the vibrations get transmitted further into the ear, reaching the bones of the middle ear.

Occicles

The occicles is made up of three mini bones. These are called the malleus, incus and the stapes bones. The malleus bone is the largest out of the three bones. It is also known in its informal term as a hammer. This is because of its shape. When sound reaches the eardrum, the malleus transmits these sound vibrations to the incus, which then travels to the stapes bone, which is connected to the oval window or as shown above known as the round window. It is unlikely that the malleus will be the cause of any hear loss that you may encounter. This is because it is connected directly to the eardrum. The occicles chain (malleus, incus and the stapes) is often effected by abnormal skin growth which is known as the cholesteatoma. This can cause loss of hearing. The malleus and or the incus bone may have to be removed in order to remove the overgrown skin around the bones. After this procedure is taken, you may have to undergo more surgery in order for reconstruction of the ear.

After traveling through the external part of the ear, the vibrations produced by sound waves are transmitted through these bones, which is then passed through to the cochlea. After this the sound is then transmitted through nervous system signals leading to the brain. The incus bone lays in the centre of the three bones, connecting the malleus to the stapes. It is known to be shaped like an anvil, which is where its term, the anvil, is originally from. Just because it looks like an anvil. The bone has many surfaces. One in which is called the head which forms a joint with the malleus bone. Is also has extensions. One short and one long. These are calls crus. At the end of each crus is “the lenticular process, a hooked-shaped part of the incus that forms a joint with the head of the stapes.” (annonymous 2005-2015) The short crus joins to the back wall of the ear cavity. The centre of the incus bone is also known as the body.

Cochlea labyrinth

The cochlea is located in the inner section of the ear. This is after the semi-circular nerves and the little bones that transmit vibrations to the cochlea. The cochlea is filled with fluid membrane that helps with the detection of sound. This also helps you with your balance. The use of the cochlea is to detect low frequencies, such a bass in music. If your cochlea is a smaller size then you are more likely to pick up higher frequencies than those with a larger cochlea. The cochlea is known to be one of the most sensitive structures in the human ear. It is known to be sensitive to the vertebrobasilar ischemic stroke. The vertebrobasilar ischemic stroke is when blood flow to the area located at the back of the brain is cut off. This area supports brainstem, occipital lobes, and cerebellum, which means it supports functions such as the need to breath, swallow, the vision and the coordination.

The cochlea also has a liquid in it called the endolymph which is low in sodium and high in potassium. This liquid helps us with our balance. This is because when we tilt out head, the liquid will move telling us in which direction our head is and if we are not up right.

Hearing loss from this part of the ear may be from low frequencies. This creates hearing loss and result from irreversible deterioration of the cochlea. This cannot be fixed. This happens during aging of humans. This is normal, but unfortunately cannot be fixed.

Semi-circular canals

These bones are lined with very minute hairs that can only be seen by a microscope they are that small. These hairs are also called cilia. The bones are also filled with a liquid substance. This is also known as the endolymph. This works as a motion sensor. This is when the head moves the liquid moves the tiny hairs in the bone and as they move it then sends signals to the brain. This helps the body balanced.

These tiny hairs in the ear pass on vibrations to the brain, and if one of these hairs snaps, then the frequency that that hair is assigned to, is then the only frequency that is permanently on. This can be caused from loud noises or being around noise that can damage your ears after a certain amount of time. This is also known as noise induced hearing loss. You can also get this by listening to music at a very high volume. Once you damage one or more of the hairs it can no longer be fixed. People may also experience a ringing in the ear if they have been to a very loud concert, or you can also experience tinnitus, which is something that causes you to constantly hear a ringing in the ear. Some people with tinnitus will have to have different noise in the background at night in order to drown out the tinnitus, so that they can sleep at night.

Tensor tympani

The tensor tympani muscle is one of the two muscles in the middle ear. This muscle tenses to protect the ear drum form suffering any damage that it may be in danger of.

Hearing damage

Noise induced hearing loss is one was that we lose our hearing. What is noise induced hearing loss? Well we experience sound in our everyday life, such as the sound of people talking, cars if you are traveling, birds, television, and music when we want to isolate ourselves from the world. Normally these things are at safe levels that don’t damage our hearing at all. But sounds can be more harmful to our hearing than you think. This can be when they are too loud for a long period of time. Or really really loud really quickly. The range that a human can hear at is from 20htz to 20khtz (20000htz). However as we age we tend to stop hearing really low frequencies and really high frequencies. This is just the natural process of aging. We are more likely to lose more of our hearing bb isolating ourselves to loud sounds for a short or long periods of time. These sounds can damage sensitive structures of the human ear, such as the ear drum and the cochlea. This is called noise induced hearing loss or NIHL for short.

NIHL can happen over a long period of time or can happen immediately. It can also be temporary or permanent. A permanent form of NIHL is known as tinnitus. This is where the person is always hearing a high pitch frequency and cannot get rid of it. Some may even need a background nose to drown out the noise at night just so they are able to sleep.

Even if you cannot tell that you are damaging your hearing and every precious part onside the ear, you may suffer with hearing loss in the future. You may have trouble with hearing when you are older. This will result from damage earlier on in your life. This can also effect both ears. Not just one. Something to add, you can also loss hearing from having multiple ear infections. This could cause damage to the inner ear and also may cause blockage which result in poor hearing.

You may experience things like not being able to hear somebody that well when they talk, especially when talking on the phone or in a noisy room. Regardless of how it might affect you, one thing for certain is NIHL is something that you can prevent. To prevent things like this you could wear hearing protection when you are in a really noisy area for a long period of time. Making sure you don’t have your music too loud if you have in ear buds while listening to music. Don’t listen and stand near really harsh loud sudden noises, such as a really loud drum or a bang of a bomb or anything loud and damaging. All of these precautions can be taken in order to preserve your hearing for as long as possible, and not suffer from hearing loss at an older age.

Here is a list of things that we are exposed to, reasonable to damaging, on how we could lose our hearing.

• The humming of a refrigerator 45 decibels

• Normal conversation 60 decibels

• Noise from heavy city traffic 85 decibels

• Motorcycles 95 decibels

• An MP3 player at maximum volume 105 decibels

• Sirens 120 decibels

• Firecrackers and firearms 150 decibels

“When your hearing is working normally, information is being passed through the different parts of the ear to the brain. The type of hearing problem you may have depends on which part of the ear is not responding well.” (N/A 2015)

Other ways we may lose our hearing?

Hearing loss Isa very common thing. Even if you don’t realise this. Around on in 6 people in the UK is deaf or hard of hearing. There are several ways that you may be able to tell if you are losing your hearing. The most common cause of hearing loss is from the natural process of aging. This will normally begin at the age of 21, but at a later age at around 50, our hearing will become worse and will begin to deteriorate. Being exposed to music that is too loud or any loud noises for that matter will result into hearing loss. It is a shame because most people take our hearing for granted. It is also like the saying, you never know what you have until it’s gone. Well once your hearing is gone, it cannot be undone. And it could be from something you could have prevented such as loud music or loud noises for a long period of time. (NHS Choices 2015)

Common sound levels

We humans are exposed to different sound levels every day. Our ears are tuned for what we hear every day. This can consist with stuff like talking and a hover, cars, and a television, or even a refrigerator, or a microwave. All of these things have a different sound level.

Sound levels are measure in decibel. What is a decibel? Well it is a unit of measure. A unit that we measure the loudness of a sound. Humans can hear sound from 0-140 decibels. 0 doesn’t mean that there is no sound that we can’t hear. 0 decibels is the so-called hearing threshold for human ear.

We as people can hear up to 140 decibels. However if we were to experience this then it would be too painful for our ears and if you listen to anything loud for a long period of time or just a short period of time, this could cause you to have a high risk of permanently damaging your hearing. Here is a table showing you how loud sound is:

Decibel

Sound

Example

10

Almost inaudible

A leaf falling

20

audible

Rustles of autumn leaves

30

Very soft and quiet

Whispering

40

Normal

Living room, quiet classroom

50

Limited sound

Refrigerator working, car driving past

60

audible

Sound of human voice

80

unpleasant

Alarm clock, traffic, door bell

100

Extremely unpleasant

Truck close by, screaming, yelling, shouting

120

Human voice at its loudest, police siren

140

Permanent damage to hearing

fireworks

And there are many more.

As humans, we are very delicate to different types and loudness of sound. We can only be exposed to certain decibels for a certain amount of time before hearing damage occurs. This is because of how sensitive the human ear is to sound. For example we are only aloud to be exposed to 85 decibels for 8 hours. Now that is okay. But if we go over 8 hours that is where we start getting hearing damage. However we may not notice this until later in life when our hearing will start to deteriorate. Here is another table showing you the duration of time that we can be exposed to certain decibel levels: (annonymus 2015)

Noise Level (dBA)

Maximum exposure time per 24 hours

85

8hours

88

4 hours

91

2 hours

94

1 hour

97

30 minutes

100

15 minutes

103

7.5 minutes

And so on…

As you may have noticed, as the decibel level of the sound increases by 3 decibels, the duration time we can be exposed to it is halved. For example 85 decibels we can listen to for 8 hours. Then 88 decibels is for 4 hours. 85 plus 3 is 88 and half of 8 is 4. So if you know the decibel level of a sound you are exposed to, you could easily work it out by using this chart or know that 85 decibels can be listened to for 8 hours and then work out at how long you can be exposed to the decibel level of sound for.

Hearing in 3d?

How do we humans know where sound is coming from? What direction? How loud? Well this is all to do with the components in our ear.

“It’s all about the human ear and the human brain, and understanding how the ear preservers sound.” (Kyriakatis n.d.)

There is many reason as to why we hear in 3D. Here are some for example.

1. Phase shift

2. Loudness

3. Filtering

These are the three main reasons as to why we hear in sound.

What is phase shift? Phase shift is where direct sound has to move around objects in its pathway.

What is loudness? Loudness is where you hear a sound being a very high volume or at a very low volume. This is indicated by our ears picking up different pitch and frequency levels and the decibels of which the sound is, and transmitting this to our brain to acknowledge what we are hearing. This is how we know the loudness of something.

What is filtering? Filtering is when sound is being absorbed by something. For example if you are in a room and you ca hear a muted/ muffled sound through the wall, most of the sound is being filtered through the wall. Meaning the low frequencies are getting through and the high frequencies are being absorbed into the wall. This is why in a recording studio we have sound proofing to make the room sound duller and have less reverb.

In other cases like hearing in 3D, our head is used as a form of filter. We determine where the sound is coming from, from the size and shape of our head. It is also to do with which ear the sound enters first. But with this, the air being moved by the sound will hit one ear before the other one, which we then know where the sound is coming from, but the sound is also absorbed by our head. Which acts like a filter.

We hear in 3D with the dynamics of the sound also. This will determine whether the sound is near or far away, however this doesn’t support fully as to why we hear in 3D because we could hear something really loud and it be really close to us, and then far away things will be quieter.

We are also hearing in 3D because we have 2 ears. But why do we have two ears? This is another reason why we hear in 3D. If we have one ear it will be hard for us to determine where the sound is coming from. So having two ears helps us to define where the sound is coming from, from the direction of the sound. As well as the way our ears work, and filtering and loudness etc., we also have two ears to help us capture the sound.

If you have ever lost hearing in one ear, you will know that it is extremely difficult to determine where the sound is coming from. This is because sound hits one ear before the other saying that the sound is over on our left or right and it is at a certain volume at a certain distance away, so this is why we have two ears. This is also so that if we have loss of hearing in one ear, it may be harder for us to determine where the sound is coming from, but at least we can still speak and hear things. Communication and hear our surroundings.

Psychoacoustics

There are three different types of psychoacoustics, and maybe more. Three of those are the Mcgurk effect, holophonuics and Shepard’s tone.

The Mcgurk effect

The Mcgurk effect is where it demonstrates how the hearing and vision of speech are connected. We usually see what we hear. But the Mcgurk effect is when, for example somebody speaks and we see what they say, but if we are shown somebody saying something different but we hear something else, this is when we hear what we see even if the thing being said is different. An example of this is:

https://www.youtube.com/watch?v=G-lN8vWm3m0

This is a YouTube video of a document from BBC. This video shows that when we are shown the person saying bar and hearing bar we hear bar, but when they change the video, the audio is still bar, but the person is saying far, so we hear far because our brain is linking vision to the sound that we hear.

Holophonics

Holophonics is a term used when an audio recording is in 3D. We are also exposed to this with something called ASMR. More about that later. But Holophonics is where somebody has recorded an audio and has been able to make it sound like you are actually there in the room, and not just listening to something through headphones. This is also known as binaural recording. This is created by taking the elements that we use to hear in 3D and bringing them into the recording to make it sound 3D to our ears.

ASMR is a very similar thing. They use the Holophonics to create relaxing things, like a quiet hair cut or just tapping on things. As I have learnt recently through my own findings that everybody will have some sort of trigger to something that makes them relax. For example some people love the sound of rai. Some people love the sound of a person’s voice spoken softly or whispered, some others may just like the way some things sound while being tapped on.

ASMR stands for, Autonomous Sensory Meridian Response. ASMR “is a neologism for a perceptual phenomenon characterized as a distinct, pleasurable tingling sensation in the head, scalp, back, or peripheral regions of the body in response to visual, auditory, tactile, olfactory, or cognitive stimuli. The nature and classification of the ASMR phenomenon is controversial, with much anecdotal evidence of the phenomenon but little or no scientific explanation or verified data” (anonymous 2015)

People experience ASMR in different ways. Some ways people might experience it, they might get a cold chill, or a feeling of goosebumps from there head to their feet. They might get a shiver, or just really relaxed and drowsy. Some people use this method as falling asleep if they have trouble. It is also been known to help those who suffer mild insomnia. Or at least help them relax and sleep for even a little while.

Videos are made with this method of binary. They will make it sound like you are actually in the room with them. Either having an eye test or getting a haircut and for some people things like this is really relaxing for them.

Shepard’s tone

Shepard’s tone is an illusion of sound. An audio mp3 or anything as such that you can hear sound. This is an effect that sounds like the audio is continuously descending or inclining in pitch. An example of this ix :

https://www.youtube.com/watch?v=BzNzgsAE4F0

This shows that when the track starts it sound like it is going up all of the time, when in reality, it is not. It is just an illusion of sound to make your brain think that it is going up or down in pitch.

Bibliography

annonymous. 2005-2015. Healthline. http://www.healthline.com/human-body-maps/ear-canal.

annonymus. 2015. noise help. http://www.noisehelp.com/noise-dose.html.

anonymous. 2015. wikipedia. https://en.wikipedia.org/wiki/Autonomous_sensory_meridian_response.

Kyriakatis, doctor. n.d.

N/A. 2015. hearing link. http://hearinglink.org/how-the-ear-works?gclid=CjwKEAjw-vewBRDH1-b52Lig1hkSJACTPfVFWbQG8SjJL91-KpLzbCpnBFnJFyz37GzfR8YbRDQfdxoCWpDw_wcB.

2015. NHS Choices. 12 october. http://www.nhs.uk/Livewell/hearing-problems/Pages/losing-your-hearing.aspx.

Partners, ASHA Corporate. 1997-2015. American speech- language- hearing assosiation. http://www.asha.org/public/hearing/Outer-Ear/.