HEARING (AUDITION) AND BALANCE:The Outer Ear, Auditory Canal

<< SENSATION:The Human Eye, Cornea, Sclera, Pupil, Iris, Lens

PERCEPTION I:Max Wertheimer, Figure and Ground, Law of Closure >>

Introduction to Psychology PSY101

Lesson 16

HEARING (AUDITION) AND BALANCE

Hearing or audition is the sense of sound perception and results from tiny hair fibers in the inner ear

detecting the motion of a membrane which vibrates in response to changes in the pressure

exerted by atmospheric particles within (at best) a range of 20 to 20000 Hz. Sound can also

be detected as vibrations conducted through the body by tactician. Lower and higher

frequencies than can be heard are detected this way only. The main features regarding ear are:

· Ear is regarded as the organ of hearing.

· Like our other senses, our hearing or audition, is highly adaptive

· Sense of motion and balance is regarded as the main and important function of the ear

· Organisms have the ability to hear a wide range of sounds with different frequencies (ranging from

higher to very low faint voice)__ but more importantly we can easily detect different voices of

people whom we know or met

· For this, the important question is how we do it? How the transformation of sound waves into

neural messages takes place?

Some Interesting Facts about Hearing

· Animals have the capability of hearing more sounds than humans

· Dolphins have the best sense of hearing among all animals

· When people go up high in the mountains, the changes in pressure cause the ear to pop

· Babies can get ear aches because of the milk deposit in the eustachian tube, which helps the

bacteria to grow there and may cause problems later in life

· Children can hear more noises than adults, as their ears are more sensitive than that of adults

· Ear aches result when too much fluid causes pressure in the eardrum__ often occur due to

allergies, virus or some sort of infection

The Human Ear: Anatomy/ Structure

The primary apparatus of hearing i.e., the ear is divided into three parts

1. The outer ear

2. The middle ear

3. The inner ear

1. The Outer Ear

· The outer ear serves the function of collecting the sound waves from the environment to the

internal portions of the ear. It is shaped like a reverse megaphone

· It also plays an important role in locating the sound direction from which it originates

Introduction to Psychology PSY101

Auditory Canal

· When sound waves originate from the vibrating object, they then pass through the auditory canal,

which is a tube like passage through which the sound travels to the inner part of the ear or " the

eardrum".

Eardrum

· The part of the ear that starts vibrating when sound waves strike/ hit it.

· Its intensity of vibration is dependent on how intense the sound waves are___ the more intense the

sound, the more intensely it vibrates.

· These vibrations are then transmitted to the " middle ear".

2. Middle Ear

· A tiny chamber between the eardrum and cochlea containing three bones---- the hammer, the anvil, and

the stirrup, which transmit vibrations to the oval window.

· These three bones have only one function, i.e. to convey/ transmit the message to the inner ear.

These bones are also effective in the sense that they strengthen the stimulus (vibration) so that it can be

easily heard. Information (Vibration) Travels Through These Three

Bones

Hammer

Anvil

Stirrup

Oval window

Oval Window

· A membrane between the middle and the inner ear that increases the strength of the stimulus (vibration)

while transmitting them.

· Serves as the amplifier so that tiny or hiss voices could be heard, which otherwise may remain unnoticed.

3. Inner Ear

· The innermost region/ part of the ear that contains important structures such as cochlea, semi

circular canals and vestibular sacs, and that changes/ transforms the sound waves into the neural

impulse.

· Organs that are present in it help us to determine in locating our position and how we are moving

in space.

· In the inner ear, the sound enters into the cochlea___ a coiled, bony tube filled with the fluid that

receives information (sound) from the oval window or through bone conduction. The sound waves

that reach here help in triggering the nerve impulse. Basal Membrane

· Inside the cochlea is the basal membrane passing from the middle of cochlea___ a structure that

divides the cochlea into the upper and lower chambers/ parts.

· This basal membrane is covered/ surrounded by the tiny hair cells that are bent on the vibration, so

that neural message reaches the brain without any hindrance or difficulty; helps to transmit

information to the temporal lobe's auditory region.

· Another means

of hearing sound

besides cochlea

is through bone

conduction. As

ear is directly

connected with

the skull's bones,

the cochlea is

then able to

pickup

subtle

voices (such as

one's

own

voice). This is

largely due to

Introduction to Psychology PSY101

bone conduction. Why one's own voice seems different to one's self than to others is due to this

phenomenon. This may also occur because voice reaches one's self through the air and also

through bone conduction.

Sound and Its Physical and Psychological Aspects and Impacts

Sound is the primary stimulus for hearing.

Sound actually refers to the physical movement of air molecules in regular and wave like pattern/

sequence.

· When an object creates/ produces sound, it results in the back and forth vibration of its surface,

creating sound waves in the surrounding air. These dense and thin sound waves serve as the

stimulus for the ear/ for hearing process.

· Sound waves that are being produced differ in their intensity, amplitude, frequency and

complexity___ they afterwards produce corresponding dimensions of sound. i.e. pitch, volume and

timbre.

Frequency

· Frequency is the prominent feature/ characteristic of sound and refers to the number of complete

wave lengths/ crests that occur or pass a point in each second.

· In low frequency of sounds, there are relatively fewer and slower up- and- down wave patterns per

second__ these low frequencies are then translated in what is called " pitch".

Pitch

· Primarily related with the frequency and refers to the quality of sound that is being produced by the

frequency of the sound wave; expressed in cycles per second__ the trait that makes the sound

"high" or " low".

· The lowest and highest frequencies that humans can hear range from 20 cycles per second to

20,000 cycles per second.

Volume/ Intensity/ Loudness

· Volume or loudness can be described as " strong" or " weak"__ determined by the amount of

pressure difference between the compressed part of the sound wave and the prominent part

· Waves that have low peaks create soft sound as compared to the waves with higher peaks

· The range within which humans can hear is extensive measured in unit called decibel (db).

· If the sound exceeds 120 decibels then it become painful to human ear.

Timbre

· When fundamental tones are combined with the weaker tones, they are then to be known as over

tones.

· Partials and harmonic tones are the audible tones that help to make up timbre__ quality of sound

determined by the complexity of sound waves

· The difference in quality or timbre is determined by the complexity and arrangements of the

overtones that any instrument/ object produces which largely depends on its design and material

from which it is made.

Theories of Hearing/ Theories of Pitch Perception

Place Theory of Hearing

· The most frequent question that comes to mind is that how can our brain sort out the sound waves

of different frequencies and intensities without any hindrance or problem?

· The answer lies in the studies done in this regard. They show that the basal membrane (inner most

region of the ear near the cochlea) and its associated areas are most sensitive to high pitched

frequency sounds, and the area near the cochlea is more sensitive to low- frequency sounds.

100

Introduction to Psychology PSY101

The findings of these studies led to the formation of place theory of hearing, which says that

different areas in the basal membrane respond to different frequencies of sound; pitch corresponds

to the location of greatest stimulation along the basilar membrane.

· The most important shortcoming of this theory is that it is unable to explain the process of hearing,

i.e. sounds of low frequencies also trigger the neurons in the basal membrane and its associated

areas.

· Due to this incomplete explanation of auditory phenomena, an additional explanation came in the

form of " frequency theory of hearing".

Frequency Theory of Hearing

· This theory explains that the entire basal membrane acts as a microphone, vibrating in response to

sound i.e. activation occurs in the whole area in response to the vibration.

· The theory tends to explain that the nerve impulses in that region are directly connected/

associated with the frequencies of sound to which they are exposed___ so the higher the pitch of

the sound, the more the nerves trigger and send messages to the brain.

· Both theories are important and useful in the sense that they provide the accurate description of

the whole auditory phenomena.Specifically, place theory gives a better explanation of processing

the high- frequency sounds and frequency theory tells us that how the low- frequency sounds are

encountered and dealt with.

Auditory Information Processing

· After leaving the ear, the auditory message is directly transmitted to the auditory cortex of the brain

with the complex series of neural interconnections

· Within the cortex, there are neurons that respond to selective sounds having specific features___

there are neurons also that respond only to specific pattern/ sort of sounds and not to the

intermittent sounds.

· Auditory cortex provides us with the " map" of sound frequencies that furnishes our response to

the environmental stimuli.Auditory/ Hearing Damage

· Auditory damage occurs largely due to the following three major reasons besides some others:

1. Prolonged exposure to loud noise

2. Severe/ hard blow to the ear sensitive regions

3. Old age

(Others include illness, or damage to the middle or inner ear)

1. Prolonged Exposure to the Loud Noise

· It is also called stimulation deafness

· It includes various types of loud tones/ sounds such as speech, music, machinery,

· and other complex sounds

· The damage is irreversible as the receptors which are damaged do not regenerate

· Large amount of damage occurs between the frequency of 1000 Hz to 2000 Hz

2. Severe/ Hard Blow to the Ear Sensitive Regions

· Tinnitus refers to a "ringing in the ears" ____ it is usually a high-pitched tone.

· The origins of it may lie in either extreme stimulation (above 130 db) or in vascular

· blockage, or in muscle spasms i.e., in the tympanic muscles.

3. Old Age

· As people progress towards their old age, their hearing capability weakens in higher

frequency ranges. This is primarily due to an over all degeneration .

· Environmental factors also play role in causing auditory damage along with old age.

Types of Hearing Impairment

1. Conduction Deafness: problem in conduction of air vibrations to the cochlea; the bones in the

middle ear do not function properly.

Treatment: microsurgery for replacing the affected bone with an artificial one.

101

Introduction to Psychology PSY101

2. Nerve Deafness: deafness caused by a damage to the neural mechanism that creates nerve impulses

or relays them to the auditory cortex; deafness may also be caused by a damage to the auditory cortex

itself.

Balance and the Role of Ear

· Several ear structures are related with the sense of balance of the person much more than playing their

roles in hearing phenomena

· Three tubes or the semi circular canals (inner ear) contain the fluid that moves when the head moves;

the rotational or angular movements are signaled to the brain.

The semicircular canals contain otoliths that are tiny motion- sensitive crystals. The otoliths can sense the

pull on our body exerted by gravity, as well as that by the acceleration of forward, backward, or up-and-

down motion. When the person moves these crystals also move. Thus the system is familiar with the feeling

in case of different moves, and constantly strives for a perfectly balanced position; the otoliths can sense

immediately.

102

Table of Contents: