ear anatomy hearing tests audiograms - sivantos · ear anatomy hearing tests audiograms. page 2...

For internal use only / Copyright © Siemens AG 2006. All rights reserved.For internal use only / Copyright © Siemens AG 2006. All rights reserved.

Ear anatomyHearing testsAudiograms

May-06 Hearing Instrument Technology I

Introduction / Contents

Basic Ear Anatomy

Types of Hearing LossConductive vs. Sensorineural

Audiogram ScalesFrequency vs. Intensity

Audiogram Symbols

Labeling the Audiogram

Contents

Basic Ear Anatomy 3

Hearing Test 6

Audiogram 15

Audiogram - Examples 18


Basic Ear Anatomy

1. Outer Ear

2. Middle Ear

3. Inner Ear

The ear can be divided into 3 main divisions:

Outer Ear Middle Ear

Inner Ear


Outer Ear

The external ear has two parts:

1. Pinna which is the outside portion of the ear that is visible on the side of the head

2. External auditory meatus(ear canal) that extends from the pinna to the tympanic membrane (abbreviated TM and is commonly referred to as the eardrum).

Pinna

Ear canal


Pinna

Pinna:The pinna is mostly skin and cartilage with some muscular attachments to the back

The pinna collects and directs sounds down the ear canal

The twists and folds of the pinna enhance high frequency (pitched) sounds and also help us to determine the direction of the sound source

Sounds coming from the front and sides are slightly enhanced as they are directed into the ear canal while sounds from behind are slightly reduced.This helps us to hear what we are looking at while reducing some of the distracting background noise coming from behind.


Ear Canal

Ear Canal:The external auditory meatus is a small, twisting, tunnel-like tube that connects the pinna to the tympanic membrane.

It is about one inch in length (2.5 cm) and has a diameter about the size of a pencil eraser.

The outer half to two thirds of the canal is surrounded by cartilage and contains glands that produce cerumen (ear wax), while the inner one third to one half is surrounded by bone.

The ear canal has a natural resonance that typically boosts sound pitches around 3000 Hertz (abbreviated Hz. and is the same as cycles per second) by approximately 10-15 decibels.


Middle Ear 1

Middle Ear:

The middle ear consists of an air-filled space between the tympanic membrane and the inner ear that contains three tiny bones linked together that connect the tympanic membrane to an opening into the inner ear.

The bones are: the malleus, incusand stapes

Labyrinth

Ossicles

Middle Ear SpaceTympanicMembrane


Middle Ear 2

Sounds travel down the ear canal and strike the TM, causing it to vibrate. These vibrations are then transferred through the ossiclesto the inner ear

Sound sets this whole structure into vibration and the footplate of the stapes vibrates within the oval window opening of the cochlea, transferring sound energy to the fluids and tissues of the cochlea.

TympanicMembrane

Labyrinth

Ossicles

Middle Ear Space


Inner Ear

Inner Ear:The inner ear is comprised of two functionally separate sections: The vestibular or balance part and the cochlea, which is the hearing part. The cochlea is a coiled canal in the dense bone tissue of the skull. The shape of this canal somewhat resembles a snail shell and houses three fluid-filled membranous canals extending its full length. The cochlear connects to the auditory nerve that messages to the brain that a sound has been heard.

Labyrinth

Middle Ear Space

Cochlea

Hearing Nerve

Balance Nerve

FacialNerve


Hearing Test

When we do a hearing test with conventional headphones we are testing the all three parts of the ear…..


Hearing Test

When we do a hearing test with a bone conductor we are bypassing the outer and middle ear…..


Hearing Test

The headphones and bone conductor give us different information:

A sensorineural hearing loss is when the headphone (air conduction) and bone conduction sensitivity test is equal…

This means the problem is occurring in the inner ear or beyond

A conductive hearing loss is when the bone conduction sensitivity is better than the headphone sensitivity

This means the problem is occurring in the middle ear or external ear


Hearing Test

Tone tests are done by air conduction and by bone conduction. Air conduction tests evaluate the sensitivity of the entire hearing organ and are tested with earphones that are placed over the ears or inserted into the ear canal.

The softest sounds heard by the subject at each pitch are recorded as the thresholds and are compared to normative values.


Hearing Test

Bone conduction is tested when air conduction testing shows a loss. They are done as in air conduction testing, except that, instead of using earphones, a small bone-conduction vibrator is placed on the mastoid bone directly behind the ear and sound is transmitted through the bones of the skull directly to the inner ear, bypassing the outer and middle ear.

Thus, a difference between air and bone conduction thresholds indicates a loss caused by a problem with the outer or middle ear - a conductive loss.


Hearing Test

Why do we need to know this ?

Headphone sensitivity or thresholds and Bone conduction thresholds are represented differently on the Audiogram

Also, a conductive and sensorineural hearing loss will have different implications for hearing aid selection and fitting


Audiogram

Audiogram is chart that hearing test is marked on

soft

loud

Volumemeasured in dB/HL

low highFrequency (Hz)


Audiogram

Symbols are placed on the audiogram that tell us the persons bone conduction and air conduction thresholds at each frequency

Right Air conduction

Left Air conduction

Right Bone conduction

Left Bone conduction


Audiogram

Symbols are placed on the audiogram that tell us the persons bone conduction and air conduction thresholds at each frequency

Left Air conduction

Right Air conductionRight Bone conduction

Left Bone conduction


Audiogram

Degree of hearing loss is labeled below: p 104 Sandlin

Normal Hearing

Mild Hearing Loss

Moderate Hearing Loss

Severe Hearing Loss

Profound Hearing Loss

Note:this may differ from Textbook to Textbook


Examples

Mild sensorineural hearing loss, right


Examples

Mild conductive hearing loss, right

ear anatomy hearing tests audiograms - sivantos · ear anatomy hearing tests audiograms. page 2...

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