PHYSIOLOGY and PHYSIOLOGY and METHODS of METHODS of

EXAMINATION of the EXAMINATION of the ACOUSTIC ACOUSTIC ANALYZERSANALYZERS

PHYSIOLOGY and PHYSIOLOGY and METHODS of METHODS of

EXAMINATION of the EXAMINATION of the ACOUSTIC ACOUSTIC ANALYZERSANALYZERS

The acoustic analyzer

Each analyzer is a physiological transformer of the energy of an external stimulation into a nervous process

The main rules of acoustic analyzer

• It has definite frequency range of the sounds.

• The sensitiveness of the different frequency is not equal.

• A person can determine the absolute pitch of tone.

• A person can determine the source of sound location (ototopika)

The acoustic analyzer

• The acoustic analyzer is divided into three parts: the peripheral section, the pathway and the cortex zone.

• The peripheral section consists of the sound-conducting and sound-perceiving parts.

The sound-conducting part

The outer ear –

the eardrum –

the ossicles –

the oval window –

the perilymph –

the endolymph of the inner ear –

the basilar membrane.

The sound-perceiving part - the sound transforms into

nerve impulse

Pathways:• The spiral ganglion (the

body of the first neuron)• the eight nerve – the nucleus

of the medulla (the body of the second neuron)

• brain bridge – olive (the body of the third neuron)

• the midbrain – the geniculate body (the body of the forth neuron).

Cortex zone• The temporal lobe of

brain is the cortex zone of acoustic analyzer.

The middle ear mechanism

• The sound protection (the function of the screen)

• The sound transformer mechanism

Air and bone conduction

The cochlea can be stimulated directly by bone conduction as well as by sound passing through the middle ear.

Conductive hearing loss

The results from any interruption to the passage of sound

Sensori-neural hearing loss

The damage of the cochlea or the upper parts of analyzer

Mixed hearing loss

Methods of examination

• Examination of the hearing with help of whisper speech.

• Examination of the hearing with help of ordinary speech.

• Tests with help of tuning forks (experiments performed by Rinne, Veber, Schwabach).

• Pure-tone, speech and game (in childhood) audiometry.

Examination of the hearing

with help of speech

Normal human ear must hear sounds of whisper speech on 6-meter distance and more. And it must hear sounds of ordinary speech on 20-meter distance and more.

Tuning forks

These are the instruments generating the sounds of certain frequency.

Rinne’s test.

Rinne’s test – the comparison between air and

bone conduction

Air>Bone

Air<Bone

Positive - Normal

Perceiving hearing loss

Negative - Conductive hearing loss

Weber’s test.

Weber’s test

Normal hearingNormal hearing

Weber’s test - lateralized to the health side

Normal hearingPerceiving type of hearing loss

Weber’s test - lateralized to the sick side

Normal hearingConductive type of hearing loss

Schwabach's test.

Schwabach's test.

Perceiving type of hearing loss

Conductive type of hearing loss

elongated shortened

The difference between two types of hearing lossConductive

hearing loss

Test Sensori-neural

hearing loss

Negative Rinne’s test Positive

Lateralization to the sick ear

Weber’s test Lateralization to the healthy ear

Elongated Schwabach’s test

Shortened

The audiometer• The usual way of recording hearing

is by the audiometer, of which there are two types: pure-tone and speech.

• There are two ways to conduct sound to the inner ear: air conduction and bone conduction. Each audiometer has ear-phones for air conduction and bone microphone for bone conduction. So the audiogram consists of two curves (air and bone conduction).

Pure-tone audiometry

Normal hearing – • Thresholds from 0

to 10 dB for all frequencies

• There is no difference between air and bone curves.

Characteristic of the audiogram in case of

conductive hearing loss: • Reduced

perception of low tones by air.

• Normal perception of all tones by bone.

• There is a bone-air gap

Characteristic of the audiogram in case of

sensori-neural hearing loss

• Reduced perception of high tones by air and by bone.

• The threshold by air and by bone are increased equally .

• There is no bone-air gap.

Characteristic of the audiogram in case of mixed

hearing loss • Reduced perception

of high tones by air and by bone.

• Reduced perception of low tones by air but normal perception of low tones by bone.

• There is a difference between air and bone conduction (bone-air gap).