Post on 16-Dec-2014
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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).