Structure and Function

Slides:



Advertisements
Similar presentations
ANATOMY AND PHYSIOLOGY OF THE EAR
Advertisements

Physiology of Hearing & Equilibrium
Psychoacoustics Riana Walsh Relevant texts Acoustics and Psychoacoustics, D. M. Howard and J. Angus, 2 nd edition, Focal Press 2001.
HEARING Sound How the Ears Work How the Cochlea Works Auditory Pathway
Unit Ten: The Nervous System: B. Special Senses
Sensation and Perception - audition.ppt © 2001 Laura Snodgrass, Ph.D.1 Audition Anatomy –outer ear –middle ear –inner ear Ascending auditory pathway –tonotopic.
3/16/2010IB Physics HL 21 Medical Physics:Hearing - IB Objectives I.1.1Describe the basic structure of the human ear I.1.2State and explain how sound pressure.
Chapter 6: The Human Ear and Voice
HEARING. Audition  What is Audition?  Hearing  What sounds do we hear the best?  Sounds with the frequencies in the range corresponding to the human.
Ears, Hearing.
From Vibration to Sound
The Auditory System Dr. Kline FSU. What is the physical stimulus for audition? Sound- vibrations of the molecules in a medium like air. The hearing spectrum.
Hearing. Functions of the ear Hearing (Parts involved): External ear Middle ear Internal ear Equilibrium sense (Parts involved): Internal ear.
1 Hearing or Audition Module 14. Hearing Our auditory sense.
صدق الله العظيم الاسراء اية 58. By Dr. Abdel Aziz M. Hussein Lecturer of Physiology Member of American Society of Physiology.
By: Ellie Erehart, Angie Barco, Maggie Rieger, Tj Myers and Kameron Thomas.
SENSE OF HEARING EAR. Ear Consists of 3 parts –External ear Consists of pinna, external auditory meatus, and tympanum Transmits airborne sound waves to.
Hearing Test ng_test/ ng_test/
Auditory Sensation (Hearing) L13
© 2011 The McGraw-Hill Companies, Inc. Instructor name Class Title, Term/Semester, Year Institution Introductory Psychology Concepts Hearing.
The Ear.
Sound Waves, Hearing, and the Human Ear. the frequency of a wave is the number of waves per unit of time usually measured in Hz (1 wave per second) humans.
ANATOMY AND PHYSIOLOGY OF THE EAR
IB Assessment Statements Option I-1, The Ear and Hearing: I.1.1.Describe the basic structure of the human ear. I.1.2.State and explain how sound pressure.
 Focuses sound waves onto the ear drum  Two parts 1. The pinna which concentrates sound waves into the auditory canal. 2. The auditory canal which.
Hearing Physiology.
SOUND & THE EAR. Anthony J Greene2 Sound and the Ear 1.Sound Waves A.Frequency: Pitch, Pure Tone. B.Intensity C.Complex Waves and Harmonic Frequencies.
The Ear Change the graphics to symbolize different functions of the ear that are brought up on the next slide.
Bell Ringer 1. How would your life be effected if you suddenly lost your hearing? 2. How would your life be different if you were never able to hear?
Perception: Hearing Sound: Amplitude – loudness (decibels)
HEARING Structure and Function. Function of auditory system Analyse Discriminate -sounds -widely varying intensity widely varying frequencies any spatial.
52 The Sense of Hearing Dr. A.R. Jamshidi Fard 2011.
AUDITORY FUNCTION.  Audition results from sound conduction by either air or bones of the skull or both. Sound waves are converted (mechanically in.
Hearing. Anatomy of the Ear How the Ear Works The outer ear The pinna, which is the external part of the ear, collects sounds and funnels them through.
Hearing As with the eye, the ear receives waves, this time of sounds. As with the eye, the ear receives waves, this time of sounds. Length of wave = pitch.
PSY2301: Biological Foundations of Behavior The Auditory System Chapter 10.
Anatomy of the Ear Three Main Sections
Ear Ossicles Malleus, incus, and stapes Transmit vibrations to the oval window Dampened by the tensor tympani and stapedius muscles.
ANATOMY AND PHYSIOLOGY OF THE EAR Yard.Doc.Dr.Müzeyyen Doğan.
HEARING LOSS.
Hearing or audition.
Auditory System: Sound
Hearing and other senses.
Review: Hearing.
Lab 11 : Human Ear Anatomy Biology Department.
Hearing. (Perception of Sound)
ANATOMY THE EAR Dr. J.K. GERALD, (MD, MSc.).
Hearing. (Perception of Sound)
Hearing. (Perception of Sound)
ANATOMY AND PHYSIOLOGY OF THE EAR
Hearing. (Perception of Sound)
8 Special Senses.
Hearing.
Hearing. (Perception of Sound)
Special Senses The Ear.
Auditory.
MECHANISM OF HEARING.
Section 14.3 Hearing and Equilibrium
THE AUDITORY SYSTEM: HEARING
The Auditory Pathway This graphic depicts the events in the stimulation of auditory receptors, from channeling sound waves into the external ear and onto.
Hearing, not trying out for a play
Journal#5: What would happen if you were born without cones
ANATOMY AND PHYSIOLOGY OF THE EAR (HEARING)
The Special Senses: Part D
How We Hear.
The Special Senses Hearing
ANATOMY AND PHYSIOLOGY OF THE EAR
Hearing.
Hearing The Auditory Systems
The Ear: Hearing and Balance
Presentation transcript:

Structure and Function HEARING Structure and Function

Function of auditory system Analyse Discriminate -sounds - widely varying intensity widely varying frequencies any spatial direction  complex varying patterns of pressure and frequency which differ at the two ears

Action of human ears is to interpret sound input by perceiving: intensity, frequency, timbre, localisation & masking of one sound by another.

Definitions (subjective correlations) Intensity = Loudness Frequency = Pitch Timbre = Musical quality Localisation = Spatial position Masking = One sound is selectively heard in preference to others

Measurement Sound intensity is normally measured in N/m² or Pascals The vast range of sound pressures perceived by humans is more conveniently described by a smaller range expressed in a logarithmic scale as decibels as a ratio of a reference intensity (2 x 10⁻⁵ N/m²)

Measurement Human range is: 0 db - 130 dB “absolute” threshold pain threshold

0 dB is a reference point for the “average” Step sizes less than 1 dB are rarely detectable Changes in intensity of equal numbers of dB correspond to approximately equal steps in loudness

0 dB is a reference point for the “average” Step sizes less than 1 dB are rarely detectable Changes in intensity of equal numbers of dB correspond to approximately equal steps in loudness

0 dB is a reference point for the “average” Step sizes less than 1 dB are rarely detectable Changes in intensity of equal numbers of dB correspond to approximately equal steps in loudness

Some levels From 1 m - whisper - 30 dB - conversation - 60 dB - shout - 90 db - discomfort - 120 dB

Definitions (subjective correlations) Intensity = Loudness Frequency = Pitch Timbre = Musical quality Localisation = Spatial position Masking = One sound is selectively heard in preference to others

Measurement Frequency is measured in Hz Frequency has the subjective correlate of pitch which is how the ear perceives changes in frequency However, complex sound has no clear specific pitch and the hearing apparatus has to sort the complex input and produce an intelligible interpretation

modern piano keyboard is 25Hz – 4000Hz Measurement Human ear can appreciate frequencies between 12Hz and 20 000Hz (some people have greater range) modern piano keyboard is 25Hz – 4000Hz “Speech range” is 200Hz - 10 000Hz (mostly utilise 500-4000 Hz) Music 50Hz - 20 000Hz

Definitions (subjective correlations) Intensity = Loudness Frequency = Pitch Timbre = (musical) quality Localisation = Spatial position Masking = One sound is selectively heard in preference to others

Timbre The fundamental frequency is the lowest note in a complex sound The overtones or harmonics are simple multiples of the fundamental frequency and are responsible for the quality of the sound

Definitions (subjective correlations) Intensity = Loudness Frequency = Pitch Timbre = Musical quality Localisation = Spatial position Masking = One sound is selectively heard in preference to others

Ear Conducting apparatus - auricle - EAC - TM - ossicular chain - IE fluids - Perceiving apparatus - end-organ (Corti) - VIII - cerebral cortex -

External ear Pinna / auricle Skin covered cartilage “Directs” sound into EAC

External ear canal Skin covered cartilage and bony canal Channels acoustic energy to TM

Tympanic membrane fibrous tissue 3 layers: Squamous epithelium Respiratory mucous membrane

Middle Ear Contains: malleus - hammer incus - anvil stapes - stirrup Small “auditory muscles”

Transformer Acoustic energy arrives at TM & is transmitted to the stapes footplate - area ratio TM : footplate = 14:1 - lever effect of ossicles = 1,3:1 - overall “transformer ratio” = 18:1

Amplitude of vibration at TM is reduced by the time it reaches the footplate Force entering fluids is increased in same proportion Widely differing acoustic resistances between air & fluid are matched Transfers maximum energy from air to fluid

Stapedius & tensor tympani muscles reflexly contract above 90 dB This attenuates loud sound to protect IE against acoustic trauma Impact / explosion noise reaches cochlea before reflexes can act – damage is worse than with steady state noise

Physiology Sound is transmitted to IE in three ways: Via the ossicular chain - most important Bone conduction – through bones of the skull, sound energy taken up and transmitted to cochlea Directly across ME – on to round window when there is TM perforation

Physiology Airborne sound – vibrations of atmosphere – pass along the EAC to the TM - set in motion Transmitted to ossicles – which rotate around fulcrum & transmit vibrations to oval window

Physiology Transmitted through oval window to perilymph in scala vestibuli around the helicotrema to round window (reciprocal movement)

Physiology This sets up a travelling wave starting from the cochlea base & progressing toward the helicotrema with increasing amplitude There is a sharply defined region of maximum displacement – position depends on frequency

Physiology High frequency – maximum displacement at basal turn of cochlea Low frequency – longer travelling wave with maximum amplitude nearer the helicotrema

Physiology Vibrations displace basilar membrane – shearing movement between hair cells and tectorial membrane – hairs displaced in relation to their bodies Not fully understood but this displacement results in neuronal stimulation - nerve impulses in VIII

Neuronal stimulation 3 main theories Attempt to explain conversion of all varied dimensions of sound Possible variations in nerve action potentials depend upon

Neuronal stimulation Particular nerve fibre being activated – place along basilar membrane Total numbers of fibres activated louder sound – more activated Threshold of individual fibres – majority of fibres have threshold 10-15 dB only a few above 80 dB

Internal Auditory Canal ± 1 cm long In petrous temporal bone Transmits - VII - VIII - internal auditory art. & vein

Audiometry Pure Tone Audiogram (PTA) is the cornerstone of assessment of hearing Establishes subject’s pure tone hearing threshold – the minimum sound level at which a specific response can be obtained

Audiometry Test 125, 250, 500, 1000, 2000, 4000, 8000 Hz (3000 & 6000 for noise-induced loss claims ) Air conduction Bone conduction - not 125 & above 4000 as unreliable - indication of cochlea function

Audiometry Soundproof room Earphones / bone conductor Subject signals by pressing button Pure tones produced by calibrated audiometer Intensities - - 20 dB + 110 dB

Normal audiogram

Speech vs Pure tone Main function of human ear is perception of spoken word Speech consists of very complex sound Varying frequencies – fundamentals & harmonics Vowels & consonants Accents Languages

Speech vs Pure tone PTA is not always good assessment of speech discrimination Speech Audiometry measures actual disability produced by any hearing loss

Definitions (subjective correlations) Intensity = Loudness Frequency = Pitch Timbre = Musical quality Localisation = Spatial position Masking = One sound is selectively heard in preference to others

Localisation - Binaural hearing - differences in time of arrival (10-20μs) - differences in intensity at two ears - phase differences ( at less than 1500Hz)

Localisation - Pinnae - spectrum of sound entering ear modified by pinna in a way that depends on direction of sound source

Localisation - Precedence effect Many different paths - direct - reflected (echoes) Several sounds in close succession are the direct sound & its echoes. These are perceptually fused and the location of the total sound is determined by the combination of the direct sound and its echoes.

Complex? Fascinating? Want to know more?