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Presentation on theme: "HEARING."— Presentation transcript:


2 The Nature of Sound Sound, like light, comes in waves
Sound is vibration Features of sound include: Pitch Hertz Decibels

3 Pitch A sound’s highness or lowness
Dependent on the frequency of the sound wave Is measured as hertz (Hz) High pitched sounds Low pitched sounds

4 Hertz (Hz) A measure of the number of sound wave peaks per second; measures “frequency” Determines the pitch of the sound Human hearing goes from 20 Hz to 20,000 Hz

5 Frequency of Sound Waves
The frequency of a sound wave is measured as the number of cycles per second (Hertz) 20,000 Hz Highest Frequency we can hear 4,186 Hz Highest note on a piano 1,000 Hz Highest pitch of human voice 100 Hz Lowest pitch of human voice 27 Hz Lowest note on a piano

6 Decibel (dB) A measure of the height of the sound wave
Determines the loudness of the sound Sometimes called amplitude Loud sounds Soft sounds


8 Above are examples of Frequency & Amplitude/decibels
Who hits the higher pitch? Christina or Mariah? Discovering PSY p. 94 Figure 3.7 Above are examples of Frequency & Amplitude/decibels Timbre – distinctive quality of a sound determined by the complexity of the wave and its different combinations of frequencies. (Figure C is more complex than Figures A or B)

9 The Structure of the Auditory System

10 Hearing: Sound Waves Auditory perception occurs when sound waves interact with the structures of the ear Audition (sense of hearing) results in sound waves being collected in the outer ear, amplified in the middle ear and converted to neural messages in the inner ear.

11 Purpose of the structures in the ear:
Anatomy of Ear Purpose of the structures in the ear: Measure the frequency (pitch) of sound waves Measure the amplitude (loudness) of sound waves

12 Parts of the Ear – Sound Waves enter through the Pinna

13 Hearing: Sound Localization

14 Localization of Sound Locating where sound is originating from
Done through two cues: Which ear hears the sound first? Which ear hears the louder sound?

15 Localization of Sound

16 Parts of the Ear – Auditory Canal

17 Auditory Canal Sound Waves enter through the pinna then travel through the auditory canal. The opening through which sound waves travel as they move into the ear for processing Ends at the tympanic membrane (eardrum)

18 Parts of the Ear – Tympanic Membrane (Eardrum)

19 Tympanic Membrane (eardrum)
The tissue barrier that transfers sound vibration from the air to the tiny bones of the middle ear Can be damaged by objects in the ear or exceptionally loud noises

20 Parts of the Ear - Ossicles

21 Ossicles Three tiny bones that transfer sound waves from the eardrum to the cochlea Hammer, anvil and stirrup In old age they may become brittle or damaged resulting in conduction deafness

22 Parts of the Ear - Cochlea

23 Cochlea A hearing organ where sound waves are changed into neural impulses The major organ of hearing Filled with fluid; a snail shaped body tube

24 Parts of the Ear – Oval Window

25 Oval Window The point on the surface of the cochlea which receives the sound vibration from the ossicles As the oval window vibrates, the fluid in the cochlea vibrates moving hair cells along the basilar membrane.

26 Hair cells along the Basilar Membrane move as the fluid vibrates

27 Anatomy of the Cochlea Another View
Outer ear Middle ear Inner ear A sound causes the basilar membrane to wave up and down. Basilar membrane Hair cells Tectorial Round window Eardrum Oval window Cochlea, partially uncoiled Stirrup Anvil Hammer Sound waves Auditory canal

28 Hair Cells The receptor cells for hearing in the cochlea that change sound vibrations into neural impulses. When they move they trigger action potential in the base of the hair cell (transduction). Similar to the rods and cones within the eye except hair cells are sensitive to vibrations rather than light. If these are damaged (due to prolonged loud noises) then you have nerve deafness which cannot be helped by a hearing aid.

29 Parts of the Ear – Auditory Nerve

30 Auditory Nerve The nerve that carries sound information from the ears to the thalamus then to the auditory cortex in the temporal lobes of the brain The auditory nerve is stimulated by the hair cells in the basilar membrane of the cochlea.

31 Major Divisions of the Ear
Outer Ear—acts as a funnel to direct sound waves towards inner structures Middle Ear—consists of three small bones (or ossicles) that amplify the sound Inner Ear—contains the structures that actually transduce sound into neural response

32 Divisions of the Ear

33 Divisions of the Ear

34 Divisions of the Ear

35 Anatomy of the Ear: A final look
Hockenbury Powerpoint (schulman)

36 Transduction of Sounds
Sound waves are captured by the Pinna and sent down the ear canal where they stimulate the eardrum. The eardrum’s vibrations are amplified by the ossicles (hammer, anvil, stirrup). These vibrate the oval window on the cochlea which in turn vibrates the fluid around the basilar membrane. The fluid bends the hair cells on the basilar membrane triggering action potential in the base of the hair cells. This message is transmitted to the auditory nerve which carries the info to the thalamus and then to the auditory cortex of the temporal lobe. Review using this Nobel Prize site on Hearing

37 How Can I Remember This? Please – Pinna Eat – Ear Canal
Everything – Eardrum Offered – Ossicles On – Oval Window Cuisine – Cochlea Buffet – Basilar Membrane Helpful – Hair Cells Attendants – Auditory Nerve Take – Thalamus Away – Auditory Cortex Trash – Temporal Lobe

38 Or Maybe This Works Better…
Portenga- [Pinna] evaluates- [ear canal] exams- [eardrum] on- [Ossicles] ominous- [oval window] charts- [cochlea] between- [basilar membrane] hungry- [Hair Cells] architects- [Auditory nerve] that- [Thalamus] always- [Auditory cortex] titter- [Temporal lobe]

39 Distinguishing Pitch Frequency theory—basilar membrane vibrates at the same frequency as the sound wave/oval window The higher the frequency wave the faster the firing of hair cells Theory used to explain how you hear low frequencies Place theory—different frequencies cause larger vibrations at different locations along the basilar membrane Different pitches stimulate different areas on the basilar membrane The brain receives these messages and interprets them as different pitches. Theory used to explain how you hear high frequencies. Use both theories when you listen to sounds with both high and low frequencies. See this website to see how it works.

40 Direction of traveling wave
Frequency Theory The Basilar Membrane vibrates according to the same Frequency of the sound wave Basilar membrane Distal end Proximal Oval window Direction of traveling wave

41 Place Theory: Different Frequencies stimulate different areas of the Basilar Membrane

42 Coding and Auditory Masking
The way in which waves travel down the Basilar Membrane causes some sounds to interfere with (or mask) our ability to hear other sounds Low frequency sounds provide better masking than high frequency sounds

43 Auditory Masking Piccolo, soft Bassoon, loud Piccolo, loud Bassoon, soft Distance along basilar membrane (a) (b) Effect of bassoon on basilar membrane Vibration amplitude of basilar membrane Effect of piccolo on basilar membrane Low frequency sounds effectively mask high frequency sounds High frequency sounds cannot effectively mask low frequency sounds Hockenbury Powerpoint (schulman)

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