Major Divisions of the Ear: Peripheral and Central Mechanism

1. Chapter 9Auditory Perry C. Hanavan, Au.D.

2. Major Divisions of the Ear Peripheral Mechanism Central Mechanism

3. Pinna

4. Function of Outer Ear • Collect sound • Localization • Resonator • Protection • Sensitive (earlobe) • Other?

5. Outer Ear Resonance • Influence of pinna (p) • Influence of ear canal (c) • Combine influence (t) • At 3000 Hz, the final amplification (t) is 20 dB

6. Pinna • The visible portion that is commonly referred to as "the ear" • Helps localize sound sources • Directs sound into the ear • Each individual's pinna creates a distinctive imprint on the acoustic wave traveling into the auditory canal

7. External Auditory Meatus • Extends from the pinna to the tympanic membrane • About 26 millimeters (mm) in length and 7 mm in diameter in adult ear. • Size and shape vary among individuals. • Protects the eardrum • Resonator • Provides about 10 decibels (dB) of gain to the eardrum at around 3,300 Hertz (Hz). • The net effect of the head, pinna, and ear canal is that sounds in the 2,000 to 4,000 Hz region are amplified by 10 to 15 dB. • Sensitivity to sounds greatest in this frequency region • Noises in this range are the most hazardous to hearing

8. Outer Ear Resonance • Influence of pinna (p) • Influence of ear canal (m) • Combine influence (t) • At 3000 Hz, the final amplification (t) is 20 dB

9. Middle Ear Virtual Tour of the Ear Middle Ear Cavity Ossicles Middle Ear Muscles Mastoid Eustachian Tube Function Amplifier Tympanic Cavity Tympanic Membrane Ossicles Middle Ear Muscles Eustachian Tube Mastoid

10. Function of Middle Ear • Conduction • Conduct sound from the outer ear to the inner ear • Protection • Creates a barrier that protects the middle and inner areas from foreign objects • Middle ear muscles may provide protection from loud sounds • Transducer • Converts acoustic energy to mechanical energy • Converts mechanical energy to hydraulic energy • Amplifier • Transformer action of the middle ear • only about 1/1000 of the acoustic energy in air would be transmitted to the inner-ear fluids (about 30 dB hearing loss)

11. Transformer/Amplifier • Area ratio • Thumbtack • Lever • crowbar

12. Area Ratio

13. Middle Ear Muscles • Tensor tympani • Attached to malleus • Innervated by V, trigeminal nerve • Stapedius • Attached to stapes • Innervated by VII, facial nerve • Middle Ear Muscle Function: • Protect inner ear from excessive sound levels • When ear exposed to sound levels above 70 dB, the muscles contract, decreasing amount of energy transferred to inner ear

14. Inner Ear Virtual Tour of the Ear Vestibular semicircular canals utricle and saccule Cochlear traveling wave traveling wave traveling wave Auditory Vestibular

15. Organ of Corti

16. Hair Cells • Outer Hair Cells • Inner Hair Cells • OHC movie

17. Hair Cells • Outer Hair Cells • Inner Hair Cells • OHC movie

18. Traveling Waves • Traveling wave • Basilar membrane • Traveling Wave info • Cochlear Traveling Wave

19. Basilar Membrane: Tonotopic

20. VIII CN: Afferent Neurons

21. OHC: Motile/Amplifier

22. Basilar Membrane: Tonotopic

23. VIII Cranial Nerve Auditory Branch Vestibular Branch Virtual Tour of the Ear Auditory Branch Vestibular Branch Spiral ganglion Acoustic Tumors

24. Major Divisions of the Ear Central Mechanism

25. Temporal Lobe: Tonotopic

26. Central Auditory Path

27. Speech Perception • How do we perceive speech? • Individual sounds (phonemes)? • Syllables? • Words? • Sentences? • How do we derive meaning from the ocean of sounds we hear? • Speech is variable • Speakers vary in speech • Variant or invariant cues?

28. Taking Statistics

29.  "gaaaa" slowly turn into "water"

30. Perception of Phonemes

31. Audibility

32. Alvin Liberman (1917 – 2000) Liberman and colleagues (1957) showed a phoneme boundary effect: A smaller change in delay was necessary to distinguish /b/ from /p/, than to distinguish two phonemes within these categories.

33. The phoneme boundary effect Motor theory of speech perception: The phoneme boundary effect is caused by activation of the motor program required to produce a phoneme.

34. Category boundary effects in the colour domain Question: Is the way we sense colour affected by the words for colours in our language? Benjamin Lee Whorf (1897-1941)

35. The question about colour perception can be operationalized: Color can be objectively measured in terms of its wavelength: 400n m 550nm 700nm Wavelength

36. The question about colour perception can be operationalized: The number of basic color terms in a language can be measured. Basic color terms are: • Single words. • Not subsumed by another term. • Not restricted to a particular class of objects.

37. Early research on color naming Different languages have a variation in the number of words for colour categories. Dani (New Guinea): Two basic colour terms - mili (light), mola (dark). English: eleven basic color terms – white, black, grey, red green, blue, yellow, orange, purple, pink, brown.

38. Kay and Kempton (1984) Compared English and Tamahumara speakers. Tamahumara does not make a distinction between blue and green. Kay and Kempton theorized that the perceptual distance between blue and green would be exaggerated in English speakers.

39. Kay and Kempton (1984) 3 green G G G 2 green, 1 blue G G B B 3 blue B B

40. Kay and Kempton (1984) Tamahumara speakers were equally likely to choose either extreme for all three types of triplet.

41. Kay and Kempton (1984) English speakers were the same when all chips came from the same category. When there was an odd one out, they were more likely to choose that one.

42. Perception of Vowels • /a/ vowel has greatest intensity with unvoiced /θ/ as weakest consonant • Front vowels perceived on basis of F1 frequency and average of F2 and F3, whereas back vowels are perceived on the basis of the average of F1 and F2, as well as F3 • So is it the absolute frequency values of the formants? • Or the ratio of F2 to F1? • Perhaps it is the invariant cues (frequency changes that occur with coarticulation F1/F2 F3 F1 F2/F3

43. Invariant and Variant Cues Showing how onset formant transitions that define perceptually consonant [d] differ depending on the identity of the following vowel. (Formants highlighted by red dotted lines; transitions are the bending beginnings of the formant trajectories.) /di/ /da/ /du/

44. Perception of Diphthongs • Perceived on basis of formant transitions • Salient feature: rapidity of transition

45. Consonant Perceptions • Perception different for consonants than vowels • Greater variety of consonant types than vowels • Greater complexity for consonants

46. Question Which is TRUE regarding the following statements about categorical perception? • Experience of percept invariances in sensory phenomena that can be varied along a continuum. • Can be inborn or can be induced by learning. • Related to how neural networks in our brains detect the features that allow us to sort the things in the world into separate categories • All the above are true • All the above are false

47. Categorical Perception • Experience of percept invariances in sensory phenomena that can be varied along a continuum. • Can be inborn or can be induced by learning. • Related to how neural networks in our brains detect the features that allow us to sort the things in the world into separate categories  • area in the left prefrontal cortex has been localized as the place in the brain responsible for phonetic categorical perception

48. Categorical Perception

49. Identification/Recognition • Hearing loss affects the ability to correctly identify or label sound(s) • Vowels relatively easy • Consonants more difficulty to identify • Place of production errors common • High frequency consonants (sibilants) extremely difficult to identify

50. QuickSin/BKBSIN SNR Loss