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I LLI ..... :::l C o :E Hearing MODULE OVERVIEW Introduction and The Stimulus Input: Sound Waves (214-215) This module describes the sense of hearing, including the structure of the ear and the process through which the stimulus energy is transmitted through the ear and interpreted in the brain. It concludes with a discussion of types of hearing loss and the views of Deaf culture advocates regarding cochlear implants. In this module there are many terms to learn. Many of the terms are related to the structures of the ear. Doing the module review several times, labeling the diagram of the ear, and rehearsing the material frequently will help you to memorize the parts of the various structures and their functions. NOTE: Answer guidelines for all Module 14 questions begin on page 173. David Myers at times uses idioms that are unfamiliar to some readers. If you do not know the meaning of the following expressions in the context in which they appear in the text, refer to page 175 for an explanation: sensitive to faint sounds, an obvious boon; A piccolo produces much shorter, faster sound waves than does a tuba. - Objective 14-1: Define audition, and describe the pressure waves we experience as sound. 1. The stimulus for hearing, or ~ __ ~ ~_ , is sound waves, created by the compression and expansion of MODULE REVIEW 2. The amplitude of a sound wave determines the First, skim each section, noting headings and boldface items. After you have read the section, review each objective by answering the fill-in and essay-type questions that follow it. As you proceed, evaluate your performance by consulting the answers on page 173. Do not continue with the next section until you understand each answer. If you need to, review or reread the section in the textbook before continuing. sound's ~ _ 3. The pitch of a sound is derived from the ~ of its wave. 4. Sound energy is measured in units called ________ . The absolute threshold for hearing is arbitrarily defined as ________ such units. The Ear (pp. 216-219) If you do not know the meaning of any of the following words, phrases, or expressions in the context in which they appear in the text, refer to page 175 for an explanation: earlids; If a car to the right honks; cock your head. 169 170 Module 14 Hearing Objective 14-2:Describe the three regions of the ear, and outline the series of events that triggers the electrical impulses sent to the brain. 1. The ear is divided into three main parts: the ~ ________ ________ ear, the ear, and the ear. 7. A second theory proposes that neural impulses, 2. The outer ear channels sound waves toward the ________ vibrates. cochlea's basilar membrane; this is the ________ theory. This theory has difficulty accounting for how we hear ________ -pitched sounds, which do not have such localized effects. , a tight membrane that then 3. The middle ear transmits the vibrations through a piston made of three small bones: the ,and sent to the brain at the same frequency as the sound wave, allow the perception of different pitches. This is the theory. This theory fails to account for the perception of ________ -pitched sounds, because individual neurons cannot fire faster than ________ times per second. 8. For the higher pitches, cells may alternate their 4. In the inner ear, a coiled tube called the ~ contains the receptor cells for hearing. The incoming vibrations cause the ________ ~ to vibrate the fluid that fills the tube, which causes ripples in the ~ _ ________ , which is lined with ________________ . This movement triggers impulses in adjacent nerve fibers that converge to form the auditory nerve, which carries the neural messages (via the ________ )to the _ lobe's auditory cortex. The brain interprets loudness from the of hair cells a sound activates. 5. (Close-Up) On tasks requiring alert performance, people in noisy environments work ________ (more/less) efficiently. People who live in noisy environments suffer elevated rates of -related disorders such as _ ,and firing to match the sound's frequency, according to the principle. Objective 14-4:Describe how we pinpoint sounds. 9. We locate a sound by sensing differences in the _ and _ with which it reaches our ears. 10. A sound that comes from directly ahead will be ________ (easier/harder) to locate than a sound that comes from off to one side. 11. As with visual information, the brain uses _ ~ as specialized neural teams work on different auditory tasks simultaneously. Hearing loss and Deaf Culture (pp. 219-222) If you do not know the meaning of the following expression in the context in which it appears in the text, refer to pages 175-176 for an explanation: the culprits are ... ear-splitting noise or music. ----- Noise is especially stressful when it is ~ or Objective 14-5:Contrast the two types of hearing loss, and describe some of their causes. _ Objective 14-3:Contrast place and frequency theories, and explain how they help us to understand pitch perception. 6. One theory of pitch perception proposes that different pitches activate different places on the 1. Problems in the mechanical conduction of sound waves through the outer or middle ear may cause 2. Damage to the cochlea's hair cell receptors or their associated auditory nerves can cause ________ hearing loss. It may be caused by disease, but more often it results from the biological changes linked with ________ and prolonged exposure to ear-splitting noise or music. 3. Scientists have discovered ways to ~ hair cell regeneration. Objective 14-6:Describe how cochlear implants function, and explain why Deaf culture advocates object to these devices. 4. An electronic device that restores hearing among nerve-deafened people is a _ 5. Advocates of _ ~ object to the use of these implants on before they have learned to . The basis for their argument is that deafness is not a 6. Sign language (is/is not) a completelanguage,~ _ (with/without) its own grammar, syntax, and semantics. Those who learn only sign language during childhood (have/ do not have) difficulty later learning to read and write. 7. People who lose one channel of sensation (such as hearing) (seem to/do not seem to) compensate with a slight enhancement in their other sensory abilities. Thus, people who become deaf, or who lose another channel of sensation, often experience _ ________ in another ability. 8. (Close-Up) Deaf children raised in a household where sign language is used express higher ~ and feel more ~ _ PROGRESS TEST Multiple-Choice Questions Circle your answers to the following questions and check them with the answers beginning on page 173. If your answer is incorrect, read the explanation for why it is correct and then consult the appropriate pages of the text. 1. Progress Test 171 _ is to Frequency is to pitch as a. b. c. d. wavelength; loudness amplitude; loudness wavelength; intensity amplitude; intensity 2. The place theory of pitch perception cannot account for how we hear: a. low-pitched sounds. b. middle-pitched sounds. c. high-pitched sounds. d. chords (three or more pitches simultaneously). 3. The hearing losses that occur with age are especially pronounced for: a. low-pitched sounds. b. middle-pitched sounds. c. high-pitched sounds. d. chords. 4. Nerve deafness is caused by: a. wax buildup in the outer ear. b. damage to the eardrum. c. blockage in the middle ear because of infection. d. damage to the cochlea. 5. The frequency theory of hearing is better than place theory at explaining our sensation of: a. the lowest pitches. b. pitches of intermediate range. c. the highest pitches. d. all of the above. 6. Which of the following is the most accurate explanation of how we discriminate pitch? a. For all audible frequencies, pitch is coded according to the place of maximum vibration on the cochlea's basilar membrane. b. For all audible frequencies, the rate of neural activity in the auditory nerve matches the frequency of the sound wave. c. For very high frequencies, pitch is coded according to place of vibration on the basilar membrane; for lower pitches, the rate of neural activity in the auditory nerve matches the sound's frequency. d. For very high frequencies, the rate of neural activity in the auditory nerve matches the frequency of the sound wave; for lower frequencies, pitch is coded according to the place of vibration on the basilar membrane. 172 Module 14 Hearing 7. Which of the following correctly lists the order of structures through which sound travels after entering the ear? a. auditory canal, eardrum, middle ear, cochlea b. eardrum, auditory canal, middle ear, cochlea c. eardrum, middle ear, cochlea, auditory canal d. cochlea, eardrum, middle ear, auditory canal 8. Dr. Frankenstein has forgotten to give his monster an important part; as a result, the monster cannot transduce sound. Dr. Frankenstein omitted the: a. eardrum. c. semicircular canals. b. middle ear. d. basilar membrane. Summing Up Use the diagram to identify the parts of the ear, then list them in the order in which they contribute to hearing. Also, briefly explain the role of each structure. 1. 2. 3. 4. 5. 6. 7. 8. 9. Seventy-five-year-old Claude has difficulty hearing high-pitched sounds. Most likely his hearing problem involves: a. his eardrum. b. his auditory canal. c. the bones of his middle ear. d. the hair cells of his inner ear. Answers 173 Matching Items Match each of the structures, theories, or conditions with its function or description. Structures or Conditions 1. 2. 3. 4. 5. 6. place theory frequency theory conduction hearing loss sensorineural hearing loss pitch frequency Key Terms Using your own words, on a piece of paper write a brief definition or explanation of each of the following terms. 1. audition 2. pitch and frequency 3. middle ear 4. cochlea 5. inner ear 6. place theory 7. frequency theory 8. conduction hearing loss 9. sensorineural hearing loss Functions or Descriptions a. the number of complete wavelengths that can pass a point in a given time b. results from damage to the outer or middle ear c. a tone's highness or lowness d. sound waves trigger activity at different places on the cochlea's basilar membrane e. results from damage to the auditory receptors of the cochlea or the auditory nerve f. the nerve impulses in the auditory nerve match the frequency of a tone 4. cochlea; oval window; basilar membrane; hair cells; thalamus; temporal; number 5. less; stress; high blood pressure; anxiety; feelings of helplessness; unanticipated; uncontrollable 6. place; low 7. frequency; high; 1000 8. volley 9. speed (timing); loudness 10. harder 11. parallel processing Hearing Loss and Deaf Culture 1. conduction hearing loss 2. sensorineural; aging 3. stimulate 10. cochlear implant 4. cochlear implant 5. Deaf culture; children; speak; disability ANSWERS 6. is; with; have 7. seem to; sensory compensation 8. self-esteem; accepted Module Review Introduction and The Stimulus Input: Sound Waves 1. audition; air molecules 2. loudness 3. frequency 4. decibels; 0 The Ear 1. outer; middle; inner 2. eardrum 3. hammer; anvil; stirrup Progress Test Multiple-Choice Questions 1. b. is the answer. Just as wave frequency determines pitch, so wave amplitude determines loudness. a. Amplitude is the physical basis of loudness; wavelength determines frequency and thereby pitch. c. & d. Wavelength, amplitude, and intensity are physical aspects of light and sound. Because the 174 Module 14 Hearing question is based on a relationship between a physical property (frequency) of a stimulus and its psychological attribute (pitch), these answers are incorrect. 2. a. is the answer. b. & c. Although the localization of low-pitched sounds along the basilar membrane is poor, that for sounds of middle and, especially, high pitch is good. Therefore, place theory accounts well for high-pitched sounds and, together with frequency theory, can account for middle-pitched sounds. d. As long as the notes of a chord are within the range of responsiveness of the basilar membrane, chord perception can be accounted for by place theory. 3. c. is the answer. d. Chord perception, except for chords comprised exclusively of high-frequency notes, shows no age-dependent decline. 4. d. is the answer. Sensorineural hearing loss is caused by destruction of neural tissue as a result of problems with the cochlea's receptors or the auditory nerve. a. & c. Wax buildup and blockage because of infection are temporary states; sensorineural hearing loss is permanent. Moreover, sensorineural hearing loss involves the inner ear, rather than the outer or middle ear. b. Damage to the eardrum impairs the mechanical system that conducts sound waves; it could therefore cause conduction hearing loss, not sensorineural hearing loss. 5. a. is the answer. Frequency theory best explains the lowest pitches. Place theory best explains the highest pitches, and some combination of the two theories probably accounts for our sensation of intermediate-range pitches. 6. c. is the answer. a. This answer describes how pitch is sensed in the case of high-pitched, but not low-pitched, sounds. b. This answer describes how pitch is sensed in the case of low-pitched, but not high-pitched, sounds. d. This answer is incorrect because it reverses the range of frequencies. 7. a. is the answer. 8. d. is the answer. The hair cells, which transduce sound energy, are located on the basilar membrane. a. & b. The eardrum and bones of the middle ear merely conduct sound waves to the inner ear, where they are transduced. c. The semicircular canals are involved in the vestibular sense, not hearing. 9. d. is the answer. Hearing losses that result from aging are greatest in the higher frequencies and involve damage to the hair cells on the basilar membrane of the cochlea. a' b" & c. Damage to the eardrum, auditory canal, or bones of the middle ear would probably cause conduction hearing loss and reduced sensitivity to sounds of all frequencies. I Summing Up 1. Outer ear. Hearing begins as sound waves enter the auditory canal of the outer ear. 2. Auditory canal. Sound waves passing through the auditory canal are brought to a point of focus at the eardrum. 3. Eardrum. Lying between the outer and middle ear, this membrane vibrates in response to sound waves. 4. Middle ear. Lying between the outer and inner ear, this air-filled chamber contains the hammer, anvil, and stirrup. 5. Hammer, anvil, and stirrup. These tiny bones of the middle ear concentrate the eardrum's vibrations on the cochlea's oval window. 6. Inner ear. This region of the ear contains the cochlea and the semicircular canals, which play an important role in balance. 7. Cochlea. This fluid-filled multichambered structure contains the hair cell receptors that transduce sound waves into neural impulses. 8. Auditory nerve. This bundle of fibers carries nerve impulses from the inner ear to the brain. Matching Items 1. d 2. f 3. b 4. e 5. c 6. a Key Terms 1. Audition refers to the sense of hearing. 2. The pitch of a sound is determined by its frequency, that is, the number of complete wavelengths that can pass a point in a given time. Frequency, in turn, is directly related to wavelength: longer waves produce lower pitch; shorter waves produce higher pitch. Focus on Vocabulary and Language 3. The middle ear is the chamber between the eardrum and cochlea containing the three bones (hammer, anvil, and stirrup) that concentrate the eardrum's vibrations on the cochlea's oval window. 4. The cochlea is the coiled, bony, fluid-filled tube of the inner ear where the transduction of sound waves into neural impulses occurs. 5. The inner ear contains the semicircular canals and the cochlea, which includes the receptors that transduce sound energy into neural impulses. Because it also contains the vestibular sac, the inner ear plays an important role in balance, as well as in audition. 6. The place theory of hearing states that we hear different pitches because sound waves of various frequencies trigger activity at different places on the cochlea's basilar membrane. Memory aid: Place theory maintains that the place FOCUS ON VOCABULARY AND LANGUAGE Introduction and the Stimulus Input: Sound Waves We also are remarkably sensitive to faint sounds, an obvious boon for our ancestors' survival when hunting or being hunted or detecting a child's whimper. Humans are very good at detecting very quiet noises (faint sounds), which was clearly beneficial (a boon) to our predecessors' ability to survive when they were both predator (hunter) and prey (being hunted). Likewise, the ability to notice and respond to a youngster's quiet cry of distress (a child's whimper) would have had adaptive value. We are also very sensitive to changes in sounds and we have the ability to differentiate among thousands of human voices. A piccolo produces much shorter, faster sound waves than does a tuba. Musical instruments produce stimulus energy called sound waves~molecules of air that bump and push each other along~and these may be long (low frequency) or short (high frequency). A tuba (a large, deep-toned, brass-wind instrument) produces low-frequency sound waves and thus has a lower pitch than a piccolo (a small flute), which produces high-frequency waves and has a higher pitch. 175 of maximum vibration along the cochlea's membrane is the basis of pitch discrimination. 7. The frequency theory of hearing presumes that the rate, or frequency, of nerve impulses in the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch. 8. Conduction hearing loss refers to the hearing loss that results from damage in the mechanics of the outer or middle ear, which impairs the conduction of sound waves to the cochlea. 9. Sensorineural hearing loss (nerve deafness) is hearing loss caused by damage to the auditory receptors of the cochlea or to the auditory nerve due to disease, aging, or prolonged exposure to ear-splitting noise. 10. A cochlear implant is an electronic device that converts sounds into electrical signals that stimulate the auditory nerve. The Ear (Close-Up): If only our ears had earlids. Myers makes it clear that prolonged exposure to loud and unpredictable noise can affect our well-being and seriously damage our hearing. So, in a noisy urban environment it would be nice if we could close our ears (with earlids) as we can our eyes (with eyelids). If a car to the right honks, your right ear receives a more intense sound, and it receives sound slightly sooner than your left ear. We locate sounds because our ears are about 6 inches apart and there is a time, as well as a loudness difference, between auditory reception in each ear. If we hear the sound of a car horn (it honks) to our right, the left ear receives a less intense sound somewhat later than the right ear, and thus we locate the direction of the sound to the right. That is why, when trying to pinpoint a sound, you cock your head, so that your two ears will receive slightly different messages. When a sound is equidistant from our two ears (directly ahead, behind, or above), and there is no visual clue, we have trouble locating (pinpointing) the source. In this situation it helps to tilt (cock) our heads so that each ear receives a slightly different message (the sound will be a little louder and sensed a little 176 Module 14 Hearing sooner by one ear, and the brain uses this information to detect where the sound is coming from). Hearing Loss and Deaf Culture Occasionally, disease causes sensorineural hearing loss, but more often the culprits are biological changes linked with heredity, aging, and prolonged exposure to ear-splitting noise or music (Figure 14.5). Sensorineural hearing loss, or nerve deafness (cochlear damage), can sometimes be caused by illness, but the agents responsible (the culprits) are more likely to be age-related biological factors and extended encounters with extremely loud (earsplitting) music or noise. While digital hearing aids are a partial remedy, the latest cochlear implants can restore hearing for children and most adults.