Instruction Manual. Audiology Clinic V2. By Parrot Software

Transcription

1 Instruction Manual Audiology Clinic V2 By Parrot Software

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3 Contents Introduction 1 Using The Audiology Clinic, Version Screen Area... 1 File Menu... 1 Case Menu... 2 Test Menu... 2 Audiogram Menu... 4 Auto Test Menu... 4 Immittance Menu... 5 Options Menu... 6 Case Menu revisited... 7 Controlling the Audiometer with the Keyboard... 7 Summary... 7 Chapter One 8 Audiologic Screening... 8 Procedure... 8 Additional Considerations... 8 Practice... 9 Technique... 9 Summary... 9 Chapter Two 10 Air And Bone Conduction Threshold Audiometry...10 Auditory Thresholds...11 Clinical Audiometry...11 Earphones...11 Threshold Testing Procedure...11 Modified Hughson-Westlake Method...12 Automatic Testing...12 Interpreting Automatic Tests...13 Response Chart...13 Manual Testing...13 The Audiogram...14 Practice...14 Audiogram Interpretation...14 Threshold Considerations...15 Instruction Manual Audiology Clinic V2 Contents i

4 Maximum Intensity Limits...15 Summary...16 Chapter Three 16 Masking Air Conduction Thresholds...16 Crossover...16 Masking...17 Three Masking Rules...17 Example Of Crossover...17 Synopsis Of Rule One...18 Masking Strategies...19 The Plateau Method...19 Automatic Testing...20 Establishing The Plateau...20 Interpretation Of Results...22 Four Parts Of The Masking Curve...22 Determining The Real Threshold...23 Overmasking...23 Definition Of A Plateau...24 Limitations To Plateau Definitions...25 Summary...26 Chapter Four 26 Masking Bone Conduction Thresholds...26 Interaural Attenuation By Bone Conduction...26 Air-Bone Gap...27 Occlusion Effect...27 Air-Bone Gaps In Only One Ear...28 Practice...29 Bilateral Air-Bone Gaps...29 The Masking Dilemma...30 Summary...31 Chapter Five 32 Re-examining Air Conduction Thresholds...32 Retesting Only One Ear...32 Practice...33 Disparity Between Air And Bone Thresholds...33 Realistic Clinical Responses...34 Summary...35 Chapter Six 35 Variability In Listener Responses...35 Practice...36 Summary...36 ii Contents Instruction Manual Audiology Clinic V2

5 Chapter Seven 36 Aural Acoustic Immittance...36 Impedance Basics...37 Resistance...37 Reactance...37 The Problem Of Timing...37 Acoustic Admittance...38 Static Admittance...39 Summary...40 Chapter Eight 40 Tympanometry...40 Tympanometry Procedure...41 Tympanometric Norms...42 Tympanogram Classification...43 Tympanometric Screening For Middle Ear Disorders...45 Summary...45 Chapter Nine 45 Acoustic Reflex...45 Ipsilateral Stapedial Reflex...46 Contralateral Stapedial Reflex...47 Normative Stapedial Reflex Behavior...47 Clinical Patterns...48 Summary...55 Chapter Ten 55 Speech Audiometry...55 Speech Recognition Threshold...55 Word recognition...56 Recorded vs. Live Voice Presentation...56 Descending Threshold Protocol...56 Calibration of the Speech Signal...57 Masking Speech Thresholds...57 Practice...58 Summary...58 Index 59 Instruction Manual Audiology Clinic V2 Contents iii

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7 Introduction Using The Audiology Clinic, Version 2 Did you ever hear of a computer program that wasn t user-friendly and easy to use? On the other hand, did you ever try one the first time that was? The point is that most computer programs are not simple and intuitive until after you have learned how to use them. The objective of this chapter is to get you over the hurdle of learning a new program so that you can use it readily to simulate the tests used in audiology to assess hearing. It is assumed, incidentally, that you know how to manipulate Windows programs. If not, it would be advisable to get some help. You will find installation instructions at the end of the book, just before the Index. Screen Area Version 2 of The Audiology Clinic automatically detects the screen area of your computer monitor. The numbers that are displayed represent how many pixels your screen can show horizontally and vertically. The larger the set of numbers, the more things can be shown on the screen. Three settings are checked for: 1) 640x480, the setting used by Version 1, 2) 800x600, and 3) 1024x768. To simplify, we will call the 1024x768 screen area high resolution, the 800x600 screen area medium resolution, and the 640x480 screen area low resolution. You can learn the screen area of your computer by starting The Audiology Clinic and clicking the Options menu. The last item on that menu indicates the current screen area of your monitor. Ideally, your computer should have high resolution because this permits most Instruction Manual Audiology Clinic V2 Introduction 1

8 windows used in The Audiology Clinic to be displayed on the screen simultaneously without any overlapping. Furthermore, if your computer is set to high resolution, the program can be run on a portion of the screen so that it looks exactly like Version 1 by clicking Options and then Run in Window. This cannot be done with low or medium resolution. Using Run in Window permits the remainder of the screen to be used for other programs. It is possible to switch back and forth between full-screen and partial screen by clicking Run in Window on the Options menu. If a case is currently displayed, it must be closed (on the menu click Case, then Close) before the display can be changed. Remember that high resolution is the recommended setting because more windows are visible at one time. The screen area setting can be changed on most computers, so you may want to experiment with the different settings to ascertain the one that is best for you. If you are working in a lab, check with the lab supervisor first. However, if you are using your own computer, the screen area can be adjusted by clicking Start, Settings, and Control Panel. Then double click the Display icon. In that window click the Settings tab. Finally, drag the arrow in the Screen Area box to the desired setting. Finally, click OK. If you have made a change, a second window will appear, so click OK again. The screen area setting can be changed on most computers, so you may want to experiment with the different settings to ascertain the one that is best for you. If you are working in a lab, check with the lab supervisor first. However, if you are using your own computer, the screen area can be adjusted by clicking Start, Settings, and Control Panel. Then double click the Display icon. In that window click the Settings tab. Finally, drag the arrow in the Screen Area box to the desired setting. Finally, click OK. If you have made a change, a second window will appear, so click OK again. File Menu After starting The Audiology Clinic, the first step is to open a data file. Data files come in two varieties: the Standard data file and Extra data files. The former contains all the cases discussed in this text/manual, while the latter enable you to access additional cases that your instructor may want you to test. Extra data files are not accessible from the Lite edition of the program. 2 Introduction Instruction Manual Audiology Clinic V2

9 Figure 1-1. File menu. To open a data file, on the menu bar click File, and a submenu will appear. Pick the type of file you want on this submenu (see Figure 1-1). Case Menu The Case menu now becomes available, so the next step is to select the Case you want to test. On the menu bar click Case, followed by Select Case on the submenu, as revealed in Figure 1-2. Figure 1-2. Case menu This action will open the Case Selector window (Figure 1-3). You may type in the number of the case you wish to test if you know it. Alternatively, you may click the down arrow to reveal a list of all available case numbers, using the scroll bar to move among the choices. Click the case desired. Finally, click OK. Figure 1-3. Case selector. Test Menu Instruction Manual Audiology Clinic V2 Introduction 3

10 The last step is to select the type of test you want to conduct. The Test item on the menu has now become enabled. Click Test to see the submenu, which is shown in Figure 1-4. Figure 1-4. Test menu. If your immediate objective is to begin pure tone or speech testing, then click Pure tone audiometry; however if you want to do immittance first, then click Immittance. Selecting one type of testing protocol does not prevent your performing the other test because you may switch at any time. Just return to the Test menu and click on the other name to change testing modes. If you choose Pure tone audiometry, your screen will look like Figure 1-5 on a monitor that has high resolution. Notice that there are five parts to the display, which are identified in the figure below. Figure 1-5. Screen display for high resolution. On the other hand, if you are using the program with low or medium resolution or have selected the Run in Window option, then the screen will appear like the representation shown in Figure 1-6. Notice that the screen is divided into three major parts. On the left the listener is in the upper window, and the audiometer is in the lower window. On the right is the audiogram. Behind the audiogram is the immittance form, which also reveals the case history. 4 Introduction Instruction Manual Audiology Clinic V2

11 Figure 1-6. Screen for pure-tone audiometry. On the other hand, if your choice on the Test menu was Immittance, your screen will look like the picture below (Figure 1-7). You can see that the immittance instrument is at the left and the immittance and case history form at the right with the audiogram behind it. Figure 1-7. Screen for immittance. It is important to understand that to switch back and forth between these two forms click on the title bar of the one that is underneath. Refer to Figure 1-8. In this instance the audiogram is active, and the immittance/history form is mostly hidden underneath. Only its title bar is visible above the audiogram. To make the entire immittance/history form visible, click on its title bar. The immittance/history form then moves to the front, and the audiogram goes behind. To view the whole audiogram again, click on its title bar. Instruction Manual Audiology Clinic V2 Introduction 5

12 Figure 1-8. Audiogram and immittance title bars. Remember that you can easily alternate testing modes between audiometry and immittance. Simply click Test and then click the type of test desired. For instance, if you are doing pure tone testing and you want to switch to immittance, click Test and then click Immittance. Audiogram Menu Assume that from the Test menu you picked Pure tone audiometry. This activates the Audiogram menu and affords the choices presented in Figure 1-9 below. Most importantly, you can plot the audiogram of the person represented by the current case. This grants you the opportunity to check your results against the correct results. Recognize, however, that it is possible for your instructor to revoke this privilege. Another choice on the Audiogram menu is Erase. This will delete all pure tone thresholds and speech and immittance results. After an audiogram is plotted, it may be printed by clicking Print. The final choice on the Audiogram menu is Symbols. Clicking this opens a window that reveals the explanation of the symbols used on the audiogram. Figure 1-9. Audiogram menu. Auto Test Menu Again assume that from the Test menu you selected Pure tone audiometry. Observe that Auto Test has become available on the menu. It offers five alternatives (Figure 1-10) A primary feature of The Audiology Clinic is its capacity to find pure tone unmasked and 6 Introduction Instruction Manual Audiology Clinic V2

13 masked thresholds automatically. The first item on the submenu, Modified H-W, measures the unmasked pure tone threshold at the current audiometer setting (Left or Right ear, Air or Bone conduction, at the selected frequency). Clicking this item will display a new window, the Response Chart. This chart will appear on top of the Immittance instrument, if operating in high resolution mode (Figure 1-5) or on top of the Audiogram and Immittance windows at the right of the screen, if operating in low or medium resolution mode or Run in Window (Figure 1-6). Figure Auto test menu. It should be emphasized that during auto testing using low resolution or Run in Window mode there are three overlapping windows on the right half of the screen. It is possible to view any one of them in its entirety by clicking on its title bar. This action will bring that window to the front and place it on top of the others. The unmasked threshold can be obtained manually by repeatedly clicking the Next button on the Response Chart or automatically by setting the Speed to a value between 1 and 9 by clicking the arrows above the Speed label. Setting 1 is the slowest and 9 is the fastest. The process can be interrupted at any time or reset when completed by clicking the Reset button. These controls are revealed in Figure Figure Top part of Response Chart. Instruction Manual Audiology Clinic V2 Introduction 7

14 The masked threshold can be acquired by choosing Standard masking or Complete masking from the Auto Test menu. These procedures are described in Chapter Three. The Complete masking operation reveals the masking curve at all masking levels and is intended to illustrate theoretical concepts useful for learning purposes. It is not the method that would be used clinically. Normal clinical protocol is illustrated by the Standard masking selection. When you are performing tests or having the computer do automatic Standard masking or Complete masking, the Crossover diagram option becomes available (for bone conduction testing the non-test ear must be occluded - see Chapter 4). Choosing this menu item opens a window on the screen that depicts a schematic of the head showing the amount of hearing loss in the conductive mechanism, in the sensorineural mechanism, and the total loss for each ear. It also reveals the signal and masking levels at each ear and any crossover that may be occurring. Using this diagram permits thorough examination of the variables involved in obtaining correct thresholds when masking. The Crossover window is depicted in Figure Figure Crossover diagram. Lastly, it is possible to click Close auto test and remove the Response or Masking chart and the Crossover diagram from the screen. Immittance Menu The Immittance menu item is accessible only when there is not an active case. To close the current case, click the Case menu and then click Close Case. Now Immittance can be chosen. Clicking this item opens the submenu displayed in Figure 1-13 below. 8 Introduction Instruction Manual Audiology Clinic V2

15 Figure Immittance menu. The Probe tip presents an animation of tympanometry in the normal and pathological ear. The Ipsilateral reflex arc and the Contralateral reflex arc demonstrate the neural pathways involved when eliciting acoustic reflexes. Impedance opens a submenu that demonstrates instances of the mathematics involved in calculating acoustic impedance. Finally, Examples accesses illustrations referred to in Chapter 9. Options Menu Last of all, the Options menu item provides nine alternatives. These are shown in Figure 1-14 on the next page. All choices are visible in this figure, although when the program is running, not all choices are available at all times. These operations are described below. Figure Options menu. Instruction Manual Audiology Clinic V2 Introduction 9

16 1.Transducer allows you to switch between standard circumaural earphones and the newer insert earphones (unless your instructor has authorized only one kind of earphone to be used). This choice must be made after choosing Pure tone audiometry as the type of test but before any further action is taken. Otherwise said, the kind of earphones in use cannot be changed once a test is begun (by clicking the mouse or pressing any key on the keyboard). 2.Audiometer lets you pick either a clinical or a portable audiometer to test with. This item is only available when there is no active case. Close the current case to obtain access to this option. 3.Listener enables you to opt to test a particular listener; otherwise one of four listeners is selected randomly when a case number is picked. 4.Non-test ear occluded prepares for the measurement of masked bone conduction thresholds by placing a circumaural earphone on or an insert earphone in the non-test ear (Chapter 4). 5.Calibrate speech is only available when Speech has been selected as the mode on the audiometer. It opens a window with a pointer that lets you calibrate the level of the speech signal prior to doing speech audiometry (Chapter 10). 6.Sound on determines whether the program produces sound. If your computer has a sound card, then the Sound on item has a check mark before it, and the program produces sound. Sound output can be defeated, however, by clicking this item to remove the check mark. This may be preferable in a laboratory. If there is not a sound card in the computer then this item is unchecked and cannot be selected, and there is, of course, no sound output. 7.Show privileges informs you whether for the current case you can view the correct audiogram, the immittance results, the speech results, and the case history It also notifies you whether you can do the three types of auto testing. These privileges can be controlled by your instructor. When any of these privileges is denied, it will not be available for selection on the menu. 8.Run in Window permits you to run the program on a reduced portion of the entire screen, if your computer monitor has high resolution as discussed above. 9.Screen area discloses the current screen area setting of your computer monitor. Case Menu revisited 10 Introduction Instruction Manual Audiology Clinic V2

17 When the Case menu was presented above, two items were not discussed: Record results and Save case(s). These two items are not accessible from the Lite edition of the program. For evaluative purposes your instructor may require you to test one or more cases and submit the results to him or her. In order to record the results of your testing procedures, click the Case menu followed by Record results before selecting the case to be evaluated. After you have finished all the tests you want to administer, click Case again, followed by Save case(s), select the disk you want to save the case(s) on, and name the file according to instructions given to you. Controlling the Audiometer with the Keyboard When performing pure tone audiometry (Chapters One through Six), the audiometer can be controlled with the mouse or with the keyboard (your preference). When using the keyboard, the function of the relevant keys is shown in the table below. These keys are consistent with the older Pure Tone Simulation program. The audiometer window must be the active window to use the keyboard to control the audiometer (i.e., the title bar that says Audiometer must be blue). If the audiometer window is not the active window, click anywhere on the window with the mouse to activate it. Note: if the audiometer window cannot be activated, then the program is in a mode, such as Auto Test, which does not permit the audiometer to be activated. Exit that mode first, then click on the audiometer window. Function Change Output: Left - Right Change Mode: Air - Bone - Speech Intensity - increase Intensity - decrease Frequency - increase Frequency - decrease Present signal Plot threshold Erase audiogram & immittance Key HOME END UP ARROW DOWN ARROW RIGHT ARROW LEFT ARROW SPACE BAR P E Summary Instruction Manual Audiology Clinic V2 Introduction 11

18 An overview of the operation of The Audiology Clinic has been presented by explaining the menu choices. Practice manipulating the features of the program until you become comfortable with it, and refer back to this chapter when needed. Chapter One Audiologic Screening In this chapter we will discuss the techniques used in audiologic screening using the pure tone audiometer. The procedures to be used are described by the Guidelines for Audiologic Screening published by the American Speech-Language-Hearing Association (ASHA) in The purpose of screening is to detect, among apparently healthy persons, those individuals who demonstrate a greater probability for having a disease or condition, so that they may be referred for further evaluation (ASHA, 1997, p. 6). These guidelines are extensive, and only the specific details that relate to pure-tone audiometry will be presented here. If you are administering a screening program, it is strongly suggested that you read these guidelines and become thoroughly familiar with their content. Procedure The recommended screening procedure differs somewhat depending on the goal of the screening and the age group being screened. We will concern ourselves with screening for hearing impairment in three age groups: 1) 3-5 yrs., 2) 5-18 yrs., and 3) adults. In all cases the frequencies to be used are: 1000, 2000, and 4000 Hz. 12 Chapter One Instruction Manual Audiology Clinic V2

19 1.The first group, ages 3-5 yrs., is screened at 20 db HL. Each stimulus is to be presented at least twice at each frequency in each ear, and the criterion for passing is to respond to at least 2/3 of the presentations. 2.The second group comprises school-aged children between 5 yrs. and 18 yrs. This group is also to be screened at 20 db HL. To pass they must respond to all the signals; otherwise they are to be rescreened after repositioning the earphones and being reinstructed. 3.The third group is comprised of adults. They are to be screened at 25 db HL and must hear all the signals to pass the screening. Another group, 7 mo. - 2 yrs., is included in the guidelines, but screening this group involves specialized techniques. Consequently, the details will not be covered here. The guidelines provide actions to be taken, if a listener fails the screening. These differ depending on the age group. Of interest here is simply whether the listener passes or fails the screening test. Additional Considerations Other details of the screening procedure will be mentioned only briefly. As always in audiometry the instructions to the listener are of the utmost importance. They should be as concise as possible without causing the person being tested to be confused due to insufficient information about the task expected of them. Although multiple presentations of the signal can be delivered to the listener, under no condition should the tone be presented repeatedly until the listener responds. The criterion for the 3-5 yrs. group serves as a good rule of thumb: present the tone at each frequency a maximum of three times and consider two or more responses as passing. In addition, as with all audiometric testing, a sufficiently quiet acoustic environment and a properly calibrated audiometer are of paramount importance. A checklist of the steps is provided in the box below. Operational Checklist Preparation: 1. Adjust the Intensity to 20 or 25 db depending on the age group. 2. Confirm that the Frequency is 1000 Hz. 3. Set the Output to Right, the Mode to Air, and be sure the Masking is off (0 db). Instruction Manual Audiology Clinic V2 Chapter One 13

20 Testing: 1. Present the signal for approximately one second and observe whether the listener heard the signal. 2. Continue by offering a second, and if necessary a third, presentation; note whether there was a response. 3. Decide whether the signal was heard on a majority of the presentations. 4. Repeat at other frequencies in current ear and in other ear. Practice If you haven t already read the Introduction to find out how to use The Audiology Clinic, be sure to do that now. Screening audiometry is typically done with a portable audiometer. The type of audiometer you want to use must be selected before a case is chosen. Immediately after starting the program click Options followed by Audiometer; finally click Portable. (If there is a case currently being tested, click Case, then Close case before going to the Options menu as previously stated.) Let s begin with Case No. 1, so select that case. Convention dictates that you always start at 1000 Hz in the right ear, unless you have reason to do otherwise. In general, it is advisable to begin the test in the ear that is known (or believed) to have the better hearing sensitivity. The steps in the ASHA guidelines for screening are summarized in the following panel. Let s assume that this listener is an adult; therefore the proper intensity to use is 25 db. Now begin to screen the hearing of this listener (i.e., test at 1000 Hz). You will discover that the listener heard the 1000 Hz tone in the right ear. Now change the frequency to 2000 Hz and present the tone; once more the listener hears the tone. Continue by switching to 4000 Hz and deliver the signal. At this point you should have presented three tones and noted three responses. Next switch to the opposite ear, the left ear, and continue the test. Don't forget to reset the frequency to the starting setting: 1000 Hz. Complete the test (i.e., present tones at 2000 and 4000 Hz). You have now completed the screening text on the first listener. Note that he or she passed the test because a hand was raised after each of the six tones was presented. To continue, choose Case on the Menu, followed by Select Case, and pick Listener No. 2, another adult. Employ the same technique that you have just used to test this listener. The listener associated with Case 2, as you will discover, fails the screening test because he or she did not respond to all three tones in 14 Chapter One Instruction Manual Audiology Clinic V2

21 the left ear. There are a total of ten listeners to be screened (5 in the Lite edition), so continue with Case 3. Assume that Case 3, 4, and 5 are ages 18 or younger, so set the intensity to 20 db HL. Consider the remainder to be adults, so reset the intensity to 25 db HL. Technique There are two aspects of a clinician s technique that are important to consider at all times. First, it is essential to present the signal to the listener with a duration that is sufficiently long for the listener to perceive it. The length of a tonal signal should be approximately one second. Durations shorter than one second may not be perceived, while signals longer than one second do not improve detection and are inefficient time-wise. The listeners in The Audiology Clinic will not respond to very short stimuli regardless of the intensity. The second factor is the temporal pattern with which the signals are presented. It is necessary to vary the interstimulus interval and not to present the signals with a fixed, predictable pattern. In other words vary the amount of time between one signal presentation and the next. Otherwise, the listener will consciously or unconsciously anticipate the next signal presentation and respond accordingly, since reacting to very soft signals often involves making a guess. Summary This chapter has described pure tone screening tests for different age groups using procedures defined in the ASHA guidelines. In the next chapter the topic of air conduction threshold tests will be explained. Instruction Manual Audiology Clinic V2 Chapter One 15

22 Chapter Two Air And Bone Conduction Threshold Audiometry The purpose of this chapter is to master the technique of obtaining hearing thresholds by both air conduction and bone conduction. Furthermore, you will learn to use several new features of The Audiology Clinic. Let us begin by quickly reviewing the reasons for measuring hearing thresholds by both air and bone conduction. The objectives are primarily to quantify the individual's sensitivity at each frequency and secondarily to specify the locus of the hearing impairment. Testing performed with the earphones directs sound waves into the ear canal toward the middle ear, thus the term air conduction; e.g., the sound waves are conducted through the air to the eardrum. In contrast, testing done with the bone conduction vibrator placed behind the pinna (or, much less frequently, on the forehead) vibrates the temporal bone and stimulates the cochlea directly; this testing mode is called bone conduction. Signals presented by air conduction (AC) must pass through the entire auditory mechanism: first the outer ear, then the middle ear, next the inner ear, and finally along the auditory nerve. Air conduction testing, therefore, indicates how much hearing loss an individual has. This total loss may be comprised of abnormalities in any or all of the four sections of the auditory mechanism. On the other hand, signals introduced through the bone conduction (BC) vibrator bypass the outer and middle ears and directly quantify the amount of the sensorineural deficit; so the bone conduction thresholds unambiguously reveal the amount of loss in sensitivity due to impairment of the inner ear and/or the auditory nerve. Together the air conduction threshold and the bone conduction threshold determine what kind of hearing impairment a person has. The establishment of the kind of hearing loss is straightforward. As already stated, the bone conduction thresholds directly indicate the 16 Chapter Two Instruction Manual Audiology Clinic V2

23 amount of sensorineural loss (inner ear and/or auditory nerve). Ascertaining the amount of conductive loss (outer and/or middle ear) necessitates subtracting the bone conduction thresholds (sensorineural loss) from the air conduction thresholds (total loss). To illustrate these ideas, let us consider three different people. 1.Assume that person "A" has air and bone conduction thresholds of 50 db HL in both ears at all frequencies. Since the air and bone conduction thresholds are equivalent, this person has a sensorineural deficit. There is no conductive involvement because AC (50) - BC (50) = 0. 2.Now let s assume that person "B" has the following thresholds in both ears at all frequencies: air conduction = 50 db HL and bone conduction = 0 db HL. Clearly, this individual has no sensorineural involvement because there is no reduction in sensitivity for bone conduction stimuli; however he or she does have a 50 db conductive loss because AC (50) - BC (0) = Lastly, let s suppose that person "C" has air conduction thresholds equal to 50 db HL and bone conduction thresholds equal to 30 db HL. This individual has a mixed hearing loss, which is to say that part of the loss is conductive and part is sensorineural. The magnitude of the conductive component is 20 db, as AC (50) - BC (30) = 20, while the degree of the sensorineural component is 30 db, because the bone conduction thresholds were obtained at 30 db HL. Be sure to avoid confusing the terms: air conduction and conductive. Air conduction refers to a type of testing, namely presenting stimuli through earphones, while the word conductive implies a kind of hearing impairment, that is one involving the outer and/or the middle ear. It is not advisable to refer to an "air conduction loss"; instead refer to a "conductive loss" (vs. a "sensorineural loss"). Auditory Thresholds As was the case with Audiologic Screening, discussed in Chapter 1, guidelines for pure-tone threshold audiometry have been published by ASHA (ASHA, 1978). You are urged to become thoroughly familiar with them. There has been much discussion in the scientific literature, especially in sensory psychology, regarding the definition of auditory "threshold". In audiometry we are primarily concerned with the measurement of absolute thresholds (Humes, 1994), or the softest intensity an individual can hear 50% or more of the time. We shall use an operational definition that has been published by ASHA to quantify this threshold. Simply stated, a threshold is the lowest intensity tone Instruction Manual Audiology Clinic V2 Chapter Two 17

24 that can be heard on three (usually nonconsecutive) presentations. The thresholds for tones across the frequency range from 125 to 8000 Hz for a listener with perfectly normal hearing would be 0 db HL. 0 db HL thresholds are analogous to the commonly used term 20/20, when referring to vision. At the opposite end of the intensity continuum is the threshold of feeling. The extremely loud sounds that elicit this sensation are very unpleasant to the listener, and the audiometer cannot deliver such excessively intense stimuli to most people. The maximum output of most portable and clinical audiometers through the earphones is 110 db HL in the mid-frequencies ( Hz). Tones of this intensity usually will not elicit the sensation of feeling, but they will be uncomfortably loud for individuals with recruitment. Consequently, the clinician must always be cautious when presenting stimuli at or near maximum intensity so as not to cause distress to the listener. Clinical Audiometry Clinical audiometry involves both air conduction and bone conduction testing. The frequencies used for air conduction measurements include the octave frequencies Hz, in other words, 125, 250, 500, 1000, 2000, 4000, and 8000 Hz. The intraoctave frequencies, 750, 1500, 3000, and 6000 Hz, need only be tested when there is a 20 db or greater difference between any adjacent octave frequencies. For example, according to this provision, if you got a threshold of 40 db HL in the right ear at 4000 Hz and a threshold of 70 db HL in the same ear at 8000 Hz, then you should subsequently obtain a threshold in that ear at 6000 Hz because the difference in the thresholds at the adjacent octave frequencies is 30 db. The lowest frequency, 125 Hz, need be tested only when there is a low frequency hearing loss. Because the vast majority of hearing impairments are high frequency, it is usually unnecessary to test at 125 Hz. Bone conduction thresholds are typically measured at the octave intervals between 250 and 4000 Hz, that is at 250, 500, 1000, 2000, and 4000 Hz. But bone conduction thresholds may be assessed at 750, 1500, and 3000 Hz as well, if the difference between the thresholds at adjacent octave frequencies is 20 db or greater. Earphones There are two types of earphones commonly used in clinical audiometry. One kind is the older, larger earphone with a rubber cushion that makes contact with and surrounds the pinna. Such 18 Chapter Two Instruction Manual Audiology Clinic V2

25 earphones are referred to by several terms. The one we will use is circumaural earphones. In contrast, the smaller, newer type is called the insert earphones. This name is somewhat of a misnomer because it suggests that the earphone is inserted into the ear canal, which it is not. Rather the earphone is external to the ear, from a few millimeters to several centimeters depending on the brand. In either case a narrow tube leads from the actual earphone to an earplug which is inserted into the ear canal to deliver the sound. Insert earphones offer several advantages including ease in fitting and placement because of their small size and light weight, avoidance of closure of the ear canals (called collapsed canals), and most importantly increased interaural attenuation. This last factor is very significant and will be explained in the next chapter. The Audiology Clinic will permit the use of either type of earphone but defaults to the standard, circumaural earphones for the cases described in this text/manual. The results obtained, of course, will be identical except in a few very difficult cases. The intricacies of these cases will be the topics of future chapters. Also in the next chapter you will learn how to select between the two kinds of earphones with this simulation. Threshold Testing Procedure The ASHA guidelines describe two phases to obtaining each threshold: familiarization of the signal and measurement of the threshold. The motive for this two-stage method is that the pure-tones used for determining hearing thresholds are not common sounds in many people's lives. Furthermore, ascertaining a threshold involves, by definition, the use of a stimulus of very low intensity. Therefore, it is of foremost importance to familiarize the listener with the nature of the signal before presenting it at low levels just below and just above threshold. For the familiarization part of the procedure, the tone is presented initially at 30 db HL. The choice of this intensity presumes a listener with normal or near normal sensitivity. Because many individuals receiving hearing tests will not have normal thresholds, the following steps are further reported by the guidelines. If there is not a response at 30 db HL, then increase the intensity to 50 db HL. If there is still no response, then continue to increase the intensity in 10 db steps, until there is a response to the tone. The first response to the tone concludes the familiarization phase of the threshold determination. If the maximum output of the audiometer at the frequency being tested is reached, then present the tone three times at this maximum level. If the listener responds to fewer than half of these presentations (i.e., none or Instruction Manual Audiology Clinic V2 Chapter Two 19

26 one), the threshold is unmeasurable at the current frequency. On the other hand, if the listener hears more than half of the tones (i.e., two or all three), then his or her threshold is this maximum intensity. Usually the listener will respond at a level less than the maximum intensity, so next the threshold measurement phase of the test commences. Actually, we would label an additional phase called a transition step, as it leads to the measurement of the threshold which begins after the listener is no longer able to hear the signal. In the transition phase, the level of the tone is decreased by 10 db and presented to the listener. If there is a response, the tone is again decreased by another 10 db and the signal introduced. This process is repeated until an intensity is reached at which the listener does not respond. If the listener responds to the tone at the lowest intensity the audiometer can produce, which is -10 db HL, then the tone is again presented at that level. Finally, a third presentation is made. If the listener has responded either two or three times in a row to the -10 db HL signal, then his or her threshold at the frequency being tested has been obtained at -10 db HL. Moreover, this person has better-thannormal hearing at that frequency. The more normal situation is for the listener to stop responding to the tones before -10 db HL is reached. After the first non-response, the actual threshold search (or what the ASHA document calls measurement) begins. The intensity of the tone is increased by 5 db and presented to the listener. If he or she hears it, a note is made of this level. Initially, you should make a notation (i.e., write it down) of this intensity; after much practice and experience you will learn to make only a mental note of this level. If the listener does not respond to the 5 db increase in intensity, again raise the signal by 5 db and present it. Keep increasing the tone in 5 db steps until the listener hears it. As soon as you obtain a positive response, repeat the above procedure: that is, decrease the intensity of the tone in 10 db steps until you get a non-response, then increase the tone in 5 db steps until you do get a response. Each time you get a response after increasing the intensity of the tone, record the level. Threshold is reached as soon as the listener has responded to the tone at the same intensity three times. This procedure is indeed cumbersome to describe in words, but fortunately it lends itself to graphical representation with great ease. Thus, we will very shortly view this process using The Audiology Clinic. To summarize the threshold-measuring process, first increase the intensity of the tone until there is a response, then decrease the level of the tone until there is not a response, then alternately increase and decrease the intensity of the tone until three responses are recorded. 20 Chapter Two Instruction Manual Audiology Clinic V2

27 Modified Hughson-Westlake Method The process just portrayed is widely known as the modified Hughson- Westlake procedure, and it was discussed in detail by Carhart and Jerger (1959). This method of measuring thresholds is known in sensory psychology as an "ascending" technique, as responses are recorded only when the signal is being increased in intensity. Unlike strictly ascending methods, however, each different frequency is first presented at a supra-threshold level to familiarize the listener with what the stimulus sounds like. Obtaining thresholds quickly and reliably using the modified Hughson-Westlake technique is the quintessence of pure-tone audiometry. The adept clinician must be able to execute this procedure with great efficiency and expertise. Both air and bone conduction thresholds are obtained using the same procedure. Ordinarily, air conduction testing is done first in both ears. Then the earphones are removed, and the bone conduction vibrator is positioned behind one pinna (and one earphone may be replaced in or on the opposite ear as we shall see in Chapter 4). Bone conduction thresholds are obtained for that ear at all frequencies, and finally, after the bone conduction vibrator is placed behind the other pinna, bone conduction testing takes place in the opposite ear. Automatic Testing Before attempting to measure some thresholds yourself, let s watch The Audiology Clinic obtain some. This is done by selecting Modified H-W from the Auto test menu as described in the Introduction. The case we want to examine is Case 11, so select that case now. Furthermore, let s use the clinical audiometer from now on. A summary of the steps appears below. Setup checklist: 1. File: Open - Standard data file 2. Options: Audiometer, Clinical 3. Case: Select case (choose Case 11) 4. Test: Pure-tone audiometry (be sure that the Masking is set to 0 db) 5. Auto test: Modified H-W 6. Speed: manual Action: 1. Click Next repeatedly until the threshold is obtained; watch the explanation in the green box at the bottom Instruction Manual Audiology Clinic V2 Chapter Two 21

28 Interpreting Automatic Tests Notice that the threshold measuring process was graphed on the Response chart. This chart characterizes the intensities presented and the results of each presentation: an "R" means that the listener responded, and an "N" shows that the listener did not respond. The recurrent presenting of the tone and recording of the response on the graph will continue until the threshold is measured, or until it is found that the listener cannot hear this frequency even at the maximum intensity. The test proceeded in accordance with the rules outlined previously. There are several factors to observe. First the intensity of the tone was adjusted to 30 db HL. You could observe the numbers change in the intensity window of the audiometer. The dialog at the bottom of the Response Chart explained each step. When the level of the tone reached 30 db HL, the tone was sounded. The listener, who heard the signal, responded by raising his or her hand. Afterwards, the level of the tone was decreased by 10 db HL, and presented again. The tone continued to be lowered in 10 db steps until there was not a response on the part of the listener (at 0 db). This was because the signal was too soft to hear, in other words, below his or her threshold. Next, the intensity of the tone was increased by 5 db and presented; the listener heard it and raised his or her hand. And so the test continued until the listener heard the tone at the same level three times. The intensity representing threshold is 5 db HL. Click Reset and repeat the process until you are able to follow all the steps in the modified Hughson-Westlake procedure. If you wish, change the Speed to a number between 1 and 9 to have the entire process completed automatically. Response Chart When interpreting the response graph after a threshold has been automatically obtained by The Audiology Clinic, keep in mind the three phases of the threshold-measuring procedure that have been defined. First, familiarization (increase the intensity until audible); second, transition (reduce intensity to below audibility); and third, measurement (increase and decrease intensity until the tone is heard three times). As already stated, initially you should keep a written record of the listener's responses. Later, you will be able to keep track of the responses mentally. 22 Chapter Two Instruction Manual Audiology Clinic V2

29 Unless contraindicated by the case history information (the object is to test the ear having the better hearing first), air conduction testing generally begins in the right ear at 1000 Hz. Such was the case in the automatic sequence just witnessed. To experience a different threshold being measured, change the output of the audiometer to Left by clicking the Left button on the Output of the audiometer or by pressing the Home key. Again perform an automatic test by executing all the steps outlined above. Watch the screen. You will discover that the threshold in the left ear is 10 db HL, which reflects slightly reduced sensitivity, but hearing that is still considered to be within the normal range (as will be explained later in this chapter). Manual Testing Now that you have viewed The Audiology Clinic while it measured hearing thresholds, it is time to try it yourself. A checklist of the steps to complete before starting the test is presented in the box on the next page. Next obtain the air conduction thresholds at the remaining frequencies. Recall that if there are no differences between any two octave frequencies of more than 20 db, you need not test at the intraoctave frequencies; i.e., 750, 1500, 3000, and 6000 Hz. The usual order is to follow 1000 Hz by 2000 Hz and then proceed to 4000 and 8000 Hz. After that 1000 Hz should be retested to verify reliability. Lastly, measure the thresholds at 250 and 500 Hz. IMPORTANT! You must use a bracketing threshold technique like the modified Hughson-Westlake procedure in order to plot your thresholds. Proceed by obtaining all the air conduction thresholds for the right ear followed by the left ear. You can verify your results by having The Audiology Clinic show the correct results. If you are using high resolution, click Audiogram followed by Show results. For low or medium resolution or Run in Window the Response Chart (if visible) mostly covers the Audiogram, so click on the title bar of the Audiogram, which will enable the Audiogram menu. Now click Audiogram followed by Show results. An alternative procedure would have been to remove the Response Chart, thus returning the Audiogram to its position on top. This is done by clicking Auto test, then Close auto test. Note: as indicated in Chapter 1, your instructor can revoke your privilege to view any or all of these results. Instruction Manual Audiology Clinic V2 Chapter Two 23

30 Operational Checklist 1. Adjust the audiometer to the initial settings. This can be done by clicking the controls on the audiometer with the mouse or by using the keyboard as indicated in the last chapter. 2. Confirm that the Frequency is 1000 Hz., the Intensity is 30 db HL, the Output is set to the better ear, or to the Right ear if the better ear is unknown or hearing is believed to be equivalent. 3. Present the signal for about one second by clicking the Present Signal button or pressing the Space bar on the keyboard. 4. Observe whether the Listener responds. A response is indicated by a hand-raise and the Response light at the top of the audiometer glows red. 5. Adjust the intensity and go to Step 3. Normally, all frequencies are tested by air conduction in both ears before removing the earphones and placing the bone conduction vibrator, so next measure the bone conduction thresholds. Reset the ear to Right, as the right ear is usually tested first unless contraindicated. Finally, set the output to Left and get the left bone conduction thresholds. The Audiogram The thresholds obtained from threshold audiometry in the clinic are recorded one at a time on the audiogram. To do this, you can use the audiogram utilized at your clinic or office, or you can employ the audiogram feature of The Audiology Clinic. To use the on-screen audiogram, first find the correct threshold using the modified Hughson-Westlake technique. Then click on the plot symbol (shown below) on the audiometer or press P on the keyboard. "P" stands for "plot", and your just-measured threshold will be plotted on the audiogram, using the correct symbol for the ear you are testing. Practice 24 Chapter Two Instruction Manual Audiology Clinic V2

31 Ten cases are affiliated with this chapter (5 in the Lite edition), each displaying a different configuration of hearing. Practice by measuring the air conduction and bone conduction thresholds of each of the remaining cases (Cases 12-20). The correct results for all of the audiograms can be found by plotting the audiogram (Click Audiogram, then Show results). Of course these audiograms should only be examined after you have acquired your own results. For additional practice return to Chapter 1 and find the thresholds for Cases Audiogram Interpretation There are two aspects to the specification of every hearing loss: 1) what kind of loss, and 2) how much loss. The first of these was discussed at the beginning of this chapter. The second consideration, how much loss, is determined from the air conduction thresholds, which directly reflect the total impairment. Many audiologists describe categories of hearing, such as: hearing within normal limits, slight loss, mild loss, moderate loss, moderately-severe loss, severe loss, profound loss, and no measurable hearing. These categories, listed in Table 2-1 below, are discussed in an article by Goodman (1965) and were modified by Clarke (1981). For instance, if an individual had thresholds of 35, 40, and 50 db HL at 500, 1000, and 2000 Hz respectively in the left ear, then the average threshold across these three frequencies would be 42 db HL. According to Table 2-1, this person's loss would be defined as "moderate". Using these same words to describe every individual's hearing sensitivity may an oversimplification as different people with the same numeric thresholds have very different handicaps resulting from their hearing losses. A parallel situation might be to report one's visual acuity as a "little" nearsighted. As a result using a phrase, like "severe loss", must always be considered carefully. Nevertheless, many clinicians prefer to use a single word to summarize hearing test results, rather than merely reporting a set of numbers. Table 2-1. Descriptive terms for hearing loss categories and the associated range of thresholds (after Goodman, 1965, and Clarke, 1981). Descriptive Term Normal Limits Slight Loss Mild Loss Moderate Loss Moderately-Severe Loss Severe Loss Average of Hearing Thresholds at 500, 1000, and 2000 Hz -10 to 15 db 16 to 25 db 26 to 40 db 41 to 55 db 56 to 70 db 71 to 90 db Instruction Manual Audiology Clinic V2 Chapter Two 25