TM262 AutoTymp Operating Instructions

Contents Section 1-Introduction 1.1 Instrument Description ... 1 1.2 Tympanometry and Gradient ... 1 1.2.1 Tympanometry ... 1 1.2.2 Gradient ... 2 1.3 Screening Acoustic Reflex ... 3 1.4 Manual Audiometry ... 4

Section 2-Installation 2.1 Unpacking and Inspection ... 5 2.2 Probe Indicators ... 5 2.3 Front Panel Controls and Indicators ... 6 2.4 Printer and Display ... 8 2.4.1 Liquid Crystal Display (LCD) ... 8 2.5 Rear and Bottom Panel Labels/Connectors ... 10 2.6 Initial Setup ... 11 2.6.1 Loading the Paper ... 12 2.6.2 Paper Storage ... 12 2.7 Pretest Tympanometry Checks ... 13 2.7.1 Calibration ... 13 2.7.2 Altitude Adjustment ... 14 2.8 Pretest Audiometric Checks (Models with Audiometer Only) ... 16 2.8.1 Noise Recovery Period ... 16 2.8.2 Elimination of Ambient Noise ... 16 2.9 Biological Check ... 17

Section 3-Operation 3.1 Eartip Care ... 18 3.2 Probe Care ... 18 3.2.1 Probe Nose Cone Cleaning ... 18 3.2.2 The O-Ring ... 19 3.2.3 The Probe Wire ... 20 3.2.4 Probe Reassembly ... 20 3.3 Earphone Care (Models with Audiometer Only) ... 20 3.4 Paper Supply ... 21 3.5 Tympanometry Testing Information ... 22 3.5.1 Helpful Hints ... 22 3.5.2 Obtaining a Seal ... 22 3.6 Audiometry Testing Information ... 24 3.6.1 Instructing the Subject ... 24 3.6.2 Placement of Earphones ... 25 3.6.3 Response Handswitch (Optional Accessory) ... 25 3.7 Program Mode ... 25 3.7.1 Reflex Format ... 26 3.7.2 Print Header Format ... 27 3.7.3 Audiometric Format During Printing ... 28 3.7.4 Normal Box Format ... 29 3.7.5 Audiogram Range ... 30

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3.7.6 Exit Program Mode ... 30 3.8 Tympanometry Only Mode ... 31 3.8.1 Exit Tympanometry Only Mode ... 32 3.9 Tympanometry and Ipsilateral Reflex Mode ... 32 3.9.1 Programming Ipsilateral Acoustic Reflex Test Frequencies ... 33 3.9.2 Exit Tympanometry/Reflex Mode ... 34 3.10 Audiometry Test Sequence (Models with Audiometer Only) ... 34 3.10.1 Screening Audiometry ... 35 3.10.2 Threshold Audiometry ... 36 3.10.3 Exit Audiometry Mode ... 37 3.11 Tests In Memory ... 37 3.12 Memory Erase ... 37 3.13 Printing Test Results ... 37

Section 4-Test Results 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8

Ear Canal Volume ... 39 Compliance Peak... 39 Pressure Peak ... 40 Gradient ... 40 Acoustic Reflex ... 41 Audiometry ... 42 Special Messages and Error Codes ... 42 Sample Test Results ... 42

Section 5-RS-232 Interface 5.1 Introduction ... 46 5.2 Operation ... 46 5.3 Record Formats ... 47 5.3.1 General Record Format ... 47 5.3.2 Tympanometry and Reflex Test Results Record ... 47 5.3.3 Audiometry Test Results Record ... 50 5.3.4 Notes ... 51 5.4 Data Transmission Protocol ... 52 5.5 Data Transfer Program Mode ... 53 5.6 RS-232 Interface ... 54 5.6.1 Interface Configuration ... 54 5.6.2 Cable Connections ... 54 5.6.3 Communications Flow Control... 54 Service and Warranty Information ... 55 Specifications ... 56 Glossary of Terms ... 61 Bibliography ... 62

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Section 1-Introduction 1.1 INSTRUMENT DESCRIPTION TM

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The TM 262 Auto Tymp is a versatile combination instrument which provides testing capability for tympanometry alone, tympanometry combined with screening acoustic reflex measurements, and manual audiometry. Two different versions are available to meet your individual testing needs. The basic version provides two modes of operation, tympanometry alone and tympanometry plus screening ipsilateral acoustic reflex testing. The second version adds manual audiometry. It is possible to field retrofit the manual audiometer to the basic version after the time of original purchase. An RS-232 port is also available as an option. This allows the transfer of data from the instrument to a computer. A soft-sided carrying case, a dust cover, patient handswitch, patch cords, and earphone sound enclosures may also be purchased as optional accessories (see page 60).

1.2 TYMPANOMETRY AND GRADIENT 1.2.1 Tympanometry Tympanometry is an objective technique used since the late 1960’s to measure the middle-ear function. During tympanometry, a low frequency tone (226 Hz) is presented to the ear canal via the probe. The probe tone is used to measure the compliance (admittance) changes within the middle-ear system while air pressure within the hermetically-sealed ear canal is changed from positive to negative. In the normal ear, positive pressure introduced into the ear canal space causes the middle-ear system to stiffen up or become less mobile. Because the pressure difference between the sealed ear canal space and the middle-ear space forces the tympanic membrane to stretch inward, this stiffened middle-ear system displays little or no compliance. As the pressure within the ear canal is brought back toward atmospheric (ambient or 0 daPa) pressure, the pressure difference between the ear canal space and the middle-ear space is reduced in normal ears. At or near atmospheric pressure (0 daPa), the greatest amount of sound (probe tone) enters the middle-ear system. In other words, this is the air pressure value where the middle-ear system displays the maximum amount of compliance (admittance). As negative pressure is introduced, a pressure difference is once again established and the middle-ear system becomes less compliant. Thus, by varying the pressure within the ear canal, it is possible to make a series of compliance measurements by means of the probe tone. The tracing which depicts these compliance changes is referred to as a tympanogram.

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The point on the tympanogram which represents the point of maximum compliance (admittance) is the compliance peak of the tympanogram. The air pressure (pressure at the peak) where this compliance peak occurs approximates the pressure within the middle-ear system, since maximum mobility is only possible when there is little or no pressure difference between the ear canal and the middle-ear space. Compliance is measured with respect to the ability of an equivalent volume of air to conduct sound and the scientific quantity used is cm3. Air pressure is measured in decapascals (daPa). NOTE 1.0 daPa = 1.02 mm H2O

The presence of a pathological condition which interferes with the mobility of the tympanic membrane, the ossicular chain, or the air pressure within the middle-ear space can be detected during tympanometry. For example: • If the air pressure within the middle-ear space becomes negative due to a blocked Eustachian tube, tympanometry permits the measurement of this negative pressure and its effect on middleear compliance. • If fluid builds up within the middle-ear space, this fluid will restrict the ability of the ossicular chain to conduct sound to the cochlea. If small air pockets exist within the fluid, the tympanogram will indicate the negative pressure where the restricted mobility occurs. With a totally fluid-filled middle-ear space, no mobility will be measured during tympanometry at any pressure value. • In the case of a “glue-ear”, the ossicular chain is restricted in mobility but the air pressure within the middle-ear space is at atmospheric pressure. This tympanogram would depict a restricted compliance peak at or near 0 daPa.

1.2.2 Gradient Gradient (width) measurements are used to describe the shape of a tympanogram in the vicinity of the peak. Often, the presence or absence of fluid in the middle ear is not clearly indicated by otoscopy and the tympanometric peak alone. This evaluation is especially difficult when the peak pressure is in the normal range. The presence of fluid within the middle-ear space alters the shape of a tympanogram, i.e., makes the tympanogram wider near its peak. A larger-than-normal gradient can indicate the presence of fluid in the middle ear when other parameters are within normal limits. In this way, the gradient acts as an adjunct to the peak and ear canal volume measurements by helping to differentiate between tympanograms with similar peak values.

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The TM 262 Auto Tymp determines tympanometric width (gradient) by measuring the pressure interval at one-half of the peak height. Differing peak widths can point to different middle-ear conditions, even when peak height and pressure are within normal range. For example, middleear effusion brought on by secretory otitis media might result in an increased tympanogram width and, therefore, an increased gradient value. This would occur because the ossicular chain cannot react to the change in pressure introduced during the tympanogram in the same way that it would if the middle ear were properly aerated. The continued presence of effusion, leading eventually to a completely fluid-filled middle-ear cavity, will reduce the magnitude of the tympanogram to the point where no change in compliance is detectable across the pressure range. Under this condition, no gradient measurement is possible.

1.3 SCREENING ACOUSTIC REFLEX An acoustic reflex occurs when a very loud sound (stimulus) is presented to the auditory pathway. During ipsilateral acoustic reflex testing, the stimulus is presented to the ear canal through the probe. This stimulus then travels through the middle ear to the cochlea. From the cochlea, frequency and intensity information are transmitted via the 8th nerve to the brain stem. If the intensity of the stimulus is high enough to elicit the reflex response, a bilateral response occurs, i.e., the right and left 7th nerves innervate their respective middle-ear muscles (stapedial muscles) causing them to contract. As these muscles contract, they stiffen their respective ossicular chains. This stiffening of the ossicular chain reduces the compliance of each middle-ear system. As in tympanometry, a probe tone is used to measure this decrease in compliance. During ipsilateral acoustic reflex testing, both the stimulus and the probe tone are presented via the hand-held probe. Acoustic reflex measurements are useful in determining the integrity of the neuronal pathway involving the 8th nerve, brainstem, and the 7th nerve. Since the acoustic reflex test is performed at high intensity levels and since it involves a measurement of middle-ear mobility, acoustic reflex testing is not a test of hearing. The acoustic reflex test also serves as a good validation of tympanometric results, since an acoustic reflex cannot be measured in the absence of a compliance peak. In other words, if the tympanometric results indicate no mobility over the pressure range available with the TM 262, no reflex can be measured. If the test results indicate a reflex response in the absence of a compliance peak, one has cause to question the validity of the tympanometric test results. This indicates that the tympanogram should be repeated. Clinical middle-ear instruments allow the measurement of the acoustic reflex threshold, since they provide the ability to manually change the intensity of the stimulus to a level where a reflex response is just barely

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detectable for each patient tested. However, the TM 262 Auto Tymp automatically presents the stimulus in a very definite stimulus intensity sequence. This preset intensity sequence may start at a level above an individual’s acoustic reflex threshold level. Since the TM 262 uses a hand-held probe, noise from hand motion can be detected by the instruments circuitry. The magnitude of a detectable response must be somewhat higher than the criterion generally used during clinical acoustic reflex threshold testing, in order to avoid artifact caused by hand motion. Thus, the acoustic reflex measurements made with the TM 262 are referred to as screening acoustic reflex testing. The purpose of these screening reflex tests is to determine if a reflex is detectable or not, rather than to determine the lowest intensity at which the reflex occurs (i.e., threshold testing).

1.4 MANUAL AUDIOMETRY While tympanometry and acoustic reflex measurements check the integrity of the middle-ear system, audiometry provides a means for checking the integrity of the entire auditory pathway. Manual audiometry provides a method to check an individual’s ability to hear a test signal at a particular intensity level or at the lowest possible intensity level without the use of masking. During threshold audiometry, the test signal is generally presented through an earphone to the ear under test. Different test protocols define the frequencies and intensity sequence to be used to obtain a response. Audiometric testing requires a behavioral response. This consists of having the individual raise a finger/hand or press a handswitch (optional) whenever the test signal is heard. The finger/hand is lowered or the handswitch is released when the test signal is no longer audible. Thus, the individual being tested must be able to understand a set of simple instructions and have the ability to provide some physical sign when the test signal is heard.

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Section 2-Installation 2.1 UNPACKING AND INSPECTION Examine the outside of the shipping container for any signs of damage. Notify your carrier immediately if any damage is observed. Carefully remove your TM 262 from its shipping container. If the TM 262 Auto Tymp appears to have suffered mechanical damage, notify the carrier immediately so that a proper claim can be made. Save all packing material so the claim adjuster can inspect it as well. When the carrier has completed the inspection, notify your Welch Allyn, Inc. distributor. TM

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TABLE 2-1 Accessories Supplied Probe Assembly Power Module or Internal Supply Eartips (6 sizes, 2 each) Paper (3 rolls)

Test Cavity Instruction Manual Test Headset (Models with audiometer only)

NOTE Keep the original packing material and shipping container so the instrument can be well packaged if it needs to be returned for repair or calibration.

Inventory the accessories in Table 2-1. If any accessories are missing or damaged, notify your Welch Allyn, Inc. distributor or the factory immediately. See page 60 for a listing of optional accessories.

2.2 PROBE INDICATORS The probe indicators are shown in Figure 2-1 and a description follows. P1 P2 P3

FIGURE 2-1: PROBE INDICATORS

P1

P2

P3

Yellow lamp: The probe is occluded; remove the probe and inspect for cause of occlusion Green lamp: Blinking-TM 262 Auto Tymp is ready to begin a test Steady green-test successfully started and in progress Orange lamp: A pressure leak has been detected TM

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2.3 FRONT PANEL CONTROLS AND INDICATORS The front panel controls and indicators are shown in Fig. 2-2 and are described follows. F11 F10 F1

F3

F4

F5

F6

F2

FM

F9

+10dB

M+

F13

F16

F7

AUD

dBHL

PROG

PAGE

TYMP

TYMP REFLEX

R

L

F12

F25

F26

M-

M--

DATA TRANSFER

F23

Hz

F8

F24

F14

500 Hz

F19

1000 Hz

F20

2000 Hz

F21

4000 Hz

F22

F15 F18

F17

FIGURE 2-2: FRONT PANEL

F1 F2 F3

FM

F4 F5

F6

F7

F8

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Power: Indicator is illuminated when the TM 262 is receiving power. Print Screen: Used to print the currently displayed page of memory. Print All Memory: Used to print all pages of data from memory. Paper Advance: Used to feed paper through printer. FM: Used during the Audiometry mode to select a frequencymodulated test tone. When the present bar is depressed, the letters FM appear on the display. Steady Tone: Used during Audiometry mode to select a continuous test tone. When present bar is depressed, the steady symbol appears on the display. Pulsed Tone: Used during Audiometry mode to select a pulsed tone. When the present bar is depressed, the pulsed tone symbol appears on the display. Attenuator Knob (dB HL): Used to increase or decrease the intensity of the test tone presented in Audiometry mode. Counter-clockwise rotation decreases the intensity. Clockwise-rotation increases the intensity.

+10 dB

M+

PROG

AUD

TYMP TYMP REFLEX

R

L

500 Hz 1000 Hz 2000 Hz

4000 Hz PAGE

M-

M-DATA TRANSFER

F9

+10 dB: Used to temporarily extend the audiometry intensity range by 10 dB. When selected, a large plus + sign appears on the display. F10 Save: During Audiometry mode, saves the threshold information (per frequency) on the display; during Program mode, selects a particular option; during Tymp/Reflex mode, stores a frequency as a default parameter. F11 < and > Hz: Selecting Hz button causes the cursor to move to the next lower frequency; selecting Hz button, causes the cursor to move to the next higher frequency. F12 Present Bar: Depress to present test signal to appropriate earphone; release to turn test tone off. F13 PROGRAM: Depress to select Program mode screen which lists settings available for Reflex presentation format, printout header format, audiogram vs. tabular format, display normal box, and identify frequency range for Audiometry mode. F14 AUD: Press to select Audiometry mode (available in models with audiometer only). F15 TYMP: Press to select Tympanometry only mode. F16 TYMP REFLEX: Press to select Tympanometry and Reflex mode. F17 RIGHT: Used to identify right ear under test so that data stored in memory and/or printed is properly identified; used to select right earphone for audiometry. F18 LEFT: Used to identify left ear under test so that data stored in memory and/or printed is properly identified; used to select left earphone for audiometry. F19 500 Hz: Selects 500 Hz as a stimulus during reflex testing. F20 1000 Hz: Selects 1000 Hz as a stimulus during reflex testing. F21 2000 Hz: Selects 2000 Hz as a stimulus during reflex testing. F22 4000 Hz: Selects 4000 Hz as a stimulus during reflex testing. F23 PAGE: Used to scroll through test results stored in memory. F24 ERASE: Used to erase currently displayed page of data from memory. F25 ERASE ALL: Used to erase all pages of data from memory. F26 DATA TRANSFER: Used to transfer test results to an attached computer.

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2.4 PRINTER AND LIQUID CRYSTAL DISPLAY (LCD) The printer cover can be removed to reload paper (see Figure 2-3). Section 2.6.1 (page 12) provides paper loading instructions.

Printer Cover LCD display

ECV 1.4 cm3 PEAK 0.0 cm3 H OP 70 daPa 0 daPa

I 1000 Hz 95 HL 0.1 cm3

[

I 2000 Hz 95 HL

-400

daPa

0

+200

0.1 cm3

[ 0 0.7 sec

FIGURE 2-3: PRINTER COVER LOCATION

2.4.1 Liquid Crystal Display (LCD) The display indicates test mode, parameters for test and test results. Figures 2-4 through 2-8 show the individual display format for each test mode.

FIGURE 2-4: Display format for Tympanometry

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FIGURE 2-5: Display format for Reflex test (results reported as “Yes” or “No”).

FIGURE 2-6: Display format for Reflex test (results reported in “dB HL”).

FIGURE 2-7: Display format for Reflex test (results reported in “dB HL” and also shown with a “tracing”).

Cursor

Tone Left ear presentation symbol symbol

Plus 10 dB HL symbol Selected intensity level Selected frequency

Handswitch symbol

Pulsed tone symbol

FIGURE 2-8: Display format for Audiometry

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2.5 REAR AND BOTTOM PANEL LABELS/CONNECTORS The rear panel labels and connectors are shown in Figure 2-9 and a description of each one follows. R1

R2 R3 R4

R5

R6

R7

R8

R10 R

L

R9

FIGURE 2-9: REAR PANEL

R1

Company name, address, model, serial number and country of origin. R2 Symbol denotes a Type B, Class II Product per IEC 878 as referenced in IEC 601 Standard. R3 Symbol denotes Attention, consult accompanying documents. R4 Symbol indicates a service adjustment part that is intended for service personnel use only. R5 Connector for handswitch. Input impedance (47 K ohms) pulls up to 5 volts. R6 Contra Insert Phone. Function not available. R7 Connectors for right and left earphones. 130 ohm, 2.50 volts rms L maximum open circuit. R8 Label describing low input voltage and current from wall mounted power supply. R9 Power Input Jack. 5-pin DIN connector for external wall mounted power supply. R10 Power Switch with ON/OFF indicators.

R

NOTE Symbol on the bottom panel indicates entry by qualified service personnel only.

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2.6 INITIAL SETUP TM

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Place the TM 262 Auto Tymp on a stable counter or table where it will subsequently be used, and near a properly grounded wall outlet. Attach accessories to their appropriately-labled connectors on the rear panel of the TM 262 (see Figure 2-9). Locate the POWER switch on the rear panel of the TM 262 and move the switch to the ON ( ) position. Note that the lamp (F1) on the front panel is illuminated, indicating the TM 262 is receiving power. The TM 262 symbol will then appear on the display along with a listing of the revision number for the Tymp/Reflex and Audiometry (if purchased) software. Next, the display will default to the Tymp/Reflex mode and the probe’s green lamp will begin to blink, indicating that the TM 262 is ready to begin a test. If both the green and yellow lamps are illuminated at the same time, either the probe is occluded or the tymp/ reflex software did not properly initialize. Simply move the power switch to the OFF ( ) position, inspect the probe tip for any signs of an occlusion, and reposition the power switch to ON ( ). If both green and yellow lamps are still illuminated and you are certain that the probe is not occluded, contact the Welch Allyn Technical Service Department (see page 55). In the meantime, it is still possible to select the Audiometry mode (if purchased). Allow the instrument to warm-up for about five minutes before conducting a test. This allows the electronic circuits to stabilize prior to use. If the storage temperature is lower than the room temperature, allow some additional time for the instrument to reach room temperature. Warning The TM 262 is designed to be used with a hospital grade outlet. Injury to personnel or damage to equipment can result when a three-prong to two-prong adapter is connected between the TM 262 power plug and an AC outlet or extension cord. Additionally, those TM 262 Auto Tymps that are equipped with power transformers use a specific transformer (8000-0260, 8000-0261 or 80000262) which should not be interchanged with any other transformer or supply. The TM 262 is a specifically-calibrated device and the periodic service and adjustments which the instrument may require should be done only by an authorized Welch Allyn service technician.

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2.6.1 Loading The Paper Remove the printer cover (see Fig. 2-3 for location) by placing your fingers along the back edge of the printer and pulling upward on the cover. Cut the printer paper so that the leading edge of paper is straight across. Place the roll of paper inside the paper well so that the paper will unroll from the lower surface. See paper loading label for additional help (Figure 2-11). Paper exit

Paper loading label

INTO ELY THE UAR ING E SQ ESS NEL EDG E PR T PA G ADIN ADING E WHIL FRON ER LO E LE ANCON THE PAPERT TH ENTR INS PAPERVANCE THE ER AD PAP

Paper entrance

FIGURE 2-11: Paper Loading

Position the leading edge of the paper roll into the paper entrance while pressing the PAPER ADVANCE button. The paper will begin to appear out of the printer mechanism. Continue to advance the paper so that a section of paper is long enough to pass through the printer cover once it is repositioned over the printer.

2.6.2 Paper Storage TM

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The TM 262 Auto Tymp utilizes a thermal printer, which requires a heat-sensitive paper to create an image. For maximum paper life, any spare rolls of paper should be stored as follows: 1) Store in the dark, i.e., in a drawer or cabinet 2) Do not store above 77°F (25°C) 3) Store at less than 65% relative humidity The above recommendations are for the maximum paper life (greater than five years). Storing your TM 262 thermal paper at high temperatures or high humidity levels will only shorten the total paper life.

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2.7 PRETEST TYMPANOMETRY CHECKS TM

For your convenience, a test cavity is provided with your TM 262 Auto Tymp . This test cavity enables you to quickly verify the proper calibration of your unit. Welch Allyn, Inc. strongly recommends that you make this quick check a part of your daily routine. TM

2.7.1 Calibration To initiate the quick check, select the Tymp only TYMP mode and insert the probe (without a tip on it) into the 0.5 cm3 opening on the test cavity. See Figure 2-12. NOTE Since the TM 262 is designed to start automatically, it is important that the probe is inserted as quickly and as smoothly as possible. During the calibration check, the probe must be held carefully and without movement. Do not place the probe on the same counter as the instrument or any moving object during this check, as mechanical noise will be picked up by the probe and interfere with the calibration check. 0.5 cm3 5.0 cm3 2.0 cm3

FIGURE 2-12: Test Cavity

The calibration check will start automatically if the probe has been inserted into the cavity properly. This is confirmed by the green lamp changing from blinking to a steady condition. If the orange lamp is illuminated, the probe is not properly positioned within the cavity so that a large pressure leak exists. If the yellow lamp is illuminated, the probe tip has been occluded. In either case, remove the probe and wait for the blinking green lamp. Insert the probe once again. Clean the probe tip if necessary (see Section 3.2).

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When the test sequence is completed, the green lamp on the probe is no longer illuminated. Remove the probe from the test cavity and note that the green lamp is blinking once again. The display will indicate a flat line on the tympanogram along with the value of the test cavity next to the letters ECV (ear canal volume), i.e., 0.5. The letters NP will appear next to the labels cm3 and daPa and three dashed lines will appear next to the letters GR (gradient). Since the test cavity is a hardwalled cavity, the tympanogram should be a flat line, indicating that there is no mobility in the system. The TM 262 Auto Tymp places the letters NP next to the cm3 and daPa headers to indicate that there is no peak compliance and, therefore, no peak pressure can be determined during the quick check. Also, since there is no compliance peak detected, it is not possible to calculate a gradient. Therefore, the TM 262 displays the dashed lines when a gradient calculation isn’t possible. Using the same sequence, place the probe in the test-cavity opening labelled 2.0 cm3. Note that the display looks the same as with the 0.5 cm3 measurement, except for the value placed next to the letters ECV (2.0). If you wish, the same sequence can be followed with the 5.0 cm3 opening on the test cavity. To keep a record of this test-cavity-calibration check, simply press the PRINT ALL button on the front panel of the TM 262. TM

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2.7.2 Altitude Adjustment Since sound pressure will vary with altitude and barometric pressure, some variation from the 0.5, 2.0 and 5.0 cm3 readings may be observed. Your TM 262 is carefully calibrated at our factory, which is at approximately 250 feet above sea level. If you are located at an elevation of 1000 feet or higher, your instrument may need to be recalibrated to account for your elevation. It is not necessary to recalibrate for barometric pressure changes on a daily basis. Just keep in mind that a change in barometric pressure (i.e., from low to high or high to low) will slightly affect the test-cavity readings. The altitude calibration adjustment allows for “corrections” to the Ear Canal Volume (ECV) measurement and test cavity volume measurement for variations due to altitude. Because the TM 262 is a pressuresensitive device which makes measurements relative to ambient air pressure, changes in air pressure due to weather or altitude will affect the Ear Canal Volume (ECV) read-out of the instrument. The slight pressure change resulting from changing weather conditions will usually yield volume read-outs within ±0.1 cm3 of the expected cavity value; however, pressure changes due to altitude can shift these cavity values by as much as 30%. These changes in pressure do not affect the accuracy of the compliance measurement system in any way. But, many instrument operators prefer that their equipment give ECV values as they would appear at sea level. The altitude calibration mode allows the operator to adjust his/her Auto Tymp without the services of a qualified Welch Allyn Service Technician.

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TABLE 2-2: Altitude Correction Altitude Correction Altitude (ft.) 0 to 1,500 2,000 to 3,500 4,000 to 6,000 6,500 to 7,500 8,000 to 9,000 9,500 to 10,000

Altitude Table (cm3) 2.0 2.1 ± 0.1 2.2 ± 0.1 2.3 ± 0.1 2.4 ± 0.1 2.5 ± 0.1

The altitude calibration mode can only be entered when the TM 262 is powered up from its “off” state while the PROGRAM PROG mode button, is depressed. Hold the PROGRAM PROG button for approximately five seconds. STEP 1 When entering the altitude mode the display will read as follows: Altitude Mode ECV 2.0 cm3 9.99 Standard (E71) is displayed in the bottom right corner of the display until the probe is in the 2.0 cm3 cavity. STEP 2 Place the probe into the 2.0 cm3 cavity provided with the instrument and check cm3 value against the altitude correction table for accuracy. STEP 3 If the measured volume is not within the published table value ±0.1cc, then the operator should exit the altitude mode by pressing the PROGRAM PROG button and contact field service. Providing the measured volume agrees with the published table ±0.1cc, the operator may proceed with the altitude adjustment. STEP 4 With the probe still in the 2.0 cm3 cavity, select the PAGE PAGE button to enter the custom calibration mode. Custom will appear on the fourth line of the display. STEP 5 The value now displayed in the cm3 display area is the volume measured and adjusted to the current altitude. If the value displayed is 2.0 cc, then the volume is adjusted to the current site. If the value is not 2.0 cc ±0.1, then press the SAVE M+ button to customize the volume measurement to the current altitude. The measured volume should now read 2.0 cc. STEP 6 To exit the altitude mode, press the PROGRAM PROG button to return to normal mode.

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2.8 PRETEST AUDIOMETRIC CHECKS (Models with Audiometer Only) 2.8.1 Noise Recovery Period Exposure to high levels of sound (e.g., unmuffled lawn mowers, loud music, gunfire) tends to create a Temporary Threshold Shift (TTS) which diminishes with time after exposure. Any subject tested soon after such exposure may exhibit a hearing loss that does not reflect his/her normal hearing threshold. This test procedure, therefore, generally prescribes a 16 hour interval between the last exposure to high-level sounds and the administration of any hearing test.

2.8.2 Elimination of Ambient Noise Excessive noise in the test environment during audiometric testing, such as that produced by conversation, computers and public address systems reduces test validity because it tends to mask the test signals, particularly at the lower frequencies where earphone cushions provide less effective attenuation. An acoustically-treated room may be required if ambient noise reaches objectionable levels, i.e., sufficient to cause apparent hearing loss at the low frequencies. Also, earphone sound enclosures are available from Welch Allyn as an optional accessory. If the person being tested is in the same room as the audiometer, it is recommended that he/she be seated about three feet (one meter) away from the TM 262 Auto Tymp . Maximum permissible noise levels are specified by the American National Standards Institute-Criteria for Permissible Background Noise during Audiometric Testing, ears covered with earphones (S3.1-1991 revised). Table 2-3 shows the maximum background levels that can be present inside the room while a valid hearing test is being conducted. For more comprehensive information about hearing testing and hearing conservation, refer to the Bibliography. TABLE 2-3: Permissible Noise Levels TM

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Test Tone

Frequency (Hz)

125 250 500 750 1000 1500 2000 3000 4000 6000 8000

Test Room

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Ears covered maximum permissible octave band levels

34.0 22.5 19.5 21.5 26.5 26.5 28.0 33.5 34.5 38.0 43.5

Ears covered maximum permissible one-third octave band levels

29.0 17.5 14.5 16.5 21.5 21.5 23.0 28.5 29.5 33.0 38.5

2.9 BIOLOGICAL CHECK To determine that your TM 262 is functioning properly, perform a daily check on a normal ear-your own if possible. This allows you to listen for the probe tone and the stimulus tone (during reflex) and determine if the air-pressure system is working properly. Keep a copy of your chart for a day-to-day reference in checking your TM 262. If you purchased the TM 262 Auto Tymp with audiometry, select the AUDIOMETRY AUD button located in the center section of the front panel. Note that the display changes to an audiogram format. The Hz and Hz buttons allow you to select each frequency and the dB HL knob allows you to alter the intensity of each frequency. Position the test headset on your head so that each earphone is covering the appropriate ear (i.e., red is right and blue is left). Select the right earphone by pressing the front panel button labelled R and check for the following while depressing the present bar: • Depressing the Hz button causes the frequency to change to a lower frequency, depressing the Hz button causes the frequency to change to a higher frequency. • Each frequency or tone is pure, i.e., there is no distortion or crackling sound present. • Rotating the dB HL knob in a clockwise direction increases in intensity of the tone. • Rotating the dB HL knob in a counter-clockwise direction decreases the intensity of the tone. TM

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