2 -400 GR C -200 PRESSURE R GR A 1 0 TEST 0 +200 Vea - cc Ya - mmh o 1.0 0.
Acknowledgments Welch Allyn gratefully acknowledges the assistance of Robert H. Margolis, Ph.D. of the University of Minnesota for his assistance in preparing the Guide to Tympanometry and Glossary sections of this manual. Trademarks Welch Allyn and MicroTymp are registered trademarks of Welch Allyn, Inc. in the United States and other countries. Patents MicroTymp – U.S. Patent Number 4,688,582 Conductive Path ESD Shield – U.S.
Contents MicroTymp 2 – Introduction MicroTymp 2 Handle Components ............................................................. 2 MicroTymp 2 Printer/Charger Components ................................................ 3 Preparing to Use the MicroTymp 2 Handle and Printer/Charger ................ 3 Setting up the MicroTymp 2 Handle and Printer/Charger ...................... 4 MicroTymp 2 – Completing a Test Obtaining a Tympanogram .........................................................................
Appendix C – Maintaining the MicroTymp 2 Equipment The MicroTymp 2 Battery ..................................................................... C-43 Recharging the Battery .................................................................... C-46 Recycling the Battery ....................................................................... C-47 Paper Replacement ............................................................................. C-48 Cleaning, Disinfection and Sterilization ........................
MicroTymp 2 – Introduction Thank you for purchasing the Welch Allyn MicroTymp 2 Portable Tympanometric Instrument.
2 GR A 1.0 1 0.
MicroTymp 2 Printer/Charger Components CHARGE Indicator Tip Box FEED Button PRINT Button POWER Indicator POWER CHARGE FEED IEC Power Cord Receptacle PRINT Charging Well for MicroTymp 2 Printer/Charger Switches 1 TM 2 3 4 OFF Paper Slot Paper Access Cover Power Cord To IEC Power Cord Receptacle To Power Receptacle Figure 1B Preparing to Use the MicroTymp 2 Handle and Printer/Charger The following is a list of important facts to note before using the MicroTymp 2.
• If the MicroTymp 2 set has not been stored at room temperature, allow 45 minutes for it to return to operating temperature range (15-35˚C or 59-95˚F) before using. • Do not store either the MicroTymp 2 Handle or Printer/Charger at temperatures which exceed 66˚C (150˚F). Continual exposure to extremely high temperatures can permanently damage components. ! Refer to Operating Instructions manual. DANGER: Explosion risk if Printer/Charger is used with flammable anesthetics.
Obtaining a Tympanogram Selecting a Probe Tip 1. After examining the subject’s ear canal opening, select a tip which is large enough to seal the entrance of the ear canal. See Figure 2. To change tips, either pull the tip off by hand or slide the tip ejector towards the tip. NOTE: Tips are not intended to be deeply inserted into the ear canal. Using an improper tip size causes leaks, and will make it difficult to complete a test.
Testing 3. Turn on the MicroTymp 2 Handle by pressing the TEST button below the Liquid Crystal Display (LCD). The word “OPEN” appears on the LCD. Figure 3 illustrates the TEST button and the OPEN message. TEST 1.0 OP 0 -20 0 PR ES SU RE TE ST 2 GR A 1 GR C 0 - Da Pa 20 0 - EN -40 R 00 ccVea Ya 0.5 0 +2 - mm ho TEST L Figure 3 NOTE: The MicroTymp 2 automatically turns off 15 seconds after the last test or activation of any button. Figure 4 Figure 5 4.
If a seal is not achieved, the LCD will display a LEAK, BLOCK, or OPEN message. Reposition the instrument to attempt another test. 6. Once a seal is achieved, the TEST message appears on the LCD, followed by the volume indication on the +200 Vea scale. Data points are then displayed from right to left across the LCD as the test progresses. If the BLOCK, LEAK, or OPEN messages appear during the test, reposition the tip to restart the test. 0 -400 GR C -200 0 1 0.
The memory buttons are labeled for the right ear and L for the left ear. When test results are stored in memory, the RIGHT STORE or LEFT STORE message (see Figure 7A) appears momentarily on the LCD. Then the tympanogram which has been stored reappears along with the or left L symbol (see Figure 7B) to indicate the contents of right that memory. R 2 GR A 1.0 1 0.5 GR C +200 Vea - cc Ya - mmho R 0 -400 -200 0 200 PRESSURE - daPa 1 0.5 GR C 0 -400 1 0.
MicroTymp 2 Completing a Test LIQUID CRYSTAL DISPLAY Normal Static Admittance and TPP (Children) 2 GR A 1.0 1 0.5 GR C +200 Vea - cc Admittance Axis Ya - mmho Normal Static Admittance and TPP (Adults) Gradient (Width) Adult Gradient (Width) Child 0 -400 -200 0 200 PRESSURE - daPa Pressure Axis Figure 8 A sample of the Liquid Crystal Display is shown in Figure 8. 2 GR A 1.0 1 0.
2 GR A 1.0 1 0.5 GR C +200 Vea - cc Ya - mmho TEST 0 -400 -200 0 200 PRESSURE - daPa Figure 10 The TEST message indicates that the test has started. Immediately following this message, test data will begin to appear. 2 GR A 1.0 1 0.5 0 -400 GR C -200 0 +200 Vea - cc Ya - mmho BLOCK 200 PRESSURE - daPa Figure 11 The test cannot continue since the measured admittance is less than 0.2 mmho.
MicroTymp 2 Completing a Test 2 GR A 1.0 1 0.5 GR C 0 -400 -200 0 +200 Vea - cc Ya - mmho LEAK 200 PRESSURE - daPa Figure 12 The test cannot proceed since desired pressures within the ear have not been achieved.
0 -400 GR C 2 GR A 1.0 1 0.5 GR C +200 Vea - cc 1 0.5 Ya - mmho 2 GR A 1.0 +200 Vea - cc Ya - mmho RIGHT CLEAR/LEFT CLEAR 0 -200 0 -400 200 -200 0 200 PRESSURE - daPa PRESSURE - daPa Figure 14A Figure 14B The designated right or left memory location contains no data. Either no data has been stored, or previously stored data has been erased. See page 7 for information on storing and erasing data. R L 2 GR A 1.0 1 0.
MicroTymp 2 Completing a Test 2 GR A 1.0 1 0.5 0 -400 GR C -200 0 +200 Vea - cc Ya - mmho RANGE ERROR 200 PRESSURE - daPa Figure 16 The RANGE ERROR message indicates that a large pressure change occurred during a test. If this message appears, press the TEST button and start the test again. TEST 2 GR A 1.0 1 0.
2 GR A 1.0 1 0.5 0 -400 GR C -200 0 +200 Vea - cc Ya - mmho NEEDS CAL(ibration) 200 PRESSURE - daPa Figure 18 Something has caused the MicroTymp 2 to fail an internal calibration test. All MicroTymp 2 buttons have been disabled because the instrument needs to be returned to a Welch Allyn service location for calibration. Any results already stored in the handle may be printed. Annual recalibration is recommended to insure instrument accuracy.
Follow the steps listed below to print tympanometric data stored in the MicroTymp 2 Handle: 1. Place the MicroTymp 2 Handle in the well with the Liquid Crystal Display (LCD) and buttons facing you. See Figure 20. When the MicroTymp 2 is properly seated in the well, the green CHARGE indicator illuminates. 2. Press the PRINT 3. To feed extra paper, press the FEED button. Paper continues to feed as long as the button is depressed. button.
4. To remove the printout, pull the paper forward and to the left or right to tear it along the cutting edge. 5. To obtain an additional copy of the test results, leave the Handle in the well and press the PRINT button again. Removing the MicroTymp 2 Handle from the well causes the data to be removed from the Printer/ Charger memory. NOTE: • The Printer/Charger has been pre-set at Welch Allyn to print a complete printout as illustrated in Figure 21 on page 17, and to print in manual mode.
MicroTymp 2 Completing a Test Tympanogram Data (Optional) Interpretive Message (Optional) Figure 21 Tympanogram Section of Printout The tympanogram is a graph which records the admittance of the ear as a function of air pressure. Data Section of Printout The data section displays numeric values for the four key characteristics of the tympanogram: • Peak Ya — the compensated static acoustic admittance (height) of the peak, measured in acoustic millimhos (mmho).
If the numeric values are greater or less than the 90th percentile of the normative data for a child or an adult, an asterisk appears under the C(hild) or A(dult) column. The normative data are listed in Table 1 below. For some tympanometric results, no data will be printed. These occasions are: • Peak Ya is greater than 1.5 mmhos. The message “High Peak Ya” will appear at the top of the tympanogram. • Peak Ya less than 0.3 mmhos.
The computer in the Printer/Charger examines the data for clinically-significant deviations from the normal values. For example, a tympanogram which is too wide may be indicative of a developing or resolving otitis media; the message reads “Tympanogram Is Wide”.
Selecting Printout Formats The four switches used to select the printout format and printer mode of operation are located on the bottom of the Printer/Charger. See Figure 22. NOTE: Switch #4 is used during manufacturing only. If Switch #4 is ON, the Printer/Charger will not operate normally. Changing from Manual to Automatic Printout Use Switch #1 to change from manual to automatic printout. Use a pointed object to depress appropriate ON or OFF portion of the switch.
1 2 3 4 Depress the OFF portion of the switch to select this option. This causes the printout to begin only when button is depressed. the PRINT OFF NOTE: In the manual mode, a beep will occur as a reminder that data has been transmitted; however, it is not necessary to wait for the beep before pressing the PRINT button. Changing Printout Format Use Switches #2 and #3, located on the bottom of the Printer/Charger, to change printout format. Printout options are shown in Figure 23.
Printing Interpretive Messages (Switch #2) No messages Depress the ON portion of the switch to select this option. This causes messages which interpret the 1 2 3 4 tympanogram to not be included on the printout. Refer to Description of Formats on page 16 for more information on these messages. OFF Messages 1 2 3 4 Depress the OFF portion of the switch to select this option. This causes the messages which interpret the tympanograms to be included on the printout.
If tympanometric results are not printed, a message will appear describing the reason. These messages are listed in Table 2. Table 2 – Printer Function Messages Printer Function Message Possible Cause Possible Solution No Data Reinsert Handle The MicroTymp Handle Seat the handle in is not located in the well. the well. The MicroTymp Handle is not seated properly in the well. Insure that the handle is fully seated in the well with the Liquid Crystal Display (LCD) and buttons facing you.
Printer Service Codes When the Printer/Charger is plugged into an electrical outlet, the green POWER indicator illuminates and the instrument beeps to indicate that the printer is ready for use. If a problem exists, the green POWER indicator flashes. The number of flashes correspond to the specific problems listed in Table 3. Table 3 – Printer/Charger Flashing Indicators Number of Flashes Problem Solution One Printer/Charger is out of paper. Replace paper. See page C-48 for instructions.
Appendix A Guide to Tympanometry The Welch Allyn MicroTymp 2 is a single-component, aural acoustic admittance meter that records a tympanogram with a 226-Hz probe tone. Basic Principles of Tympanometry Acoustic admittance is the ease with which acoustic energy is transferred from one system to another. If the air in the ear canal is easily set into vibration, the admittance is high. If the air is difficult to set into vibration, the admittance of the system is low.
Tympanogram Characteristics Figure 24 illustrates a MicroTymp 2 tympanogram. A description of the key characteristics of the tympanogram follows. 1 2 4 3 Figure 24 1 Static Admittance (Peak Ya) is a measure of the height of the tympanometric peak. Given appropriate normative values, static admittance is a useful indicator of middle ear disease. 2 Tympanometric Gradient (GR), or tympanometric width, is a measure of the width of the tympanometric peak.
How the MicroTymp 2 Instrument Works A block diagram of a Welch Allyn MicroTymp 2 is illustrated in Figure 25. Sound Out Pressure Airflow Transducer Tip Pump Microphone Sound In Microcomputers Liquid Crystal Display (LCD) Figure 25 A 226-Hz probe tone is introduced into the sealed ear canal by a miniature loudspeaker. A miniature microphone records and monitors the sound pressure produced in the ear canal.
Normative Values for the MicroTymp 2 The normative values listed in Table 4 are taken from a study by Margolis and Heller (1987), and from the “Guidelines for Screening for Hearing Impairments and Middle Ear Disorders” (1990). Table 4 — Normative Tympanometric Values Tympanometric Measurement Child’s Ear (Under Age 10) 90% Range Adult’s Ear (Age 10 & Over ) 90% Range Peak Ya 0.2 to 0.9 mmho 0.3 to 1.
Interpreting Tympanogram Results Otitis Media with Effusion • Produces low static admittance (low peak height) tympanogram • Tympanogram is also typical of tympanosclerosis, cholesteatoma, and middle ear tumor Normal Middle Ear • Produces tympanogram within normal limits relative to height and width Tympanic Membrane Abnormalities or Ossicular Disruption • Produces high static admittance (high peak height) tympanogram Negative Middle Ear Pressure • Produces negative Tympanometric Peak Pressure (TPP) tymp
Positive Middle Ear Pressure • Produces positive Tympanometric Peak Pressure • Indicative of acute otitis media, if peak is extremely positive Tympanogram with Too Much Artifact • Caused by patient or practitioner movement • Requires repeating measurement Ear Canal Occlusion • Can produce flat tympanogram with ear canal volume lower than expected • May also produce BLOCK message • Requires repeating measurement Patent Tympanostomy Tube or Perforated Tympanic Membrane • Can produce flat tympanogram with e
Obtaining a Valid Tympanogram Tympanometric results, although accurate and objective, do require careful interpretation in conjunction with the patient’s overall clinical condition. In addition, there are conditions which can cause artifact such that a tympanogram is uninterpretable, or which artificially flatten the tympanogram. These conditions are described in more detail below. Indeed, it maybe good clinical practice to repeat all clinical measurements whenever possible.
Conditions Which Artificially Flatten the Tympanogram In order to measure the mechanical properties of the middle ear, a tympanometric device must be capable of changing the pressure differential across the eardrum. Any occlusion of the ear canal, such as impacted cerumen, foreign body, tumor, stenosis, atresia, or a pocket created by the incorrect placement of the probe, can prevent this pressure differential from happening and can artificially flatten the tympanogram.
1 0.5 0 -400 GR C -200 0 200 PRESSURE - daPa Flat Tympanogram with too High Volume Persistent OPEN Message (can’t seal ear) Figure 28 The Normal Ear An example of a tympanogram from a normal ear is depicted in Figure 29. Figure 29 A-33 +200 Vea - cc Ya - mmho 2 GR A 1.
Low-Admittance Pathologies: Otitis Media with Effusion, Middle Ear Tumor, Ossicular Fixation, Tympanosclerosis Low static admittance of the middle ear is produced by space-occupying lesions in various ways. A lesion that displaces air in the middle ear space causes low admittance by reducing the middle ear volume. The lesion also may interfere with the vibration of the ossicular chain, contributing to the low admittance.
Middle Ear Tumor A wide variety of neoplastic processes exist that invade the middle ear. The most common is the keratoma (cholesteatoma), a collection of keratinizing squamous epithelium that frequently originates from Shrapnel’s membrane (pars flaccida) of the tympanic membrane or the ear canal wall and invades the middle ear space. Other middle ear tumors include the cholesterol granuloma, glomus tumor, and squamous cell carcinoma (Goodhill, 1979).
Tympanic Membrane Abnormalities “Floppy” Tympanic Membrane The tympanic membrane is normally a stiff, conically-shaped structure that derives its stiff characteristic from the lamina propria, a layer of connective tissue that is situated between the outer layer of squamous epithelium (skin) and the inner layer of mucous membrane. When the eardrum heals after a relatively large perforation, the lamina propria may be absent or thin in the region of the scar.
Conditions Which Cause Negative Middle Ear Pressure Appendix A Figure 32 Negative pressure within the middle ear space will produce a tympanogram with a negative tympanometric peak. Some degree of negative pressure is normal (see normal TPP values listed in Table 1 on page 18). Negative middle ear pressure often accompanies a cold or allergies, or can be a result of eustachian tube dysfunction. Negative middle ear pressure is not usually associated with effusion when peak Ya is normal.
A-38
Appendix B Guidelines for Screening for Hearing Impairments and Middle Ear Disorders In a non-medical setting, tympanometry can be useful in determining the need for a medical referral. However, abnormal tympanometric results occur not only in patients with ear disease that requires medical attention, but also in subjects with transient conditions that resolve without medical intervention and in ears that have residual effects of previously-controlled disease.
START 1 /wPain, Ear Discharge? Yes No 2 Visual Inspection Fail Pass 4 Repeat Audiometric Screen 3 Audiometric Screen Fail Pass Fail Pass WAIT 4-6 WEEKS 6 Volume Too Large? 5 Peak Ya Too Low? Yes No Yes No 7 1st Time 8 Gradient Too Wide? Peak Ya Too Low 1st or 2nd Time? 9 1st or 2nd Time? Yes No 2nd Time 2nd Time 1st Time AUDIOLOGIC/MEDICAL REFERRAL NO FURTHER ACTION Figure 34 B-40
Recommended Screening Protocol The recommended screening protocol is based on a four-part procedure consisting of case history, visual inspection, pure-tone audiometry, and tympanometry. These guidelines can be used for all ages, however, they are designed specifically for children and young adults (through age 40). Referral criteria are presented in Table 6 on page B-42. These criteria may require alteration for various clinical settings and populations.
7 Low static admittance (Peak Y [Ya]) may or may not be associated with significant middle ear disorders. In the absence of other positive findings, a Peak Y (Ya) below the 90% range listed in Table 6 requires observation over an extended period before a medical referral is warranted. Only after two successive abnormal findings over an interval of 4-6 weeks should medical referral be made.
Appendix C Maintaining the MicroTymp 2 Equipment The MicroTymp 2 Battery The MicroTymp 2 rechargeable nickel-cadmium battery is intended for many charge/discharge cycles and is warranted for two years. The warranty expiration date is imprinted on the battery. ! ! ! BATTERY REPLACEMENT: Replace with Welch Allyn model #72900 battery only. NOTE: This instrument contains components which are static sensitive.
3. Remove the battery cover by lifting the bottom of the cover away from the probe tip. See Figure 36. USE ONLY SPECIFIED CHARGER RECHARGEABLE BATTERY 2.4 VOLTS 600mAh CATALOG NO. 72900 Figure 36 4. Push down on the positive (+) end of the battery. Battery will eject. See Figure 37. Battery will eject U REC SE ON HAR LY S CAT GEAB PEC ALO LE B GN A O.
5. Insert the replacement battery by placing the positive (+) end of the battery against the spring in the holder. Push the battery lightly to compress the spring, and lower the battery into the compartment. See Figure 38. NOTE: Insert the battery only as shown. Failure to observe the correct polarity will prevent the instrument from functioning. USE ONLY SPECIFIED CHARG ER RECHARGEABLE BATTER Y 2.4 VOLTS 600mAh CATALOG NO.
Recharging the Battery To recharge the MicroTymp 2 battery, place the MicroTymp 2 Handle in the Printer/Charger well with the LCD and buttons facing you. See Figure 39. ! NOTE: Charge only with the MicroTymp 2 Printer/Charger (#71170, #71175) or special AudioScope Charging Stand (#71126). The 2.4 V nickel-cadmium battery used in the MicroTymp 2, when fully charged, provides a full day of operation without the need for recharging — yielding a minimum of 300 double ear tests.
Figure 39 Recycling the Battery Welch Allyn RECYCLE BATTERY 4341 State Street Road Skaneateles Falls, NY 13153-0220 Welch Allyn Canada RECYCLE BATTERY 160 Matheson Blvd. East, Unit 2 Mississauga, Ontario CANADA L4Z 1V4 Nickel-Cadmium Battery. Must be Recycled or Disposed of Properly.
Paper Replacement The MicroTymp 2 Printer/Charger signals the need for changing the paper in one of two ways: • A pink strip appears along the edge of the paper indicating the paper is nearing the end of the roll. indicator flashes in single pulses indicating that there is • The POWER no paper, and no printing can occur. NOTE: • Use only an appropriate heat-sensitive paper or the Printer/ Charger life may be shortened and the warranty voided.
2. Depress the FEED button to advance any remaining paper through the printer. Do not pull paper backwards through the printer. Remove and discard old paper roll, saving the black spindle. 3. Pull the paper lever forward. See Figure 41. Figure 41 Figure 42 4. Place the roll of paper behind the Printer/Charger for easier handling. 5. Insert the paper (from of the bottom of the roll) into the slot under the pinch roller, making sure that the paper is centered. See Figure 42. 6.
Cleaning, Disinfection and Sterilization Cleaning the MicroTymp 2 Handle Do not sterilize the MicroTymp 2 Handle. Clean the Handle by wiping it with a dry cloth or a cloth that has been lightly dampened with 70% Isopropyl alcohol. Make sure liquid does not seep into the instrument, especially in the probe area. Inspect the probe opening and the three inside ports for debris monthly. Dust, cerumen, or other material in the probe may affect the accuracy and/or functioning of the instrument.
Appendix D Functional Checks of the MicroTymp 2 Handle and Printer/Charger Functional Checks of the MicroTymp 2 Handle A MicroTest Cavity is included with the MicroTymp 2 Handle. The cavity provides a functional test of the MicroTymp 2 Handle to determine if it is working properly. The 0.5 cc cavity is used to test the Low Range of ear canal volume (Vea). The 2.0 cc cavity is used to test the High Range of the ear canal volume (Vea).
1 GR B 0.5 0 -400 -200 0 +200 Ya - mmh 0.5cc 2.0cc MicroTest CAVITY 2 GR A 1.0 cc Vea - A properly functioning instrument will produce a flat tympanogram and an ear canal volume (Vea) which corresponds to the cavity tested. There is an acceptable range for each cavity (see Table 7) both at sea level and at different altitudes. An example is provided in Figure 44 below. Note that all data points must fall within the two bottom rows of the graph. o 5. 200 PRESSURE - DaPa R Tympanogram from 0.
2 Troubleshooting the MicroTymp 2 Handle Symptom Handle Does Not Turn On Possible Cause Possible Solution No battery. Put battery in. Battery in backwards. Reposition battery observing polarity. Battery not charged/dead. Charge/replace battery. If symptom still persists, return to local Welch Allyn service location for service. Too Much Artifact on LCD “Frozen” Display on LCD Too much movement during test. See page A-31. Handle has too much internal noise. Check handle in cavity (page D-51).
2 Software Version The test pattern also includes the software version for the MicroTymp 2 Printer/Charger. 3 Normative Data Reference The test pattern is followed by normative data for tympanometric characteristics for both the original MicroTymp and MicroTymp 2 Handle. This is provided along with the test pattern for the convenience of the user, not specifically as a functional check.
Service and Warranty Information Service Repair Repair must be performed by authorized personnel. Failure to do so invalidates the MicroTymp 2 warranty. For customers in North America, please return instruments requiring service to a Welch Allyn Technical Service Department listed below or to an authorized Welch Allyn distributor. Technical Service Department Welch Allyn, Inc. 4341 State Street Road Skaneateles Falls, NY 13153-0220 U.S.A.
Warranty MicroTymp 2 Instrument Welch Allyn Inc. warrants the MicroTymp 2 Handle and Printer/Charger to be free of original defects in material and workmanship and to perform in accordance with manufacturer’s specifications for a period of one year from the date of purchase.
Appendix F Technical Specifications 3.68 in 9.35 cm Appendix F 7.32 in 18.6 cm 2 GR A 1.0 1 0.5 GR B +200 Vea - cc Ya - mmho 1.94 in 4.94 cm POWER CHARGE FEED 0 -400 -200 0 PRINT 200 PRESSURE - DaPa R TEST L 4.82 in 12.2 cm 9.70 in 24.6 cm 9.62 in 24.
Probe Tone: Frequency: 226 Hz ±3% Amplitude: 85 ±3 dB re 20 µPa in an ANSI HA-1 (2.0 cc) coupler Distortion: 5% maximum total harmonic distortion in an ANSI HA-1 (2.0 cc) coupler Pump: Direction of sweep: positive to negative pressure Speed: 400 ±40 daPa/s average during data acquisition period Pressure Measurement System: Range: +200 to -400 daPa Display resolution: 20 daPa Accuracy: ±15% or ±10 daPa, whichever is greater Compensation: Auto-zero every test cycle Admittance Measurement System: Range: 0.
Printer Paper (Welch Allyn #56100): 4.
Standards Compliance ETL listed to comply with UL 2601 ETL listed to compy with CSA C22.2 No. 601-1 ETL listed to comply with IEC 601-1, Amendment 1 MicroTymp 2 Handle: Class I Equipment, Type BF MicroTymp 2 Printer/Charger: Class I Equipment, Type B FCC Part 15, Class A This device complies with CFR 47 Part 15 Class A of the FCC rules.
Appendix G MicroTymp 2 Replacement Parts and Accessories MADE EXCLUSIVELY FOR USE ONLY SPECIFIED CHARGER RECHARGEABLE BATTERY 2.4 VOLTS 600mAh CATALOG NO. 72900 Battery #72900 2.4 V Nickel-Cadmium Battery Screw for Battery Cover #236081 Screw Driver for Battery Cover #236200 2.0 cc 0.
Replacement Power Cords #761076-4 230 V, United Kingdom #761076-6 230 V, Australia, New Zealand 2 GR A 1.0 1 0.5 GR B +200 Vea - cc #761076-2 230 V, Europe Ya - mmho #761076-0 120 V, Canada, Japan, U.S.
References American National Standards Institute (1987). “Specifications for Instruments to Measure Aural Acoustic Impedance and Admittance (Aural Acoustic Immittance).” New York: ANSI. ANSI S3.39-1987 (ASA71-1987). American Speech-Language-Hearing Association (1985). “Guidelines for Identification Audiometry.” ASHA, 27, 49-52, May, 1985. American Speech-Language-Hearing Association (1990). “Guidelines for Screening for Hearing Impairments and Middle Ear Disorders.” ASHA 32 (Suppl. 2): 17-24 (1990).
Occupational Safety and Health Administration (1992). “Occupational Exposure to Bloodborne Pathogens.” OSHA 3127, 1992. Terkildsen, K., Thomsen, K. A., (1959). “The influence of pressure variations on the impedance of the human eardrum.” J. Laryngol. Otol. 73:409-418. U.S. Department of Health and Human Services (1994). “Managing Otitis Media with Effusion in Young Children.” AHCPR Publication No. 94-0623, 1994. U.S. Department of Health and Human Services (1994).
Glossary acoustic admittance (Ya) The ease with which acoustic energy is transferred into a system; the ratio of volume velocity to sound pressure. acoustic millimho (mmho) The unit of acoustic admittance; 1 mmho = 10-8 m3/Pa s. aural acoustic immittance A term used to refer to aural acoustic admittance, acoustic impedance, or any of their components. cholesteatoma See keratoma.
otorrhea External ear discharge. otosclerosis A genetic abnormality of the temporal bone, frequently causing fixation of the stapes and conductive hearing loss. sound pressure The average (rms) difference between the air pressure that occurs during sound transmission and the ambient air pressure. tympanogram A recording of the admittance of the ear as a function of ear canal air pressure. tympanometric gradient See tympanometric width.
TM Printed in U.S.A. Welch Allyn, Inc. 4341 State Street Road P.O. Box 220 Skaneateles Falls, New York 13153-0220 U.S.A. Tel.: 800-535-6663 (U.S.A. only) 315-685-4560 Fax.: 315-685-3361 Part No.
