Welch Allyn TM 262 User manual

Operating
Instructions
.............
...........
I 1000 Hz
95
HL
0.1
cm3
I 2000 Hz
95
HL
0.1
cm3
0 0.7 sec
ECV 1.4 cm3 PEAK 0.0 cm3 H
OP 70 daPa 0 daPa
-400 daPa 0 +200
[
[
Audio Menu
Service Manual

67
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

68
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 Ear Canal Volume .......................................................39
4.2 Compliance Peak........................................................39
4.3 Pressure Peak ............................................................40
4.4 Gradient......................................................................40
4.5 Acoustic Reflex ........................................................... 41
4.6 Audiometry .................................................................42
4.7 Special Messages and Error Codes ........................... 42
4.8 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

1
Section 1—Introduction
1.1 INSTRUMENT DESCRIPTION
The TM 262TM Auto TympTM 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 individ-
ual 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.

2
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 mo-
bility 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 middle-
ear 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 in-
dicate the negative pressure where the restricted mobility occurs.
With a totally fluid-filled middle-ear space, no mobility will be mea-
sured during tympanometry at any pressure value.
• In the case of a “glue-ear”, the ossicular chain is restricted in mo-
bility but the air pressure within the middle-ear space is at atmo-
spheric 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 ab-
sence 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.

3
The TM 262TM Auto TympTM determines tympanometric width (gradient)
by measuring the pressure interval at one-half of the peak height. Differ-
ing peak widths can point to different middle-ear conditions, even when
peak height and pressure are within normal range. For example, middle-
ear 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 contin-
ued 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 present-
ed 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 mus-
cles) 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 tympano-
metry, 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 tympano-
metric 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 indi-
cates 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

4
detectable for each patient tested. However, the TM 262TM Auto TympTM
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 in-
struments 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 pur-
pose of these screening reflex tests is to determine if a reflex is detect-
able 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 hand-
switch (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.

5
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 262TM Auto TympTM 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.
TABLE 2-1 Accessories Supplied
Probe Assembly Test Cavity
Power Module or Internal Supply Instruction Manual
Eartips (6 sizes, 2 each) Test Headset (Models with audiometer only)
Paper (3 rolls)
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 im-
mediately. 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.
FIGURE 2-1: PROBE INDICATORS
P1 Yellow lamp: The probe is occluded;
remove the probe and inspect
for cause of occlusion
P2 Green lamp: Blinking—TM 262TM Auto TympTM is ready to
begin a test
Steady green—test successfully started and
in progress
P3 Orange lamp: A pressure leak has been detected
P3 P2
P1

6
2.3 FRONT PANEL CONTROLS AND INDICATORS
The front panel controls and indicators are shown in Fig. 2-2 and are
described follows.
FIGURE 2-2: FRONT PANEL
F1 Power: Indicator is illuminated when the TM 262 is
receiving power.
F2 Print Screen: Used to print the currently displayed page
of memory.
F3 Print All Memory: Used to print all pages of data from
memory.
F4 Paper Advance: Used to feed paper through printer.
F5 FM: Used during the Audiometry mode to select a frequency-
modulated test tone. When the present bar is depressed,
the letters FM appear on the display.
F6 Steady Tone: Used during Audiometry mode to select
a continuous test tone. When present bar is depressed,
the steady symbol appears on the display.
F7 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.
F8 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. Clock-
wise-rotation increases the intensity.
FM
+10dB
Hz
dBHL
M+ AUD TYMP TYMP
REFLEX
PROG PAGE M- M--
500 Hz
1000 Hz
2000 Hz
4000 Hz
R
L
DATA
TRANSFER
F12
F2
F9
F8
F1 F3 F4 F5
F11
F6
F10
F7
F13 F16
F23
F25F24
F19
F20
F21
F22
F15
F14
F18 F17
FM
F26

7
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 informa-
tion (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.
M+
+10 dB
AUD
PROG
TYMP
M-
TYMP
REFLEX
R
L
1000 Hz
2000Hz
4000Hz
M--
PAGE
500 Hz
DATA
TRANSFER

8
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.
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.
I 1000 Hz
95
HL
0.1
cm3
I 2000 Hz
95
HL
0.1
cm3
0 0.7 sec
ECV 1.4 cm3 PEAK 0.0 cm3 H
OP 70 daPa 0 daPa
-400 daPa 0 +200
[
[
LCD display
Printer
Cover
FIGURE 2-4: Display format for Tympanometry

9
FIGURE 2-8: Display format for Audiometry
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”).
Selected
intensity level
Selected
frequency
Cursor Left ear
symbol
Pulsed tone
symbol
Handswitch
symbol
Plus 10 dB HL
symbol
Tone
presentation
symbol

10
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.
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 docu-
ments.
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
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.
NOTE
Symbol on the bottom panel indicates entry by qualified service
personnel only.
RL
R1 R2 R3 R4 R5 R6 R7 R8
R10
R9
L
R

11
2.6 INITIAL SETUP
Place the TM 262TM Auto TympTM 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 illumi-
nated 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 conduct-
ing 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 per-
sonnel 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 8000-
0262) 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.

12
2.6.1 Loading The Paper
Remove the printer cover (see Fig. 2-3 for location) by placing your fin-
gers 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).
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 ap-
pear 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
The TM 262TM Auto TympTM 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.
PAPER LOADING
INSERT THE LEADING EDGE SQUARELY INTO
THE PAPER ENTRANCE WHILE PRESSING THE
PAPER ADVANCE ON THE FRONT PANEL
Paper loading
label
Paper exit
Paper
entrance

13
2.7 PRETEST TYMPANOMETRY CHECKS
For your convenience, a test cavity is provided with your TM 262TM
Auto TympTM. 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.
2.7.1 Calibration
To initiate the quick check, select the Tymp only mode and insert
the probe (without a tip on it) into the 0.5 cm3opening 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 calibra-
tion 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.
FIGURE 2-12: Test Cavity
The calibration check will start automatically if the probe has been in-
serted into the cavity properly. This is confirmed by the green lamp
changing from blinking to a steady condition. If the orange lamp is illu-
minated, 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).
0.5 cm3
2.0 cm3
5.0 cm3
TYMP

14
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 ap-
pear next to the labels cm3and daPa and three dashed lines will ap-
pear next to the letters GR (gradient). Since the test cavity is a hard-
walled cavity, the tympanogram should be a flat line, indicating that
there is no mobility in the system. The TM 262TM Auto TympTM places the
letters NP next to the cm3and 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 de-
tected, 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 la-
belled 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 cm3open-
ing 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.
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 cm3readings may be observed.
Your TM 262 is carefully calibrated at our factory, which is at approxi-
mately 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 baro-
metric 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 measure-
ment for variations due to altitude. Because the TM 262 is a pressure-
sensitive 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 pres-
sure change resulting from changing weather conditions will usually
yield volume read-outs within ±0.1 cm3of 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.

15
TABLE 2-2: Altitude Correction
Altitude Correction
Altitude (ft.) Altitude Table (cm3)
0 to 1,500 2.0
2,000 to 3,500 2.1 ± 0.1
4,000 to 6,000 2.2 ± 0.1
6,500 to 7,500 2.3 ± 0.1
8,000 to 9,000 2.4 ± 0.1
9,500 to 10,000 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 mode button,
is depressed. Hold the PROGRAM button for approximately
five seconds.
STEP 1
When entering the altitude mode the display will read as follows:
Altitude Mode
ECV 2.0
cm39.99
Standard
(E71) is displayed in the bottom right corner of the display until the probe is
in the 2.0 cm3cavity.
STEP 2
Place the probe into the 2.0 cm3cavity provided with the instrument and
check cm3value 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
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 cm3cavity, select the 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 cm3display 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 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 button to return to
normal mode.
PROG
PAGE
PROG
M+
PROG
PROG

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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 262TM Auto TympTM.
Maximum permissible noise levels are specified by the American Na-
tional 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
Test Tone
Frequency (Hz) 125 250 500 750 1000 1500 2000 3000 4000 6000 8000
Test Room
Ears covered 34.0 22.5 19.5 21.5 26.5 26.5 28.0 33.5 34.5 38.0 43.5
maximum
permissible octave
band levels
Ears covered 29.0 17.5 14.5 16.5 21.5 21.5 23.0 28.5 29.5 33.0 38.5
maximum
permissible one-third
octave band levels

17
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 262TM Auto TympTM with audiometry, select the
AUDIOMETRY 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 ap-
propriate 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 follow-
ing while depressing the present bar:
• Depressing the Hz button causes the frequency to change to
a lower frequency, depressing the Hz button causes the fre-
quency 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 de-
creases the intensity of the tone.
AUD