Maico MA 50 User manual

Operating Instructions
MAICO MA 50

Operating Instructions MA 50
Geba_MA50_Fe_11a.doc 1 851 406/2 11/11
Table of Contents Page
1 Introduction............................................................................................... 3
2 Description ................................................................................................ 4
3 Getting started .......................................................................................... 5
3.1 Unpacking your instrument..................................................................... 5
3.3 Getting familiar with the MA 50 ............................................................. 7
3.3.1 Using the keyboard of the MA 50 ........................................................ 8
3.3.2 The display of the MA 50..................................................................... 8
4 Pure tone audiometry ................................................................................ 9
4.1 Air Conduction (AC) Testing ................................................................... 9
4.2 Uncomfortable Hearing Level (UCL) Testing............................................10
4.3 Bone Conduction (BC) Testing ...............................................................11
4.4 Masking of the opposite ear ................................................................11
4.4.1 Crossover:.......................................................................................11
4.4.2 Masking theory: ..............................................................................12
4.4.3 Manual masking: ............................................................................12
4.4.4 Automatic masking: ........................................................................13
5 Quick reference guide...............................................................................14
5.1 Startup settings .....................................................................................14
5.2 Receiver selection ..................................................................................14
5.3 Frequency selection ...............................................................................14
5.4 Warble tone (FM)...................................................................................14
5.5 Pulse tone..............................................................................................14
5.6 Test channel selection............................................................................14

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5.7 Tracking function...................................................................................14
5.8 STIM Mode selection .............................................................................15
6 Recommended literature...........................................................................16
7 Computer interface ..................................................................................17
8 Care and maintenance of the instrument ..................................................18
9 Trouble shooting ......................................................................................19
10 Technical Data......................................................................................20
11 Warranty, Maintenance and After-Sales Service ....................................24
12 Safety Regulations ................................................................................25
12.1 Electrical Safety:...................................................................................25
12.2 Measuring security:..............................................................................25
12.3 Device control:.....................................................................................25
Checklist for Subjective Audiometer Testing.................................................26

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1 Introduction
Thank you very much for purchasing a quality product from the MAICO
family. This MA 50 audiometer is manufactured to meet all quality and safety
requirements, and has been certified with the CE-symbol according to
Medical Directive 93/42/EEC.
In designing the MA 50 we placed particular importance in making it a user-
friendly device, meaning its operation is simple and easy to understand. And
because MA 50 functions are software controlled, upgrading later to new,
extended measurement functions will be simple and inexpensive. That means
that you have invested in a device that will adjust to your future needs.
This user manual should make it as easy as possible for you to become
familiar with the functions of the MA 50. Please open out the flap of
illustrations on the last page. The description of the position (e.g. ➄) of
controls, displays and connections, found again in the text, will make it easier
for you to learn how to operate the MA 50.
If you have problems or have ideas for further improvements, please get in
touch with us. Simply call.
Your MAICO-team

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2 Description
The MA 50 is an audiometer for pure tone audiometric tests. It can be used
for ENT diagnostics in the office, and for mobile audiometry in clinics, homes
and abroad.
Tests can be performed using the TDH 39 headphones (AC), B 71 bone
conduction receiver (BC) or optional insert phones. Built-in test signals are
pure tone, pulse tone, warble tone and narrow band noise.
The MA 50 audiometer delivers 11 air conduction (AC) test frequencies from
125 Hz to 8 kHz, with levels from -10 dBHL to 120 dBHL.
Bone conduction (BC) can be tested with 11 test frequencies from 125 Hz to
8 kHz with levels from -10 dBHL to 70 dB HL (with the standard bone
conductor B 71 the frequency range is limited from 250 Hz to 6 kHz).
The optional insert phones EAR 3A submit levels from -10 dBHL to 120 dBHL
with 11 test frequencies from 125 Hz to 8 kHz.
The hearing level is controlled independently for the signal and the masking
channel by two detented knobs on the left and right of the instrument which
can be operated from the side or the top. The level steps are 5 dB. The signal
STIM bar and the frequency up/down keys are just beside the level control
knobs for easy one handed control of level, frequency and signal
presentation.
The bright LED-display shows level and frequency for each channel.
As a result of modern microprocessor technology, the MA 50 is easy to use
and is extremely reliable.
The audiometer is designed to be extremely service friendly. Automatic test
programs make trouble shooting and the yearly calibration as easy as
possible.
PC-Interface:
A serial RS 232C interface for data transfer to a connected computer is built
in. The optional MAICO-audiometry module for NOAH enables the
automatic data transfer of all test results of the MA 50, likes tone audiogram.
For more information see chapter 7.

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3 Getting started
3.1 Unpacking your instrument
Your MA 50 was carefully inspected and packed for shipping. However, it is
a good practice to thoroughly inspect the outside of the shipping box for
signs of damage. If any damage is noted, please notify the carrier
immediately.
Carefully remove the instrument from the shipping box. Remove the plastic
bag from the instrument and inspect the case for any damage.
Notify the carrier immediately if any mechanical damage is noted. This will
assure that a proper claim is made. Save all packing material so the claim
adjuster can inspect it as well. Notify your dealer or MAICO when the
adjuster has completed the inspection.
SAVE ALL THE ORIGINAL PACKING MATERIAL AND THE SHIPPING
CONTAINER SO THE INSTRUMENT CAN BE PROPERLY PACKED IF IT NEEDS
TO BE RETURNED FOR SERVICE OR CALIBRATION.
All accessories are already packaged in the compartment connected with the
MA 50. Please check that all accessories listed below are received in good
condition. If any accessories are missing or damaged, immediately notify your
dealer or MAICO.
Standard accessories:
- 1 Headphone TDH 39
- 1 Bone conduction receiver B 71 with headband
- 1 Patient response switch
- 1 Power cable
- 1 Audiogram form (50 sheets)
Calibration of the device:
The instrument, headphones, bone conduction receiver as well as the
optional insert phone match one another and have the same serial number
(e.g. 6631520). Because they have been calibrated with this particular
instrument, use of other transducers is not allowed. If one of the acoustic
transducers is replaced, the instrument must be recalibrated.
The use of non-calibrated audiometers leads to incorrect measurements!

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3.2 Preparing the MA 50 for use
The MA 50 with its integrated compartment for
the accessories is perfect for portable use. The
rugged housing, light weight and the
comfortable handle make it easy and convenient
to transport the instrument. Carry it, as shown,
with the bottom away from the leg. That helps
protect the front cover from damage, and due
to the asymmetrical handle position it provides
more space for your leg.
To get started first move the handle under the
housing. Unlatch the cover by pressing in the
two black locks located on the left and right
sides near the front of the instrument. Open the
front cover and rest it on the back cover of the
accessory compartment. To open the
compartment, press the two black locks in the
upper middle of the instrument. Open the
compartment cover as seen in picture 2. Take the
headphone, the bone conduction receiver, the
patient response switch and the microphone out
of the compartment and connect the power
cable to power. The MA 50 operates with
voltages from 96 to 240 V~ AC, 44 Hz to 440
Hz. To avoid pinching the cables when closing
the cover, lay the cables in the slots provided.
Close the back cover and latch it with slight
pressure.
The MA 50 should be operated in a quiet room,
so that the audiometric examinations are not
influenced by outside noises. For use in noisier
environments headphones with optional sound
insulation muffs are available.
Picture 3 MA 50 in operation Electro medical
instruments, which emit strong electromagnetic
fields (e.g. microwaves - radiotherapy devices),
can influence the function of the audiometer.
Therefore the use of these instruments is not
allowed in close proximity to the audiometer.
The test room must be at normal temperature,
usually 15 C / 59 F to 35 C / 95 F, and the instrument should be switched on
about 10 minutes before the first measurement to guarantee precise
measuring results. If the device has been cooled down (e.g. during transport),
please wait until it has warmed up to room temperature.
Picture 1 Transport of MA 50
Picture 2 Portable with open cover
Picture 3 MA 50 in operation

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3.3 Getting familiar with the MA 50
Turn on the instrument with the power switch which is located at the right
side of the MA 50. The device
performs its initial test and auto
calibration. If an error is detected
the test is stopped and the code of
the error is shown on the LED-
display . In this case please
contact your local dealer or service.
If the test is passed, the instrument
is setup to air conduction and pure
tone for the right ear and narrow
band masking noise for the left
s above
the receiver and the test channel
selector are lighted. The
frequency is set to 1 kHz and the
level to 30 dBHL for the right test
channel and to -10 dB for the left
masking channel. All these settings
are also shown on the display 
(see picture 5).
The hearing level can be easily
adjusted with the right knob 
and the masking level with the
knob on the left side of the
instrument.
For optimal convenience these level
control knobs are usable from the
top or the side of the instrument.
They are detented in 5 dB steps.
The STIM bars and ↔ are
located beside the level control
knobs , . The STIM LED light
up when you press the STIM bar
↔ to present the test signal. The
STIM LED lights continuous
because the the masking noise is
continuous presented. The
frequency is changed with up 
and down buttons. The design
of the MA 50 makes it easy to control level, signal presentation and
frequency with one hand.
Picture 4 MA 50 power switch, display and selection
Buttons for receiver and test channel
Picture 5 MA 50 display with initial settings
Picture 6 MA 50 level and frequency control

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3.3.1 Using the keyboard of the MA 50
All main functions of the MA 50
are directly accessable by pressing
a single button.
Following is the description of the
functions of each button:
frequency up:
change to next higher frequency
frequency down:
change to next lower frequency
FM - modulation (warble
tone):
changes test signal from pure tone
to warble tone.
receiver selector:
changes the receiver from AC to
BC or INSERT (if option
assembled). The lighted LED above
shows the current selection.
pulse tone:
enables pulsing of pure tone or warble tone.
stim mode:
changes the signal presentation from presenter to interrupter mode.
tracking function:
enables the automatic tracking (see chapter 4.4 masking).
channel selector key:
selects the right or left test ear.
3.3.2 The display of the MA 50
The bright LED-Display of the MA 50 shows levels and frequency. The
display shows the individual levels for the left channel on the left and the
right channel on the right. The
frequency is displayed in the
middle. Also the position of the
dot in the middle indicates the
kind of measurement. If the dot position is left from the center HL test is
indicated. The dot in the center stands for UCL measurement and a dot right
from the middle is MCL measurement. The example picture 8 shows the
initial setting for AC threshold test. The right test channel is set to 30 dBHL ,
the left masking channel is set to -10 dBHL narrow band noise for masking.
The test frequency is 1000 Hz and the test is a HL measurement (dot left
from the middle).
Picture 7 MA 50 keyboard
Picture 8 MA 50 display for pure tone HL-test

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4 Pure tone audiometry
4.1 Air Conduction (AC) Testing
In the hearing threshold test, the hearing threshold
of the patient is measured in comparison with the
normal hearing threshold for air conduction. The
test is started on the ear with better hearing.
- The patient should sit at a distance of at least
1 m from the device.
- Eliminate any obstructions which will
interfere with the placement of the earphone
cushions on the ear (i.e. hair, eyeglasses).
- Ensure the headphones are put on correctly.
Red side on the right, blue side on the left. Adjust the headband of the
headphones so that the
receivers are at the correct
height (the sound output grid
exactly facing the ear canal).
Start with the “better”
indicated ear at 1 kHz. (After
switching on, the frequency is
automatically set to 1 kHz.) In
the following example we
assume that the right is the
“better” ear.
- Set the receiver selector
to AC.
- Set the left level control
knob ↕ to a value just below
expected hearing loss.
- Explain to the patient
that he should press the button
of the patient response switch
if he just hears the test tone.
- Press the STIM bar ↔ for a certain time to present the test tone. The
STIM LED should light on.
- If the patient hears the test tone, the patient response display lights
red. In this case decrease the level with the level control knob ↕. Proceed
with presenting the test signal as described before.
- If the patient doesn’t hear the test tone, increase the level with the
level control knob. Proceed with presenting the test signal as described
before.
- When you find a stable threshold value, note the level and frequency. If
the MA 50 is connected to a PC, the value was stored with your last STIM
presentation.
Picture 10 Headphone
Picture 11 MA 50 controls and display for
airconduction threshold test

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- Test through the frequencies. Starting at 1 kHz, set the higher
frequencies first, then the lower frequencies.
- Use the frequency up key to select the higher frequencies and use
the frequency down key to select the lower frequencies.
- Select the next frequency, increase the level again and proceed with
presenting the test signal as described before.
- Once all frequencies are tested choose the poorer ear and repeat the
hearing threshold test. You can do this just by pressing the test ear button .
The corresponding LED L lights and you test the left ear using the controls on
the right side. The masking is controlled with the level knob on the left
side of the instrument. (For masking see chapter 4.4).
- The correct marks in an audiogram are: O (red) = right and X (blue) =
left
Pulse tone: If required, the test can also be performed with a pulsed tone.
Press the PULSE button and the pure tone will be switched 0.25 s on and
0.25 s off.
Warble tone: If required, the test can also be performed with a warble tone.
Press the FM button and the pure tone will frequency modulate. The
warble tone can also be pulsed as described before.
For hygienic reasons it is important to clean the ear cushions of the
headphone (see chapter 8).
4.2 Uncomfortable Hearing Level (UCL) Testing
Testing of UCL can be measured using pure tone stimuli. The purpose is to
determine the dB level at which the stimuli becomes uncomfortable to the
patient. This information is valuable for determining the patient’s upper
dynamic range limit for proper hearing aid fittings and for determining
symptoms of recruitment.
Warning! Because the UCL test uses high sound pressure levels, it is
extremely important to perform this test using the utmost caution to
avoid damaging the ear. To prevent the possibility of extreme
discomfort by the patient, it is important to start the test with levels
near the patients MCL (Most Comfortable Level).
The UCL level is described as the level between very loud and loud perception
of the test signal.
Press the test channel selector
button longer than 2 seconds.
The dot in the middle of the LED-
display moves to the center of the display.
(see picture 12).
- Start as described in chapter 4.1 with a
test level of 60 dBHL.
- Present the tone briefly (max. 1s)
Picture 12 MA 50 display for UCL-test left
Picture 13 Bone conductor

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- If the signal was recognized by the patient as not uncomfortable
increase the level and proceed as described before.
- If the signal was uncomfortable for the
patient note the values.
- Proceed accordingly with other test
frequencies.
For hygienic reasons it is important to clean
the ear cushions of the headphone (see
chapter 8).
4.3 Bone Conduction (BC) Testing
Bone conduction, i.e. the transmission of
sound waves through the skull directly to the
inner ear conways information about the
function of the inner ear. For a neural hearing
loss the values of air conduction (chapter 4.1) and bone conduction are the
same. In this case a hearing loss of the middle ear can be eliminated.
- Place the bone conduction receiver so that the flat, circular side of the
transducer Y is placed on the mastoid, at the noticeable ledge of the cranial
bone behind the auricle (see picture 14). The other side of the headband is
placed in front of the opposite ear.
- Set the receiver selector to BC.
- Perform the test the same way as for air conduction (see 4.1). Enter the
measurements for all frequencies on the form, connect all points with dotted
lines marked on the audiogram form as follows: > = right and < = left.
For hygienic reasons it is important to clean the bone conductor (see chapter
8).
4.4 Masking of the opposite ear
The basics of masking are explained below. To begin testing immediately,
please go directly to 4.4.3 Manual masking.
4.4.1 Crossover:
When measuring a pure tone audiogram you assume that the measured
hearing threshold is correct. But if you recognize that sound is also
transmitted through bone conduction over the entire skull it is probable that
the opposite ear has also received sound. This is called “crossover”.
Crossover can also occur when measuring air conduction because a small
amount of air conducted sound is received by the skull and transmitted by
bone. Whether the crossover signal can hear by the opposite ear depends on
its inner ear function.
Picture 14 correct seating
of the bone conductor

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Relevant to crossover is the sound level which is received by the opposite ear.
The difference between the original test signal at the test ear and the
received signal at the opposite ear is called “interaural attenuation”.
For bone conduction measurement the interaural attenuation is 0 to 15 dB.
Bone conduction crossover is therefore possible even with a slight difference
in hearing loss between ears.
Important: Please advise the patient to tell you in which ear he hears the test
signal. It is thereby easier to detect crossover.
4.4.2 Masking theory:
To ensure that the patient will not experience crossover you must mask the
opposite ear. Masking increases the hearing threshold of the opposite ear.
The masking is done with a noise signal which is transmitted by the
headphone. For pure tone audiometry a narrowband noise is used. This noise
changes its center frequency according to the frequency of the test signal.
4.4.3 Manual masking:
If you have to mask use the common masking
rules. See chapter 7 for recommend literature.
Masking is an important part of practical
audiometry. It is necessary to be familiar with this
topic to avoid errors which would lead to a wrong
diagnosis.
- Select the ear you like to test with the
channel
selector key . For the opposite ear narrow band
masking noise is automatically set.
- Adjust the required masking level with the
levelcontrol knob .
- Notice that the masking sound is
continuously presented for effective
masking. You can interrupt the masking signal
by pressing the corresponding
interrupter key .
- To mask when performing bone
conduction testing, place the headphone on the
opposite ear so that the receiver is at the correct
height (the sound output grid exactly faces the
ear canal). Adjust the headband of the
headphones. The receiver on the side where the
bone conductor is placed should sit directly on the cheek bone.
The marking for air conduction with masking should be done with the
symbols ▲ the right side and ■the left side on the audiogram form. The
marking for bone conduction with masking should be done with the symbols
[ = the right side and ] = the left side on the audiogram form.
Picture 15 Headphone
Picture 16 correct seating of the
bone conductor

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4.4.4 Automatic masking:
With the manual masking, as described before, you have to readjust the
masking level every time you change the test signal level. The MA 50 has a
tracking feature for easy masking.
- Adjust for the test signal using the level control knob ↕, then with the
masking level control knob adjust for the corresponding masking level.
- Now press the TRACK button . The masking level is automatically
changed if you adjust the test signal level. (e.g. if the test level was 30 dB
and the masking level 50 dB and you change the test level to 45 dB the
masking level is automatically adjusted to 65 dB.

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5 Quick reference guide
5.1 Startup settings
Air conduction on both channels
Pure tone with a level of 30dBHL on the right ear
Narrow band noise with a level of -10dBHL on the left (masking) ear
Presenter mode
5.2 Receiver selection
Press the RECEIVER key to select the receiver (AC, BC, INSERT). The
corresponding LED above the key lights.
Not available receivers will be skipped.
After a new selection the level will be reset to 30dBHL for the signal and -
10dBHL for masking.
5.3 Frequency selection
Use the frequency keys and to select the frequency. The maximum and
minimum frequency depends on the receiver you have selected.
5.4 Warble tone (FM)
Press the FM key to activate the warble tone.
Press the FM key again to switch back to pure tone.
5.5 Pulse tone
Press the PULSE key to activate the pulse tone.
Press the PULSE key again to deactivate pulsing.
5.6 Test channel selection
Press the test channel selector key to select the left or right ear for testing.
5.7 Tracking function
Press the TRACK key to activate tracking. The selected test channel tracks
now the masking level at the opposite ear.
Press the TRACK key again to deactivate tracking.

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5.8 STIM Mode selection
Press STIM MODE key to switch between continuous presentation and
presentation by pressing the STIM bar ↔. When in continuous presentation
mode the STIM bars and function as interrupters. The light above the
STIM MODE key is on if continuous presentation is selected.
Masking noise is always in continuous presentation.
Press the STIM MODE key again to deactivate continuous presentation.

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6 Recommended literature
Audiometric Interpretation: A Manual of Basic Audiometry
Lloyd, Lyle L., and Harriet Kaplan
Baltimore: University Park Press, 1980
Auditory Disorders: A Manual for Clinical Evaluation
Jerger, Susan, and James Jerger
Boston: College Hill Press, 1981
Handbook of Clinical Audiology
Katz, Jack
Baltimore: William & Wilkins, 1994
s Audiology Desk Reference
Roeser, Ross J.
New York / Stuttgart: Thieme, 1996
Auditory Diagnosis
Silam, Shlomo and Carol A. Silvermann
San Diego / London: Singular Publishing Group, 1997

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7 Computer interface
The MA 50 has a built-in serial RS 232 PC-interface for data transfer to a
connected PC. The serial cable to connect the MA 50 with the PC should be
a normal, non twisted 9-pin extension cable. It has a male and a female
connector and all wires are direct 1:1 connected. It is also sold as monitor
extension cable.
Caution: The computer you are using must meet electrical safety
requirements, such as IEC 950 or UL. This is to avoid electrical shock of either
the patient or you.
All test results are online transferred to the PC and stored in the database.
- In pure tone audiometry initially
all measured data is transferred as
hearing threshold data. This is
indicated by the dot left from the
center of the LED-display (see
picture 17).
- To test the uncomfortable level
(UCL) press the test channel selector
key longer than 2 seconds and the dot moves to the center of the LED-
display . All measured data is now transferred as UCL data.
- To test the most comfortable
level (MCL) press the test channel
selector button longer than 2
seconds and the dot moves to a
position right of the center of the LED-display . All measured data is now
transferred as MCL data.
Picture 17 MA 50 display with
pure tone threshold setting
Picture 18 MA 50 display with UCL setting
Picture 19 MA 50 display with MCL setting

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8 Care and maintenance of the instrument
Disconnect the power plug before cleaning!
- To clean the instrument, headphones, bone conduction receiver,
loudspeaker and other accessories use a soft cloth
dampened with a little warm soapy water or
washing-up liquid; no alcohol or spirits should
be used.
- The ear cushions Zof the headphone can
be detached for cleaning. To remove the ear
cushion Zpull it gently from the earphone. To
assemble the cleaned or changed ear cushion
press it on the earphone and make sure that it
sits properly. The sound outlet hole must be
exactly in the middle of the earphone.
- During cleaning, please ensure that no
liquid runs into the switches, level control,
headphone capsules or loudspeaker openings.
Picture 20 changing of the
ear cushions