MA 51 Operating Instructions Feb 2005

MAICO

Operating Instructions MA 51

Table of Contents

Page

1. Introduction

2

2. Description

3

3. Getting started 3.1 Unpacking your instrument 3.2 Preparing the MA 51 for use 3.3 Getting familiar with your MA 51 3.31 Using the keyboard of the MA 51 3.32 The display of the MA 51

5 5 6 7 8 9

4. Pure tone audiometry 4.1 Air Conduction (AC) Testing 4.2 Uncomfortable Hearing Level (UCL) Testing 4.3 Bone Conduction (BC) Testing 4.4 Masking of the opposite ear

10 10 11 12 13

5. Speech audiometry 5.1 Connecting the speech source (microphone, tape or CD-Player) 5.2 Speech calibration 5.3 Adjustment of the monitor phone and talk back microphone 5.4 Speech audiometry 5.5 Masking

15 15 16 17 18 19

6. Quick reference guide

20

7. Recommended literature

23

8. Computer interface

24

9. Care and maintenance of the instrument

26

10. Trouble shooting

27

11. Technical data

28

12. Warranty, maintenance and after-sales service

34

13. Safety regulations

35

14. List for subjective instrument check

36

15. Certificate of conformity

37

16. Front panel layout and rear panel connections

39

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1 Introduction Thank you very much for purchasing a quality product from the MAICO family. This MA 51 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 51 we placed particular importance in making it a userfriendly device, meaning its operation is simple and easy to understand. And because MA 51 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 51. Please open out the flap of illustrations on the last page. The description of the position (e.g. ! ) of controls, displays and connections, found again in the text, will make it easier for you to learn how to operate the MA 51. 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 51 is an audiometer for pure tone and speech audiometric tests. It can be used for ENT diagnostics and hearing aid fittings 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 and loudspeakers (FF). Built-in test signals are pure tone, pulse tone, warble tone, narrow band and broadband noise. The MA 51 has a microphone for live speech audiometry and an input for an optional tape/ CD player with speech test material. The MA 51 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 10 test frequencies from 250 Hz to 8 kHz with levels from -10 dBHL to 80 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. Optional loudspeakers are available for free sound field measurements (FF). The portable loudspeakers MAICO SBC have a dynamic range from -10 dBHL to 80 dBHL at 1m distance, for nine test frequencies from 500 Hz to 8 KHz. The passive loudspeakers Canton Plus XS (not available in the USA), deliver levels up to 80 dBHL at 1m distance over the entire frequency range from 125 Hz to 8 kHz. The MA 51 also has separate line level outputs for an external amplifier. The hearing level is controlled independently for each channel by two detented dials on the left and right of the instrument which can be operated from the side or the top. The level steps are 5 dB and can be changed to 2 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, frequency and other information for each channel. As a result of modern microprocessor technology, the MA 51 is easy to use and is extremely reliable. GEBA51_e.05a.wpd

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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 51, like tone and speech audiogram. For more information see chapter 8.

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3 Getting started 3.1 Unpacking your instrument Your MA 51 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 51. 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 microphone with stand (only for export outside USA) 1 audiogram form (50 sheets) 1 monitor headset with microphone (USA only) 5 sound room cords (USA only) Calibration of the device: The instrument, headphones, bone conduction receiver as well as the optional insert phone and loudspeaker 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 51 for use The MA 51 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 Picture 1 Transport of MA 51 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 51 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 Picture 2 Portable with open cover provided. Close the back cover and latch it with slight pressure. You can place the microphone or a tape or CD-player on top of the cover (see picture 3). The MA 51 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. 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 Picture 3 MA 51 in operation 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. GEBA51_e.05a.wpd

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3.3 Getting familiar with the MA 51 Turn on the instrument with the power switch " which is located at the right side of the MA 51. The device performs its initial test and - 10 1. 0 0 0 30 autocalibration. If an error is detected the test is stopped and a desciption of the error code is shown on the LEDdisplay #. In this case please contact your local dealer or service. If the test is passed, the instrument is MAICO setup to air conduction and pure tone for the right ear and narrow band 17 masking noise for the left ear. The 8 16 18 26 corresponding LED's above the receiver $ , the signal % and the test channel Picture 4 MA 51 power switch, display and selector & are lighted. The frequency is selection buttons receiver, signal and channel set to 1 kHz and the level to 30 dBHL for the right test channel and to -10 1. 0 0 0 30 dB for the left masking channel. All - 1 0 these settings are also shown on the Picture 5 MA 51 display with initial settings 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 - 10 1. 0 0 0 30 optimal convenience these level control knobs are usable from the top or the side of the instrument. They are detented in 5 dB steps. You can adjust the level step to 2 dB with button ). The corresponding LED lights when 2 dB level step is selected. The STIM bars MAICO * and + are located beside the level control knobs (, '. The STIM LED , 1 3 5 13 23 25 24 light up when you press the STIM bar 2 4 + to present the test signal. The STIM LED - lights continuous because the Picture 6 MA 51 level and frequency control the masking noise is continuous presented. The frequency is changed with up . and down ! buttons. The design of the MA 51 makes it easy to control level, signal presentation and frequency with one hand. STIM

STIM

PAT

+

INSERT FF BC AC

Talk Over

STIM MODE

FM

Hz

TRACK

MIC TAPE / CD TONE

L R

2dB

MA 51

STIM

STIM

PAT

+

Talk Over

STIM MODE

FM

Hz

INSERT FF BC AC

2dB

TRACK

L R

MIC TAPE / CD TONE

MA 51

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3.3.1 Using the keyboard of the MA 51 All main functions of the MA 51 are directly accessable by pressing a single button. Not frequently used procedures like the calibration of the speech source are hidden as a “second level function”. To select this function just press the addressed button more than two seconds. A user menu for the customization of the MA 51 is available for advanced users (see chapter 6). Following is the description of the main and second level functions of each button: . frequency up: change to next higher frequency ! frequency down: change to next lower frequency - 10 1. 0 0 0 30 / talk over microphone: switches on the talk over microphone as long as the button is pressed. The level can be adjusted with the knobs ( or '. The actual value is displayed in dBHL at the MAICO right side of the LED-display #. $ receiver selector: 5 9 11 13 15 17 changes the receiver from AC to 4 6 8 14 16 Picture 7 MA 51 keyboard BC or FF or INSERT (if option assembled). The lighted LED above shows the current selection. STIM

STIM

PAT

+

Talk Over

STIM MODE

FM

Hz

INSERT FF BC AC

2dB

TRACK

L R

MIC TAPE / CD TONE

MA 51

2nd level: Calibration of monitor phone or talk back microphone (see chapter 6.11)

0 FM - modulation (warble tone): changes test signal from pure tone to warble tone. 2nd. Level: to enter the user menu press button during power on.

1 pulse tone: enables pulsing of pure tone or warble tone. ) 2 dB level step: selects 5 dB or 2 dB level step. 2 stim mode: changes the signal presentation from presenter to interrupter mode. 3 tracking function: enables the automatic tracking (see chapter 4.4 masking). & channel selector key: selects the test ear. Right, left and binaural are possible settings. 2nd. Level: selects test mode HL, UCL, MCL for selected receiver (see chapter 4.2)

% signal selector key: changes the test signal from pure tone to tape/CD or microphone 2nd level: Calibration of CD or microphone (see chapter 6.13)

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3.3.2 The display of the MA 51 The bright LED-Display # of the MA 51 shows levels, frequency and test results. The display shows the individual settings for the left channel on the left - 1 0 1. 0 0 0 30 and the right channel on the right. The frequency or the speech score are Picture 8 MA 51 display for pure tone HL-test 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 9 shows the display for a speech .4 2 90 UCL-test. In the middle of the LED- - 1 0 display # the result of speech Picture 9 MA 51 display for speech UCL-test discrimination (.42) in per cent are shown. The dot right from the center indicates that a UCL-test is done. The dot in the middle stand in speech mode for single syllable test. The dot left from the center stands for for multi syllable speech 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 4 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 Picture 10 Headphone is the “better” ear. Set the receiver selector $ to AC and the signal selector % to TONE. Set the left level control knob ' to a value just below expected hearing loss. Explain to the patient that he - 10 1. 0 0 0 30 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. MAICO If the patient hears the test tone, 17 23 25 the patient response display 5 1 2 3 4 5 8 12 16 18 24 lights red. In this case decrease Picture 11 MA 51 controls and display for the level with the level control airconduction threshold test 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 STIM

STIM

PAT

+

Talk Over

STIM MODE

FM

Hz

INSERT FF BC AC

2dB

TRACK

L R

MIC TAPE / CD TONE

MA 51

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-

-

MA 51 is connected to a PC, the value was stored with your last STIM presentation. 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 2. 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 Binaural tone audiometry: For tone presentation one both ears press the channel selector button & until both LED's R and L light. (Pressing the button & several times changes the test channel from R (right) to L (left) to RL (binaural) to R and so on). The hearing level for the left ear is now adjusted with the level control knob ( and the knob ' controls the level for the right ear. The test signal can be presented with the according STIM bar * and +. Pulse tone: If required, the test can also be performed with a pulsed tone. Press the PULSE button 1 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 0 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 9).

4.2 Uncomfortable Hearing Level (UCL) Testing Testing of UCL can be measured using pure tone stimuli or speech (live voice or tape/CD). 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. GEBA51_e.05a.wpd

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Warning! Because the UCL test uses high sound pressure levels, it is extremly 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 patient's 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 1 0. 0 0 60 # moves to the center of the - 1 0 display. (see picture 12). Picture 12 MA 51 display for UCL-test left Start as described in chapter 4.1 with a test level of 60 dBHL. Present the tone briefly (max. 1s) 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 9). 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 and the signal selector % to TONE.

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Picture 13 Bone conductor

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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 9).

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 heard by the opposite ear depends on its inner ear function. 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. GEBA51_e.05a.wpd

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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 level control knob (. Notice that the masking sound is continuously presented for effective masking. You can interrupt the masking signal by pressing the corresponding interrupter key *. Picture 15 Headphone 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 4 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 6 = the right side and 7 = the left side on the audiogram form. The marking for bone conduction with masking should be done with Picture 16 correct seating the symbols [ = the right side and ] = the left side on the of the bone conductor audiogram form. 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 51 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 3. 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 Speech audiometry 5.1 Connecting the speech source 5.1.1Connecting of CD-Player or Tape To conduct speech tests using speech test material you can connect a CD- or tapeplayer to the MA 51. Use a standard phono plug cable to connect the right and left outputs of the device with the corresponding inputs 8 and 9 on the rear panel of the MA 51 (see picture 17). To avoid pinching the cables when closing the cover, lay the cables in the slots provided. If you are using a small portable CDplayer or tape you can place it on top of the cover of the MA 51 similar as shown in picture 18 for the microphone. This saves space and makes the usage of the CD-player or tape very convenient. Caution: If you are using a CD- or tapeplayer powered by electrical current, the player must meet the electrical safety requirements, such as IEC 601-1 or UL. This is to avoid electrical shock of either the patient or you. If you are not sure if your player meets these requirements it is safer to use battery power. 5.1.2 Connection of Microphone Connect the microphone to the SPEECH MIC connector : on the rear panel of the MA 51 (see picture 19). To avoid pinching the cables when closing the cover, lay the cables in the slots provided. Place the microphone on top of the cover of the MA 51 (as shown in picture 18). The microphone can be used for live speech audiometry and communication with the patient. If your instrument is supplied with a combination monitor/mic headset, connect the phone plug labeled E with the SPEECH MIC connector :. GEBA51_e.05a.wpd

R

R

FF

L

SIGNAL L

BC MASK

BC

TAPE / CD R L

R INSERT L

R

MONITOR TB MIC

AC

L

SPEECH MIC

L M

Picture 17 MA 51 rear panel with TAPE/CD input

Picture 18 MA 51 in operation with microphone for live speech audiometry

R

R

SIGNAL L

FF

L

BC MASK

BC

TAPE / CD R L

R INSERT L

R

MONITOR TB MIC

Picture 19 MA 51 rear panel with SPEECH MIC input

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5.2 Speech calibration 5.2.1 Calibration of the CD or tape with speech test material The MA 51 must be calibrated to the particular speech test material in use to ensure valid test levels. That means every time you change the CD or tape you must recalibrate the instrument. To calibrate the Tape/CD speech input select TAPE/CD with the SIGNAL selector key %. Press the SIGNAL key % longer - 10 1. 0 0 0 30 than 2 seconds. In the middle of the display # the text SCAL appears. You also see the actual settings in % of the maximum calibration for both channels (see picture 21). On every CD or tape with speech MAICO test material you have a reference signal, such as a reference tone 3 17 7 2 18 or speech simulating noise. Picture 20 MA 51 controls and displays Perform the reference signal with for speech calibration Tape or CD. Use the left knob ( to adjust the 80 SCAL 80 level until the VU-meter ; Picture 21 MA 51 display shows all yellow and one green with speech calibration light. If one or more red lights are on, reduce the level using the knob (. Store the calibration by pressing the STIM bar *. STIM

STIM

PAT

+

Talk Over

STIM MODE

FM

Hz

INSERT FF BC AC

2dB

TRACK

L R

MIC TAPE / CD TONE

MA 51

5.2.1 Calibration of the microphone for live speech test -

To calibrate the SPEECH MIC select MIC with the SIGNAL selector key %. Press the SIGNAL key % longer than 2 seconds. In the middle of the display # the text SCAL appears. You see also the actual settings in % of the maximum calibration for both channels (see picture 21). Position yourself the customary distance from the microphone and speak test words. Use the left knob ( to adjust the level until the VU-meter ; shows all yellow and one green light. If one or more red lights are on, reduce the level using the knob (. Store the calibration by pressing the STIM bar *.

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5.3 Connection and calibration of the monitor phone 5.3.1 Connection of the monitor phone Connect the monitor phone to the MONITOR connector < at the rear panel of the MA 51 (see picture 22).To avoid pinching the cables when closing the cover, lay the cables in the slots provided. The monitor phone allows you and the patient to hear the speech test material simultaneously. This helps in determining if the test word was understood by the patient. If the talk back option of the MA 51 is installed, the communication from the patient to audiologist will be heard with the monitor phone.

R

R

SIGNAL L

FF

L

BC MASK

BC

TAPE / CD R L

R INSERT L

R

MONITOR TB MIC

AC

L

SPEECH MIC

O Picture 22 MA 51 rear panel with MONITOR phone output

5.3.2 Adjustment of the monitor phone and talk back microphone -

-

To adjust the output level of the monitor phone press the receiver selector key $ longer than 2 seconds. In the middle of the display # the text TboP appears. Right you see the actual settings of the monitor phone, left the setting of the talk 28 TboP 80 back microphone (if installed). Picture 23 MA 51 display with The settings are displayed in % adjustment of the monitor phone (right) of the maximum output level and talkback microphone (left) (see picture 23). Perform a test signal with Tape , CD or the speech microphone. Use the right knob ' and adjust the output level of the monitor phone to a level that is comfortable for you. If you have an installed talk back microphone speek test words into the microphone and adjust the level with the left knob (. Store the adjustment by pressing the STIM bar * or +.

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5.4 Speech Audiometry The speech-recognition threshold SRT is the hearing threshold for speech.It is the lowest level at which the patient correctly recognizes the stimuli 50% of the time. Usually, recognition is indicated by repetition of the speechstimulus item. The speech test can be done with recorded speech test material from CD or tape or with the microphone and live voice using standardized word lists. Different methods for speech tests are standardized worldwide such as the ASHA guidlines for determining the threshold level for speech (Asha 21, page 353-356). Explain to the patient that he should repeat each word he hears. 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 4 exactly Picture 24 Headphone facing the ear canal). Set the receiver selectors $ to AC and the signal selector % to TAPE/CD (if you are using recorded speech test material) or to MIC (if you wish to perform a speech test with live speech). On the LED-display # the initial . 0 30 setting for speech audiometry - 1 0 (see picture 25) appears. The Picture 25 MA 51 display with result of speech discrimination in initial settings for speech audiometry per cent is shown in the middle. If you are using CD or tape, put the monitor phone on to hear the test words. Depending on your test method, use the level control knob + to set the start level. Perform the test words. Tally the correct words by pressing the frequency up key .. Tally the incorrect words by pressing the frequency town key !. If you are working online with a PC press the STIM bar + to transfer the test result to the PC (see also chapter 8). To clear the counter for the next test, press the FM key 0.

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It is also possible to perform the speech test with loudspeakers (e.g. for the verification of hearing aid fitting) or bone conduction. Select the required transducer with the RECEIVER selection button $ and proceed as described before. 5.6 Masking Speech audiometry has similar masking rules to those desribed in chapter 4.4 for pure tone audiometry. When TAPE/CD or MIC is selected on one channel, and NOISE masking on the opposite channel, the MA 51 automatically performs speech masking noise.

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