Testing FM Systems with FONIX FP40 Analyzers FRYE FRYE ELECTRONICS, INC. P.O. Box 23391 Tigard, OR 97281-3391 USA (503) 620-2722 (800) 547-8209 Fax: (503) 639-0128 http://www.frye.com e-mail: general@frye.com 2000, Frye Electronics, Inc. 8/11/00 All Rights Reserved
Contents How to Use This Guide... iii Special Setups... iii Section 1 Setup for Electroacoustic Evaluation of FM Systems 1.1 How to Attach the 2cc Coupler... 1 1.2 Testing Transmitting/Receiving Systems... 3 1.2.1 General Setup Information This section applies to all units.... 3 1.2.2 FM Microphone Inside the Sound Chamber (small, non-directional microphones)... 5 1.2.3 FM Microphone Outside the Sound Chamber (large or directional microphones)... 5 1.3 Testing Environmental Microphones...7 1.3.1 Environmental Microphones on Body-worn Receivers... 8 1.3.2 Environmental Microphones on Ear-level Receivers... 10 1.3.3 Lapel Environmental Microphones... 10 Section 2 Setup for Real-Ear Evaluation of FM Systems 2.1 Real-Ear FM Microphone Response... 11 2.2 Environmental Microphone Response... 12 Section 3 Recommended Fitting Protocol and Test Signals 3.1 Introduction... 15 3.2 General fitting protocol... 16 3.3 Step one electroacoustic tests... 16 3.3.1 Situation A: electroacoustic tests for mild to moderately-severe loss (<80 db HL) or use of FM only signal option... 16 3.3.2 Situation B: electroacoustic tests for severe to profound hearing loss (>80 db HL) or use of FM + ENV signal option... 19 3.4 Step two real ear verification... 22 3.4.1 Situation A: real ear verification for mild to moderately-severe loss (<80 db HL) or use of FM only signal option... 22 3.4.2 Situation B: Real ear verification for severe to profound hearing loss (>80 db HL) or Use of FM + ENV signal option... 24 ii
How to Use This Guide An FM system can take many forms, so there are many possible ways you can test. Sections 1 and 2 of this guide give the general setups and procedures for coupler and real-ear tests of FM systems, respectively. Section 3 gives a step-by-step fitting protocol, including the recommended test signals. Most of today s assistive systems for use in noisy environments rely on frequency-modulation (FM) transmitters and receivers. Other methods infrared (IR), for example are in use as well. The procedures given here, although primarily aimed at FM systems, can also be used with IR systems, as long as there is a line of sight between the transmitter and the receiver. Special Setups Some of the equipment setups given here take advantage of the optional FP40 FM Kit. The kit contains the following items: Floor stand with screw-on platform adaptor Extra Fun-Tak Probe microphone extension cable (deleted for units with probe, which already have this item) 6-inch (15 cm) square foam pad Use these items for testing outside the sound chamber. If you don t have the optional FM Kit, improvise with what you have. Keep in mind that any setup should prevent sound reflections from interfering with tests as much as possible. Whenever you test outside the sound chamber, choose a test area that is especially free of background noise. iii
1 Setup for Electroacoustic Evaluation of FM Systems 1.1 How to attach the 2cc coupler A variety of output devices can be used with FM systems. These include button earphones and BTE units with an internal FM receiver, an external FM receiver boot, or options for coupling such as direct audio inputs, silhouette coils, or neck loops. This section tells you how to arrange the 2cc coupler with each type of output device. 1.1.1 Button earphone (Refer to Figure 1) 1. If necessary, remove the ear-level adaptor from the HA-2 coupler. 2. Snap-on the button earphone to the HA-2 coupler. 3. Place the coupler/hearing-aid assembly on a foam pad outside the text box, 2 ft. (60 cm) from the transmitter during testing. FM Receiver FM Receiver FM Receiver Foam Pad Foam Pad Foam Pad to Analyzer to Analyzer to Analyzer A Button Earphone B Internal FM Receiver, External FM Boot Receiver, or Direct Audio Input C Silhouette Coil Figure 1 Figure 2 Figure 3 Section 1: 2cc Coupler Tests of FM Systems 1
1.1.2 BTE microphone/receiver or BTE aid with internal FM receiver, external FM boot receiver, or direct audio input (Refer to Figure 2) 1. Attach the ear-level adapter to the HA-2 coupler, if necessary. 2. Attach the BTE hearing aid to the HA-2 coupler. 3. Set the switch on the position to receive the signal. 4. Place the coupler/hearing-aid assembly on a foam pad outside the test box, 2 ft. (60 cm) from the transmitter during testing. 1.1.3 BTE aid with silhouette coil (Refer to Figure 3) 1. Attach the ear-level adapter to the HA-2 coupler, if necessary. 2. Attach the BTE hearing aid to the HA-2 coupler. 3. Place the coupler/hearing-aid assembly on a foam pad outside the test box on a nonmetallic surface during testing. 4. Choose a location free of stray magnetic fields (away from video monitors and other electrical devices), while also maintaining the required separation (2 ft./60 cm) from the transmitter. 5. Align the silhouette coil underneath the hearing aid, simulating the way it would be worn on the ear. 6. Set the hearing aid for T. 1.1.4 BTE aid with neck loop (Refer to Figure 4) 1. Within the range of the coupler microphone cable, choose a location to seat the listener that is free of stray magnetic fields (away from video monitors and other electrical devices), while also maintaining the required separation (2 ft./60 cm) from the transmitter. 2. Place the neck loop around the listener s neck or around the neck of a person of similar size. 3. Attach the listener s hearing aid to the HA-2 coupler and set it to the T position with a normal use setting of the volume control. 4. While holding the coupler in hand, place the hearing aid at the listener s ear, as typically worn. 5. Take care not to move or touch the coupler microphone while testing. 2 Testing FM Systems with FONIX FP40 Analyzers
FM Receiver to Analyzer Figure 4 Neck Loop 1.2 Testing transmitting/receiving systems This section gives the setup for testing the transmitting/receiving part of an FM system. If the system is equipped with an environmental microphone, turn the environmental microphone off during testing. Procedures for testing the environmental microphone are given in Section 1.3. 1.2.1 General setup information This section applies to all units. 1. The cord of the transmitting microphone is the antenna of the transmitter, and the cord of the output device (button earphone; or BTE with direct input, neck loop, or silhouette coil) is the antenna of the receiver. IMPORTANT: Separate the transmitter and the receiver, and their antennas, by at least 2 ft. (60 cm) during testing. 2. Attach the output device (button earphone or BTE) to a 2cc coupler and place the assembly on a foam pad or other vibration-free surface at least 2 ft. (60 cm) from the test area. Section 1: 2cc Coupler Tests of FM Systems 3
3. A probe microphone extension cable may be used with your coupler microphone during testing to achieve the required separation between the receiver and the transmitter parts comfortably as shown in Figure 5. 4. Transmitters with non-directional lapel microphones can be tested with the transmitter microphone inside the sound chamber. But you must use a probe microphone extension cable with your coupler microphone during testing, to get the required separation between the transmitting parts and the receiving parts. Details are given in section 1.2.2 and Figure 5. 5. Transmitters with directional lapel microphones or microphones too large to fit in the sound chamber must be placed outside the sound chamber during testing (if a microphone has more than one sound-entry port, it is likely a directional microphone). Details are given in section 1.2.3 and Figure 6. 6. For units with the probe option, be sure the FP40 is in the coupler test mode and the reference microphone for coupler tests is set to OFF. 2 ft. (60 cm) Lapel Microphone FM Transmitter Figure 5 FM Receiver Setup for testing an FM system with a non-directional lapel microphone 4 Testing FM Systems with FONIX FP40 Analyzers
1.2.2 FM microphone inside the sound chamber (small, non-directional microphones) Leveling 1. If not already done, attach the probe microphone extension cable to the coupler microphone. 2. During leveling, stow the excess cable (and the probe microphone, if applicable) between the front wall of the FP40 case and the foam wall of the test area. 3. Perform leveling exactly as you would when testing a regular hearing aid: Place the coupler microphone at the test position. Close the lid. Press LEVEL and then press START. Testing (refer to Figure 5) 1. Insert the coupler microphone into the 2cc coupler, and place at least 2 ft. (60 cm) from all transmitter parts. 2. Place the FM transmitting microphone at the test position in the chamber, exactly where the coupler microphone was during leveling. 3. Arrange the microphone cables so they exit the sound chamber at the front right corner of the FP40. This will let you close the lid completely during testing. 4. Close the lid. 5. Test according to Section 3 or the FM manufacturer s instructions. 1.2.3 FM microphone outside the sound chamber (large or directional microphones) Leveling (Refer to Figure 6) 1. Place the FP40 slightly overhanging the edge of a table. 2. Release the lock at the rear of the loudspeaker in the sound chamber and raise the loudspeaker to its erect position. 3. Using Fun-Tak, affix the coupler microphone to the platform at the top of the floor stand, 6 inches (15 cm) in front of the loudspeaker, with the microphone pointing toward the loudspeaker. The sound-entry port should be well clear of the platform. This will ensure that during testing, the directional ports of the FM microphone will not be obscured by the platform. (If you don t have a floor stand, the back of a chair can suffice. But be sure the chair is facing to the side of the setup to avoid reflections from the back of the chair.) 4. Stand clear of the test area. 5. Press LEVEL and then press START. Section 1: 2cc Coupler Tests of FM Systems 5
Directional Microphone 6" (15 cm) Figure 6 Leveling setup for testing an FM system with a directional or large microphone Testing 1. After removing the coupler microphone, place the FM transmitting microphone at the test position, exactly where the coupler microphone was during leveling. Try to keep all sound-entry ports clear of the platform. 2. Place the transmitter and its cord behind the transmitting microphone. If you use the seat of a chair to hold the transmitter (as Fig 7 shows), be sure the chair is facing to the side of the setup to avoid reflections. 3. Insert the coupler microphone into the 2cc coupler and attach the output of the FM receiver. Place on a foam pad 2 ft. (60 cm) from the transmitter. 4. Stand clear of the test area. 5. Test according to Section 3 or the FM manufacturer s instructions. 6 Testing FM Systems with FONIX FP40 Analyzers
2 ft. (60 cm) 6 in. (15 cm) FM Transmitter FM Receiver Figure 7 Setup for testing an FM system with a directional or large microphone 1.3 Testing environmental microphones Environmental microphones are used in a manner similar to that of an ordinary hearing aid. The FM transmitter microphone should be turned off and the Environmental microphone turned on. Section 1: 2cc Coupler Tests of FM Systems 7
1.3.1 Environmental microphones on body-worn receivers Leveling 1. Affix the receiving unit to the platform stand in the manner shown in Figure 8. 2. For FP40 units with probe, set REFERENCE MICROPHONE to ON in the COUPLER SETTINGS of the setup menu. The probe-tube microphone will then serve as the leveling microphone. For units without probe, the coupler microphone temporarily serves as the leveling microphone, as usual. 3. Using Fun-Tak, affix the leveling microphone to the receiving unit so the entrance to the leveling microphone is very close to that of the environmental microphone. Choose a place to stand during testing, preferably away from the loudspeaker and microphone (but, of course, near enough to operate the test controls). Stand precisely in this place during both leveling and testing. 4. Place the receiving unit one inch (2.5 cm) from, and facing, the loudspeaker (Refer to Figure 9). 5. Press [LEVEL] and then [START/STOP]. This calibrates the test signal at the place where the FM receiver microphone will be during testing. Probe Microphone Coupler Microphone A: Units with Probe B: Units without Probe Figure 8 Leveling for testing environmental microphones on body-worn receivers 8 Testing FM Systems with FONIX FP40 Analyzers
Testing 1. For units without probe, carefully remove the coupler (leveling) microphone from the receiving unit; do not disturb the position of the receiving unit. For units with probe, leave the leveling (probe) microphone in place; it will be the reference microphone during testing. 2. Insert the coupler microphone into the 2cc coupler, and attach to the button receiver or ear level receiver as explained in Section 1.1. For all coupling options except neckloop, the 2cc coupler can be placed in the open sound chamber (Refer to Figure 9). 3. Test according to Section 3 or the FM manufacturer s instructions. Only 1 inch (2.5 cm) between receiving unit and loudspeaker. Figure 9 Leveling and testing with self-contained environmental microphones on body-worn receivers Section 1: 2cc Coupler Tests of FM Systems 9
1.3.2 Environmental microphones on ear-level receivers Leveling Testing Level the sound chamber as you would when testing any hearing aid (i.e., lid closed, leveling microphone at the test position.) 1. Attach the ear-level receiver to the 2cc coupler. 2. Insert the coupler microphone into the 2cc coupler. 3. Place the ear-level receiver and coupler at the test position in the sound chamber and close the lid. (HINT: To make it easy to close the chamber lid fully, arrange the microphone wires so they exit the chamber at the right-front corner.) 4. Test according to Section 3 or the FM manufacturer s instructions. 1.3.3 Lapel environmental microphones Leveling Testing Level the sound chamber as you would when testing any hearing aid (i.e., lid closed, leveling microphone at the test position.) 1. Place the lapel microphone at the test position in the sound chamber and close the lid. 2. Attach the output transducer from the FM receiver to the 2cc coupler outside the sound chamber in the same manner as for testing the transmitting/receiving function (e.g. foam pad etc.), with the exception that 2 ft. (60 cm) of separation is not required. 3. Insert the coupler microphone into the 2cc coupler. 4. Test according to Section 3 or the FM manufacturer s instructions. 10 Testing FM Systems with FONIX FP40 Analyzers
2 Setup for Real-Ear Evaluation of FM Systems Two setups are given for assessing the real-ear response of FM systems: Section 2.1, FM Microphone Response, and Section 2.2, Environmental Microphone Response. These arrangements can be used with the Recommended Fitting Protocol and Test Signals given in Section 3. 2.1 Real-ear FM microphone response If the FM receiver is equipped with an environmental microphone, set it to the off position. Leveling 1. Press F5 to go to PROBE mode. 2. Press F1 for MENU, and set test conditions as desired. The settings below are for the prot ocol in Section 3. PURE/COMP* to COMPOSITE (far left column) GAIN/SPL to SPL (far right column) *units not having the Composite Option always use puretone. (Note: When SPL is chosen, the reference microphone will be turned on during leveling and turned off during measurement. This is true regardless of the menu setting for REFERENCE MIC.) 3. Press F1 to exit the menu. 4. Place the reference microphone 6 inches (15 cm) in front of and facing the loudspeaker (Figure 6). 5. Choose a place to stand during testing, preferably away from the loudspeaker and microphone (but, of course, near enough to operate the test controls). Stand precisely in this place during both leveling and testing. 6. Press [LEVEL] and then [START/STOP]. This calibrates the test signal at the place where the FM transmitting microphone will be during testing. Section 2: Real-Ear Evaluation of FM Systems with the FP40 11
Testing 1. Carefully remove the reference microphone from in front of the loudspeaker and replace it with the FM transmitting microphone. (Note: The reference microphone is not used during measurement, so you can drape it over the client s shoulder or lay it aside. There is no need to use the headband.) (Figure 10) FM Microphone 6" (15 cm) Receiving Earpiece in ear Probe Microphone Reference Microphone (inactive at this time) Probe Remote Control FM Transmitter 2 ft. (60 cm) minimum FM Receiver Figure 10 2. After marking the probe tube to ensure the desired insertion depth, place the probe tube and the earpiece of the receiving unit in the client's ear. The insertion depth of the probe tube should be the same as used to test the client's hearing aid The client should be at least 2 ft (60 cm) from the loudspeaker to avoid being in the sound field. 3. Test according to Section 3 or the FM manufacturer s instructions. 2.2 Environmental microphone response The FM transmitter microphone should be set to off position and environmental microphone set to the on position. Leveling 1. Select signal options as described in Section 2.1. 2. Arrange the reference microphone and FM receiver environmental microphone as shown in Fibure 8B. Place the FM receiver one inch from and facing the loudspeaker as shown in Figure 9. 3. Choose a place to stand during testing, preferably away from the loudspeaker and microphone (but, of course, near enough to operate the test controls). Stand precisely in this place during both leveling and testing. 12 Testing FM Systems with FONIX FP40 Analyzers
Testing 4. Press [LEVEL] and then [START/STOP]. This calibrates the test signal at the place where the FM receiver microphone will be during testing. 1. Carefully remove the reference microphone from in front of the loudspeaker and drape it over the client s shoulder or lay it aside. 2. Insert the probe and seat the client as described in Section 2.1, #2. 3. Test according to Section 3 or the FM manufacturer s instructions. Section 2: Real-Ear Evaluation of FM Systems with the FP40 13
3 Recommended Fitting Protocol and Test Signals 3.1 Introduction As with most hearing aids, both the gain and the maximum output (SSPL) of an FM system should be adjusted to meet the listener s auditory requirements. One way to achieve this goal is to match the performance of the FM system to that of the listener's hearing aid, assuming the performance of the hearing aid is acceptable. There are several issues to consider when comparing the hearing aid and FM performance. With FM systems, the pickup microphone is normally worn at the chest, 6-8 inches (15-20 cm) under the mouth of the talker, whereas with hearing aids, the pickup microphone is worn by the listener, typically at a minimum of 3 ft. (1 m) from the talker. This difference affects both the level and the frequency content of typical input signals. With FM systems, typical speech input levels range from 75 to 85 db SPL, as compared with 60 to 70 db SPL for hearing aids. With the chest-worn location of the pickup microphone, the high frequencies are relatively lower in level (about 5 db at 5 khz) and the low frequencies are relatively higher in level (about 5 db at 500 Hz) as compared with directly in front of the talker's mouth. The increased vocal effort by teachers in a classroom situation may create further changes to the speech spectrum at the input to an FM system, as compared with the speech spectrum at the input of a hearing aid (Cornelisse et al., 1991). FM systems often have an automatic gain control (AGC) or other nonlinear characteristic that could interact with that of the hearing aid being used to deliver the FM signal if such a hearing aid is being used in this fashion. The frequency response of an FM system is often not as adjustable as that of a hearing aid, limiting the range of electroacoustic modifications available. The procedures recommended in this section are based on the ASHA guidelines for fitting and monitoring FM systems (1999), available at www.asha.org/audiology/fm_guidelines.htm. For further study of evaluating and fitting FM systems, please refer to the articles listed at the end of this guide. Section 3: Recommended Fitting Protocol and Test Signals 15
3.2 General fitting protocol Goals: Situation A*: For students who use FM only or have mild to moderately-severe losses (<80 db HL), the goal is the match the OUTPUT of the hearing aid and the FM system when typical input signals are used. With typical inputs, the FM response will be the same intensity as the hearing aid response. Situation B: For students who use FM+ENV settings or have severe to profound losses (>80 db HL), the goal is to match the GAIN of the hearing aid and the FM system when typical input signals are used. With typical input signals, the FM response will be about 10 db more intense than the hearing aid response. Testing Order: Start with 2cc-coupler tests and adjustments if possible. Follow up with real-ear verification. If time doesn t permit both test conditions, omit the 2cc-coupler tests. For both 2cc-coupler and real-ear tests: 1. First test the user s hearing aid alone, with low signal levels at user settings. 2. Then adjust FM system to match, by using FM controls first, then hearing aid controls if necessary. 3. Then adjust FM system to match with high signal levels using FM controls first, then hearing aid controls if necessary. 3.3 Step one electroacoustic tests 3.3.1 Situation A: electroacoustic tests for mild to moderatelysevere loss (<80 db HL) or use of FM only signal option 3.3.1.1 Equipment setup 1. Press [F1] which is the left-most key of the row of function keys to enter the SETUP MENU. 2. Under General Settings, press [START/STOP] repeatedly to cycle through the choices for SOURCE. Set the source to Composite. 3. For units without the composite option, set source to TONE. Under Puretone Settings use [START/STOP] to set SWEEP TYPE to fast. This will give you a continuous puretone sweep. *Also use procedures for Situation A for FM Systems that incorporate an FM precedence feature to reduce the environmental signal relative to the FM whenever close speech input is detected in the FM channel. 16 Testing FM Systems with FONIX FP40 Analyzers
4. Select EXIT by pressing [F1] to return to the test screen. 5. Set Multicurve to On by pressing [F2] and noting the corresponding confirmation ON MULTICRV in the left side of the bottom line of the display. Verify that it is set to 1 CURVE by noting the display above the [F6] key. If not set to 1 CURVE, use the [F6] key to toggle through the four curve choices to find 1. 6. Set Gain to Off by pressing [F3] and noting the corresponding confirmation of OFF GAIN just above that key. 3.3.1.2 First test the hearing aid in the 2cc coupler with low-level input 1. Attach the hearing aid set to user settings to the 2cc coupler in the usual way (refer to Chapter 3 of the FP40 Operator s Manual). 2. Adjust the signal level to 65 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 3. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the first curve memory. 4. This will be referred to as the Electroacoustic Hearing Aid Response or EHA65. 3.3.1.3 Next test with the FM system using a low-level input signal to the FM microphone 1. Set up the FM system following the instructions in Sections 1.1 and 1.2 of this guide. 2. Press [F6] to select 2 CURVE for the FM response. 3. Adjust the signal level to 80 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 4. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the second curve memory and will be displayed on the screen labeled as 2. If the first curve is not also on the screen, there is a greater than 50 db difference between the two curves and the display cannot show both at once. 5. This second curve will be referred to as the Electroacoustic FM Response or EFMR. 6. Compare the Curve #1, EHA65, and #2, EFM80, and adjust the FM volume control if necessary to obtain a better match. As a last resort, adjust the settings on the hearing aid. If this must be done, the teacher, parents, and therapists must be made aware that when the FM system is used, the settings on the hearing aid must be changed for optimum performance. In the example in Figure 11, the FM output is greater than the hearing aid output in the high frequencies and an adjustment could be made if possible to obtain a better match. However, no adjustment would be made if more high-frequency output was desirable. Section 3: Recommended Fitting Protocol and Test Signals 17
Figure 11 3.3.1.4 Now test the hearing aid with high-level input 7. Press [F6] to select 3 CURVE for the HA response. 8. Adjust the signal level to 90 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 9. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the third curve memory. 10. This third curve will be referred to as the Electroacoustic Hearing Aid Saturation Response or EHA90. 3.3.1.5 Now test with the FM system using a high-level input signal 1. Press [F6] to select 4 CURVE for the FM response. 2. Adjust the signal level to 90 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 3. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the fourth curve memory. 4. This fourth curve will be referred to as the Electroacoustic FM Saturation Response or EFM90. 5. Compare the Curve #3, EHA90, and #4, EFM90, and adjust the FM output control to reach a match within plus or minus 5 db. As a last resort, adjust the settings on the hearing aid. If this must be done, the teacher, parents, and therapists must be made aware that when the FM system is used, the settings on the hearing aid must be changed for optimum performance. As shown in Figure 12, the FM response is just below the hearing aid response in the low frequencies. Such a slight difference is considered acceptable for maximum output. 18 Testing FM Systems with FONIX FP40 Analyzers
Figure 12 3.3.2 Situation B: electroacoustic tests for severe to profound hearing loss (>80 db HL) or use of FM + ENV signal option 3.3.2.1 Equipment setup Same as 3.3.1.1 for Situation A except for: 1. Press [F1] which is the left-most key of the row of function keys to enter the SETUP MENU. 2. Under General Settings, press [START/STOP] repeatedly to cycle through the choices. Set the source to TONE. 3. Select EXIT by pressing [F1] to return to the test screen. 4. Set Gain to ON by pressing [F3] and noting the corresponding confirmation of ON GAIN just above that key. 5. Set Frequency to 1000 Hz by turning the right-hand large black dial and noting the frequency in the lower right-hand status box. 6. Room noise must be minimal (<50 dba) to reduce interference from the FM or environmental microphone that is active but not receiving input. 3.3.2.2 First test the hearing aid in the 2cc coupler with low-level input 1. Attach the hearing aid set to user settings to the 2cc coupler in the usual way (refer to Chapter 3 of the Operator s Manual). 2. Adjust the signal level to 65 db SPL by turning the left large dial and noting the corresponding source intensity in the lower right-hand status box. 3. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. Note the HEARING AID OUTPUT shown in the lower right-hand status box. Section 3: Recommended Fitting Protocol and Test Signals 19
3.3.2.3 Next test with the FM system using a low-level input signal to the FM microphone 1. Set up the FM system following the instructions in Sections 1.1 and 1.2 of this guide. Set FM to receive the FM and the ENV signals. 2. Leave the signal level to 65 db SPL or adjust to that by turning the left large dial and noting the corresponding source intensity shown in the lower right-hand status box. 3. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. Note the FM OUTPUT signal level shown in the lower right-hand status box. Adjust the FM receiver volume control so that the hearing aid and FM outputs are matched. Now the gain of the hearing aid and of the FM system have been matched. 3.3.2.4 Next test with the FM system and a typical input level to verify increase in signal level 1. Increase the signal level to 80 db SPL by turning the left large dial and noting the corresponding source intensity shown in the lower right-hand status box. 2. Note the output from the FM receiver in the lower right-hand status box. 3. Compare the output from the hearing aid and the FM system and adjust the FM receiver volume control if necessary according to the following: If the increase is: 10 db, no further adjustments are needed. 15 db, reduce the FM receiver volume control so that the output in the 2cc coupler falls by 5 db. 5 db, increase the FM receiver volume control so that the output in the 2cc coupler increased by 7 or 8 db. 0 db, the FM transmitter may have very low compression threshold, so increase the FM receiver volume control to provide a 5 db increase in output. 3.3.2.5 Compare the full response curves from hearing aid and FM system with input to the FM microphone Hearing Aid 1. Select the signal source as complex if possible, otherwise use sweep-frequency pure tones. 2. Set Multicurve on. Press [F6] to select 1 Curve. 3. Attach the hearing aid set to user settings to the 2cc coupler in the usual way (refer to Chapter 3 of the Operator s Manual). 20 Testing FM Systems with FONIX FP40 Analyzers
4. Adjust the signal level to 65 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 5. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the first curve memory. 6. This will be referred to as the Electroacoustic Hearing Aid Response or EHA65. FM System 1. Set up the FM system following the instructions in Sections 1.1 and 1.2 of this guide. Be sure FM system is set to receive the FM and the environmental signals and the FM microphone is in the test box (Figure 5) or six inches from the speaker (Figure 7) depending on the microphone type. 2. Press [F6] to select 2 CURVE for the FM+environmental response. 3. Adjust the signal level to 80 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 4. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the second curve memory and will be displayed on the screen labeled as 2. If the first curve is not also on the screen, there is a greater than 50 db difference between the two curves and the display cannot show both at once. 5. This second curve will be referred to as the Electroacoustic FM & Environmental Response or EFE80. 6. Compare the Curve #1, EHA65, and #2, EFE80, 2 to confirm that the desired FM advantage is maintained over the 500 to 2000 Hz range. As shown in Figure 13, Curve 2 (EFE80) is about 10 db higher than Curve 1 (EHA65). Further adjustments may be made if necessary. Figure 13 3.3.2.6 Now test with the FM system using a low level input signal delivered to the environmental microphone 1. Set up equipment as described in Section 1.3 in this guide so that the environmental microphone is in the test box or close to the speaker (Figure 9). Section 3: Recommended Fitting Protocol and Test Signals 21
2. Press [F6] to select 3 CURVE to now be used for the ENV+ FM response when the environmental microphone is receiving the input. 3. Adjust the signal level to 65 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 4. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the third curve memory. This third curve will be referred to as the Electroacoustic Environmental and FM Response or EEF65. 5. Compare the EHA65 (Curve 1), EFE80 (Curve 2), and EEF65 (Curve 3). For a successful fit, the EHA65 and the EEF65 should be similar and the EFE80 should be 7-10 db higher, as shown in Figure 14. Figure 14 3.3.2.7 Now test the hearing aid with a high-level input signal Follow steps for Situation A in 3.3.1.4. 3.3.2.8 Now test with the FM system using a high-level input signal Follow steps for Situation A in 3.3.1.5. 3.4 Step two real ear verification 3.4.1 Situation A: real ear verification for mild to moderately-severe loss (<80 db HL) or use of FM only signal option 22 Testing FM Systems with FONIX FP40 Analyzers
3.4.1.1 Equipment setup 1. Follow procedures listed in 3.3.1.1 of this guide to set the source to Composite and Multicurve to 1 Curve. 2. Select PROBE by pressing the [F7] key. 3.4.1.2 First test the hearing aid alone with low-level input 1. Set up the probe mic system as described in Chapter 7 in the FP40 Operator s Manual for testing real ear response. 2. Level the system according to instructions in Chapter 7 in the FP40 Operator s Manual. 3. Adjust the signal level to 65 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 4. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the first curve memory. 5. This will be referred to as the Real Ear Hearing Aid Response or RHA65. 3.4.1.3 Next test with the FM system using a low-level input signal 1. Set up the FM system according to Section 2.1 of this guide. 2. Press [F6] to select 2 CURVE for the FM response. 3. Adjust the signal level to 80 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 4. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the second curve memory. 5. This will be referred to as the Real Ear FM Response or RFM80. 6. Compare the Curve #1, RHA65, and #2, RFM80. If the aid and FM have been matched electroacoustically, these two curves should be very similar, as shown in Figure 15. If not, adjust the FM volume control if necessary to obtain a better match. As a last resort, adjust the settings on the hearing aid. If this must be done, the teacher, parents, and therapists must be made aware that when the FM system is used, the settings on the hearing aid must be changed for optimum performance. Section 3: Recommended Fitting Protocol and Test Signals 23
Figure 15 3.4.1.4 Now test the hearing aid with high-level input Follow procedures suggested in 3.3.1.4 except the response will be referred to as Real Ear Hearing Aid Saturation Response or RHA90. 3.4.1.5 Now test with the FM system with a high-level input signal Follow procedures suggested in 3.3.1.5 except the response will be referred to as Real Ear FM Saturation Response or RFM90. 3.4.2 Situation B: Real ear verification for severe to profound hearing loss (>80 db HL) or use of FM + ENV signal option 3.4.2.1 Equipment setup 1. Follow procedures listed in 3.3.2.1 of this guide to set the source to Tone and the Multicurve to 1 Curve. 2. Select PROBE by pressing the [F7] key. 3.4.2.2 First test the hearing aid using a low-level input signal 1. Set up the hearing aid for real ear testing in the usual way (refer to Chapter 7 of the Operator s Manual). 2. Adjust the signal level to 65 db SPL by turning the left large dial and noting the corresponding source intensity in the lower right-hand status box. 3. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. Note the HEARING AID OUTPUT shown in the lower right-hand status box. 24 Testing FM Systems with FONIX FP40 Analyzers
3.4.2.3 Next test with the FM system using a low-level input signal delivered to the FM microphone 1. Set up the FM system following the instructions in Sections 1.1 and 1.2 of this guide. Set FM to receive the FM and the ENV signals. 2. Leave the signal level to 65 db SPL or adjust to that by turning the left large dial and noting the corresponding source intensity shown in the lower right-hand status box. 3. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. Note the FM OUTPUT signal level shown in the lower right-hand status box. Adjust the FM receiver volume control so that the hearing aid and FM OUTPUTS are matched. Now the GAIN of the hearing aid and of the FM system have been matched. 3.4.2.4 Next test with the FM system and a typical input level to verify increase in signal level 1. Increase the signal level to 80 db SPL by turning the left large dial and noting the corresponding source intensity shown in the lower right-hand status box. 2. Note the output from the FM receiver in the lower right-hand status box. 3. Compare the output from the hearing aid and the FM system and adjust the FM receiver volume control if necessary according to the following: If the increase is: 10 db, no further adjustments are needed. 15 db, reduce the FM receiver volume control so that the output in the 2cc coupler falls by 5 db. 5 db, increase the FM receiver volume control so that the output in the 2cc coupler increased by 7 or 8 db. 0 db, the FM transmitter may have very low compression threshold, so increase the FM receiver volume control to provide a 5 db increase in output. 3.4.2.5 Compare the full response curves from hearing aid and FM system Hearing Aid 1. Select the signal source as complex if possible, otherwise use sweep-frequency pure tones and press [F6] to select 1 Curve. 2. Set up the hearing aid for real ear testing in the usual way (refer to Chapter 7 of the Operator s Manual.) 3. Adjust the signal level to 65 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. Section 3: Recommended Fitting Protocol and Test Signals 25
4. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the first curve memory. 5. This will be referred to as the Real Ear Hearing Aid Response or RHA65. FM System 1. Set up the FM system following the instructions in Sections 2.1 of this guide. Be sure FM system is set to receive the FM and the environmental signals. 2. Press [F6] to select 2 CURVE for the FM+environmental response. 3. Adjust the signal level to 80 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 4. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the second curve memory and will be displayed on the screen labeled as 2. If the first curve is not also on the screen, there is a greater than 50 db difference between the two curves and the display cannot show both at once. 5. This second curve will be referred to as the Real Ear FM & Environmental Response or RFE80. 6. Compare the Curve #1, RHA65, and #2, RFE80, 2 to confirm that the desired FM advantage is maintained over the 500 to 2000 Hz range, as shown in Figure 16. Further adjustments may be made if necessary. Figure 16 3.4.2.6 Now test with the FM system using a low-level input signal when the input is delivered to the ENV microphone 1. Set up the equipment as described in Section 2.2 of this guide for real ear testing of environmental microphones. 2. Press [F6] to select 3 CURVE to now be used for the ENV+ FM response when the environmental microphone is receiving the input. 26 Testing FM Systems with FONIX FP40 Analyzers
3. Adjust the signal level to 65 db SPL by turning the left large dial and noting the corresponding intensity at the bottom of the STATUS window. 4. Press [START/STOP] to start the signal and press it again to stop the signal once a stable response is observed. The response is now stored in the third curve memory. This third curve will be referred to as the Real Ear Environmental and FM Response or REF65. 5. Compare the RHA65 (Curve 1), RFE80 (Curve 2), and REF65 (Curve 3). For a successful fit, the RHA65 and the REF65 should be similar and the RFE80 should be 7-10 db higher, as shown in Figure 17. Figure 17 3.4.2.7 Now test the hearing aid with high-level input Follow procedures suggested in 3.3.1.4 except the response will be referred to as Real Ear Hearing Aid Saturation Response or RHA90. 3.4.2.8 Now test the FM system with high-level input Follow procedures suggested in 3.3.1.5 except the response will be referred to as Real Ear FM Saturation Response or RFM90. Section 3: Recommended Fitting Protocol and Test Signals 27
Glossary: Electroacoustic Measures EHA65 EFM80 EHA90 EFM90 EFE80 EEF65 Electroacoustic Hearing Aid Response Electroacoustic FM Response Electroacoustic Hearing Aid Saturation Response Electroacoustic FM Saturation Response Electroacoustic FM and Environmental Response with input to the FM microphone Electroacoustic Environmental and FM Response with input to the Environmental microphone Real Ear Measures RHA65 RFM80 RHA90 RFM90 RFE80 REF65 Real Ear Hearing Aid Response Real Ear FM Response Real Ear Hearing Aid Saturation Response Real Ear Saturation Response Rear Ear FM and Environmental Response Real Ear and Envrionmental and FM Response 28 Testing FM Systems with FONIX FP40 Analyzers
Acknowledgments and References Frye Electronics, Inc. gratefully acknowledges the personal assistance of Dawna Lewis and Pat Stelmachowicz of the Boys Town National Research Hospital, Richard Seewald, Shane Moodie, and Sheila Sinclair of the University of Western Ontario, and Cynthia Compton of Gallaudet University. The procedures given in this guide do not necessarily reflect the recommendations of these audiologists; Frye Electronics, Inc. is solely responsible for the contents of this guide. Frye Electronics, Inc. also thanks Telex, Comtek, and Phonic Ear for providing the equipment used in developing this guide. This guide was revised in August, 2000 with considerable assistance from Dr. Linda Thibodeau of the Advanced Hearing Research Center, University of Texas at Dallas. For further study of methods and procedures for testing FM systems and auditory trainers, the reader is referred to the following resources: American Speech-Language-Hearing Association. (1999, In Press) Guidelines for Fitting and Monitoring FM Systems. Cornelisse LE, Gagné J-P, and Seewald RC. Long-term average speech spectrum at the chestlevel microphone location. Journal of Speech Language Pathology and Audiology (Canada), Vol. 15., No. 3, pp. 7-12, 1991. Lewis DE. FM systems and assistive devices: selection and evaluation. In Pediatric Amplification, Proceedings of the 1991 National Conference, J. Feigin and P. Stelmachowicz (eds.), Boys Town National Research Hospital, Omaha, NE, 1991. Lewis DE, Feigin JA, Karasek A, and Stelmachowicz PG. Evaluation and assessment of FM systems. Ear and Hearing, 12, pp. 268-280, 1991. Seewald RC and Moodie KS. Electroacoustic considerations. In FM Auditory Training Systems, M. Ross (ed.), Chapter 4, York Press,Timonium, MD, 1992. Section 3: Recommended Fitting Protocol and Test Signals 29