Chapter Setting the Hearing Aid Response and Verifying Signal Processing and Features in the Test Box

Authors: Catherine Palmer, Lori Zitelli

Abstract

The test box can be used for fitting hearing aids (verifying audibility for the individual), for setting and fine-tuning specific signal processing (e.g., directional microphones, noise reduction, frequency lowering, telecoil responses), and for setting the response for specific accessories (e.g., remote microphones). If you have selected these features for your patient, it is important to make sure they are working properly and turned on. In addition, these tests can help you address specific patient complaints. Let us start by using the test box to pre-set a hearing aid and then we will move on to speech tests of signal processing and features.

How Can I Pre-set This Hearing Aid for a Patient Who Won't Be Able to Sit Through or Isn't Available for Probe Microphone Real-Ear Aided Response Measures?

Speechmapping in the Text Box

When you complete Speechmapping in the test box, you are simulating the response that would be expected in the individual's ear canal if you account for the difference between the coupler and the patient's real ear. “Speechmapping” is Audioscan's proprietary word for measuring hearing aid output in either the real ear (real-ear aided response [REAR]) or the test box. Test box measurements are often used with young children who cannot sit still for repeated real-ear probe microphone measures while the hearing aids are adjusted, and the fitting is verified. Speechmapping in test box mode can be used for any hearing aid fitting where we cannot conduct the REAR measures. To truly simulate the real-ear fitting in the test box, we need the real-ear to coupler difference (RECD) which is described in more detail below. These data allow us to account for the individual's ear canal characteristics (difference from the coupler which represents an average individual) in the hearing aid fitting without having the individual present. If you pre-set the hearing aid in the test box without having RECD, then you are verifying the fitting based on an average ear and your gain and output may not be appropriate for the specific individual you are fitting.

By using Speechmapping in test box mode, you can spend your appointment time with the child and family on the important topics of use, care, et cetera, rather than struggling with trying to have the child sit still during REAR measurements. Correct use of test box Speechmapping (including RECD) saves appointment time, assures that the output of the hearing aid is correct for the individual (child or adult), and that hearing will not be damaged to a greater degree due to overamplification. If this method is not used, it is necessary to perform REAR measures with the hearing aids in the patient's ears. Note, RECD is still necessary when using REAR measures because this measurement produces the data that allow conversion of the dB hearing level (HL) data from the traditional audiogram to dB sound pressure level (SPL) data that are needed to calculate your hearing aid fitting targets. Without RECD, the HL to SPL conversion is done with average ear data (average, white, male adult) and again, your fitting will not be individualized to the patient with whom you are working.

Real-Ear to Coupler Difference Tutorial

We hope you will take a few minutes to read this RECD tutorial. RECD is perhaps the most powerful data we collect to individualize hearing aid fittings. This is one key element that the audiologist brings to the table, creating a customized hearing aid fitting that ensures audibility is returned to the individual based on their hearing and ear canal characteristics. Please feel free to share this section broadly to try to support evidence-based hearing aid fittings for our patients.

We can think about measuring real-ear to coupler difference (RECD) for two purposes. The first purpose applies to both adult and pediatric patients. The second applies to pediatric patients.

• A decibel (dB) HL audiogram is used to record an individual's hearing thresholds across frequency. dB HL is not a measurement of actual sound, it is a mathematical correction to make the softest sound a human can hear across frequencies “0” on the scale. In Figure 1 , you can see the minimum threshold for sound across frequencies (for humans) as measured in dB SPL. This is referred to as the minimum audibility curve. As audiology started, it was determined that different dB levels at different frequencies would be confusing (i.e., it might look like there was hearing loss in the low and high frequencies); so, a graph was wanted where all the minimum thresholds were “0 dB.” For example, at 1,000 Hz the threshold for normal hearing in humans is 7 dB SPL (see Figure 1 ); so, we would subtract 7 and get 0 dB HL, and so forth for all the frequencies, applying the appropriate correction at each frequency.
• For children who cannot tolerate sitting through REAR measures (measuring the output for soft, moderate, and loud inputs across frequency multiple times in the real ear as we program the hearing aids to meet targets), RECD allows us to do the entire fitting in the test box. Importantly, the output targets are being corrected with RECD and the output measurements are being corrected based on our patients' ear canal characteristics as well. Therefore, the test box is “simulating” the real ear response because we are applying the individual's RECD to the output measures. This helps us simulate the output that would be expected to build up in our patient's ear. The RECD gives us this dB SPL correction so the output measured in the coupler can be corrected with these data and displayed correctly relative to the expected output in that child's ear. This lets us see what we would expect at this child's eardrum in terms of output in dB SPL without needing a probe microphone and hearing aid in the child's ear at the time of programming.

Adults typically can sit through REAR measures; so, this second reason is not relevant for most adult patients. With the probe microphone in the individual's ear, we are measuring the actual output that is being achieved near the eardrum. This will now be compared to the targets for soft, moderate, and loud sounds across frequencies. These targets will be accurate if the individual's RECD was used to convert HL to SPL (targets are derived from the SPL data). If you are working with an adult who cannot be present or cannot remain still for these measurements, then you can use this same process to pre-program the hearing aid for the adult.

Materials Needed for this Activity

For these activities, you will need a hearing aid test box, hearing aid.

Activity 1

For students, this activity can be completed by simply measuring an existing, pre-programmed hearing aid and the person completing the activity can use the data to evaluate what changes would need to be made in the programming to achieve the desired results (matching the targets). If your instructor wants you to connect the hearing aid to the manufacturer's software, they will provide these instructions.

Alternatively, for clinicians, the hearing aid in this activity can be connected to the manufacturer's software and changes can be made to achieve the desired fitting. The instructions below assume you are working with a hearing aid that has been pre-set and that you are not using the manufacturer's software in this exercise.

• Set up the equipment following the instruction in Chapter 1.
• Connect the hearing aid to the appropriate coupler and place it in the test box (follow instructions in Chapter 1).
• If the hearing aid has a volume control, it should be placed at user setting (if known) or half on. For most pediatric patients, the volume control will not be enabled.
• Right-click the mouse and select Speechmap under test box. While in single view, at the top right of the screen select the instrument (BTE + mold, ITE, CIC, etc.). Test box mode indicates that you are simulating the response of the hearing aid in the ear, but that the hearing aid is not actually in the ear. This simulation is accurate only if you have chosen the actual style of instrument that will be used, entered the individual's audiogram, and entered RECD data (in order to enter the data, it needs to have been measured in a previous appointment). Select the appropriate mold/dome option and vent selections below the instrument menu.
• Continue down the right side of the screen and select Audiometry . Select the appropriate options (e.g., targets, age, HL transducer, RECD, and RECD coupling) as they apply to the patient ( Figure 2 ).
• Select the green check mark and enter ear-specific thresholds ( Figure 3 ) and then the green check mark again.
• Select 0.4-cc Wideband RECD (WRECD) ( Figure 4 ) because this is the coupler you will use for this measurement. The 0.4-cc (silver) coupler allows for wideband measurements extending to 16,000 Hz, while the 2-cc (blue) couplers allow for comparisons between other data obtained with 2-cc couplers. Keep in mind that you can calculate equivalent RECD if you measure WRECD (see Chapter 4 for more information about this).
• Enter the previously measured WRECD ( Figure 5 ). If you had chosen to measure WRECD at this time, the equipment would prompt you to do this measurement.
• The patient's HL thresholds have been entered and you have entered the patient's WRECD so these thresholds can be accurately converted to SPL thresholds (the equipment does this conversion for you). You will now be looking at the individual's audiogram in SPL and these data will be used to generate evidence-based targets for you. These targets provide you with the goal for the output across frequency and across input levels. Output of the hearing aid should be measured for inputs of soft, moderate, and loud speech, and maximum power output (MPO). Just because the output of a hearing aid is matching targets at one input level does not mean that it necessarily is set correctly for all the other input levels. These output curves are modified by the RECD values so the results simulate the output levels that would be expected in this person's ear canal.
• Click the green arrow to select the input stimulus type and input level to measure. In the case of Figure 6 , we have selected a standard speech passage (“carrot passage”) delivered at a level of 50-dB SPL.
• You have already selected the target type (refer to Figure 2 ). Targets will appear on the screen. Press the red circle to record the measurement.
• When looking at the graph, compare the solid line (measured output of the hearing aid) to the targets for the chosen speech signal at the chosen level ( Figures 6 and 7 ). Note: Your output responses will look different from Figure 6 because you are using a different hearing aid.

• 13. If the output responses do not match the targets, you would make appropriate programming changes to the hearing aid(s) until output matches targets within ± 3 to 5 dB.
• 14. Repeat steps 10 to 12 until hearing aid(s) are set appropriately for the patient's hearing loss.

**Materials needed for this ** For these activities, you will need a hearing aid test box, hearing aid.

Activity 2

• Set up the equipment following in the instructions in Chapter 1.
• Connect a hearing aid in the text box according to instructions from Chapter 1.
• Refer to the steps above to conduct the simulated test box measurements (test box Speechmapping).
• Enter the audiogram and WRECD data provided in Figure 9 and Table 1 into the hearing aid measurement system to create simulated targets for a 6-year-old child. Run curves with a soft, moderate, loud, and MPO input signals. Use Table 2 to comment on how well the measured hearing aid response matches the targets (+ means you need more gain, − means you need less gain, = means the setting is correct which is evidenced by the measured output matching the targets with ± 3 to 5 dB).

You are now equipped to pre-set a hearing aid in the test box for any patient who will not tolerate the time to complete REAR measures. This is a powerful tool that supports our pediatric patients as well as our adult patients who may have unique circumstances. The key to these measures is the use of individual WRECD measures that allow us to know what output will be expected in the individual's ear canal even though we are completing the measurements in the test box.

How Do I Know the Telecoil Is Working Correctly?

Introduction

The telecoil (t-coil) for use in hearing aids was invented by Samuel Lybarger, who was the owner of RadioEar in Pittsburgh, PA. Mr. Lybarger worked on hearing aid technology in response to his father being unable to hear the radio; thus, the name of the RadioEar. He worked on telecoil technology for hearing aids to make the telephone accessible for his father and the many other people with hearing loss whom he served. 2024 marks the 100th anniversary of Mr. Lybarger's start in producing hearing aid technology and promoting individual hearing aid fitting using fitting formulae. Although Samuel Lybarger is no longer with us, his legacy of helping individuals participate fully in life's activities lives on as we see expandable use of the telecoil technology in large area listening environments. Samuel Lybarger's son, Ed Lybarger, has donated his father's papers to the University of Pittsburgh, where they can be viewed and used for historical research. The American Academy of Audiology has an award named after Samuel Lybarger to celebrate other innovators.

The telecoil setting works only for phones that are designated as “hearing aid compatible.” Historically, this included landline phones. Since January 2007, the Federal Communications Commission (FCC) has dictated that at least five models of phones for each cell phone manufacturer must be t-coil compatible. For the telecoil feature to work, the user must “switch” into the telecoil setting and the phone must interact with the telecoil circuit inside the hearing aid. To engage this while on the phone, the patient must hold the telephone over the hearing aid (up above the ear in the case of BTE hearing aids). The hearing aid user will need to move the phone around their ear (for BTEs, over their ear where the hearing aid is) to find the best reception.

Many hearing aid users now find success using cell phones with the sound from the cell phone being streamed via Bluetooth (or Bluetooth low energy [LE]) directly to the hearing aids. This produces a good, bilateral signal and reduces feedback since the phone no longer needs to be held up to the ear. Because of more advanced feedback reduction systems, many hearing aid users also can hold a cell phone or landline phone to the ear/hearing aid without producing feedback. The hearing aid user will want to position the output of the phone near the microphone of the hearing aid. In the case of BTE hearing aids, this means holding the phone up toward the top of the ear where the hearing aid microphone is located. This eliminates the need to switch the hearing aid into telecoil mode, which can support easier phone use.

Currently, the most common use of the telecoil hearing aid program is to pick up an electromagnetic signal being transmitted by a large area system (e.g., in a symphony hall, house of worship, or other community space). In these cases, a microphone picks up the signal of interest (e.g., the speaker) and this signal is transmitted to a “loop” system. This includes an amplifier that conducts the electromagnetic signal through a wire that is literally “looped” around the room (often under the carpet or flooring). Now when a hearing aid user with a telecoil program stands within this looped area and engages their telecoil program, the signal of interest will be delivered directly to the hearing aids, improving the signal-to-noise ratio and enhancing the listening experience.

For success in these situations, the hearing aid telecoil program must be set appropriately and the hearing aid user needs to be able to engage the telecoil program (e.g., pushing a button on their hearing aid or selecting the program in the hearing aid manufacturer app on their phone).

If the telecoil is a feature you have ordered on the hearing aid, you should verify that it is working appropriately before dispensing the hearing aid. Now that you are familiar with the telecoil, let us measure the telecoil response for use with a phone and a large room system.

Patient Report: “Sounds Are Too Quiet When I Am Listening to the Phone Through My Telecoil Program”

Materials Needed for this Activity

For these activities, you will need a hearing aid test box, hearing aid with a standard listening program and a separate telecoil program, tele-test handset. For students, it may be easiest to use an older hearing aid that has an actual switch on it that goes from the “microphone” setting to the “telecoil” setting, so the student is sure they are in the correct setting when measuring. Otherwise, make sure to provide directions to the student as to how to engage the telecoil setting.

Activity 3

*Materials needed for this * .

• Set up the equipment following the instructions in Chapter 1.
• Complete an ANSI test (see Chapter 2 for instructions). Assuming the hearing aid is fit correctly, the output of the hearing aid in the telecoil setting should match the output of the hearing aid in the microphone setting. The output response for the microphone setting (assuming you have programmed and verified the hearing aid fitting) is your gold standard. You are trying to match the telecoil output to this target. Figure 10 provides an example result of an ANSI test.
• Right-click the mouse and select Telecoil .
• Set the hearing aid to “T” (telecoil input).
• Click Start TMFS test . Test setup instructions provided by Audioscan are displayed in Figure 11 .
• Plug the cable from the tele-test handset into the green port on the probe dock. Position the aid on the “T” on the tele-test handset (see Figure 12 ). BTE aids should lie as flat as possible on the tele-test surface, while custom aids should be oriented with their faceplate parallel to the top surface (if possible) and touching it as shown ( Figure 11 ).
• Press the green check mark to start the test.
• While maintaining the orientation of step 5, move the hearing instrument around on the tele-test handset surface to maximize the number shown in the Maximize Average-SPLITS Value box ( Figure 13 ).
• Without moving the hearing instrument, press the green check mark to store the average HFA SPLITS value and run the SPLITS curve.
• If a RTG has been previously obtained (you did this when you ran the ANSI curve), the relative simulated equivalent telephone sensitivity (RSETS) will be shown ( Figure 14 ). A negative value means the output of the hearing aid while in telecoil is less than the hearing aid response from the ANSI test. You want the numbers to be as close as possible. In Figure 14 , the numbers are identical and therefore RSETS is 0.

If the individual is using only the telecoil with the telephone, you can interpret these results now and make changes to the hearing aid telecoil programming as needed. If your patient is using the telecoil for the phone and for room listening, continue with the instructions below to measure function in a room setting. You will then have results for both conditions and can make changes in the hearing aid telecoil programming to try to optimize the response for both uses.

Patient Report: “When I Use My Telecoil in My Synagogue, the Rabbi Sounds Are Very Quiet”

Materials Needed for this Activity

For these activities, you will need a hearing aid test box, hearing aid with a standard listening program and a separate telecoil program. For students, it may be easiest to use an older hearing aid that has an actual switch on it that goes from the “microphone” setting to the “telecoil” setting, so the student is sure they are in the correct setting when measuring. Otherwise, make sure to provide directions to the student as to how to engage the telecoil setting.

Activity 4

• Repeat steps 1 to 3 above ( Figure 10 shows the ANSI test that provides the target for the telecoil response).
• Click Start test loop test. Setup instructions from Audioscan are displayed in Figure 15 .
• Position the hearing instrument on the cross in the test box, vertically oriented as worn by a standing or seated individual ( Figure 16 ).
• Without moving the hearing instrument, press the green check mark to run the SPL in a vertical magnetic field (SPLIV) curve. If RTG has been previously obtained (you did this when you ran the ANSI curve), the relative test loop sensitivity (RTLS) will be shown ( Figure 17 ).

In the example provided, the RSETS of the hearing aid telecoil is 0 ( Figure 14 ) and the RTLS of the hearing aid is −0.5 ( Figure 17 ). This means that when the patient is talking on the telephone, the response of the hearing aid in the telecoil setting is identical to the response in the microphone setting. With these results, you would not need to increase the gain of the telecoil (given that the hearing aid has a programmable telecoil). When the patient is listening in a looped room, the RTLS of the hearing aid telecoil is −0.5. This is only slightly softer than the desired output. If possible, you would want to increase the gain by 0.5 to match the original output in the microphone setting. In many modern hearing aids, you can alter the programming for the telecoil for phone use and the telecoil for room use independently. In the case in this example, that is what you would like to do given that you need no change in one condition (phone) and a very slight change in the other condition (room loop).

Materials Needed for this Activity

For these activities, you will need a hearing aid test box, hearing aid with a standard listening program and a separate telecoil program, tele-test handset. For students, it may be easiest to use an older hearing aid that has an actual switch on it that goes from the “microphone” setting to the “telecoil” setting, so the student is sure they are in the correct setting when measuring. Otherwise, make sure to provide directions to the student as to how to engage the telecoil setting.

Activity 5

• Repeat the procedures in Activity 3 and Activity 4 to obtain your measures.

• What is this measurement telling you?

• RTS—What would you do to the telecoil gain to achieve the perfect response for phone use?

• 4. RTLS—What would you do to the telecoil gain to achieve the perfect response for looped room use?
• 5. If the telecoil is not programmable, what is another option for increasing the gain?

How Do I Know If the Directional Microphones Are Working Correctly?

Introduction

Most modern hearing aids have directional microphones, typically meaning that the microphone response to sounds coming from in front of the individual will be more sensitive than the response to sounds coming from behind the individual. Although directional microphone technology and algorithms are more and more sophisticated, at the end of the day, the primary information the hearing aid is using to understand listener intent is the direction that the microphones are facing (i.e., the direction the listener is facing).

If directionality is important to your fitting, you will want to test this feature. Or, if your patient is not perceiving a benefit in the directional setting, this feature can be tested to make sure it is working. Directional microphones can be faulty, and microphones can be damaged over time, so this can be a valuable test.

In the directional microphone test in the test box, a broadband test signal is presented simultaneously from the left and right speakers. The measured coupler SPL from the hearing aid is analyzed into two separate response curves, L (left) and R (right). The L and R response curves indicate which speaker generated the curve. The sensitivity of the front and back hearing aid microphones while the hearing aid is in the directional setting is being measured. The goal is for a lower (less intense) response to be generated from behind the listener when the directional microphones are engaged. If the listener can situate themselves where noise in the room is primarily behind them and the signal of interest is in front of them, this technology can be very helpful. Unfortunately, most noisy rooms are also reverberant, so it is hard to isolate noise only to the back of a listener. Even if this technology can only help in limited circumstances, it can be very helpful when the listening situation is right. Therefore, it is important that the directional microphones are doing what they are expected to do. In modern hearing aids, the hearing aid automatically moves from different “levels” of directionality (e.g., omnidirectional setting, adaptive directional setting) depending on the input to the hearing aid. The clinician also can make specific programs where the hearing aid is always in omnidirectional mode or a specific directional mode. Many clinicians will set a hearing aid to omnidirectional only for pediatric patients, so the young listener is hearing sound from all around them, potentially supporting incidental learning.

Let us make measurements of a hearing aid with directional microphones and interpret the data.

Patient Report: “You Told Me About the Advantage of Directional Microphones, but I'm Not Noticing a Benefit”

Materials Needed for this Activity

For these activities, you will need a hearing aid test box, hearing aid with a directional microphone setting.

Activity 6

• Set up the equipment following instructions from Chapter 1.
• Couple the hearing aid(s) to the appropriate coupler ( Figure 18 ).
• Position the hearing aid(s) in the test chamber as shown in Figure 18 .
• Right-click the mouse and select Directional under test box.
• Select Test 1 by pressing the associated green arrow . Test signals are presented from the front speaker and the back speaker.
• Select a level (ranging from 50 to 80 dB) from the Level drop-down list. You need a loud enough level to engage the directionality of a hearing aid that is set to automatic/adaptive directionality (this means the aid comes in and out of the directional setting depending on the sound it receives). For an automatic/adaptive directional instrument, a stimulus level above 60 dB should engage the directional microphone. For a hearing aid with directional microphones and noise reduction engaged, both curves (front and back) may change with time and stimulus SPL because of the effect of noise reduction. It is critical that you know you have activated the directional microphone to interpret your data. The safest way to do this is to go into the hearing aid software and move the directional setting from automatic/adaptive (meaning the setting changes depending on input and could be in the omnidirectional mode during your test) to fixed directionality during the test. Fixed directional means the microphones are always in the directional setting. In this way, you are sure that you are testing the directional setting. Remember to change the program setting back to automatic/adaptive directional when you are done testing.
• Select the Speech S/N (signal-to-noise ratio, ranging from “off” to 12 dB). A ratio between 0 and 6 dB will usually result in the device(s) switching to an automatic directional mode after 15 to 45 seconds, if they are programmed to be adaptive ( Figure 19 ).
• Click the red circle to capture the measurement.
• In Figure 20 , the hearing aids were in a fixed omnidirectional setting. Here, the two curves are fairly close to one another, which is expected. Figure 21 shows hearing aids in a fixed directional setting with a wider beam. In this situation, the sensitivity of the microphone to sound coming from the back (the thin line) is less (lower on the graph) than the front signal (heavier line). In other words, the hearing aid picks up less sound from the back than from the front. This contrast is even larger in Figure 22 , where the hearing aids are programmed in a narrow fixed directional setting. There is a more pronounced difference in the audibility of sound coming from the front versus the back.
• If the directional feature is functioning properly, the output labeled “back” (the thin line) will be 3 dB or more lower than the output labeled “front” (the heavier line). In the example in Figures 21 and 22 , the directional microphones are working correctly. If the two lines were closer together, the clinician might try using a more aggressive directional microphone setting if it was available in the hearing aid fitting software (then retest) or the hearing aid could be sent for repair if there is a concern that the microphones are not functioning properly. It would be wise to include a printout of the results to illustrate the problem.

**Materials needed for this ** For these activities, you will need a hearing aid test box, hearing aid with a directional microphone setting.

Activity 7

• Follow steps 1 to 8 from Activity 6 to collect measurements on a hearing aid set to an omnidirectional response and a hearing aid set to a directional response.
• Is the omnidirectional setting working correctly? Yes/No.
• How did you reach this conclusion?
• Is the directional setting working correctly? Yes/No.
• How did you reach this conclusion?
• If the directional setting is not adequate, what would you do to remedy this problem?

How Do I Know if the Frequency Lowering Feature Is Working Correctly? My Patient Has So Much Hearing Loss in the High Frequencies that I Can't Return Audibility with Traditional Signal Processing

Introduction

Frequency shifting may be used when it is not possible to amplify the high-frequency components of speech sufficiently to raise them above threshold. In this case, the high-frequency components may be shifted to a lower frequency with a better hearing threshold where the available gain will render them audible. To measure the effect of frequency shifting, a set of special test stimuli is used. Additional stimuli can be added to your Speechmapping menu by selecting the “add/remove” option at the bottom of the list of test stimuli ( Figure 23 ).

These stimuli are filtered in such a way that most other frequencies outside of a 1/3 octave band around the frequency in their name are reduced. Using these signals, the acoustic impact of frequency shifting can be measured.

Frequency lowering can be engaged within the hearing aid programming software. Some manufacturers set frequency lowering as a default depending on the degree of hearing loss your patient has in the higher frequencies. You always want to check the defaults in your manufacturer's software, so you are sure of what is happening in the programming.

Using frequency shifting implies that we are trying to make inaudible high-frequency sounds audible by shifting them to a lower frequency range where the patient has aidable hearing. You will always make sure you have made sound audible where possible without frequency lowering, but if you cannot return needed sounds, frequency lowering may be worth trying. If you are engaging this feature, like any other signal processing, you need to verify that it has returned audibility in the manner you planned. By definition, any type of frequency shifting adds distortion to the signal, but without it some signals will be inaudible. Some patients adapt well to using these new auditory cues and others do not adjust to this type of distortion. If used in young children, they will likely adapt because they will not have another listening experience to which they can compare the sound quality.

Now that you've had an introduction to frequency lowering, let's make some measurements.

Patient Report: “I Still Can't Hear My Phone Ring/Doorbell Ring/Grandchildren's Speech”

**Materials needed for this ** For these activities, you will need a hearing aid test box, one hearing aid with frequency shifting off in program 1 and frequency shifting on in program 2. Alternatively, for students you may want to use two hearing aids (one without frequency shifting engaged and one with frequency shifting engaged, but with everything else identical).

Activity 8

• Set up the equipment following the instructions in Chapter 1.
• Couple the hearing aid to the appropriate coupler (see Chapter 1). Use the hearing aid (or setting) with frequency lowering off for these first measurements.
• Right-click and select Speechmap under Test Box measures.
• Select Audiometry to enter the patient's audiogram ( Figure 24 ) and the patient's WRECD (use the data from Figure 25 and enter it on the screen that matches Figure 26 ). You want accurate SPL hearing threshold data to make judgments about audibility.
• Select the green arrow above Test 1 and choose 65 dB from the level menu.
• Choose Speech5000 (you can repeat this with Speech3150, Speech4000 , or Speech6300 ) from the stimulus menu. Note that only the output is shown for these stimuli. Targets (if selected) will not display. You are looking to see if these frequency regions are audible, so you are comparing the output to the hearing threshold in dB SPL.
• Press the red circle to collect and store the output measure. Figure 27 is an example measurement.
• Now activate the frequency lowering feature (or use the second hearing aid that has frequency lowering engaged).
• Select the green arrow above Test 2 and select the same stimulus and stimulus level used in Test 1.
• Press the record button to collect and store the output measure. Figure 28 is an example measurement.
• If needed (as in Figure 28 ), you would make adjustments to the strength of the frequency lowering feature until the desired changes are evident and the signal reaches audibility ( Figure 29 ).
• If you can change the programming so that the frequency lowering is more aggressive, you might see a graph similar to Figure 29 . The isolated band should now appear at a lower frequency and should reach or exceed threshold at its new location as shown in Figure 29 . In this example, the stimulus at 5,000 Hz has now shifted to about 3,470 Hz and is above threshold.
• Once the frequency-shifting properties of the hearing aid(s) have been verified, use one of the Speech-std stimuli to verify aided speech audibility or target match (as described elsewhere) for frequencies below the isolated band (just as you would in any standard hearing aid verification).

**Materials needed for this ** For these activities, you will need a hearing aid test box, one hearing aid with frequency shifting off in program 1 and frequency shifting on in program 2. Alternatively, for students you may want to use two hearing aids (one without frequency shifting engaged and one with frequency shifting engaged, but with everything else identical).

Activity 9

• Follow the steps in Activity 8 to measure at least one frequency input (e.g., 3,150, 4,000, 5,000, or 6,000 Hz) with frequency lowering off and frequency lowering on. You should have two curves.
• Use the threshold and WRECD from Activity 8 so you can interpret your data.
• Describe the audibility for the frequency you choose in each condition.
• Are you satisfied with the fitting? In other words, did you achieve audibility?

How Do I Know if the Noise Reduction Feature Is Working?

Introduction

Noise reduction is a manufacturer-specific algorithm developed to acoustically analyze the sound coming into the hearing aid and alter the gain/output characteristics of that sound. Noise would be considered any unwanted sound, and this feature intends to reduce perception of noise. What some consider noise may be a wanted sound to another (e.g., speech, music, environmental sounds). At its simplest design, a hearing aid analyzes the sound that is being picked up by the microphones in real time. Sound that is fluctuating is assumed to be speech and sound that is more steady state is assumed to be noise. The hearing aid algorithm will then try to reduce the steady-state noise primarily by lowering gain and it may do this specifically by channel depending on the concentration of frequencies in the sound identified as noise. Of course, the hearing aid cannot know the user's intent or wishes, but this is a reasonable approach if the goal is comfort in noise. Noise reduction is not designed to improve hearing in noise (i.e., understanding) because it is reducing audibility (turning down gain). Some patients like this feature and others feel like sound disappears around them and they find that disconcerting. Most manufacturers have different “levels” of noise reduction (i.e., how aggressive the gain reduction is), but without measuring these settings you cannot know exactly what the hearing aid is doing. The good news is that this feature is easily measured as you are making programming decisions or troubleshooting patient complaints.

Patient Report: “When I Enter a Noisy Room, the Hearing Aids Turn Off. All of the Sound Disappears and Then Slowly Returns”

**Materials needed for this ** For these activities, you will need a hearing aid test box, one hearing aid with different noise reduction settings by virtue of programs or two hearing aids (one with noise reduction off and one with some level of noise reduction on ).

Activity 10

• Set up the equipment following the instructions in Chapter 1.
• Couple the hearing aids to the appropriate coupler (see Chapter 1). Use a hearing aid with noise reduction off for your first measurement.
• Right click and select Noise reduction under the Test box menu.
• Click the green arrow above Test 1 so you can select the input options ( Figure 30 ).
• Choose your selections and press the green arrow to present the stimulus. Given that noise reduction is off, you should not see a change in the curve over time. Click the red circle to capture the curve ( Figure 31 ).

• 6. Now change to the hearing aid setting that has noise reduction turned on (or switch to the hearing aid that has noise reduction activated ).
• 7. Follow steps 4 to 5 again, selecting Test 2 this time to capture the new curve. This curve should change over time because noise reduction is being engaged, so you will want to pause and not click the red circle until the curve settles ( Figures 32 33 34 ).
• 8. For each measurement, you can see how much noise reduction is occurring and you can monitor how much time passed before the feature became activated, reaching the maximum gain reduction.

How Do I Verify that the Amplification the Patient Receives Through the Hearing Aid Coupled to a Remote Microphone Is Correct?

Introduction

A remote microphone allows us to place a microphone right by the sound source of interest (e.g., a talker, the television). Remote microphones are not magic; they are literally just a microphone that is placed strategically. If you put the remote microphone in the middle of a table, it will pick up lots of noise from the table and will not be particularly helpful. A remote microphone is most helpful when it is placed in very close proximity to the sound source of interest, thereby picking up that sound and not extraneous noise. The best way to “explain” how a remote microphone works is to demonstrate it to your patient. They need to understand that, for this technology to work, it must be placed as close to the sound source as possible. For some patients, they cannot imagine asking another person to clip a microphone on to their collar or for a group to pass the microphone around, but once they experience the benefit, they may feel differently. Once family members see the difference it makes in their loved one participating in dinner conversations, they are much more willing to work on passing a microphone and taking turns speaking (which is good practice, anyways!). If the person's chief complaint even after using well-fit hearing aids is hearing in noise, a remote microphone is the best solution (assuming they need to hear one source). If they need to hear multiple sources, the remote microphone will not be useful unless it is passed among speakers. Always remember to counsel your patient about environmental manipulations (e.g., moving away from noise, muting the TV when trying to hear someone speaking in the room, going to a restaurant earlier in the evening when it is less busy) that may improve the signal-to-noise ratio and therefore improve communication.

The input level of speech to the remote microphone if placed properly will be higher than the input level to a hearing aid microphone. This difference is a result of the proximity of the remote microphone to the talker's mouth (usually 6–8 inches if worn on lapel). The goal is to match the output of the hearing aid attached to the remote microphone with an 80-dB input signal to the output of the hearing aid alone with a 60-dB input signal (this is your gold standard if you fit the hearing aid properly).

The procedure below is how you pre-set the remote microphone response. This procedure also could be used for troubleshooting, if a patient says listening through the remote microphone is too loud or too soft. The assumption is that the hearing aid already is set appropriately for this patient. Therefore, the hearing aid response is the gold standard (target response). The clinician will manipulate the remote microphone program (if available in the hearing aid programming software) until the output graph matches the output graph that was produced by the hearing aid alone. Let's verify the output of a hearing aid connected to a remote microphone.

Patient Report: “I Still Can't Hear My Partner Very Well, Even When We Are Using My Remote Microphone”

**Materials needed for this ** For these activities, you will need a hearing aid test box, one hearing aid that is paired to a remote microphone, remote microphone (charged and ready to use).

Activity 11

• Set up the equipment following the instructions in Chapter 1.
• Attach the hearing aid to the coupler in the test box (see Chapter 1 for instructions).
• Right-click mouse and select Multicurve under Test box.
• Using a 60-dB input signal, run the hearing aid on user setting. You will select a different curve when you run the hearing aid receiving input from the remote microphone so you can compare the two curves.
• With the hearing aid attached to the coupler, connect the hearing aid to the remote microphone according to the manufacturer's instructions. Most modern hearing aids connect directly to the remote microphone via a wireless signal (e.g., Bluetooth or some other proprietary signal). This often happens automatically when the remote microphone is powered up near the hearing aid (assuming the two devices previously were paired). Put the hearing aid in the correct setting to be receiving remote microphone input only as opposed to remote microphone and hearing aid microphone simultaneously. If the hearing aid has been set to always have some hearing aid microphone response even when the remote microphone is activated, you will need to go into the manufacturer's software and change this setting for the purpose of this measurement. Remember to go back in and re-set this when you are done measuring.
• Place the hearing aid, coupler, and remote microphone in the test box (see Figure 35 ). Remember, it is the remote microphone that will be picking up the sound that comes out of the test box speakers, not the hearing aid microphone. The hearing aid is connected to the coupler, because this is where the output will be delivered, and the coupler microphone will measure the output.
• Position the remote microphone at the reference microphone in the test box (where a hearing aid generally is placed for testing; see Figure 34 ). The remote microphone picks up the sound and then transmits it to the hearing aid. Make sure the hearing aid and remote microphone are turned on.
• In Multicurve , choose an input level of 80 to 84 dB (make sure this is a separate curve from the hearing aid response curve you already collected). This input is higher than normal conversational speech (50–60 dB) because sound is being picked up closer to the speaker's mouth when the remote microphone is being used.
• Measure the output of the hearing aid with the 80-dB input signal ( Figure 36 ).
• In Figure 36 , Test 1 illustrates the goal (hearing aid response). Test 2 indicates that the remote microphone is not set correctly (output is low). The audiologist made some changes in the programming software for the remote microphone response and then ran Test 3. The response match has improved across the frequency spectrum after programming changes.
• A good rule of thumb is for the outputs to be within 3–5 dB of each other. If the remote microphone response and the output of the hearing aid are not in good agreement, programming can be completed in the software if the remote microphone setting is programmable.

**Materials needed for this ** For these activities, you will need a hearing aid test box, one hearing aid that is paired to a remote microphone, remote microphone (charged and ready to use).

Activity 12

• Complete steps 1 to 8 from Activity 11.
• Assuming the hearing aid is fit correctly, does the remote microphone system provide an appropriate amount of gain?
• If not, what changes could you make to make this a more appropriate remote microphone fitting?

How Do I Know that the Over-the-Counter/Direct-to-Consumer Hearing Aid My Patient Purchased Provides Appropriate Audibility for Them?

Introduction

In 2017, federal legislation was passed requiring the U.S. Food and Drug Administration (FDA) to develop regulations for over-the-counter (OTC) hearing aids. 5 Provisions include a pathway for self-care (no need to see a professional for hearing testing and/or hearing aid fitting), and specific criteria, features, limitations for the devices. The FDA released their guidelines in October 2022. 6 Keep in mind that for a manufacturer to label a device an “OTC hearing aid,” the device must meet the FDA guidelines for these devices. The FDA now differentiates the hearing aids that an audiologist purchases and fits as a prescription hearing aid versus a device that is labeled an “OTC hearing aid” which can be obtained directly by the consumer. There have always been direct-to-consumer (DTC) amplifiers including personal sound amplifier products (PSAPs) and hearables (i.e., Bluetooth headsets that stream sound from an MP3, phone, and TV and provides amplification if desired). Given your access to the test box and real-ear probe microphone measures, you can measure any of these sound-producing devices and compare their output to your patient's thresholds and/or to amplification targets. Now that the FDA has published specific specification requirements for OTC hearing aids, Audioscan has added a specific test module to allow you to assess whether one of these devices is meeting specific criteria.

You may have a patient who has purchased an OTC hearing aid directly and is not coming to you for assistance or you may decide to add OTC hearing aids to the options you provide to patients. In either situation, this means the patient has come in to see you. In terms of best practices, we would expect to do a hearing test so that we know the person's actual hearing thresholds (as opposed to their perceived hearing loss) and can use these data to evaluate the audibility of the fitting. If this is an OTC hearing aid that provides adequate “tuning” features, you may be able to assist the patient in retuning the device to better address their hearing needs. Alternatively, you may find that the fitting is inadequate and with your data you will be in a good position to counsel the patient about the amplification solution that will best meet their needs within the constraints of their budget.

The simple answer to the question posed in this section “How do I know that the OTC/DTC hearing aid my patient purchased provides appropriate audibility for them?” is that you would approach this the same way you would approach verifying a prescription hearing aid fitting. You would gather their audiometric data since they've come in to see you, enter this into the real-ear probe microphone system, measure WRECD, and do REAR measures with the devices. In this way you can provide excellent advice to your patient about the pros and cons of the audibility provided by the device. Given that the FDA also has a set of requirements that OTC HAs are meant to meet, Audioscan has created a test module that allows you to assess whether the device is in compliance with these guidelines. This information can support your clinic decision about supplying an OTC HA to patients and evaluating devices a patient may have already purchased directly.

The OTC HA test provides the information needed to assess whether the OTC HA is meeting the guidelines for these devices. You can complete ANSI testing in which your results will be compared to the appropriate ANSI standard for PSAP devices (CTA 2051-2017 7 ) which the FDA has decided to apply to OTC hearing aids as well (this is not the same as ANSI S3.22- 2014, 8 which we discussed in Chapter 2). For the PSAP ANSI test battery, results that meet the FDA OTC final rule criteria are marked with a green checkmark and those that do not are marked with a yellow triangle warning signal ( Figure 37 ). The maximum output for OTC hearing aids that was in the final FDA rule is lower than the allowable maximum output in the ANSI standard for PSAPs. This is accounted for in the OTC hearing aid module, so if you see a green check mark, it means that the maximum output is not greater than the allowable level as suggested by the FDA. This test setup may be a useful tool if your patient is reporting issues with distortion, crackling, excessive noisiness, or other sound quality problems in their OTC device. If your ANSI test results indicate that the device is not meeting the criteria, your patient should contact their device manufacturer to begin the process of a refund or repair. It is very useful that Audioscan has created this specific module so that you are sure you are holding the OTC HA device to the appropriate criteria. It would not be appropriate to use the ANSI standard for prescription hearing aids since that is not the standard the FDA has required of manufacturers of OTC hearing aids.

Using the OTC/DTC test screen, you can also assess audibility of the device relative to DSLv.5 1 or NAL-NL2 2 adult targets (this would be accessed under the tab labeled Audibility Evaluation ). This is using the criteria that OTC hearing aid users are meant to have mild-to-moderate hearing loss. In actuality, the FDA rule states that the prospective user must have “perceived mild-to-moderate” hearing loss but for evaluation purposes, this is interpreted as being actual mild-to-moderate hearing loss. The Audibility Evaluation tab provides the range of output that would be expected if a device was programmed appropriately to hit targets for an individual with mild-to-moderate hearing loss. Although this is interesting, this patient has come into the clinic to see you to get your advice, so you can individualize this device and not use this general estimate. If your patient has come to see you for advice because their non-custom OTC device is not meeting their needs, a comprehensive audiogram is an appropriate next step. This is appropriate, first for diagnostic purposes so that you can assess the degree, configuration, and site of lesion of this hearing loss. Using the patient's audiogram and measured WRECD, you will be able to make customized measurements and provide accurate advice about whether their OTC device is providing the appropriate output for them. If the OTC device has reasonable controls for fine tuning, you may be able to assist your patient in getting a better fitting with the device they own. See Chapter 5 for more details about how to complete WRECD and REAR measurements to assess device output in your patient's ear.

Patient Report: “I Hear a Lot of Static in this Hearing Aid that I Bought at the Drug Store”

**Materials needed for this ** For these activities, you will need a hearing aid test box, OTC-labeled device. Note : If this is not labeled an OTC hearing aid, then you cannot hold it to the standards outlined in this test module. These standards are specific to OTC hearing aids. You can evaluate it against the audibility the person needs following instructions in Chapter 5 to help guide your patient.

Activity 13

• Set up the equipment following the instructions in Chapter 1.
• Attach the OTC hearing aid to the coupler in the test box (see Chapter 1 for instructions). If you are testing a RITE or a slim tube BTE OTC device, couple it to the TRIC adapter. If you are using an earbud-style or custom device, couple it using putty similar to an ITE or ITC coupling.
• Right-click mouse and select OTC/DTC under Test box. Select the appropriate instrument style (e.g., RITE, ITE). Click the tab labeled ANSI/CTA-2051 evaluation .
• Select your stimulus (s peech ISTS can be used to avoid measurement artifacts that are sometimes present with pure tone stimuli) and click the green arrow to start the measurement.
• Results that meet the FDA OTC final rule criteria 5 are marked with a green checkmark and those that do not are marked with a yellow triangle warning signal. Assess your graph for any test results indicating that the criteria were not met. In the example in Figure 38 , all criteria were met; this indicates that the device is functioning within the guidelines. It does not, however, mean that we know the device is providing appropriate audibility. To assess this, we would need the patient's hearing thresholds and WRECD data (see Chapter 5 for more details).

**Materials needed for this ** For these activities, you will need a hearing aid test box, OTC labeled device.

• Complete steps 1 to 4 from Activity 13.
• Assess your results. Do any test results indicate that the device is not meeting the required criteria?
• If the device does not meet criteria, what would you do next?

Conclusion

The hearing aid test box is a powerful tool. If a device makes sound, you can measure the output of the device. You may want to compare this to the hearing of an individual or to some other standard. If you have selected specific signal processing or features based on your patient's needs, you have the responsibility to verify that the signal processing and/or features are working and meeting your treatment goals. The hearing aid test box provides a way to verify that you have accomplished the goals you and your patient have established.