AccuQuest Spotlight: Successful Fittings with Oasis. Fitting Range

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Heather Phelps
5 years ago
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1 AccuQuest Spotlight: Successful Fittings with Oasis When fitting a client with hearing instruments, the experience should be positive for both the client and you, the hearing care professional (HCP). The client expects to walk out of the office with new hearing aids that match their hearing needs and provide a good listening experience. Therefore it is frustrating when the hearing aids do not perform as expected. If the hearing aids do not reach gain targets, it results in an inferior fitting and can potentially prevent the client from taking their new hearing aids home. Oasis offers tools that will help avoid these types of disappointing situations and support a successful fitting. These tools have been present within Oasis for many years, but are worth revisiting. They are designed to make sure that the client receives an appropriate hearing aid for their hearing loss, and that the fitting is optimized to provide the correct amount of gain for each client. In the following sections, we will look at simple actions you can take before you verify and fine-tune the instrument which will streamline the fitting process. These methods will also confirm that you are ordering the most suitable hearing instruments for the client s hearing loss, as well as ways to maximize the available gain and fitting potential. The goal is to maintain your efficiency and to ensure that your clients leave satisfied with their new hearing aids. Fitting Range Accuracy of Fitting Range REM is routine in the fitting process, however, you will not be able to meet targets unless the hearing aid suitably matches the client s hearing loss. Before placing an order, use the Instrument View section in Oasis to check the fitting range of the device, and then further confirm the fitting range by simulating the fitting. These are not new concepts; however, the results will be more accurate when you customize the fitting details for your specific client. Oasis has default settings that, when not adapted, could result in an inaccurate fitting range. The client experience level will default to Novice for new fittings, and the fitting rationale to Fit NL. This information must be changed to match the client. Additionally, the acoustics are prescribed by Oasis, based on the audiogram, but if you plan to use something different, this information must be updated. The acoustics, client experience level, and fitting rationale will all influence the fitting range significantly. Figure 1 and Figure 2 demonstrate the degree to which these settings impact the fitting range based on a new user with a mild to severe sloping hearing loss, fit with a Nano BTE. A comparison is made between a fitting range that uses the defaults and one that uses the client-specific settings.

Figure 1: Fitting range with default settings Figure 1 shows the fitting range that you can expect for a mild to severe hearing loss with the Fit NL fitting rationale, Novice experience level, and

If the default settings are appropriate for your client, and you intend to use these acoustics, then you can confidently order this device as the simulated insertion gain is within the fitting range.

2 Figure 1: Fitting range with default settings Figure 1 shows the fitting range that you can expect for a mild to severe hearing loss with the Fit NL fitting rationale, Novice experience level, and the prescribed acoustics of a standard ear hook, standard #13 tubing, and a large vent ( mm). If the default settings are appropriate for your client, and you intend to use these acoustics, then you can confidently order this device as the simulated insertion gain is within the fitting range. Figure 2 shows the fitting range based on the same hearing loss but with the client-specific settings using the NAL-NL2 fitting rationale, Experienced Non-Linear experience level, and the acoustics of a Thin Tube (1.3 mm) and Bass Double Vent dome. The display now shows that the fitting range cannot meet NAL-NL2 targets. This comparison demonstrates the importance of entering all of the client-specific fitting information when checking the fitting range of a device. The best way to confirm the fitting range, is to simulate the fitting. Once in simulation mode, go to the Amplification screen and change the view to the In Situ SPL view. To access this view, use the drop down named View in the upper left corner of the screen. Click on View > Graph Options > In Situ SPL. The 80 db input is the top curve in this view. It will clearly show whether the curve is outside of the fitting range. Using the In Situ SPL View in combination with the Instrument View will demonstrate whether the gain targets for all inputs are reachable with the selected device and the client-specific settings. When used correctly, these are practical tools to employ before ordering devices.

Threshold of Feedback AccuQuest Technologies recommends checking the influence of the threshold of feedback before performing any verification.

3 Threshold of Feedback AccuQuest Technologies recommends checking the influence of the threshold of feedback before performing any verification. Adaptive feedback cancellation systems do not generally limit the gain of a hearing aid. However, depending on the client s ear and the selected acoustics, you should consider the effect of the threshold of feedback on the amount of available gain. To do this, go to the Feedback Manager screen and look at the relationship between the gain curves and the predicted feedback curve. If the gain curves are in close proximity to the feedback curve, it may indicate that the threshold of feedback is limiting the available gain. An example is given in Figure 3 where the gain is reduced between 3 khz and 4 khz. Figure 3 shows the threshold of feedback curve touching the 50 db gain curve at 3kHz and 4 khz, resulting in reduced gain. There are three immediate options to remedy this problem: measuring the threshold of feedback, adjusting the feedback risk and adjusting the acoustics. When you suspect that the predicted feedback curve is limiting the available gain, as in Figure 3, measure the threshold of feedback as it may actually be higher than the predicted curve and the gain limitation could be resolved. Conversely, if the measured threshold of feedback continues to limit the gain, you can still improve the situation by adjusting the feedback risk. The feedback risk determines the strength of the feedback protection zone. The feedback protection zone is the area between the dashed and the solid purple threshold of feedback curves. The default setting is Low and provides approximately 6 db of protection. By increasing the risk setting to Moderate or High, the protection zone is reduced and more gain is available. Figure 4 shows the same example as Figure 3 but with the measured threshold of feedback and the feedback risk set to Moderate.

4 Figure 4 demonstrates the improvement in the 50 db and 65 db gain curves. Note that the feedback protection zone is narrower. Lastly, you may also consider changing the acoustics to something more occluding. To achieve an optimized fitting, you may require one of these adjustments or a combination of all three. MPO A third factor that can influence the available gain of a hearing aid is the Maximum Power Output (MPO). The MPO will not generally affect soft (50 db) or mid (65 db) input levels, but there is a higher chance of it limiting the loud (80 db) input. If the MPO limits the output of the hearing aid, then it will not reach targets when you perform verification. To proactively determine whether the MPO is limiting the output of the instrument, use a different view in the Oasis Amplification screen. Oasis shows the amplification in the Insertion Gain view as a default. However, the best view for determining whether the MPO is limiting the output is the In Situ SPL view. Figures 5 and 6 are examples of the same fitting using the Insertion Gain and the In Situ SPL view. For both views, the light pink curve is the 80 db input, the red is the 65 db, and the dark red is the 50 db input. The dotted lines are the target curves. In the Insertion Gain view, the 50 db input is on the top; in the In Situ SPL view, it is on the bottom.

You can also see that the gain provided for the 80 db input is under target. However, there is no visible reason for the 80 db curve to be below target.

5 Figure 5: Insertion Gain View. In Figure 5, the insertion gain view, you can see that there is a reasonable match to target for the 50 and 65 db inputs, and that the feedback curve is not limiting the available gain. You can also see that the gain provided for the 80 db input is under target. However, there is no visible reason for the 80 db curve to be below target. The cause of this shortcoming becomes evident in the In Situ SPL view (Fig. 6). Figure 6: In-Situ SPL view In Figure 6, the grey line is the MPO curve. Here it is apparent that the MPO is limiting the output of the 80 db input above 1 khz. Additionally, the 65 and 80 db curves are very close together which suggests that the MPO is also limiting the output of the 65 db input. Now that you know the cause of the problem, you can make the appropriate adjustments. Oasis provides an MPO fine-tuning handle for the same frequencies as those for adjusting gain. The MPO can be raised as high as the maximum output of the device in order to solve the problem of limited gain. However, before simply raising the MPO, you must consider that there may be specific reasons for the MPO setting. Depending on the hearing loss of the client or if the client is sensitive to loud sounds, the MPO may need to be low. Before adjusting the MPO, consider measuring the Uncomfortable Loudness Levels (UCLs) of the client. Both the Insertion Gain and In Situ SPL views provide useful information. When you use both views, you will better

6 understand how much gain and output the hearing instrument is capable of and, consequently, what to expect when verifying the fitting. Summary To summarize, follow these recommendations before performing REM to experience a more seamless verification process. 1. Use the Instrument View section in Oasis and the In Situ SPL view with clientspecific settings to confirm an accurate fitting range 2. Use the Feedback Manager to determine the possibility of gain limitation and adjust if needed and 3. Use the In Situ SPL view to determine the possibility of gain limitation by MPO and adjust if needed Experience the value of these Oasis tools in your next efficient and successful fitting.

AURICAL Plus with DSL v. 5.0b Quick Guide. Doc no /04

AURICAL Plus with DSL v. 5.0b Quick Guide 0459 Doc no. 7-50-0900/04 Copyright notice No part of this Manual or program may be reproduced, stored in a retrieval system, or transmitted, in any form or by