The changes in the user’s perception of his/her own voice is one of the most common negative “side effects” of wearing personal amplification. Nearly all hearing instrument wearers experience some change in the perception of their own voice when wearing a hearing aid. Sometimes this is the result of occlusion, and sometimes it is the effect of amplification on their own voice.

The management of own-voice issues has been discussed and written about frequently from the hearing care field’s early beginnings when people first started wearing hearing instruments. With the advent of small custom instruments—namely CICs—clients’ experiences and reports of occlusion are now more common.1,2,3 Another factor adding to the increase in own-voice complaints is the fact that more mild/moderate high-frequency hearing losses are being fitted than in previous years.

In Kochkin’s recent MarkeTrak study3 of people who purchase hearing aids but do not use them (i.e., “in-the-drawer aids”), 30% of survey respondents said that “side effects” such as feedback, occlusion, etc., were the reason for non-use. A study conducted in conjunction with Australian Hearing Services5 reveals that, of patient-reported problems, 28% indicated “own voice issues.”

The goal of this article is to foster a pro-active approach to management of side effects in order to increase patient satisfaction.

Cognizance of Side-Effects
One of the frequently overlooked factors in dealing with the side effects of fitting is client focus. For success, dispensing professionals need to have clients focus on benefit and value. Unfortunately, as long as clients are focused on a particular side effect—or multiple side effects—hearing care professionals have little chance for directing focus on benefit and value. In some instances, the first and only response a client has after inserting a hearing instrument into the ear is to get the foreign object out as quickly as possible because it feels and sounds unpleasant.

Thus, it is prudent to pro-actively address “side effects”—particularly the occlusion/own-voice issue—prior to the initial fitting session.

How (and Why) Did You Put My Voice in a Barrel?
In the unoccluded ear, low frequency vocal energy between 200-500 Hz enters the canal by vibration of the cartilaginous portions of the ear canal walls. In this situation, the body-conducted sound can escape through the open ear canal and the patient will not experience any occlusion problems.

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Fig. 1. In the occluded ear, low frequency energy (usually between 200-500 Hz) enters the canal by vibration of the cartilaginous portions of the ear canal.

When a hearing instrument is placed in the ear (Fig. 1), the body-conducted sound—such as the patient’s own voice or chewing—will increase the energy or sound pressure level (SPL) at the eardrum as much as 20-30 dB. With the hearing instrument inserted, sound can be trapped in the occluded ear canal, increasing the sound pressure level (SPL) at the eardrum.

Generally, occlusion or own-voice complaints will increase as a function of hearing loss. The better the hearing in the lower frequencies as compared to the higher frequencies, the more likely occlusion issues will need to be addressed, especially with CIC fittings.

The “No Surprises” Approach
During initial counseling and communication, every effort should be made to inform the client of potential side effects. Because occlusion or own-voice issues are present in nearly all cases of fitting hearing instruments, clients should be informed as to the likelihood that this will happen. Don’t let it be a surprise on the day of the initial fitting! The discussion should be broached prior to the instrument selection process and it should continue as the pros and cons of the various hearing solutions are discussed. Whether the discussion includes own-voice, occlusion or both will depend on the hearing loss and style of instrument fitted. With many clients, it would be valuable to present this information in writing.

Highlight and plan for a period of adjustment to hearing instrument use. Outline, in detail, how you plan to address the issue. This will help focus the client on value and benefit when the inevitable occurs. Another way to focus on value and benefit is to use a valid needs assessment tool, such as the Client Oriented Scale of Improvement (COSI). Recording the client’s hearing needs and objectives will help keep the client’s attention focused on his/her own goals for the amplification device.

The pre-fitting counseling will not change the occurrence of occlusion/own voice, but it will help to preserve the image of professionalism, understanding and control. This will also provide clients with the confidence to continue with your suggestions and prevent them from becoming discouraged by side-effects.

Fitting Day Strategy
Once fitting day arrives, the client will experience the expected side effects. However, if properly educated on the potential for occlusion, changes in their own voice, temporary feedback, etc., it will not be a shock to the clients. By following the suggested counseling tips (see above sidebar), there should be no “surprises.” The anticipated side effects will still occur, but only as part of the ongoing “period of adjustment.”

In the vast majority of cases, it is best to defer any adjustment for occlusion/own-voice issues as some people simply adapt to the new sound of their own voice. Many will return in one to two weeks and never mention the sound of their own voice as an issue.

The best plan management is to encourage the client to use the instrument “as is” for the initial period of adjustment. Re-focus the client’s attention to the issues previously identified through the use of the COSI or other tools. Stress the importance of evaluating the value and benefit relative to their specific hearing needs during the “period of adjustment” with their new hearing instruments.

If the client simply won’t wear or use the instrument due to occlusion or own-voice issues, then obviously an adjustment to the instrument is warranted. In these cases, the guidelines below are suggested.

No Surprises: Five Pre-Fitting Tips

1. Indicate to every client that their perception of their own voice will be different when wearing a hearing aid;

2. Caution, when appropriate, that the style selected (e.g., a CIC) may be more likely to create own-voice issues;

3. Use a needs assessment tool (e.g., COSI) that helps focus the client on specific amplification goals, as well establishes realistic expectations on the value and benefit of hearing instruments;

4. Advise that occlusion/own-voice side-effects are an expected phenomenon, and often have little consequence in the overall benefit and value of the device;

5. Indicate to the client the steps in managing own-voice issues:
    a) Informing the client.
    b) “Shelving” the complaint and allowing the client adjust to new sounds.
    c) Indicating that it is best to do nothing about the own-voice issue at the time of initial fitting. Many people adjust quickly to the new perception. Why, therefore, change a potentially excellent fitting without allowing the client first to experience the most appropriate amplification for his/her hearing loss?
    d) Indicate that, if own-voice issues are a continuing problem, adjustments can improve the perceived problem (i.e., the issue will be considered during the period of adjustment).

Three Pre-Fitting Selection Tips

1. Counsel toward selection of a style least likely to have true occlusion effects when the hearing loss warrants.

2. Request the most effective venting options available for the style of the hearing instrument:
    a) Collection Vent in CIC and MIC style;
    b) Flexible venting.

3. Consider Bony Seal CIC fitting (see Fig. 2).

f03-fig2.gif (4040 bytes)Fig. 2. Use of a bony seal CIC may help reduce the soft tissue vibration in the ear canal which is the major cause for occlusion effect.

A Post-Fitting Adjustment Protocol
If the client continues to experience own voice or occlusion that is unacceptable (i.e., if they bring it up and ask for relief), follow a consistent protocol or strategy. At times it is difficult to determine if their own-voice issues are the result of amplification (or lack of it) or due to true occlusion related to the insertion of the instrument or earmold into the external ear. The following steps will help to resolve the issue, regardless of the cause, and quickly help to determine its basis.

Initial Fitting
Day 1: YGUTI (You’ll Get Used to It) Counseling, as described above and in the sidebar;

Follow-up Adjustments (only if necessary)
Step 1: Increase low frequency gain (250-1000 Hz) by 3-5 dB. In multi-channel non-linear instruments, increase both soft and loud gain. If this resolves or improves the issue, STOP! If the issue remains, return to original settings and go to Step 2.

Step 2: Decrease low frequency gain (250-1000 Hz) by 3-5 dB. In multi-channel non-linear instruments, decrease both soft and loud gain. If this resolves or improves the issue, STOP! If the issue remains, return to the original settings and go to Step 3.

Step 3: After returning to the original settings, increase gain for soft sounds as closely as possible to 3000 Hz by 5 dB. The frequency selected should match as closely as possible the resonant peak of the “open ear.” If this resolves or improves the issue, STOP! If the issue remains, return to original setting and go to Step 4.

Step 4: This step assumes that the issue is most likely caused by the occlusion effect and the remaining adjustments are related to venting (Fig. 4).

3 For Standard Venting: Increase venting bore if possible and decrease the vent length if possible.

3 For Collection Vent: Decrease vent length and increase canal tip flare if possible.

If the Above Fails… If occlusion problems for the patient cannot be resolved satisfactorily following the above strategies and counseling, the last resort would be a new impression using established impression-making techniques1 and a change in the style of instrument for the client. For example, switching from a CIC to an ITC instrument with a vent of 1.5-3.0 mm, the occlusion effect can be reduced to 8.6 dB as evidenced by Dempsey6 compared to 20-30 dB as evidenced by Killion7 and Revit.8

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Fig. 3. Impression for a bony-seal CIC fitting shows that the impression must extend a significant distance past the second bend to reach the bony portion (at least 22 mm). From the photo, a quick way to tell if you have reached the bony portion is to examine the impression: the material becomes smoother once it reaches the bony area.
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Fig. 4. A variety of vents are available with CIC fittings. The smallest vent is the tube vent, which can increase the complaint of own-voice issues by blocking the escape route of low frequency sounds. The use of the collection vent may offer the best solution for occlusion problems, but this vent is dependent on the size/shape of the ear, as more room is needed to manufacture the flared-out portion of the canal.
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Fig. 5. Measuring the effects of venting options. The occlusion effect was measured using the Audioscan 500P. For all the graphs, the middle blue line shows the REUR, the top black line is the REAR with the bottom black line as the difference between the two or the actual occlusion effect measured. With both the tube and cast vents, the occlusion effect measured is approximately 25 dB at 250 Hz. The collection vent measured occlusion effect is 10 dB.

Conclusion
The pro-active management of “side effects” can increase satisfaction and use of amplification by helping the client realize the benefit and value of the fitting. Avoidance of “surprises” through anticipation of side effects, informative counseling and explanatory written information will prepare the client for the initial experience. Preparing the client with a planned “period of adjustment” encourages use and attention to benefit and value rather than dwelling on the “side effect.”

Following the counseling-based approach to occlusion/own-voice issues described in this article can take discipline. The initial instinct of many hearing care professionals is to address any client complaint immediately by whatever means available (parameter manipulation, shell grinding, venting, etc). However, this approach is generally not the most effective course of action for own-voice issues. Counseling the client and allowing him/her time to adjust to new sounds and sensations—before extensive modifications are applied to the instrument—usually provide better overall results.

Following adjustment guidelines will systematically provide a stable routine of adjustments which not only frequently work, but additionally conveys to the client that the dispensing professional is knowledgeable and “in control,” imparting a greater sense of professionalism and concern for client issues.

f03a.jpg (6007 bytes)f03b.jpg (5212 bytes)Correspondence can be addressed to HR or Randi Pogash, MS, Oticon Inc., 29 Schoolhouse Rd., Somerset, NJ 08875-6724; email: rpp@oticonus.com.

References
1. Pirzanski C: Diminishing the occlusion effect: Clinician/ manufacturer-related factors. Hear Jour 1998; 51: 66-78.
2. Mueller G, Bright K & Northern J: Studies of the hearing aid occlusion effect. Sem Hear 1996; 17: 21-32.
3. Sweetow R & Valla A: Effects of electroacoustic parameters on ampclusion in CIC hearing instruments. Hearing Review 1997 (9) 8-22.
4. Kochkin S: MarkeTrak V: “Why my hearing aids are in the drawer”: The Consumers’ Perspective. Hear Jour 2000; 53: 34-42.
5. Dillon H, Birtles G & Lovegrove R: Measuring the outcomes of a national rehabilitation program: Normative data for the Client Oriented Scale of Improvement (COSI) and the Hearing Aid User’s Questionnaire (HAUQ). J Am Acad Audiol 1999; 10: 67-79.
6. Dempsey J: The occlusion effect created by custom canal hearing aids. Amer Jour Otolaryng 1990; 11:44-46.
7. Killion M: The “hollow voice” occlusion effect. In JH Jensen’s (ed): Hearing Aid Fittings: Theoretical and Practical Views, 13th Danavox Symposium, 1988: 231-242.
8. Revit L J: Two techniques for dealing with the occlusion effect. Hear Instrum 1992: 43: 16-18.