Audiological implications and hearing instrument adjustments for face masks

Reading Time: 8 Minutes
10.02.2021

The current pandemic that we are experiencing has created many clinical challenges for hearing care professionals (HCPs) around the world. Many of these challenges were not discussed or even considered until now. With the widespread adoption of personal protective equipment (PPE), additional issues have been created for the hearing-impaired client. Conversational partners who must maintain their physical distance while wearing face masks that are potentially combined with face shields or clear plastic barriers exacerbates communication difficulties. These protective measures are currently a fact of life and something that we need to live with and help our clients to manage for the time being.

1.Challenges that are created with face masks

Face masks create two main issues for the hearing-impaired person to understand conversational speech. The first is the fact that the face mask reduces the high-frequency components of the speech signal. By how much greatly depends on the type of mask and the mask material used. One highly cited study from May 2020 showed that the frequencies that are attenuated range from 2000 Hz to 7000 Hz and that the degree of attenuation varies from 3 to 4 dB for one type of surgical mask and up to 12 dB for the N95 mask (Goldin et al., 2020). Given the wide variety of materials used to make masks around the world and even the use of homemade masks, the degree of attenuation may vary even more than the values reported by Goldin et al. (2020).

The second issue that hearing-impaired individuals face is the removal of visual cues that are normally relied upon in face-to-face conversations to augment acoustic speech. While this is somewhat mitigated using masks with clear screens, it is safe to say that these are not widely used, nor are they widely available. It is common knowledge within our field that even individuals with normal hearing rely on visual cues to help perceive speech especially in noisy environments (e.g., Sumby and Pollock, 1954). With a hearing loss, this reliance on visual cues increases. So, the sudden removal of these visual cues along with a corresponding loss of emotional context with the use of face masks create many challenges for the hearing-impaired person.

In addition to the removal of acoustic and visual cues for the hearing-impaired individual, all individuals are faced with the additional emotional and physical stress of coping with the current pandemic (e.g., Wang et al., 2020). Individuals are often isolated physically and emotionally. New and frequently changing public safety measures need to be considered in accomplishing even mundane daily tasks such as shopping for food which adds to the daily communication challenges faced by the hearing-impaired individual (Saunders et al., 2020). HCPs as a profession spend time with their clients helping them to hear better and there may be an increased need, due to the current situation, to listen actively to the concerns and experiences of the hearing-impaired person.

Given the challenges that are currently being faced, here are several suggestions that can be followed to help clients to compensate for the use of face masks by their conversational partners.

2. Four different suggestions to compensate for face mask use

The first suggestion is to use a fitting rationale such as DSL 5.0 (Scollie et al., 2005) or NAL NL2 (Keisder et al., 2012) and turn the Adaptation Manager in Oasisnxt to 100 %, as shown in Figure 1.

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Figure 1 - Figure 1: Adaptation Manager in Oasisnxt

Ideally, verify the amplification with real ear measurements (REM) using a speech-weighted broadband signal and different input levels to ensure that speech is optimally amplified for audibility and comfort. When trying to maintain a physical distance, instead of measuring REM on the ear, the same measurement can also be simulated in a test box. In a 2008 study on the perception of speech while wearing masks, it was found that while the speech was lowered in intensity with the face mask, it did not change speech understanding for both hearing-impaired individuals and individuals with normal hearing (Mendel et al., 2008). So perhaps it can be surmised that the ideal solution for some users may be to amplify speech to a predefined target designed for audibility and verify this with REM. The advantage of this option is that the individual may find that speech in other situations i.e. without a mask may be clearer and comfortably amplified.

A second proposal is to encourage the end-user to use his or her volume control. This may sound obvious, but some hearing instrument users may be reluctant to call attention to the fact that they are using amplification and so have been reluctant to use their volume controls in the past. In Oasisnxt, it is good to verify that the volume control is enabled, and that the VC range is set to provide the maximum range possible, as shown in Figure 2. Another option is to help the client download the EasyControl-A remote control app. This is an easy way to change the volume for those that might have difficulty with buttons on their hearing instruments.

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Figure 2 - Figure 2: VC range adjustment in Oasisnxt

A third suggestion is to set up a dedicated mask program or even multiple mask programs for different mask types and increase the amplification in this program. This must be done carefully in order not to create discomfort or even create an increased risk of acoustical feedback. It is important that muffled speech is not just turned into louder and potentially uncomfortable muffled speech. Some suggestions for how to create a new mask program are as follows:

  1. In Oasisnxt, go to the Program Assignment Screen. Either create a copy of the current Dynamic program in P2 based on P1 if you would like to keep the fine tuning that you may have already done, or create a new Dynamic program and set it to Target if you would like to create a new fitting for this program. It is possible for you to name this program “Mask” if desired, as shown below in Figure 3.

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    Figure 3 - Figure 3: Program Assignment screen with renamed P2 as “Mask” in Oasisnxt

  3. Once this program has been created, you can do the following. Ensure that the gain adaptation is set to 100 % for your chosen fitting rationale if the program in slot 1 was created and fine-tuned purely for comfort and verify the audibility of speech with REM, as discussed earlier. You can then modify the gain to try to offset the acoustic attenuation created by face masks by applying offsets manually in Oasisnxt. Any modification in gain needs to be conducted in dialog with your client to ensure not only audibility but comfort. A good starting point is the table of gain values that have been published by the National Acoustic Laboratories (NAL) (National Acoustic Laboratories, 2020). These gain values can be applied to the 50 dB and 65 dB input levels first and then to the 80 dB input levels if needed in order to counteract the attenuation effects of a typical face mask. The gain screens shown in Figure 4 illustrate the difference in amplification between an NAL NL2 fitting with the gain adaptation at 100 % for P1 and with the gain offsets applied to the 50 and 65 dB inputs in P2. The audiogram used was N4 for a moderate to severe hearing loss (Bisgaard et al, 2010). In order to prevent a dip in the response, the same gain offset for 4000 Hz was applied to 5000 Hz in this example.

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    Figure 4: These gain screens show the difference in amplification between an NAL NL2 fitting with adaptation at 100 % for P1 (top) and with the gain offsets from NAL applied to the 50 and 65 dB inputs in P2 (bottom).

  5. The NAL recommendations also comment on optimizing the noise reduction features (National Acoustic Laboratories, 2020). So, depending on the instrument, and with input from your client, increase the amount of directionality, and apply more noise reduction if possible. Once the noise has been reduced, it is also possible for those instruments with the Dynamic Amplification Control™ (DAC™) feature, to set the speech-in-noise setting to Max Audibility. Or increase the Speech Balancer to the highest level for a similar effect for hearing aids with Hybrid Speech Balancing™. These adjustments can be seen in Figure 5.

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    Figure 5: Speech in Noise Environment and Hybrid Speech Balancer™ settings in Oasisnxt

 

In addition to adjusting the hearing instruments, another suggestion is to revisit some aural rehabilitation techniques. The IDA Institute in Denmark has a list of communication tips when wearing face masks. It is good to remember our counseling skills and also the power of actively listening to our clients during this very difficult time. In general, due to the current situation patience is required by both the hearing-impaired individual and their conversational partners. It is difficult for everyone to carry on conversations without visual cues and so this needs to be considered by everyone.

In this short article, I have presented a few ideas about how to help a hearing-impaired individual cope with the reduced amount of information that is available when face masks are used. This list of ideas is not exhaustive nor prescriptive. New research is being conducted on the effect of face masks on communication and may provide other ideas to try. What might work for one individual might not work for another. It is therefore up to the expertise of the HCP to assess the communication needs of his or her client and find solutions that best fit each client’s needs.

References

Bisgaard, N., Vlaming, M. S., & Dahlquist, M. (2010). Standard audiograms for the IEC 60118-15 measurement procedure. Trends in amplification, 14(2), 113-120.

Goldin, A., Weinstein, B.E., & Shiman, N. (2020). How Do Medical Masks Degrade Speech Reception? The Hearing Review, 27(5), 8 – 9. Retrieved from: https://www.hearingreview.com/hearing-loss/health-wellness/how-do-medical-masks-degrade-speech-reception

Keidser, G., Dillon, H., Flax, M., Ching, T., & Brewer, S. (2011). The NAL-NL2 prescription procedure. Audiology Research, 1(1), 88-90.

Mendel, L. L., Gardino, J. A., & Atcherson, S. R. (2008). Speech understanding using surgical masks: a problem in health care? Journal of the American Academy of Audiology, 19(9), 686-695.

National Acoustic Laboratories. (2020). NAL Mask Adjustments. Retrieved from: https://www.nal.gov.au/nal-mask-adjust/

Saunders, G. H., Jackson, I. R., & Visram, A. S. (2020). Impacts of face coverings on communication: an indirect impact of COVID-19. International Journal of Audiology, 1-12. Retrieved from: https://www.tandfonline.com/doi/full/10.1080/14992027.2020.1851401

Scollie, S., Seewald, R., Cornelisse, L., Moodie, S., Bagatto, M., Laurnagaray, D., ... & Pumford, J. (2005). The desired sensation level multistage input/output algorithm. Trends in Amplification, 9(4), 159-197.

Sumby, W. H., & Pollack, I. (1954). Visual contribution to speech intelligibility in noise. The Journal of the Acoustical Society of America, 26(2), 212-215.

The Ida Institute. (2020). Communication tips when using facemasks. Retrieved from: https://idainstitute.com/what_we_do/news/detail/making_communication_clear_when_your_face_mask_isnt/

Wang, C., Pan, R., Wan, X., Tan, Y., Xu, L., McIntyre, R. S., Choo, F. N., Tran, B., Ho, R., Sharma, V. K., & Ho, C. (2020). A longitudinal study on the mental health of general population during the COVID-19 epidemic in China. Brain, Behavior, and Immunity, 87, 40–48. Retrieved from: https://doi.org/10.1016/j.bbi.2020.04.028

 

About the author:

Neil Hockley
Neil Hockley, M.Sc. Human Communication Disorders (Audiology: Research and Clinical program) McGill University, Montreal, Quebec, Canada. BaH Psychology (Perception) Queen´s University Kingston, Ontario, Canada.
Neil is the team leader of Product Management Audiology at Bernafon AG in Bern. He plays a key role in developing and bringing to market audiological hearing instrument and fitting software features. Prior to joining Bernafon in 2001, he worked in clinical and academic settings in the Niagara region of Ontario (Canada). When he is not at work, you can find him at home spending time with his children, cooking, listening to music, in the allotment, or out and about on one of his vintage bicycles.