Since the onset of the Coronavirus disease (COVID-19) pandemic, face masks have become commonplace and are a crucial component of mitigating its spread through the population. Public health officials have reinforced the need for all individuals to wear a face mask at all times when in public, particularly when in a place where 6 feet (approx. 2 meters) of distance between individuals cannot be maintained.1
Although face masks are important for public health and reducing the spread of disease, they have a deleterious effect on the acoustic properties of speech. Research has shown, depending on the type of mask, the high-frequency content of speech may be attenuated by as much as 12 dB.2 This may pose additional challenges to the hearing impaired population, the majority of whom experience the greatest hearing impairment in the high frequencies—precisely where the attenuation from a face mask is greatest.3
Benefit of Roger™ – our study findings
Research at PARC aimed to investigate how the loss of high frequency information caused by a face mask affects the benefit of using a Roger microphone for individuals with moderate to severe hearing loss.
17 adult participants were recruited for this investigation. Each participant was fit with Audéo™ P90 devices programmed with default recommendations using APD 2.0 gain calculations. Roger was installed in these devices and a RogerDirect™ program was set to activate automatically, receiving the signal from a Roger Touchscreen Mic when switched on. An acoustic scene was designed to surround the participants in diffuse cafeteria noise, and a talking KEMAR equipped with a Roger Touchscreen Mic was placed six feet away, facing the listener.
The American English Matrix test was used to assess speech perception in noise. The test constructs test sentences from five lists of ten words each; each sentence follows the same structure (name, verb, number, adjective, noun). In constructing sentences in this way, the test features syntactically valid but semantically unpredictable sentences. As such, the participant is unlikely to guess any word not heard or understood, even though he might be able to guess the correct part of speech.4 Testing was preceded by one familiarization run, and the test was performed twice for each of the following conditions:
- No mask / no Roger
- No mask / with Roger
- Cloth mask / no Roger
- Cloth mask / with Roger
- ClearMask™ / no Roger
- ClearMask™/ with Roger
The score from each trial was averaged, such that each participant had a single score for each of the six experimental conditions. Test lists were randomized, and conditions were counterbalanced for both mask type and Roger condition. The American English Matrix test was set to adapt the level of the speech stimuli in constant 70 dB(A) cafeteria noise to find the signal-to-noise ratio at which participants achieved 50% of all words correct (SNR50).
The study found no significant interactions between Roger use and either type of mask, which suggests that Roger benefit is neither heightened nor degraded by the use of a face mask. While the researchers did see a deleterious impact on speech perception with a cloth mask (without Roger), clients can expect to receive at least the same degree of benefit from Roger whether the talker wears a face mask or not. It is important to note; although KEMAR offers a satisfactory medium for evaluating the acoustic effects of different masks and resulting speech perception, this study did not account for the additional visual cues that are accessible in conditions without a face mask, or with a ClearMask™ (or similar style) in the real world.
The current importance of infection control in daily life may preclude the use of Roger in situations where a transmitter would typically be passed around to multiple parties. While this study has proven that there is no degradation to the benefit of Roger with talkers wearing face masks, the researchers also sought to provide hearing aid fine-tuning recommendations for instances in which Roger may not be a viable option.
Four internal participants were recruited for this secondary component of the study. The audiometric characteristics of this population are not relevant, as this portion of the study sought to validate fine-tuning changes to compensate for mask-related changes to speech, regardless of type and severity of hearing loss.
This investigation utilized a similar setup as the Roger Benefit portion of the study. In this investigation, talking KEMAR was in the same position in reference to the participants, and was used as an external loudspeaker in conjunction with an Audioscan© Verifit2. Background noise was omitted for this part of the experiment. This investigation, along with technical measures of the attenuation of different masks, created a basis for general guidelines for clinicians interested in creating a mask program for their clients.
Clinicians should consider creating a mask program using these steps:
- Increasing gain at G50 and G65 by 3 steps at 3-4 kHz and by 6 steps (total) above 4 kHz.
- Particularly small ears may require no increase at 3-4 kHz and only 3 steps above 4 kHz.
- Increasing G50 and G65 gain may raise compression ratios (CR). If a lower CR is needed for a given client, G80 can be increased by 1-2 steps to reduce the CR.
In the four subject experiment at PARC, these adjustments removed any appreciable difference in real ear output for speech with and without a mask.
Considerations for practice
To apply these research findings into a clinical setting, readers should keep these key points in mind:
- With the current widespread use of face masks, Roger remains a viable hearing solution for overcoming negative effects of background noise and distance.
- Clinicians should consider creating a custom hearing aid program intended to help clients communicate during the pandemic where there is widespread use of face masks.
To learn more about this research conducted at PARC, you can read this interesting article in the format of a Field Study News and watch this short video
- Centers for Disease Control and Prevention. (2020). Coronavirus Disease 2019. Retrieved from https://www.cdc.gov/coronavirus/2019-nCoV/index.html, accessed
- Goldin, A., Weinstein, B., and Shiman, N. (2020). How do medical masks degrade speech reception? Hearing Review. May 2020. Retrieved from www.hearingreview.com/hearing-loss/health-wellness/how-do-medical-masks-degrade- speech-reception, accessed September 24th, 2020.
- Pittman, A. L. and Stelmachowicz, P. G. (2003). Hearing loss in children and adults: Audiometric configuration, asymmetry, and progression. Ear and Hearing. 24(3), 198-205
- Kollmeier, B., Warzybok, A., Hochmuth, S., Zokoll, M. A., Uslar, V., Brand, T., & Wagener, K. C. (2015). The multilingual matrix test: Principles, applications, and comparison across languages: A review. International Journal of Audiology, 54(sup2), 3-16.