Perspectives from a Deaf audiologist: How masks, face coverings and shields affect my speech perception ability

We got a new audiometer in my office so my co-worker, Beth, and I decided we would put it through the paces, learning how to find buttons to push, word lists to play and other features as we went along. We had discussed doing some INFORMAL testing (i.e., n = 1…me) with the various types of masks and shields we had available so I got in the booth on the patient side and Beth worked the audiometer.

The results below were taken on two separate days – some of you may have seen my Facebook post where I posted my Day 1 results. Day 1 word recognition (WR) testing was all done in quiet and we forgot to test the paper mask. After some specific requests, Day 2 incorporated the paper mask and we also did WR testing in noise.

Here is the (informal) testing protocol that we used:

• NU-6 word list – one syllable consonant-vowel-consonant words, open-ended list
• Presentation level = 50 dB HL via Monitored Live Voice (MLV) with boom microphone positioned in front of masks and shield in the same position, simulating what a teacher might be doing
  • Testing done in quiet
  • Testing done in background noise condition – we used 4-talker babble and had a +5 signal-to-noise (S/N) ratio which meant that the speech signal (in our case, 50 dB) was 5 dB louder than our competing background noise (so it was set to 45 dB). These are the same conditions that I use when I test students.
• Testing was done without and then with visual cues

Some background on me and my hearing history in case you didn’t know: I am a late-deafened adult who lost my hearing at age 29. I’ve now had my Advanced Bionics cochlear implants for 20 and 15 years, respectively, and I’m so grateful for this technology! I have always done very, very well with my cochlear implants as evidenced by my scores with “no mask” above. There are still times when I struggle and masking and distancing have definitely played more of a role in this. I’m so thankful that I am also fluent in ASL and tech savvy for those times when I need help!

These results only reflect MY abilities and it is more of an intra-subject analysis and personal account. That being said though, if I, as a high-functioning auditory communicator struggled as much as I did, what about our students who have been deaf/hard of hearing since birth or have had minimal benefit from their hearing aid or cochlear implant or don’t have a complete language or… ???

My interpretation of these results:

• My cochlear implants benefit me tremendously for listening (auditory learner effect)
• Even with 50-year old eyes and need for progressive lenses, they still benefit me for lipreading/speechreading cues (visual learner effect)
• The “paper mask” had the least effect on causing me to have WR errors.
• The full “cloth mask” didn’t really affect me until background noise was introduced
• The “mask with clear window” and “ClearMask” had the same effect for me of causing more WR errors whether it was in quiet or in background noise and I was listening only
  • When I was able to lipread, my scores jumped back up near ceiling levels. I was shocked that I was even able to benefit from visual cues while lipreading Beth behind a fogged up “mask with clear window”!
  • Beth noticed subjectively that my responses appeared more confident and quicker when she was using the ClearMask – perhaps it was because I could see so much more of her mouth and there was less fogging. I should also note that people love or hate this mask – its design definitely is not universal.
• I really, really, really don’t do well with face shields if listening only! To be honest, this was disappointing to me because I have been a shield advocate because it seemed a good solution for people that need visual cues and can be more comfortable to wear (though not as protective against SARS-CoV-2 as masks). It may still be better for some people but definitely not me.
  • This was the most difficult condition for Beth to keep her voice at a steady loudness level. She noticed as soon as she put the shield on that her voice was echoing back and sounded different. She also looked at the VU meter on the audiometer (this is what we look at to make sure our voice isn’t too soft or too loud and is steady) and it was noticeably quieter by about 10 dB. She kept her voice at the same level as much as her muscle memory allowed and it was amazing how the shield really just decimated the energy of her voice. In essence, instead of her voice being +5 (i.e., her voice being 5 dB louder than the background noise), it was more like -10 dB (i.e., her voice being 10 dB quieter than the background noise). That’s significant for me to score ZERO PERCENT. Besides that, think about how hard talking behind a shield can be for a teacher!
  • Having been hearing for most of my life, I was shocked (and pleasantly surprised) that I did as well as I did basically with all lipreading with the shield in noise with visual cues.
• The more rigid the plastic, the more of an effect it had on me – my scores auditory only were significantly worse compared to the “paper mask” and “cloth mask”. The shield had the most detrimental effect across the board.

Final thoughts:

• There is no one perfect mask, face covering or shield that will accommodate all students (or adults)!!!
  • I know this may not be what you want to hear (I’m looking for the “holy grail” of masks and shields, too!) but I feel like we’re still on the hunt for something “better”.
• You need to figure out if the student is a…
  • Auditory learner – I would recommend a “paper mask” or “cloth mask”
  • Visual learner – Some students will need a “mask with clear window”, “ClearMask” or “Face Shield” to access lipreading cues. Consult your educational audiologist to consider using a remote microphone system to overcome the effects of sounds being muffled. This is critical if you have a teacher using a face shield. Remind your student to keep in visual contact with the teacher as much as possible.
• Based on the answer above, you should choose the appropriate mask, face covering or shield taking into account which kind of learner they are.
• If you or your student have multiple slots on your personal amplification or implantable device, I highly suggest getting some kind of “mask program” where:
  • overall output is increased (to compensate for social distancing making all sounds quieter) and
  • frequencies above 1000 Hz and especially above 4000 Hz have increased gain due to the loss of these high frequencies being filtered by masks and shields
  • You’ll want to experiment with this with your audiologist since this is not an exact science yet and really, depends on if you are listening mostly to people with masks, face coverings or shields (those with a clear window will need more output and gain in the high frequencies).

There have been quite a few studies that have also looked at the acoustic effects of masks and shields – this is just my contribution with my own scores and thoughts.

Just this morning, Abram Bailey of Hearing Tracker alerted me to a new study done just down the road from me (!!) at the University of Illinois at Urbana-Champaign. They looked at how different kinds of masks, face coverings and shields impacted high frequency-speech sounds. The high frequencies contain the “energy” for consonant sounds and consonant sounds help you distinguish one word from another – if you can’t hear them, it sounds like everyone is mumbling. Check out how these different conditions are almost exactly reflected in my scores! (I did not do any testing with an N95 respirator nor a mask with cotton/spandex blend jersey)

If you’d like to see some more mask and shield studies, you can go to my social bookmarking page at https://raindrop.io/collection/2663069 and type #Masks in the Search Bar.

If you’d like to see some user comments and thoughts on different masks, face coverings and shields that they’ve used, check out this previous blog post where colleagues, Mary Beth Napoli, Carrie Spangler and I created some surveys to see if we could find a trend. SPOILER: we didn’t but the comments were still valuable!

I also had the privilege of collaborating with Catharine McNally on possible solutions involving assistive technology for situations like teleconferencing and using speech-to-text technology. Please check out our Knowledge Base at connect-hear.com!

I’d like to finish this post with a plea to anyone that has sewing skills and has experience making masks. This is my Wish List of features for a mask that I have yet to find:

• USE OF QUILTING FABRIC – for protectiveness, coolness and breathability
• MEDIUM THICKNESS VINYL WINDOW – to hold its shape and not get wrinkly, anti-glare and anti-fog would be bonuses but I know difficult to achieve
• WINDOW SIZE – enough to see the whole mouth but not so much that it affects coolness and breathability
• METAL NOSE PIECE – to prevent my glasses from fogging up and keep my nose covered, may have to be external if the mask is washable because it might be prone to rust out if sewn in
• DARTED DESIGN (i.e., not flat) – so that the mask sits away from my face which makes it easier to breathe and so the window doesn’t get sucked onto my lips when I breathe or talk
• RETENTION OPTIONS – ear loops don’t work for me but do for others, I prefer an adjustable head loop style with a toggle or something to make it bigger/smaller, if it was a little stretchy that would be great, too
• AVAILABILITY IN ADULT AND KID SIZES
• REPLACEABLE VINYL WINDOW – so I can throw the cloth portion in the laundry (this would be a total bonus but not absolutely necessary)

Any takers? 🙂