BTS gives deaf people everywhere ‘Permission to Dance’
July 16, 2021
Phone captioning apps for people with hearing loss
July 21, 2021Study: How face masks affect acoustics and speech understanding
The Covid-19 pandemic changed lives around the world. Many people lost their jobs or worked from home, were prevented from seeing their loved ones, and took extra precautionary measures to stay healthy. But the deaf and hard of hearing community faced another challenge; trying to communicate while wearing face masks, which prevented them from lip-reading and affected the quality of speech they could hear.
Now, a new study shows just how big of an impact face masks have contributed to acoustic effects of speech.
The Effect of Face Masks on Speech
A study published in The Journal of the Acoustical Society of America reports that surgical masks lowered conversation levels to 3-4 dB (decibels).
That may not sound like much, but A 1 dB change in a sound equates to about a 26% difference in sound energy, LogiSon, a company that specializes is acoustics. A 3dB change results in a 100% increase in sound energy.
The effect is even stronger with the respirator masks, which reduce sound levels by up to 12 dB, according to the study.
This is disastrous for anyone with hearing loss.
The Impact of Face Masks on People with Hearing Loss
For people who lipread or use American Sign Language (ASL), facial cues and the ability to see a person’s mouth are crucial. It isn’t just muffled sounds or lowered voices that affect communication. The loss of lipreading, coupled with obscured voices, led to a very quiet world for many people.
Throughout the pandemic, solutions such as transparent face coverings became an option, but they still obscured sound.
Read more: Face Masks for Hearing Aid Users
Studying the Acoustics of Face Masks?
The new study on acoustic effects of face coverings by audiologists Samuel R. Atcherson, B. Renee McDowell, and Morgan P. Howard expanded on previous work and more closely examined face masks than ever before.
Atcherson et al.’s new study was an investigation into the attenuation of speech with transparent and non-transparent face masks. Speech attenuation refers to the reduction in decibel level of speech. Many things can cause speech attenuation, such as face coverings, background noise, or even someone with a sore throat.
Transparent face masks are made with heavier material and thus perform poorly acoustically. Still, because of the visual cues they allow, they are possibly a better option for people who are deaf or hard of hearing.
The new study included plastic face shields, which had not been studied previously.
What Did the Study Entail?
The study utilized over 15 different face masks, including:
- Two normal surgical masks
- Two respirator masks
- One carbon filter mask
- Two homemade cloth masks (one with a HEPA filter, one without)
- Two transparent masks
- Two homemade masks with transparent windows
- One transparent shield type mask
- Two plastic shields with coverings (one homemade, one not)
- One transparent nose-and-mouth shield mask
- One generic plastic shield
A styrofoam head was used as a “talker” in conjunction with a loudspeaker producing white noise. The “talker” was tested with different face masks. Sound levels were measured by a listener microphone placed six feet away from the “talker” in line with social distancing guidelines. (For many of us, social distancing increases the difficulty of hearing or the ability to understand ASL.)
Read more: What to know about clear medical masks for lipreading
What Did the Study Find?
The study into the acoustic effects on face coverings established that all face masks attenuate speech. You’d think that transparent face coverings would help us understand speech. Because of the visual cues, they do. However, the study found that transparent face masks are worse at attenuating speech, probably due to their heavier materials.
Atcherson et al.’s study found that speech attenuation is minimal in all masks. The higher frequencies are more obscured than lower tones. This is a problem for anyone with sensorineural hearing loss (SNL), as SNL affects the ability to hear higher-pitched sounds and voices.
“…all face masks attenuate speech. “
The study also discovered that full-face shields have increased speech attenuation than nose-and-mouth shields. Full-face shields also deflect sound to the back and sides of the speaker’s head. Nose-and-mouth shields don’t deflect sound as much.
Non-transparent face masks cause a few dBs of speech attenuation. A shield can cause up to 16 dB of speech attenuation by itself and up to 25 dB when used with one or more other masks.
However, Atcherson et al. believe that visual cues enhance understanding and go a long way towards making up for the increased speech attenuation of the heavier transparent materials.
Read more: Tips for communicating with the deaf community when wearing a face mask
What Did the Study Miss?
Further work needs to be done to find out which transparent and non-transparent materials cause the most minor speech attenuation. The study could have been done using authentic voices and tested out on real people, as a receiver picking up sound is entirely different from a human being picking up words. For many deaf or hard of hearing people, hearing sound is not the only problem. It’s clarifying the words that were said. This requires much more study than anything a simple microphone with white noise can achieve.
Atcherson et al.’s study into the acoustic effects of non-transparent and transparent face coverings is helpful, but doesn’t go far enough. However, the addition of face shields and other previously untested masks in a study is vital.
As the world begins to recover from the Covid-19 pandemic, hopefully we won’t need face masks in the near future. But until then, please be aware of the effects of speech with face masks, and try your best to help those in need communicate more efficiently.
