CHAMPAIGN, Ill. — Although face masks may be helping to curb the spread of coronavirus, there are a number of things they can make inconvenient. A researcher at the University of Illinois says speaking is one of those things; an issue especially problematic for those dealing with hearing loss. A new study finds disposable surgical masks are the best option if you want to be heard clearly, even more than masks that let you see someone’s lips moving.
Researcher Ryan Corey says he was recently contacted by a friend who teaches students dealing with hearing loss. The friend wanted to find some ideas of how to better communicate with others while wearing a face mask. Since Corey also lives with hearing loss, the predicament led him to work with the Illinois Augmented Listening Laboratory to find the answer.
“Previous research performed on this subject has focused on medical masks worn in health care settings,” Corey says in a university release. “But no one has looked at the acoustic effects caused by different kinds of fabric masks, so that’s where I focused our study.”
‘Sound frequencies most affected by mask-wearing’
The electrical and computer engineering postdoctoral researcher and his team tested the acoustic effects of several different masks. They included disposable surgical masks, masks with clear plastic windows, homemade options, and store-bought masks made of different fabrics and numbers of layers.
“We put the different masks onto the head-shaped loudspeaker and played the same sound for every test,” Corey explains. “We also placed the speaker onto a turntable to add a directional component to our data.”
Researchers also tested these masks using a human volunteer as well. Although no two people are going to sound exactly the same, these tests helped to gauge how lip reading is affected by mask wearing.
“Using a real person makes the sounds less repeatable because we can’t say the same thing the same way every time. However, it does let us account for the real shape of the head and real movements of lips,” the U of I researcher adds. “Even though these two data sets are a bit different, they both show which sound frequencies are most affected by mask-wearing and which masks have the strongest effects.”
The results reveal every mask in the experiment muffles the quiet, high-frequency sounds that come from a person saying consonants. Corey says these sounds are particularly challenging for the hearing impaired even without a mask.
The best and worst face mask options for speaking
The team made sure to include masks with a plastic window because of their usefulness in seeing visual cues. Corey notes that even people who are not deaf still rely on seeing facial expressions and lip motions to some extent. The audio results however, reveal these aren’t as good of an option as you may think.
“Unfortunately, the trade-off is that you can see through them, but they block the most sound of all the masks we tested,” Corey reports.
The study finds disposable surgical masks provide users with the best acoustic performance. Loosely woven 100-percent cotton masks also score well in the experiment, but they aren’t as effective at blocking respiratory droplets as surgical masks.
Tightly woven cotton and blended fabrics have the opposite problem; they block more droplets but also block out more sound. Researchers find a multilayer mask made of loosely woven cotton may serve as a reasonable compromise for mask wearers.
Luckily, the study finds most masks won’t block out sound completely. Many options just deflect sounds away from the mouth. To counter this, especially in school and work settings, researchers recommend using amplification devices like a lapel microphone to boost sound quality.
“Most people do not walk around with lapel mics and amplification systems while wearing a mask, but it can help in settings where it does make sense, like classrooms and meetings,” Corey concludes.
The study appears in The Journal of the Acoustical Society of America.
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