Speech unmasked: WM linguist studies how masks impact intelligibility

Wearing a mask is one of the most effective ways to prevent the spread of the coronavirus, but there’s no question that masks make it harder to understand what people are saying.

Or that’s been the thought, anyway.

UWM associate professor of linguistics Anne Pycha is the coauthor of a new study published in the journal Cognition that examined how well people can understand the speech of speakers wearing face masks. With Wisconsin and other states across the nation under a mask mandate to prevent the spread of the coronavirus, Pycha and her coauthors, Michelle Cohn and Georgia Zellou of the University of California-Davis, realized they had a golden opportunity.

“Because we all wear face masks, the basic circumstances under which we produce and perceive speech have fundamentally changed,” Pycha explained. “We’ve all of a sudden got this barrier on our mouths that impacts how we speak. … Once we started thinking along those lines, we realized that the face masks presented a really interesting test case for researchers like us.”

UWM linguist Anne Pycha’s research shows that when told to speak clearly, mask-wearers are intelligible as ever. (UWM Photo)

Experimenting with speech

As it happens, Pycha said, humans are actually very good at communicating. In addition to signals like facial expressions and body cues, people naturally modulate their speech to reflect their environment – speaking louder in a crowded room, for example.

She and her coauthors wondered: How do masks interfere with our speech? And can speakers overcome this new barrier to communication?

To test that question, Pycha, Cohn, and Zellou had two speakers, a man and a woman, record specific sentences both while wearing a fabric face mask and not wearing a mask. The sentences were pulled from a standardized list called the “Speech Perception in Noise” set. They asked the speakers to record the sentences in three ways: Speaking in a casual, conversational tone; speaking with positive emotion; and speaking clearly to someone who might have trouble understanding.

To each recording, the researchers added a bit of background noise to mimic what a listener might hear if they were listening to speech in a casual environment. Listeners in the experiment had to hear the recordings and then type the last word of the sentence they heard. Then, Pycha and her colleagues examined their answers for accuracy.

In the sentence, “Miss Brown is considering the coast,” for example, respondents would have to type “coast” to be considered accurate. Answering “toast” or any other word would be a mark against intelligibility.

Surprising results

Some of the results were exactly what you’d expect.

“When people were speaking casually, it was more difficult for our listeners to understand. Intelligibility went down when the mask was on. We’ve all had that experience,” Pycha said.

The same held true when people were speaking with positive emotion. But, when the speakers were told to “speak clearly,” things got interesting.

“The listeners were actually better able to identify words when the speaker was wearing a mask compared to when they were not wearing one,” Pycha said.

“It’s almost as if, when you ask people to speak clearly in a noisy situation, intelligibility goes up, but when you ask them to speak clearly in a quiet situation, intelligibility goes down – which is surprising! It’s a testament of the power to the human voice to modulate itself,” she added.

Zellou noted that researchers have seen this response before in other situations.

“People adopt different speech styles when they talk to someone who may have a hard time understanding them or in a context where comprehension might be difficult (like a noisy room or wearing a face mask),” Zellou said. “(These styles) are known as clear speech. Clear speech is usually louder, slower, and more enunciated than more casual speech. This is thought to aid listeners in parsing the speech signal by helping them to identify the words more readily.”

Georgia Zellou

But how do people adapt their speech so quickly?

“We don’t totally know. What we do know is that we’re really good at doing it,” Pycha said. “Part of what we’re trying to do in this research is pinpoint why.”

Put it into practice

This new research shows that asking people to speak clearly when they wear the mask will help make their speech more intelligible, so don’t be shy about asking people to repeat themselves or enunciate.

“In my own life, this has been successful in short conversations with the cashier at the grocery store, even with the additional barrier of the plexiglass,” said Cohn. “But we want to stress that this research was done on younger, non-hearing-impaired listeners. The extent this finding generalizes to other populations (e.g., hearing impaired adults who rely on lip reading) is still an open area for future research.”

Michelle Cohn

Pycha thinks that mask-wearers also need to be proactive about speaking clearly – not just to be intelligible, but also to help those hearing-impaired adults that Cohn mentioned, or people who may not understand English well. Speaking clearly increases the intelligibility of our speech, and people should try to help out others who may have a harder time understanding, she said.

“I think it’s obvious that masks make it harder for all of us to communicate, especially because we can’t use facial cues like we can in mask-less situations,” Pycha added, “but it really only takes a small amount of effort to overcome that obstacle.”

By Sarah Vickery, College of Letters & Science

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.