A police officer's tone reveals a lot about racial disparities in policing.

That's what researchers found in a series of experiments where they played 250 audio clips of police stops to 414 people of varying races and ???? ?????? ??????? ???????? ?? ????? ??????genders.

The researchers edited the clips, which were split evenly between Black and white male drivers, so participants couldn't understand what an officer said but could still hear their tone. Researchers kept officers' race and gender secret, but it's possible participants could still infer some of those details from the audio, says Nicholas Camp, lead author on the study and assistant professor of organizational studies at the University of Michigan. The driver's speech was also omitted so participants only heard the officers' tones.

Even so, participants in the study published this week in the Journal of Personality and Social Psychologyrated police officers' tones when talking with Black male drivers as significantly less friendly and less at ease than with white male drivers. These results held true despite participant and officer demographics.

This new research underlines a concern many in the Black community have voiced for years. It also comes as the nation debates the future of policing following a wave of protests against police brutality. While routine police interactions don't make as many headlines as when police fatally shoot people, Camp thinks they're still important to analyze because they demonstrate how police act every day with the communities they're assigned to protect. These encounters can help build trust between officers and the public — or they can erode it.

"We really wanted to see if there were differences in the most common and routine interactions," says Camp. "But even with these routine encounters, we see these disparities, and they have consequences."

Camp considers all of the audio clips his team played to the participants as mundane traffic stops, meaning no arrests or use of force was involved. The 132 police officers who conducted the stops were mostly male and about 40 percent were white. The researchers denied Mashable's request to publish the audio clips.

Police interactions with the public shouldn't have to escalate to a fatality in order for body camera footage to be released, advocates for police transparency have argued.

"When we're talking about racial disparities in policing, a lot of times we're constrained by what we have records on," says Camp. "We don't know a lot about how officers actually interact and communicate with the public."

Across the country, a patchwork of laws dictate if the public has access to police body camera footage like what these researchers used. For example, when police shot and killed Ma'Khia Bryant, a Black teenager in Ohio on April 20 the Columbus Division of Police released the footage hours later because of state law. But, when police fatally shot Andrew Brown Jr., a Black man in North Carolina, the next day, a judge ruled the footage wouldn't be released publicly and only Brown's family could view it.

Camp thinks obscuring body camera footage is a missed opportunity for both police departments and the public because it can reveal police officers' behavior and how it could change with interventions.

Procedural justice trainings, which aim to respond to community concerns and champion transparency, might be one effective way to encourage officers improve how they interact with Black people, given this study's findings.

"[Some of these trainings] focus on how officers behave themselves in routine interactions, so giving drivers a chance to tell their side of the story, explaining why the officer stopped the driver," says Camp. "Part of procedural justice is building trust and respect."

Participants who felt they'd been treated unfairly by police during their last encounter with an officer tended to judge the clips as more harsh than those who said they'd been treated more fairly. White participants said more often that they had fair interactions with police, but they didn't say they received more lenient punishment, like getting a warning instead of a ticket.

Despite his research, Camp doesn't believe an officer's tone is the biggest challenge in policing.

"If I was talking to a police officer, I wouldn't say the only thing you need to change is you should have a higher-pitched voice and chuckle a couple of times," he says. "When you're communicating with a driver, is your goal to emphasize that you have control over the situation...that you think they're up to no good or is your goal here to treat the person with respect and...like they have a say in this interaction?"

While Camp doesn't find differing treatment of Black and white people by police surprising, he didn't expect the participants to pick up these disparities from the audio they played given it only included tone. Camp's previously researched the language police use and found then too that officers talk to Black people less respectfully than white people.

Tone, while just one part of communication, can be an important way for police departments to win the public's confidence.

Tone "can influence the trust that people have in police departments," Camp says.