Yes, judging from the video above, the cops are used to being screamed at. In just this one incident, we can see Floyd and his two companions were screaming constantly, "I can't breathe" was interspersed with dozens of, "I didn't do nothing," and, "I'm not that kind of guy." They've had to learn to ignore being screamed at.
During Chauvin's trial one of the witnesses, a police officer, said that, "I can't breathe" has been the common 'get out of going to jail,' call of the career criminals since the first famous breathing incident that happened when Eric Garner died in police restraint in 2014. It's a slogan of the Black Lives Movement. Unfortunately it can end up being a case of "the boy who hollered wolf," if it's used when one clearly can breathe, so it's ignored later when one really is in respiratory trouble.
It was the Cup Foods manager who cared about the 20, not the police, it's just their job to inforce the law for the manager. I always feel sorry for that young clerk who was sent out twice to ask a van full of older people doing drugs for the cigarettes back.
If only George would have returned those cigarettes, taken his counterfeit bill and driven off to try it somewhere else, none of this would have happened. If he was as terrified of the police as he pretended to be he would have done just that, knowing the bill had been spotted. If he was as claustrophobic as he pretended to be, he wouldn't have sat in a van with the windows rolled up for thirty minutes outside Cup Foods. If he truly couldn't breathe during the 28 times he screamed it, he wouldn't have had breath to also talk a steady stream of, "I'm not that kind of guy."
The police had been working with people all day long, a steady stream of people so busy shouting, "I didn't do nothing!" that they can't hear simple instructions like, "Please, put both hands on the wheel." All day long, their work had to be done in the city with bystanders calling out their two cents worth.
Going by the angry, stubborn look on Chauvin's face as he kept his knee on Floyd's neck, the crowd screaming at him, seeming to know his job better than he did, in front of his subordinates, was a factor in his refusal to let up and appear to be letting the public tell him his job. I believe Chauvin deserved his conviction, but I'll always think that screaming crowd was a big part of the problem.