The midseason finale had some serious flaws in it!
First of all when the flash saw opposite flash and he ran after him throughout the entire city flash wasn't wearing his red suit.
His red suit allows him to run at super speed without having his clothes or shoes burn
but when he was running after opposite flash and then he stopped at the football field there was no smoke in any of this clothing and did not appear ripped or anything.
secondly opposite flash was trapped in that force field, however..... the flash can speed up, speed up so fast that he becomes vibration.
he could have done that and escaped, that is why people on the outside can still hear him speak because vibration can penetrate a force field. That's all that sound is, it's vibration.
And those vibration create sound waves, and that's what we hear.
The professor said that no matter how fast you are you cannot escape a force field, this is incorrect.
this is because the sum of the potential and kinetic energies of the particle are constant, when turning into vibration then escape velocity is no longer a concern.
the only true way to create a force field that could trap the flash or opposite flash would be a double wall with no possibility of air in between them, that would effectively make opposite flash incapable of escaping however it would also mean sound insulation and people outside of the force field would not be able to communicate with sound with the flash and vice versa.
So they would not be able to talk.