I have a question concerning evidence of checkpoint abuse...

Clearly, there are multiple cameras at most checkpoints and in cases of passenger abuse, presumably a lawyer could request camera footage from the timeframe in question. However, I have often wondered if the TSA has listening devices at checkpoints too. If not, these devices would in some ways be even more useful than the camera's in that they could potentially provide evidence of actual words spoken during an altercation. Would a FOIA request need to be filed in order to find out if listening devices with recorded footage is in fact available?