(This posting includes a handout which you are welcome to use with your students.)
You,the conversation teacher, are happy because the noise level in the room is high. That means that the 12 pairs of students (24 total) are engaged in the conversation activity. At the start of the next class, you want to give them feedback on their performance today, especially because you want to give positive comments to those who are very active. There are also a couple of pairs who need some “re-direction.”
Needless to say, you’re not going to be able to give each student specific feedback specifically on what they said because you can’t actually hear them above all the talking. But you can actually see whether or not they are using conversational techniques. (See previous posts of two important techniques Conversation magic: Two most important conversation techniques (Part 1) and Conversation magic: Two most important techniques. (Part 2)
Even if you can’t hear them, you can see if they are engaging in a natural conversation; it looks like ping-pong, in which they are reacting to each other, asking follow-up questions and giving understanding responses. You can also see if they are more like bowling, in which one monologs for a while while the other “zones out,” then the other monologs. You can see if someone is dominating and if someone is very passive. Interestingly, you can even see if they have switch from English to their native language; often when they do this, their voices lower and their faces aren’t as animated perhaps to “hide” from the instructor.
If you suspect that a pair isn’t using natural conversation techniques or isn’t speaking in English, there are things that you can do.