I don't have the reputation to put these questions in a comment where they belong, so here goes:
Are all the people speaking in the same room?
Where is the sound being produced for the mics to pick it up? Are the people wearing headphones? Or listening on desktop or laptop speakers?
I'm not sure if you are asking a question about latency or bleed. In your example, you say that you hear the laugh later at an unwanted time. 3 seconds is a long latency, that won't sound like an echo or delay it will just sound like a repeat. (I get that this is what you are trying to correct, but I'm trying to get a handle on exactly what the problem is.)
If you have a delay like this, I think that is your primary problem, not the fact that it is bleeding into mics. A long delay makes makes conversation nearly impossible. To give you hints on how to correct latency, we will need to know more about your recording set up. Are these skype calls? Google Hangouts?
There are noise isolating headphones. I use Direct Sound EX-29 Dynamic Closed Headphones in my home studio when having a singer record vocals over tracked instruments. They cost $129.
There is a plug-in from iZotope called De-Bleed. It's part of the RX noise removal tool set they have created. From the product description, it sounds like it was BUILT for your problem. But at $400, it might be overkill!