Yeah, this tends to happen. I've learned to take it in stride.
It's not necessarily that people are outright ignoring you (although depending on how well you know the group, and how well they know each other, that MIGHT very well be the case).
But maybe you said something that is unrelated to the main conversation, or a real "inside joke" (one that only you know). NTs don't take very kindly to that, and they'll assume that you just like hearing the sound of your own voice. Try this: When people didn't seem to pay attention to what you said, ask them their opinion about something related to the main topic at hand. If they don't respond, then you know they're ignoring you.