Q: Audio cuts out with FaceTime when there’s ambient noise

I’ve been having some long term issues with audio on both FaceTime and Skype on 10.11.3 (and previous versions too).

When I’m in a video call using the built-in mic of my earphones, whenever there is any sound where I am (say, other people talking, or a car passing, etc.), the audio of the person I am speaking to cuts out or decreases. It appears I need to be in a totally silent room to be able to hear the person without cutouts.

When I mute my microphone, the problem goes away. This tells me it is not a bandwidth issue.

I’m using a set of Bose earphones, but had the same problem with other headphones I tried. I need to use headphones for the environments I have video calls in, but I don’t see a way to select the computer’s mic if the headphones are connected, so I can’t test that. It happens equally with FaceTime and Skype. I have tried to regulate the audio-in volume and that has no difference other than make it harder for the other person to hear me (an obvious result!).

Any ideas what might be causing it, or what I can try? Thanks!