Why do some people cough all the time for seemingly no reason?

Sometimes it's tourette syndrome. I worked with a guy who had it. Coughing, hacking then clearing his throat. It would seem that he had maybe a congestive issue. But when he wasn't coughing or clearing his throat, he was making weird religious based exclamations about something he read. Or yawning loudly. Or stretching and making a big sigh. Or making the loudest most exaggerated sneeze anyone could. It was literally something every 30 seconds.

Crazy part was, he was a professional voice-over talent for documentaries and translated pieces. He would go in the booth and do 3 hours of voice-over without one issue. Then come out and just make up for it with a barrage of noises. Great guy, great voice: but damn his decibel output was unreal.