Investigating the interference of facial hair with visual speech intelligibility poses the problem of accurately controlling the amount and shape of facial hair across several speakers while keeping the recording situation constant. Since it is difficult to find participants willing to grow and then cut their beards as needed, we decided to use artificial beards made from natural hair. Two different types were chosen: mustache and long chin beard.
(That’s an extract; Full details in the article in AIR 16:1)