声門 is read as せいもん (seimon) and means glottis.
せいもん
seimon
せいりょう
(vocal) volume
せいたい
vocal cords
せいいき
range (of voice)
こえがうらがえる
to crack (person's voice)
ぶもん
division (of a larger group)
かど
branch of learning based on the teachings of a single master
もん
にゅうもん
entering through a gate
めいもん
prestigious school, organization, business, etc.
せんもん
sole interest
と
door (esp. Japanese-style)
かんもん
barrier