For the same reason you can’t exhale while holding your nose and closing your mouth—to make the humming noise you have to pass air through your larynx. You can’t do that when no air can be exhaled. Still, seems pretty weird.
For the same reason you can’t exhale while holding your nose and closing your mouth—to make the humming noise you have to pass air through your larynx. You can’t do that when no air can be exhaled. Still, seems pretty weird.