四分律行事鈔資持記 2.1218

2.1218

列緣。第二，注釋露處；由此二屏，皆無障故。前云塵霧暗黑名見屏，常語不聞聲名聞屏。

Listing the conditions: second, the note explains "in the open"; because of both these screens, neither has an obstruction. As said earlier, dust, fog, and darkness are called screens from sight; normal speech whose sound is not heard is called a screen from hearing.