Are display smart glasses silent?
Reading a visual card can be silent, but a display tells you nothing about the other hardware in the frame. Microphones and speakers are separate features. A product may use voice input even when its answer appears only as text.
Input and output deserve separate choices
Describe a workflow as "speak a request, read the response" when that is what happens. Calling it silent would hide the spoken input. Likewise, a quiet frame can still rely on remote processing through its phone app. Sound, capture and processing are different questions.
For a meeting, consider how you start the interaction as well as how you receive the result. A button or companion control may suit a moment when speaking would interrupt someone. The presence of a display does not guarantee that every function has a nonverbal control path.