How to call from webrtc without microphone permission?

How to call from webrtc without microphone permission?

Can you please elaborate on what you are trying to achieve?
In order to place or receive a call with two way audio you need to have the microphone working. Most modern browsers will ask the user to grant permission before turning on the microphone.

i want to monitoring the conference. When user call for monitoring then microphone not needed. They just listen and monitoring the conference. @PitzKey

You can build your application in a way so when a participant joins they are muted and in order to speak they manually have to unmute themselves.

i already make this. but some user unmute and disturb the conference.

Asterisk allows an admin to mute all participants

Regardless, as mentioned, in your web application you can also build some admin functionality to prevent users from unmuting their microphone.