View Source ExTDLib.Method.SetGroupCallParticipantVolumeLevel (ExTDLib v0.0.4)

Changes volume level of a participant of an active group call. If the current user can manage the group call, then the participant's volume level will be changed for all users with the default volume level. Returns object_ptr<Ok>.

NameTypeDescription
group_call_idnumberGroup call identifier.
participant_idMessageSenderParticipant identifier.
volume_levelnumberNew participant's volume level; 1-20000 in hundreds of percents.

More details on telegram's documentation.