The Lombard effect is the involuntary tendency of speakers to increase their vocal effort when speaking in a loud noise to enhance the audibility of their voice. There is a problem in telecommunication due to the Lombard effect. A speaker talks at a louder volume than necessary for the conversation partner at a remote location. This paper proposes a volume model that is required in order to automatically adjust the volume of an operator's voice at a remote communication via a telepresence robot, and develops an optimal volume control system LombaBot equipped on a telepresence robot with the model. The volume model measures the level of noise around the robot and the distance between a conversation partner and the robot to adjust the volume of the operator's voice. It has two types of volume adjustments. Those are called comfortable volume and secret talk volume. LombaBot enables people at a remote site to listen comfortably to the voice of a robot operator. Moreover, the operator is able to talk in low voices when s/he wants to talk in secret with nearby people. We confirmed that LombaBot adjusted the volume of an operator's voice properly in the noisy remote location.