A method and system for response to ambient noise in implantable pulse generator. At least one cardiac signal is sensed with an implantable pulse generator. Cardiac depolarizations are identified in the at least one cardiac signal and cardiac depolarization markers are generated. The at least one cardiac signals are then analyzed for a noise event during a refractory period following the detected cardiac depolarization. The refractory period includes a noise window interval during which noise events are recognized. When a noise event, or events, occur during the noise window interval a first noise marker is generated. The noise window interval is then repeated as long as noise is detected in the noise window intervals. When the noise persists for a predetermined time interval a second noise marker is generated.