The start/stop beep is recorded when recording movies on multiple cameras simultaneously.
Due to the characteristics of the Wi-Fi radio technology, when recording movie on multiple cameras simultaneously, there is a brief time lag of the start/stop timing among the cameras. For this reason, the recording start/stop beep of some cameras may be recorded in the audio of other cameras.
The recording start/stop beep is not recorded when the beep of the camera is set to OFF. For details, refer to the manual of the camera.