From the camera itself, swipe up to get to settings. Go to Audio. The first choice is a toggle to turn the speaker on or off. Turn that off and all sound effects go away from both the camera itself and from the saved footage.
This really annoyed me at first too. I LIKE hearing the sound effect in the car, so that I know that things have connected and that the highlight was successful. But I HATE having that sound EMBEDDED in the video. I wouldn't mind if it were just the ambient sound of it instead of the really loud embedded sound blocking out all other recorded audio.
Where I have mine mounted I can only see a small portion of the screen, and if I forget to hit the remote button when I start the car, the first time I take a highlight it doesn't happen because it hasn't connected. So I have to look at the camera now to make sure the highlight was successful.
I really wish they would provide an update to disable the embedding of the sound effects in the video while still having the camera make the noise in the car.