I can see that you are so agitated because of the startup sound. I, on the other hand, like it. I like to know that my camera is started when I start my car. If I hear startup sound, I don't have to check camera visualy - and that's a good thing in the car.
I think the start-up beep is always when it is powered on, so if the SD card fails or whatever, the beep sound is still useless, only tells about powering on the device, but I'm not blind so I can clearly see that the screen is on. The LED light is showing that it is recording correctly. The beep sound is just annoying and very loud. Why is it so loud? Xiaomi Mijia Dash cam doesn't have that much loud sound and it is way more ear likeable sound, not sure if the sound is on start-up, but definitely it play sound when it's turning off. A400 has very poor quality speakers so the high pitch sound is just annoying, at least turning the volume to half would be good enough. Not sure what are the colors of A400 LED, but Xiaomi Mijia DVR has white when everything is fine and red when there is a problem with the SD card, like full or corrupted.