Unknown Alarm In Class 166

Hello, there is an unknown alarm going off in the cab and it isn’t the dsd or the AWS, does anyone know what it is. Thanks

 

Under what circumstances is it activating?

 

Is it the door closing chime

 

Does it sound like a slower version of the aws?

 

It kinda sounds like a slower version of dsd. It happens when you go to open and close the doors.

 

That's the actual sound the doors make when they open and close in real life