Unexplained drilling/vibrating/sounds like cell phone sound in wall!

my family is at their wits end. Every single Monday, Thurs and Fri morning between 6am-7:30am we hear from the upstairs bedroom wall/ceiling a vibrating or drilling sound that lasts like 2-5 seconds. It also sounds like a cell phone vibrating on a glass table. We live in a semi and asked our neighbours and they don’t hear it and don’t have an alarm. I think it’s an alarm because it happens at perfect times like 6:15, 7:30. but we don’t hear it ANY other time. It’s driving us crazy and waking all of us up every morning it happens. Please help me, what is this horrible sound?