I'd say the same as hattie xx
As someone who used to work in a primary school these are classed as words as when you read a book e.g the car went beep beep if you know what I mean
Teacher here, yes they count as words. Using sign language also counts up until around 18 months. Example :mine has a bank of words but also just signs for all done and more.
If they are said in context then I would say yes. E.g. looking at a car saying beep beep, a tiger saying raar etc