Resound Thin tube hearing aid beeps


I am the new owner of a resound Thin tube hearing aid. Its my first hearing aid and so  far so good. 

The only trouble I have is that it has started some strange beeping sequence when I switch it on. 

For the first week, it just had a single beep when switched on, but now it plays a short little sequence. 

Does anyone know what this means?

I've heard the battery indicator and it's it that. 

I've looked online but nothing has been  found so far. 

Any help appreciated.