New Chime ?

[Station]

So, last night driving back from Manchester airport (wife had been away, not myself) we heard a very quiet 2 tone chime.

it may have sounded louder but the weather was dreadful - standing water plus rain.

Appeared to sound at random, neither of us could say exactly where from, although we checked our phones and nothing.

I had nothing showing on the display that normally isn’t there. 
Then It stopped, weirdly / coincidentally when I put the car in Sport mode from Normal mode.

Drive was out of airport, which was when we first heard it, then onto M56, still heard it and then M6, where we heard it twice more before I changed drive mode to Sport, then we never heard it again.

Any  ideas ?

Thanks.