iPhone no longer dings twice when fast charging....

Before I explain in detail I want to make everyone aware I am using the 18w fast charging plug with 2m USB-C lightening cable.

I have the new iPhone 11 purchased a couple weeks ago.

When I first started charging the phone it would ding once then followed by another ding a few seconds later (fast charging)

Unfortunately I no longer get the two dings I only get one ding. Is this normal? It still appears to be fast charging as I have timed it takes 30 mins to reach 50% this seemed to start happening after I installed the 13.1 update.

is there something I have changed in settings that I am not aware of?