Originally Posted by
BigFlyer
Is this problem on both Android and Iphone or only Android?
There is the same problem with Google Hangouts as well - if you are on a Google Hangouts call and there is an incoming voice call, it will blow your ear out.
If there is ever a solution, I suspect it is more likely to come from complaining about Hangouts than Whatsapp, as Google makes Android and Hangouts.
Following up on my own post.
While I have the problem on my Pixel 2 - I did a test on my old LG G4 and you get a background tone instead of a loud ring when a cellular call comes in during a Whatsapp voice call. So the problem is apparently not universal for all Android phones.