How can I prevent notifications from adjusting the volume?

[iMore Question]

So I'm playing music, in the car with my phone. I won't be reading messages while driving. When a notification comes in, especially from whatsapp messages, the music volume drops out for a few seconds and comes back up. When a whole bunch of msgs come in, like a group chat, it's a complete nightmare. I want the notifications, but how can I stop it from decreasing my music volume?

 

[Highrisedrifter]

I have the same too.

I haven't found a setting that stops the volume decrease when a notification comes through and I don‘t think there is one.