Since I upgraded to Android 9 (Pie) a few days ago, my Nokia 7.1 makes alert noises every 30 seconds, 1 minute until I see the notification.
I think it has something to do with the notification settings of the environmental screen. I used to configure it in "periodically", which is supposed to be every 2 minutes and that previously only illuminated the screen, did not make noise. But now, I receive a notification noise every 30 seconds until I acknowledge the notification. I set the notification settings of the environment screen to "once" and that seems to have solved the problem of getting the notification sounds, so I think the configuration no longer works correctly.
I can live with that temporary solution for now, but it would be ideal for my screen to light up every 2 minutes without noise in the many cases in which I do not see it the first time.
I have seen a similar problem reported with a "Touch your settings, scroll down and touch accessibility, scroll down and touch the notification reminder" solution. but I Do not do have that adjustment