Hello, and welcome to Apple Support Communities andyb_93!
From your post we can see that you have a question about a noise you're receiving while in calls.
To help narrow this down, if the sound is coming through the actual calls, it can be a connection issue: If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker You'll want to go through these steps.
If this sound is coming outside from outside of the call, it could be a notification you've set up. Use this guide for help: Use notifications on your iPhone, iPad, and iPod touch As a suggestion, go to Settings > Sounds & Haptics and select any alert. Once you do this, you'll see the alert tones and ringtones selections. You will be able to listen to narrow down and see if this is the actual sound you're hearing. Once confirmed, go to Settings > Notifications and make any adjustments.
We hope this helps!