Adjust only incoming call ringtone volume

Hello,

I have connected Mac to iPhone and I am using Phone app. Nice feature, but it's really annoying there's no preference to set up how loud ringtone is in Mac. My Mac is connected to external active speakers 2 x 120 W and every now then I forget to adjust volume down when not actively working with sound. I am not sure if whole neighbourhood needs to know when someone calls me. Even better would be option no sound at all for incoming calls. Any ideas?