Here is my idea to make a simple alteration to the household or mobile telephone. This telephone continually rings when not in use, only when you receive a call will it fall silent.
When I first moved into a flat long ago it appeared to be quite noisy due to the traffic outside, but after a week or so I got used to it. I assume this would also be the case with my new telephone.
My new book of inventions is coming out in August, details here.