Been to see a house where I knew there was a trainline, the garden is less than 30 foot long and about 5 foot from the back fence is line A, then another (say) 15 foot away is line B. I suspect line B is the Gatwick express but don't hold me to it. Anyway, I knew there'd be some noise but thought let's have a look. In the 15 minutes we were there at least 6 trains went through, sometimes 2 trains at once - one on each line. The "express" train line was slightly higher than the other and that was quite loud. I've checked the timetable and I think the 20 trains is a good guesstimate, and it would be going around 19 hours a day.
House had lots of other thing we really wanted, but honestly, could you get used to it? We've been looking for ages so I am feeling a bit suspect at friends saying nah that'll be fine etc. (edited to say I suspect this as everyone is fed up of hearing me going on about the house search!) Also I wonder if the noise would affect the dog, again there's no way of knowing. Any thoughts?