The Northern Line Extension team have so far only released one document about the noise impact on properties in 2008, the draft Environmental Assesment which you can find by clicking here (page 15 onwards).
By clicking on this picture you can download a map that represents the findings of this document for the Kennington area. Maps showing the exact location of the tube should be available shortly on the Northern Line Extension website here.
It is worth pointing out that on the contrary of what the 2008 Environmental Assesment says, the Crossrail project is working towards a combination of a maximum sound level of Lamax 35dB and an average of 30dB for residential properties as can be seen on this document page 4, clauses 2.13 & 2.14.
