Sound Island is no longer inhabited. The Newfoundland’s Grand Banks site http://ngb.chebucto.org/ shows Communities Evacuated under 'Centralization Program' as listed in 1965 Report of Department of Public Welfare. Sound Island is included with 12 families evacuated.
The Maritime History Archives at Memorial University of Newfoundland has a number of photographs taken during the resettlement of isolated Newfoundland communities. There are several taken in 1951 of Alex and Annie Stacey’s house launched at Sound Island, Placentia Bay, and moved by sea to Garden Cove, Placentia Bay. http://www.mun.ca/mha/resettlement/moving_house_1.php#p5
Wikipedia states (without citing a source) that the residents of Sound Island were evacuated in 1953 and moved into Garden Cove. http://en.wikipedia.org/wiki/Garden_Cove,_Newfoundland_and_Labrador
Do you know when the last Brinstons left Sound Island? When did your Brinston ancestors leave and where did they settle?