For those who may not be familiar with Sound Beach:
Sound Beach is a hamlet (an unincorporated area) in the north-center part of the Town of Brookhaven, in the north-central part of Suffolk County.
Beginning on the north and moving in a clockwise direction, the Hamlet of Sound Beach in the Town of Brookhaven is bordered on the north by the Long Island Sound; on the east by the Hamlet of Rocky Point; on the south by the Hamlet of Rocky Point and the Hamlet of Miller Place; and, on the west by the Hamlet of Miller Place.
The Hamlet of Sound Beach has a different border than does the "Sound Beach, NY 11789" postal zone (i.e., a place can have other than a "Sound Beach, NY 11789" mailing address and be in the Hamlet of Sound Beach): places in the Hamlet of Sound Beach have a "Rocky Point, NY 11778" mailing address.
For a good set of town-by-town maps showing all the villages and hamlets in each of LI's 13 towns (3 in Nassau County and 10 in Suffolk County):
Excellent Long Island Geographic Resource