The Sound is described within the footnote on page 99 of Persuasion as "the sheltered inlet leading from the English Channel into Plymouth Harbour" (Austen). This location is mentioned by Captain Wentworth when he is detailing his sailing experience, specifically aboard his beloved "Asp" (98). Wentworth mentions that he had been "in the Sound" (99), most likely meaning his ship had been traveling in its sort of in-between space. Wentworth mentions getting caught in a "gale" (99), revealing the possibility of his not surviving such a vicious storm, as the story causes Anne Elliot to experience "shudderings" which "were to herself, alone" (99). The general weather of the English Channel by today's standards is "[o]ften, but especially from October to April... cloudy, chilly, and wet, with strong winds and poor visibility. At other times, it is fair and dry, with light winds and good visibility" (Wooldridge & Everard). 

Austen, Jane, and Linda Bree. Persuasion. Broadview Press, 2004.

Wooldridge, Christopher Frederick, and Everard, Cyril Ernest. "English Channel". Encyclopedia Britannica, 6 Oct. 2021, https://www.britannica.com/place/English-Channel. Accessed 4 December 2022.