Transatlantic accent

The mid-Atlantic accent, or Transatlantic accent, is a consciously acquired accent of English, intended to blend together the "standard" speech of both American English and British Received Pronunciation. Spoken mostly in the early twentieth century, it is not a vernacular American accent native to any location, but an affected set of speech patterns whose "chief quality was that no Americans actually spoke it unless educated to do so". The accent is therefore best associated with the American upper class, theater, and film industry of the 1930s and 1940s, largely taught in private independent preparatory schools especially in the American Northeast and in acting schools. The accent's overall usage sharply declined following World War II.

Generally a North American phenomenon, the terms "Transatlantic" and "mid-Atlantic accent" are sometimes used alternatively, in Britain, to refer (often critically) to the speech of British public figures (often in the entertainment industry) who affect quasi-American pronunciation features.

According to sociolinguist William Labov, "r-less pronunciation, following Received Pronunciation, was taught as a model of correct, international English by schools of speech, acting and elocution in the United States up to the end of World War II." Mid-Atlantic English was employed by some American elites in the Northeastern United States. Prior to World War II, some American elite institutions cultivated a norm influenced by the Received Pronunciation of Southern England as an international norm of English pronunciation. Recordings of American presidents Grover Cleveland (raised in Central New York) and Ohio-native William McKinley show their oratory employed a Mid-Atlantic accent. Theodore Roosevelt, McKinley's successor and a native of New York, had a more natural non-rhotic, upper-class accent.

...
Wikipedia