Katharine Hepburn and Cary Grant have a few things in common; not only were they popular actors during Hollywood's Golden Age, but they both used a way of speaking known as the Mid-Atlantic or Transatlantic accent. Although Hepburn was American and Grant was from England, you wouldn't know it by the way they spoke. By using the Mid-Atlantic accent, the top actors of Hollywood's Golden Age, like Hepburn and Grant, hid the dialect of their natural voice and adopted a fabricated accent that is hard to place.
In her 1942 book, Speak With Distinction, vocal coach Edith Skinner instructed actors and elites alike to speak with a Mid-Atlantic accent. They were required to drop the "r’s" at the end of words like "clear," use a hard "t" sound so words like "butter" sound like they are spelled, and utilize soft vowels like with the "a" in the word "dance" to make it sound more like "dahnce." How did Hollywood evolve from this completely fabricated accent to the more naturalistic voices actors use in film and television today? Like most mainstream things, the accent followed a trend, and Golden Age actors successfully used it to define their onscreen personas - until audiences demanded more realism.
The Mid-Atlantic accent is a combination of standard American English and Britain's Received Pronunciation. Since it doesn't belong to either the United States or Britain, linguists named the accent after a point in the ocean between the two countries. The accent was used so heavily in the 1930s and 1940s that it became associated with the time period and now sounds old-timey to modern ears.
Not to be confused with the accents of people who live in America's Mid-Atlantic region, which runs along the East Coast south of New England, the Mid-Atlantic accent became associated with the upper class. People in the 19th century believed British accents made speakers sound more worldly and possibly wealthy. Even though it isn't a naturally developed accent, actors and others who wanted to appear upper class adopted the Mid-Atlantic accent due to its slightly British sound.
Between 1926 and 1930, Hollywood movies transitioned from silent features to films in which audio and dialogue were recorded. This shift took a number of years, as movie theaters balked at installing the expensive and bulky equipment needed to provide a film's sound to audiences. As "talkies" became more popular, however, more and more theaters jumped on the trend, causing filmmakers to completely abandon silent movie projects.
In order to capture the best sound while filming, filmmakers experimented with different microphones and microphone placements around their sets. But because of the technological limitations of recording and broadcasting bass tones, actors on the screen and the radio had to clearly enunciate their dialog. The Mid-Atlantic accent helped as it produced a nasally tone in an actor's speech that could be easily picked up by the technology.
In the silent film era, actors used exaggerated facial expressions and gestures to express emotion, but the birth of sound film forced them to use their voices instead. For many actors, this proved to be a challenge because they were used to exaggerating their performance or relying on filmmakers shouting directions off camera. But the greatest problem was that many silent film actors had different natural speaking voices than the audience expected.
The downfall of silent film superstars like Clara Bow served as possible warnings to other actors that the transition to sound film might not be easy. Like Bow, who audiences turned against when they heard her unexpected nasal Brooklyn accent, many silent stars lost their careers partly due to the invention of sound film, leading many to turn to vocal coaches or adapt the Mid-Atlantic accent in order to keep their appeal.
As the Hollywood studio system began in the 1920s, studios took steps to make their product more marketable; they purchased theaters that would show only their films, dictated what kind of movies they'd produce, and attempted to establish monopolies. When it became clear that audiences wanted to see certain actors more than others, studios signed performers to multi-year contracts and asserted strict control over their lives.
Studios during Hollywood’s Golden Age dictated their actors' images, changed performers' names, and created carefully curated personas for their stars. As sound film became more prevalent, they also hired vocal coaches to train their actors to speak in the most pleasing and effective ways, which included adopting the Mid-Atlantic accent.