Read Discovery's headline "Why Did Old-Time Announcers Talk That Way?" and you may instantly hear that voice in your mind--the trebly, abrupt voice of a 1950s radio announcer that has become an enduring echo in popular culture. Discovery wondered why that voice is so recognizable and so distinct, at least to sports fans who still value the tradition of listening to games on the radio. Their research points to two defining elements in the announcer voice: classic training, and technology.
According to a professor in Duke University's Theater Studies program, announcers often spoke (and continue to speak) in the transatlantic style. Transatlantic or Mid-Atlantic English, is apparently still taught in acting schools. It intentionally minimizes regional accents, blending American and British accents and mannerisms into something as neutral as possible.
Technology probably played a bigger role than voice training in defining the vocal styles of a generation of announcers and broadcasters. Audio equipment of the 1950s simply wasn't capable of producing the bassy lows we now take for granted, giving voices a universal trebly tint. Over the decades, technology has improved, but that style has stuck; it lives on in old recordings, and some younger announcers have no doubt emulated it to keep the sound alive.
Archive.org is a treasure of old radio broadcasts, and a quick search yields some great examples of the transatlantic voice in action. For example, listen to a game of the Yankees playing the Boston Red Sox for the pennant in 1949, or a number of other games listed under OTR for old time radio.