In 1930 NBC started a school for radio announcers. The school was headed by the British-born Dr. Frank Vizetelly. In 1919 he published Soldier's Service Dictionary of English & French Terms. He also published his own pronunciation dictionaries including a 10 cent pamphlet called A Desk Book of Twenty-Five Thousand Words Frequently Mispronounced. There was another in 1921 The Words We Mispell and one called Mend Your Speech and yet another named A Desk Book of Errors in English. I think you get the idea.
Vizetelly became an announcer on the program Air College on WNYC-AM in 1929. In another book he later wrote specifically for NBC staff he wrote in the introduction the need for steps to establish the purity of American English. He saw it as under threat from immigrants and foreign accents and presumably regional accents. His hope was that radio would have a homogenizing effect on our speech. He wanted radio to "...iron out any jarring irregularities common to various sections..." but he wasn't alone in this thinking. The book Radio's Civic Ambition by David Goodman covers this in some detail. More here.
In 1931 NBC Vice president Henry Bellows praised the BBC on their diction "British Program announcing is a good deal better than ours, because announcers over there are all honor-graduates of Oxford and Cambridge." Bellows had a Phd in English Literature so his bias comes as no surprise. In 1935 he wrote an article for Harpers magazine that further establishes his hopes that radio would be the domain of talented educated men.There were always money men, the management staff that had their eye solely on profitability. But in that era there was also a strain of liberal-thinker that wanted radio to be an educational media with certain civic ambitions.
Those mixed goals left a mixed impression on the listening public. A year later another NBC VP, John Royal stated "If our announcers are guilty of mispronunciation, it is not because they are lacking in education, because more than eighty percent of them are college men..." NBC had a hiring policy that sought out recent college graduates. In short, this was a long standing policy for NBC and other networks. They wanted their airstaff to sound erudite and part of that meant accent-neutral.
For the staff it meant practicing perfect diction. Announcer André Baruch recalled his own time at NBC. He stated that they used to test potential announcers using copy filled with tongue-twisters and foreign names, such as “The seething sea ceased to see, then thus sufficeth thus.” Later it led to tests filled with expert-level tongue twisters including the legendary and somewhat comedic, Announcers Test passed down by Del Moore. It runs as follows:
- One hen
- Two ducks
- Three squawking geese
- Four limerick oysters
- Five corpulent porpoise
- Six pair of Don Alversos tweezers
- Seven thousand Macedonians in full battle array
- Eight brass monkeys from the ancient sacred crypts of Egypt
- Nine apathetic, sympathetic, diabetic, old men on roller skates with a marked propensity towards procrastination and sloth
- Ten lyrical, spherical diabolical denizens of the deep who hall stall around the corner of the quo of the quay of the quivery, all at the same time.