When mass transit vehicles added radio to existing vehicles there was nearly no consideration for acoustics. In the previous century acoustics had been acknowledged, but poorly understood. Even symphony halls were still designed in what's called a "shoebox configuration." The world's first scientifically designed symphony hall was only built in 1900, and it wasn't much different than those that preceded it. Imagine a 48-foot long aluminum and steel tube with an antenna, spark plugs, speakers and a radio. It's a metal box, it vibrates, sounds reflect and scatter. The saving grace of the bus was in that it is usually filled with humans. Compared to steel and aluminum we're pretty squishy. We provide a lot of acoustic absorption. In Chicago General electric and WGNB-FM tested their system and got specific complaints. One account in Billboard magazine described the reaction of the Chicagoan guinea pigs:
In the book Broadcasting the local news Lynn Boyd Hinds described committees forming opposed to radio in transit vehicles. Some people didn't like the idea of being bombarded by advertisements. In 1949, the first year of transit radio, complaints were being filed not just in Chicago, but with the transit authorities in Washington D.C. and others. Eventually it went to the courts. In 1952, after two appeals transit radio was declared constitutional. It was a show trial, with one justice even recusing himself. You can read the legal brief here. Broadcasting Magazine summed up the verdict with a bit too much entitlement:"One of the complaints of the public tested with sample uses of transit radio here has been irritation caused by lack of controlled volume. When vehicles were crowded, top volume was used. But when there were fewer riders continued high volume was disturbing."
"It sanctions the birth of a new advertising medium. It affords opportunity to a substantial number of FM broadcasters to earn a return on their investments."It may seem today to be an over-reaction. But try to compare it to the ire you give TV networks when the commercials are louder than the programs. The problem some thought, was really just one of volume. There was a valid argument for this. While loud speakers were already 70 years old, the electric amplifier was not. More here. Without a a modern amplifier, loud speakers aren't very loud in 1949 they were using tube amps, not solid state. Tubes themselves barely date to 1907 with DeForest. Radio was listed to at home in the parlor, car radios were a luxury. So in every practical sense, these engineers had little prior work to base their implementation on.