Arthur Nielsen was born the child of two accountants in Chicago back in 1897. He attended the University of Wisconsin at Madison and graduated with an engineering degree in 1919. he worked for Iskop breifly on refridgeration equipment, but it didn't stick. He needed to get back to his roots, raw math and measurement. So in 1923 he borrowed 45 grand from his frat brothers and founded the AC Nielsen Company.
He shopped around the idea of product evaluation and other consumer surveys. It was very early in the game and it was a struggle to convince advertisers that this data was both useful and accurate. 140 trained field investigators made phone calls to a sample of drug and grocery stores. It wasn't until the mid 1930s that he entered the radio arena.
His inner accountant was continually irritated that radio ratings were based on bad data. People were prone to lie and forget interviewers to lead and obfuscate. He wanted better data. He found the audimeter. Claude Robinson a student at Columbia University developed a rough experimental device to record what radio stations had been listened to. It's uncertain if he even built a model or demonstrated it, but his Professor Frank Stanton did. RCA bought the patent just in case. Two professors at M.I.T. Prof. Robert welder and Louis F. Woodruff had developed the device anopther device and encountered the Robinson patent seeking their own patent. they proceeded with funding from John Shepard, of 680 WNAC-AM. In the end they had to buy the old patent from RCA. Field tests began in 1938. It was years before the device was truly ready for field use. But by 1950 they'd also adapted it for use with television.
But in 1939 ACNielsen was expanding internationally. Hooper had killed C.A.B. and in turn Nielsen would swallow him. The audimeter was far superior to any interview system. It still had faults though. It could record what channel was on and for how long... but not if anyone was actually watching.
The earliest version of the audiometer attached to the radio and tracking channel, time and duration of tuning. The early Audimeters contained tapes or cartridges which were mailed back to Nielsen weekly from each sample home. Later versions of the meter fed the information directly to Nielsen Media Research in real time by a dedicated phone line. In 1973 Nielsen introduced the "Storage Instantaneous Audimeter" that actually stored the data locally and was retrieved in a nightly data dump. It made possible the first set of daily national ratings.