The note most American car horns make has been F sharp or A sharp since the mid-1960s. Prior to that, the first car horns for American vehicles had been in the notes of C or E flat since the 1910s. The first cars in the US in the late 1800s merely had bells until there was a demand for a device that produced a louder alert. The notes of car horns are determined by researching which ones are able to be heard over traffic and other background automobile operating sounds, while still being pleasant enough to the ear.
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