What Note Do Most American Car Horns Make?

Early American car horns were in E flat or C but since the mid 1960’s,
the notes F sharp and A sharp are used.

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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