[GreenKeys] [External] Re: Tone frequency history?

[Michael Katzmann]

I don't know if this is relevant but the USAF used a system of 6 tty
channels ...   "The carrier supply furnishes thirteen carrier tones spaced
170 cps apart in order of ascending frequency from 425 cps."
Probably chosen so that harmonic distortion interference is minimized. (the
same rationale behind OFDM)

... from "USAF GLOBAL COMMUNICATIONS SYSTEM ENGINEERING"
https://books.googleusercontent.com/books/content?req=AKW5Qaefjd6slDoYjzJDBID7uf5nuqSjIkmLQkDTxpisUKsx9GDbef1sLPxZQLvRCOASn3aoiPNo-w6RxWbEPfJmHZ-pI3QFI79lr22C3I6C_ahXDVuFAt1SFKSHYW0nAs005xOSa40gHMEcvn9cHAvsCywxviix_P-H_P__z5NfqrkEtJ1X7FcQkeUieYgCxMkBEOnxve32TT4w3IdUFkYe12kMV2y6a3s8s7wOHZ8pcStTKK3nU6WPS6cc2IIuBq9fv2vgOuunNK95VcTPkhcU66QFgvaSE6x4r3TCZv30eLaThPvUhSU

On Fri, Oct 8, 2021 at 10:48 AM Jones, Douglas W <douglas-w-jones at uiowa.edu>
wrote:

> From: Nick England [navy.radio at gmail.com] -- Friday, October 8, 2021 9:14
> AM
>
> >  wonder why 425 Hz tuning forks would have been common? Musical A is 440
> and A-flat is 415.3.
>
> It's not that simple.  Historically, there has been a process called pitch
> inflation in the music industry.  To quote the final paragraph of
> -- https://jakubmarian.com/the-432-hz-vs-440-hz-conspiracy-theory/
>
> > Virtually all commercially produced contemporary music is tuned to A =
> 440 Hz. Nevertheless, most symphony orchestras ignore the standard and tune
> to 441, 442 or 443 Hz instead, while orchestras specializing in older music
> may sometimes use a tuning close to the one for which the piece was
> originally written, which may range from 415 Hz to 470 Hz.
>
> So, 425hz is one note that is historically appropriate as A.  In 1859, the
> French government set the standard at 435.  The 440 standard dates back to
> 1939.
>
>           Doug Jones
>           jones at cs.uiowa.edu
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