Requesting information on audio frequency shifting circuits.

Archived from groups: rec.audio.tech (More info?)

I am looking for circuits that will shift ELF and VLF audio frequency
bands up to within hearing range. Likewise, I am also interested in circuits
that shift a band of ultrasonic frequencies down to within hearing range.

Any information you can point me to would be greatly appreciated. I
guess I'm not choosing the right keywords when performing web searches as I
haven't been able to find anything in the search engines. I know that there are
articles and circuits out there somewhere, I just haven't been able to find
them. Thanks to all who help.

Bob

Archived from groups: rec.audio.tech (More info?)

Bob,

> I am looking for circuits that will shift ELF and VLF audio frequency
bands up to within hearing range. Likewise, I am also interested in circuits
that shift a band of ultrasonic frequencies down to within hearing range. <

I believe this is usually done with heterodyne circuits, as opposed to
conventional audio processing used today to shift pitch and tempo
independently. Even more traditional methods, where pitch and time and bound
together like varying tape speed, is not useful if the frequencies are so
low or high that you can't even get them into an audio editor program for
processing.

The problem with heterodyne circuits is the pitch shift is not harmonically
related. That is, all frequencies are shifted by a fixed offset - say 2
KHz - as opposed to shifting by octaves or portions of an octave. Depending
on your application non-harmonic shifting may be acceptable. I recall years
ago seeing a TV show where they used heterodyne shifting to make audible the
sounds of insects and such. So they shifted everything down by a fixed 20 or
30 KHz. Had the ants been singing a barbershop quartet, their harmonies
would be out of tune. :-> )

--Ethan

Archived from groups: rec.audio.tech (More info?)

"Mark D. Zacharias" wrote:

> "Bob" <spam@not.com> wrote in message
> news93v701hqoh7gj2s05eocbha7cga76g75p@4ax.com...
> > I am looking for circuits that will shift ELF and VLF audio frequency
> > bands up to within hearing range. Likewise, I am also interested in
> circuits
> > that shift a band of ultrasonic frequencies down to within hearing range.
> >
> > Any information you can point me to would be greatly appreciated. I
> > guess I'm not choosing the right keywords when performing web searches as
> I
> > haven't been able to find anything in the search engines. I know that
> there are
> > articles and circuits out there somewhere, I just haven't been able to
> find
> > them. Thanks to all who help.
> >
> > Bob

> Seems to me programs like DCArt and Cool Edit do this with a speed change

CoolEdit, Audition can do it and maintain speed. Seems to be just what
is asked for.

> Mark Z.


Kind regards

Peter Larsen


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