How to make sound modulation?

Question

Python

Good afternoon
Is it possible to raise the frequency of the sound, for example, up to 18000 hertz?
it's just that a large number of people do not hear such frequencies.
if anyone knows how to do this in another programming language, then this is not a problem, I would understand the principle

Answer 1

Those. you want to transfer low frequency sound to high frequencies?
It is possible to transfer, but it is unlikely that something digestible will come out of this.
In theory, this is so .
You can try something like this:
1. Make a DFT
2. Add as many zeros between the first and second samples of the DFT result as necessary to achieve the new sampling rate. Don't forget about the second half of the spectrum.
3. Making an inverse DFT
. I don't know what happens :-) this is a slightly modified interpolation algorithm through the DFT. There, zero samples are added to the end (so there is no shift in the spectrum).
It is necessary to do, apparently, in small time intervals (0.5 - 1 second), then add the result. It may be necessary to take a signal with overlap. But not a fact, I had no experience with speech signals.
To implement even my simple algorithm, you need to understand a little how it all works.

Answer 2

Two very important questions: where to raise and why .

Answer 3

sin(x) * sin(x)gives a function 0.5 * sin(2x) + 0.5.
That is, to raise the signal 1 octave up, you need to calculate the value:
But what if you need to raise only 3 quarters? Interpolation gives the desired result:
y = 0.75 * sin(2x) + (1 - 0.75) * sin(x)