How to produce random audio frequencies that can theoretically produce sensible audio?

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I'm writing an article about that with endless time if we run random frequencies we would get a sensible audio, as seen below I made for random images (video) and included this code in the article to explain my point, also would you please teach me how to produce for example a basic sound beep that goes from a high pitch to a low pitch or the opposite?

What I have tried:

private void Timer1_Tick(object sender, EventArgs e)
        {
            for (int x = 0; x < 400; x++)
                for (int y = 0; y < 400; y++)
                {
                    g.DrawRectangle(new Pen(Color.FromArgb(255,
                        RN.Next(256),
                        RN.Next(256),
                        RN.Next(256))),
                        x,y,
                        1,1);
                }
        }

I don't think beep will do the job of sensible audio like human speech.

In a 1 ms timer tick:

using System.Runtime.InteropServices;
[DllImport("kernel32.dll")]
public static extern bool Beep(int freq, int duration);

Beep.Play(RN.Next(MAX_HZ),1);

Does it do the job? if yes, as I don't know about sound, what is the range frequency in Hz I should run.

Posted 20-May-19 14:45pm

john1990_1

Updated 22-May-19 8:03am

v5

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lmoelleb · Answer 1 · 2019-05-21T19:49:00

I am sure there are mathematical ways to produce the sound file you are requesting. But something like this should work.

Increasing the pitch (as an example, decreasing pitch will just be the same data backwards) basically means the frequency needs to be increasing as the file is played. Most likely you would want a sin-wave for your audio as it sounds a bit nicer, but if you just want really simple code, stick to square wave.

So loop over the length of your wave file data buffer.
Typially you would use sin(x * <frequencydefiningconstant>) * <amplitude> where x is the position in the audio buffer. If you change the value in sin to a non-linier expression, you will get variation in the pitch. so try sin(x^y * <frequencydefiningconstant>) * <amplitude> (y should be really close to 1, as samples come pretty fast in a wave file). Not sure this is the best result, you can play with other non-linier functions... or wait and hope someone comes with a better answer.

I would expect a Fourier transforms is the mathematical right way to do it as it can transform between the frequency domain (where you can specify a linier increase/decrease) and the time domain (your sample index in the wave file). If this is the right approach for your paper probably depends on the audience.

GenJerDan · Answer 2 · 2019-05-21T20:00:00

Not a solution, so much as a suggestion. If you mean music when you say "sensible audio", I'd suggest generating random integer values between 0 and 127, using that value as if it were a MIDI note, then looking up the frequency value of that note via a lookup table of some sort. EX: MIDI 60 = Middle C = 261.6 Hz

That's for regular "Western" diatonic music. There are others.

As far as playing the audio, look at public static void Beep (int frequency, int duration) for the most basic way of doing it. There are better ways, using the computers audio features rather than the Beep.

Gerry Schmitz · Answer 3 · 2019-05-20T17:29:00

Solution 1

Infinite monkey theorem - Wikipedia[^]

What is the SETI project? | Cool Cosmos[^]

Posted 20-May-19 17:29pm

Gerry Schmitz

Updated 20-May-19 18:04pm

v2

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john1990_1 21-May-19 12:06pm

I knew about the monkey thing before, but how is this related to the second link? also, any info about how to generate audio?

john1990_1 22-May-19 13:52pm

Thanks, please see updated question.

How to produce random audio frequencies that can theoretically produce sensible audio?

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