How to generate sounds according to frequency? [duplicate]

Answer 1

Here is a wrapper around the Beep function in the kernel, taking a duration and a frequency. Nowadays Beep uses the soundcard; in my days it used some piezo device glued on the motherboard.

using System;
using System.Runtime.InteropServices;

class BeepSample
{
    [DllImport("kernel32.dll", SetLastError=true)]
    static extern bool Beep(uint dwFreq, uint dwDuration);

    static void Main()
    {
        Console.WriteLine("Testing PC speaker...");
        for (uint i = 100; i <= 20000; i++)
        {
            Beep(i, 5);
        }
        Console.WriteLine("Testing complete.");
    }
}

On my Win10 box I need to set the duration (last parameter) much larger then the 5 ms here, more up to 50 ms but to get something reasonable I have to make it 100 ms.

Or use the Console.Beep(Int32, Int32) method if you want to take the easy route. That method was introduced in .Net 2.0.

Answer 2

Either way you look at it, unless you want to used unmanaged code, you're going to have to build a WAV to play it. However, below is a code snippet from Eric Lippert's blog that will show you how to roll your own WAV file using frequencies.

namespace Wave
{
   using System;
   using System.IO;
   class MainClass {
      public static void Main() {
         FileStream stream = new FileStream("test.wav", FileMode.Create);
         BinaryWriter writer = new BinaryWriter(stream);
         int RIFF = 0x46464952;
         int WAVE = 0x45564157;
         int formatChunkSize = 16;
         int headerSize = 8;
         int format = 0x20746D66;
         short formatType = 1;
         short tracks = 1;
         int samplesPerSecond = 44100;
         short bitsPerSample = 16;
         short frameSize = (short)(tracks * ((bitsPerSample + 7)/8));
         int bytesPerSecond = samplesPerSecond * frameSize;
         int waveSize = 4;
         int data = 0x61746164;
         int samples = 88200 * 4;
         int dataChunkSize = samples * frameSize;
         int fileSize = waveSize + headerSize + formatChunkSize + headerSize + dataChunkSize;
         writer.Write(RIFF);
         writer.Write(fileSize);
         writer.Write(WAVE);
         writer.Write(format);
         writer.Write(formatChunkSize);
         writer.Write(formatType);
         writer.Write(tracks); 
         writer.Write(samplesPerSecond);
         writer.Write(bytesPerSecond);
         writer.Write(frameSize);
         writer.Write(bitsPerSample); 
         writer.Write(data);
         writer.Write(dataChunkSize);
         double aNatural = 220.0;
         double ampl = 10000;
         double perfect = 1.5;
         double concert = 1.498307077;
         double freq = aNatural * perfect;
         for (int i = 0; i < samples / 4; i++) {
            double t = (double)i / (double)samplesPerSecond;
            short s = (short)(ampl * (Math.Sin(t * freq * 2.0 * Math.PI)));
            writer.Write(s);
         }
         freq = aNatural * concert;
         for (int i = 0; i < samples / 4; i++) {
            double t = (double)i / (double)samplesPerSecond;
            short s = (short)(ampl * (Math.Sin(t * freq * 2.0 * Math.PI)));
            writer.Write(s);
         }
         for (int i = 0; i < samples / 4; i++) {
            double t = (double)i / (double)samplesPerSecond;
            short s = (short)(ampl * (Math.Sin(t * freq * 2.0 * Math.PI) + Math.Sin(t * freq * perfect * 2.0 * Math.PI)));
            writer.Write(s);
         }
         for (int i = 0; i < samples / 4; i++) {
            double t = (double)i / (double)samplesPerSecond;
            short s = (short)(ampl * (Math.Sin(t * freq * 2.0 * Math.PI) + Math.Sin(t * freq * concert * 2.0 * Math.PI)));
            writer.Write(s);
         }
         writer.Close();
         stream.Close();
      }
   }
}

Break it apart for your needs, but notice the aNatural variable - it's a frequency - just like what you're looking for.

Now, you can place that into a MemoryStream and then play it with SoundPlayer if you like.