Generate Audio Tone

Program.cs

using System;
using System.IO;

namespace GenerateTone
{
    class Program
    {
        static void Main(string[] args)
        {
            // generate one second of 1khz audio
            using (var fs = File.Create("output.wav"))
            {
                const int SampleRate = 8000;
                const int BitsPerSample = 16;
                const int NumChannels = 1;

                short[] samples = new short[SampleRate];
                double amplitude = 0.25 * short.MaxValue;
                double frequency = 1000; // hz
                for (int n = 0; n < SampleRate; n++)
                {
                    samples[n] = (short)(amplitude * Math.Sin((2 * Math.PI * n * frequency) / SampleRate));
                }

                WriteRiffHeader(fs, NumChannels, BitsPerSample, SampleRate);

                for (int n = 0; n < SampleRate; n++)
                {
                    WriteByte(fs, samples[n]);
                }

            }
        }

        static void WriteRiffHeader(Stream stream, int numChannels, int bitsPerSample, int sampleRate)
        {
            // http://soundfile.sapp.org/doc/WaveFormat/
            WriteBigEndian(stream, 0x52494646);  // ChunkID: RIFF
            WriteLittleEndian(stream, 26 + 8000 * (uint)numChannels * (uint)sampleRate / 8);        // ChunkSize // TODO: We have to know the length of the data we'll be generating
            WriteBigEndian(stream, 0x57415645);  // Format: WAVE

            WriteBigEndian(stream, 0x666d7420);  // SubChunk1ID: fmt
            WriteLittleEndian(stream, 16);       // SubChunk1Size // note that this is the length of the rest of this subchunk header
            WriteLittleEndian(stream, (uint)numChannels);        // NumChannels
            WriteLittleEndian(stream, (uint)sampleRate);     // SampleRate
            WriteLittleEndian(stream, (uint)sampleRate * (uint)numChannels * (uint)bitsPerSample / 8); // ByteRate
            WriteLittleEndian(stream, (uint)numChannels * (uint)bitsPerSample / 8); // BlockAlign
            WriteLittleEndian(stream, (uint)bitsPerSample);        // BitsPerSample

            WriteBigEndian(stream, 0x64617461); // SubChunk2ID: data
            WriteLittleEndian(stream, 8000 * (uint)numChannels * (uint)bitsPerSample / 8);        // SubChunk2Size // TODO

        }

        static void WriteBigEndian(Stream stream, uint value)
        {
            if (BitConverter.IsLittleEndian)
            {
                stream.WriteByte((byte)(value >> 24));
                stream.WriteByte((byte)(value >> 16));
                stream.WriteByte((byte)(value >> 8));
                stream.WriteByte((byte)value);
            }
            else
                throw new NotImplementedException("big endian");
        }

        static void WriteLittleEndian(Stream stream, uint value)
        {
            if (BitConverter.IsLittleEndian)
            {
                stream.WriteByte((byte)value);
                stream.WriteByte((byte)(value >> 8));
                stream.WriteByte((byte)(value >> 16));
                stream.WriteByte((byte)(value >> 24));
            }
            else
                throw new NotImplementedException("big endian");
        }

        static void WriteByte(Stream stream, short value)
        {
            if (BitConverter.IsLittleEndian)
            {
                stream.WriteByte((byte)(value >> 8));
                stream.WriteByte((byte)value);
            }
            else
            {
                stream.WriteByte((byte)value);
                stream.WriteByte((byte)(value << 8));
            }
        }

    }
}