How to generate a .wav file with a sinusoidal wave and user-defined duration and frequency?

Question

The following code should create a File containing a sine wave. At typical frequencies (220Hz, 440Hz, 880Hz) it goes great, but at many other frequencies it doesn't, for example take 225Hz, 883Hz and so on. What should I do to get a nice sinusoidal wave for any frequency?

import java.lang.Math;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

public class CreateSine 
{
    static String fileNameString = "Sine.wav";

    static File file = new File(fileNameString);
    static String filePath = file.getAbsolutePath();

    static RandomAccessFile raw;

    static int byteCount = 0;
    static double pow215 = Math.pow(2, 15);

    static float freq = 440.0f;
    static int sRate = 44100;
    static int bitDepth = 16;
    static int nChannels = 1;
    static int dur = 1;

    static float changeRate = (float)((2.0 * Math.PI * freq) / sRate);

    public static void main(String[] args)
    {
        try
        {
            raw = new RandomAccessFile(filePath, "rw");

            raw.setLength(0); // Set file length to 0, to prevent unexpected behavior in case the file already existed
            raw.writeBytes("RIFF");
            raw.writeInt(0); // Final file size not known yet, write 0. This is = sample count + 36 bytes from header.
            raw.writeBytes("WAVE");
            raw.writeBytes("fmt ");
            raw.writeInt(Integer.reverseBytes(16)); // Sub-chunk size, 16 for PCM
            raw.writeShort(Short.reverseBytes((short) 1)); // AudioFormat, 1 for PCM
            raw.writeShort(Short.reverseBytes((short)nChannels));// Number of channels, 1 for mono, 2 for stereo
            raw.writeInt(Integer.reverseBytes(sRate)); // Sample rate
            raw.writeInt(Integer.reverseBytes(sRate*bitDepth*nChannels/8)); // Byte rate, SampleRate*NumberOfChannels*bitDepth/8
            raw.writeShort(Short.reverseBytes((short)(nChannels*bitDepth/8))); // Block align, NumberOfChannels*bitDepth/8
            raw.writeShort(Short.reverseBytes((short)bitDepth)); // Bit Depth
            raw.writeBytes("data");
            raw.writeInt(0); // Data chunk size not known yet, write 0. This is = sample count.
        }
        catch(IOException e)
        {
            System.out.println("I/O exception occured while writing data");
        }

        for (int i = 0; i < sRate*dur; i++)
        {
            writeSample( (float)Math.sin( i * changeRate ) );
        }

        closeFile();
        System.out.print("Finished");
    }

    static void writeSample(float floatValue)
    {
        try 
        {
            short hexSample = (short)((floatValue * pow215));
            raw.writeShort(Short.reverseBytes(hexSample));
            byteCount += 2;
        }
        catch(IOException e)
        {
            System.out.println("I/O exception occured while writing data");
        }
    }

    static void closeFile() 
    {
        try 
        {
            raw.seek(4); // Write size to RIFF header
            raw.writeInt(Integer.reverseBytes(byteCount + 36));
            raw.seek(40); // Write size to Subchunk2Size field
            raw.writeInt(Integer.reverseBytes(byteCount));
            raw.close();
        }
        catch(IOException e)
        {
            System.out.println("I/O exception occured while closing output file");
        }
    }
}

Thanks for your help.

RodrigoFranco · Answer 1 · 2016-10-26T19:04:16.803

Corrected code is below, instead of multiplying each float: float * 2^15, I'm doing: float * 0x7FFF, which as noted by jaket, turns to be: float * ((2^15)-1):

import java.lang.Math;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

public class CreateSine 
{
    static String fileNameString;
    static File file;
    static String filePath;

    static RandomAccessFile raw;

    static int byteCount = 0;

    static float freq;
    static int sRate = 44100;
    static int bitDepth = 16;
    static int nChannels = 1;
    static int dur;

    static float changeRate;

    public static void main(String[] args)
    {
        freq = Float.parseFloat(args[0]);
        changeRate = (float)((2.0 * Math.PI * freq) / sRate);

        dur = Integer.parseInt(args[1]);

        fileNameString = (String)args[2] + ".wav";
        file = new File(fileNameString);
        filePath = file.getAbsolutePath();

        try
        {
            raw = new RandomAccessFile(filePath, "rw");

            raw.setLength(0); // Set file length to 0, to prevent unexpected behavior in case the file already existed
            raw.writeBytes("RIFF");
            raw.writeInt(0); // Final file size not known yet, write 0. This is = sample count + 36 bytes from header.
            raw.writeBytes("WAVE");
            raw.writeBytes("fmt ");
            raw.writeInt(Integer.reverseBytes(16)); // Sub-chunk size, 16 for PCM
            raw.writeShort(Short.reverseBytes((short) 1)); // AudioFormat, 1 for PCM
            raw.writeShort(Short.reverseBytes((short)nChannels));// Number of channels, 1 for mono, 2 for stereo
            raw.writeInt(Integer.reverseBytes(sRate)); // Sample rate
            raw.writeInt(Integer.reverseBytes(sRate*bitDepth*nChannels/8)); // Byte rate, SampleRate*NumberOfChannels*bitDepth/8
            raw.writeShort(Short.reverseBytes((short)(nChannels*bitDepth/8))); // Block align, NumberOfChannels*bitDepth/8
            raw.writeShort(Short.reverseBytes((short)bitDepth)); // Bit Depth
            raw.writeBytes("data");
            raw.writeInt(0); // Data chunk size not known yet, write 0. This is = sample count.
        }
        catch(IOException e)
        {
            System.out.println("I/O exception occured while writing data");
        }

        for (int i = 0; i < sRate*dur; i++)
        {
            writeSample( (float)Math.sin( i * changeRate ) );
        }

        closeFile();
        System.out.print("Finished");
    }

    static void writeSample(float floatValue)
    {
        try 
        {
            char shortSample = (char)( (floatValue)*0x7FFF );
            raw.writeShort(Character.reverseBytes(shortSample));
            byteCount += 2;
        }
        catch(IOException e)
        {
            System.out.println("I/O exception occured while writing data");
        }
    }

    static void closeFile() 
    {
        try 
        {
            raw.seek(4); // Write size to RIFF header
            raw.writeInt(Integer.reverseBytes(byteCount + 36));
            raw.seek(40); // Write size to Subchunk2Size field
            raw.writeInt(Integer.reverseBytes(byteCount));
            raw.close();
        }
        catch(IOException e)
        {
            System.out.println("I/O exception occured while closing output file");
        }
    }
}

score 1 · Accepted Answer · answered Oct 26 '16 at 16:54

Your question doesn't really describe what the problem is other than to say that it is not nice. I'm going to hazard a guess that you are getting clipping in your conversion from float to int.

The largest value the sin function can output is 1.0.
you multiply the output by 2^15, or 32768.
The largest positive signed short is 32767.

The reason you are experiencing clipping at different frequencies is that the sine function only hits 1.0 at sin(1+4k*pi/2), where k is any positive integer. Certain frequencies (e.g. 441Hz) will hit 1.0 very often and others will not.

The solution is to multiply the floating point numbers by ((2^15)-1)

How to generate a .wav file with a sinusoidal wave and user-defined duration and frequency?

2 Answers2