How do I take a WAV recording and change the amplitude of a part of it in Java?

Question

Imagine having a recording of something saying "Hi there"

I'd like to chop/slice the WAV file between "Hi" and "there"

At this point, the "Hi" would be on one WAV file and the "there" on another wav file .e.g

hi.wav there.wav

From there, I'd like to change the volume/amplitude of the "there.wav" file.

Lastly, I'd like to merge the two wave files into:

hi_there.wav

Think of this as an audio editor, once finishing editing the audio, you would be able to save the edited audio as a brand new audio clip.

Answer 1

Cut the wave file:

double [] music = read("music.wav");

int start = 792478*2;
int end = 1118153*2;

double [] cutMusic = new double [end-start];

for(int i = start; i < end; i++)
{
    cutMusic [i-start] = music[i];
}

save("cutMusic.wav", cutMusic); //from StdAudio library

Change the volume/amplitude:

int multiplier = 0.5; //how much you want to change the volume by

for(int i = 0; i < cutMusic.length;i++)
{
    cutMusic[i] = multiplier * cutMusic[i];
}

Save the audio to a new wav file:

save("cutmusic.wav"), cutMusic); //from the StdAudio library
//converts the double array to a byte array

Join the two files:

ArrayList <File> joined = new ArrayList<>();

joined.add(new File("music.wav"));
joined.add(new File("cutMusic.wav"));

AudioFormat format = new AudioFormat(

                /*AudioFormat.Encoding*/AudioFormat.Encoding.PCM_SIGNED
                /*float sampleRate*/, sampleRate
                /*int sampleSizeInBits*/, 16
                /*int channels*/, 2
                /*int frameSize*/, 4
                /*float frameRate*/, 44100,
                /*boolean bigEndian*/false

joinAudioFiles(format, joined, new File("joined.wav")); 
//method needed is below

public static void joinAudioFiles(AudioFormat audioFormat,
                                      java.util.List<File> audioFiles, File output) throws IOException,
            UnsupportedAudioFileException {
        output.getParentFile().mkdirs();
        output.delete();
        output.createNewFile();

        List<AudioInputStream> audioInputStreams = new ArrayList<AudioInputStream>();
        long totalFrameLength = 0;
        for (File audioFile : audioFiles) {
            AudioInputStream fileAudioInputStream = AudioSystem
                    .getAudioInputStream(audioFile);
            audioInputStreams.add(fileAudioInputStream);
            totalFrameLength += fileAudioInputStream.getFrameLength();
        }

        AudioInputStream sequenceInputStream = new AudioInputStream(
                new SequenceInputStream(
                        Collections.enumeration(audioInputStreams)),
                audioFormat, totalFrameLength);
        AudioSystem.write(sequenceInputStream, AudioFileFormat.Type.WAVE,
                output);
    }