TestDBVolume.java

public class TestDBVolume {
    static int maxVolumeLevel = 20;
    static int minDBLevel = -100;

    public static void main(String[] args) {
        for (int volume = 0; volume <= maxVolumeLevel; ++volume) {
          int volumeInDecibels = calulateDSPVolume(volume);
          String output = String.format("volume: %d, db = %d", volume, volumeInDecibels);
          System.out.println(output);
        }
    }

    static private int calulateDSPVolume(int volume) {
       if (maxVolumeLevel == 0) {
           return 0;
       }

       int volumeInDecibels = (int) ((1 - Math.pow((volume / maxVolumeLevel), 0.125)) * (minDBLevel));

       return volumeInDecibels;
   }
}

The output is:

javac TestDBVolume.java
java TestDBVolume

volume: 0, db = -100
volume: 1, db = -100
volume: 2, db = -100
volume: 3, db = -100
volume: 4, db = -100
volume: 5, db = -100
volume: 6, db = -100
volume: 7, db = -100
volume: 8, db = -100
volume: 9, db = -100
volume: 10, db = -100
volume: 11, db = -100
volume: 12, db = -100
volume: 13, db = -100
volume: 14, db = -100
volume: 15, db = -100
volume: 16, db = -100
volume: 17, db = -100
volume: 18, db = -100
volume: 19, db = -100
volume: 20, db = 0

when fixed:

       int volumeInDecibels = (int) ((1 - Math.pow(((float)volume / maxVolumeLevel), 0.125)) * (minDBLevel));

$ java TestDBVolume
volume: 0, db = -100
volume: 1, db = -31
volume: 2, db = -25
volume: 3, db = -21
volume: 4, db = -18
volume: 5, db = -15
volume: 6, db = -13
volume: 7, db = -12
volume: 8, db = -10
volume: 9, db = -9
volume: 10, db = -8
volume: 11, db = -7
volume: 12, db = -6
volume: 13, db = -5
volume: 14, db = -4
volume: 15, db = -3
volume: 16, db = -2
volume: 17, db = -2
volume: 18, db = -1
volume: 19, db = 0
volume: 20, db = 0