Java - Creating a random key using audio signal

RandomFromAudio.java

package com.geneffects.utilities;

import javax.sound.sampled.*;

/**
 * 
 * Utility class for random number and random key creation.
 * 
 * NOTE: requires a microphone/soundcard.  (Probably won't work on your server!)
 * 
 * Turns on the microphone and collects the least-significant 8 bits out of 16-bit samples to
 * generate random numbers.
 *
 * Created by brianrisk on 8/27/17.
 */
public class RandomFromAudio {

    public static final String ALLOWED_CHARACTERS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

    // Demonstrating the methods
    public static void main(String[] args) {
        System.out.println(getRandomKey(32));
    }

    public static String getRandomKey(int keyLength) {
        int [] randomInts = getRandomIntArray(keyLength);
        StringBuilder stringBuilder = new StringBuilder();
        for (int randomInt: randomInts) {
            char randomChar = ALLOWED_CHARACTERS.charAt(randomInt % ALLOWED_CHARACTERS.length());
            stringBuilder.append(randomChar);
        }
        return stringBuilder.toString();
    }

    public static int [] getRandomIntArray(int desiredLength) {
        int [] out = null;
        AudioFormat format = new AudioFormat(8000.0f, 16, 1, true, true);
        TargetDataLine microphone;
        try {
            out = new int[desiredLength];
            byte[] data = new byte[2];

            DataLine.Info info = new DataLine.Info(TargetDataLine.class, format);
            microphone = (TargetDataLine) AudioSystem.getLine(info);
            microphone.open(format);
            microphone.start();

            // my microphone seems to need to "warm up".
            // It gets a lot of low signal at the beginning producing a lot of low numbers.
            // This loop reads signal until it shows that a decently high value can be reached.
            while (data[1] < 100) {
                microphone.read(data, 0, data.length);
            }
            byte [] leastSig = new byte[2];
            for (int i = 0; i < desiredLength * 2; i++) {
                microphone.read(data, 0, data.length);
                // saving the least significant byte
                leastSig[i % 2] = data[1];
                if (i % 2 == 1) {
                    // combining the bytes into an int
                    out[(i + 1) / 2 - 1] = leastSig[0]<<8 &0xFF00 | leastSig[1]&0xFF;
                }
            }
            microphone.close();
        } catch (LineUnavailableException e) {
            e.printStackTrace();
        }
        return out;
    }
}