Repost of http://blog.gtiwari333.com/2011/08/silence-removal-and-end-point-detection_29.html

EndPointDetection.java

package org.ioe.tprsa.audio.preProcessings;
/**
 * @author Ganesh Tiwari
 * @reference 'A New Silence Removal and Endpoint Detection Algorithm
 * for Speech and Speaker Recognition Applications' by IIT, Khragpur
 */
public class EndPointDetection {
    private float[] originalSignal; //input
    private float[] silenceRemovedSignal;//output
    private int samplingRate;
    private int firstSamples;
    private int samplePerFrame;
    public EndPointDetection(float[] originalSignal, int samplingRate) {
        this.originalSignal = originalSignal;
        this.samplingRate = samplingRate;
        samplePerFrame = this.samplingRate / 1000;
        firstSamples = samplePerFrame * 200;// according to formula
    }
    public float[] doEndPointDetection() {
        // for identifying each sample whether it is voiced or unvoiced
        float[] voiced = new float[originalSignal.length];
        float sum = 0;
        double sd = 0.0;
        double m = 0.0;
        // 1. calculation of mean
        for (int i = 0; i < firstSamples; i++) {
            sum += originalSignal[i];
        }
        m = sum / firstSamples;// mean
        sum = 0;// reuse var for S.D.

        // 2. calculation of Standard Deviation
        for (int i = 0; i < firstSamples; i++) {
            sum += Math.pow((originalSignal[i] - m), 2);
        }
        sd = Math.sqrt(sum / firstSamples);
        // 3. identifying one-dimensional Mahalanobis distance function
        // i.e. |x-u|/s greater than ####3 or not,
        for (int i = 0; i < originalSignal.length; i++) {
            if ((Math.abs(originalSignal[i] - m) / sd) > 0.3) { //0.3 =THRESHOLD.. adjust value yourself
                voiced[i] = 1;
            } else {
                voiced[i] = 0;
            }
        }
        // 4. calculation of voiced and unvoiced signals
        // mark each frame to be voiced or unvoiced frame
        int frameCount = 0;
        int usefulFramesCount = 1;
        int count_voiced = 0;
        int count_unvoiced = 0;
        int voicedFrame[] = new int[originalSignal.length / samplePerFrame];
        // the following calculation truncates the remainder
        int loopCount = originalSignal.length - (originalSignal.length % samplePerFrame);
        for (int i = 0; i < loopCount; i += samplePerFrame) {
            count_voiced = 0;
            count_unvoiced = 0;
            for (int j = i; j < i + samplePerFrame; j++) {
                if (voiced[j] == 1) {
                    count_voiced++;
                } else {
                    count_unvoiced++;
                }
            }
            if (count_voiced > count_unvoiced) {
                usefulFramesCount++;
                voicedFrame[frameCount++] = 1;
            } else {
                voicedFrame[frameCount++] = 0;
            }
        }
        // 5. silence removal
        silenceRemovedSignal = new float[usefulFramesCount * samplePerFrame];
        int k = 0;
        for (int i = 0; i < frameCount; i++) {
            if (voicedFrame[i] == 1) {
                for (int j = i * samplePerFrame; j < i * samplePerFrame + samplePerFrame; j++) {
                    silenceRemovedSignal[k++] = originalSignal[j];
                }
            }
        }
        // end
        return silenceRemovedSignal;
    }
}